RECORD: Cleaveland, Parker. 1816. An elementary treatise on mineralogy and geology: being an introduction to the study of these sciences, and designed for the use of pupils,—for persons attending lectures on these subjects,—and as a companion for travellers in the United States of America. Boston: Cummings and Hilliard; Cambridge: University Press.

REVISION HISTORY: Transcribed (single key) by AEL Data. RN1

NOTE: This work formed part of the Beagle library. The Beagle Library project has been generously supported by a Singapore Ministry of Education Academic Research Fund Tier 1 grant and Charles Darwin University and the Charles Darwin University Foundation, Northern Territory, Australia.


[page i]

AN

ELEMENTARY TREATISE

ON

MINERALOGY AND GEOLOGY,

BEING AN

INTRODUCTION TO THE STUDY OF THESE SCIENCES,

AND DESIGNED

FOR THE USE OF PUPILS,—FOR PERSONS, ATTENDING LECTURES
ON THESE SUBJECTS,—AND AS A COMPANION FOR
TRAVELLERS

IN

THE UNITED STATES OF AMERICA.

ILLUSTRATED BY SIX PLATES.

BY PARKER CLEAVELAND,

PROFESSOR OF MATHEMATICS AND EATURAL PHILOSOPHY, AND LECTURER ON
CHEMISTRY AND MINERALOGY, IN BOWDOIN COLLEGE, MEMBER OF THE
AMERICAN ACADEMY, AND CORRESPONDING MEMBER OF THE
LINNÆAN SOCIETY OF NEW ENGLAND.

itum est in viscera terræ:
Quasque recondiderat, Stygiisque admoverat umbris,
Effodiuntur opes. OVID.

BOSTON:

PUBLISHED BY CUMMINGS AND HILLIARD, NO.1, CORNHILL,

PRINTED BY HILLIARD AND METCALF, AT THE UNIVERSITY PRESS,
CAMBRIDGE, N. ENGLAND.

1816.

[page ii]

DISTRICT OF MAINE.

BE it remembered, that on the eighth day of November, A. D. 1816, in the forty first year of the Independence of the United States of America, PARKER CLEAVELAND, of the said District hath deposited in this office the title of a book, the right whereof he claims as author, in the words following, to wit;

"An Elementary Treatise on Mineralogy and Geology; being an Introduction to the Study of these Sciences, and designed for the use of Pupils—for persons attending Lectures on these subjects—and as a companion for travel1ers in the United States of America. Illustrated by six Plates. By Parker Cleaveland, Professor of Mathematics and Natural Philosophy, and Lecturer on Chemistry and Mineralogy, in Bowdoin College, member of the American Academy, and Corresponding member of the Linnæan society of New England.

itum est in viscera terræ:
Quasque recondiderat, Stygiisque admoverat umbris,
Effodiuntur opes OVID."

In conformity to the act of the Congress of the United States, entitled, "An act for the encouragement of learning, by securing the copies of maps, charts, and books, to the authors and proprietors of such copies, during the times therein mentioned;" and also to an act, entitled "An act supplementary to an act, entitled an act for the encouragement of learning, by securing the copies of maps, charts, and books, to the authors and proprietors of such copies during the times therein mentioned; and extending the benefits thereof to the arts of designing, engraving, and etching historical and other prints."

HENRY SEWALL. Clerk of the District
Court of Maine
.

[page iii]

TO

BENJAMIN VAUGHAN, LL. D.

FELLOW OF THE ROYAL SOCIETY OF EDINBURGH, OF THE AMER.
PHILOS. SOCIETY, OF THE AMER. ACADEMY, AND OF THE
MASS. MED. SOCIETY, ETC.

SIR,

You will not, I trust, be displeased, and the Public, I am assured, will not be surprised, that I should embrace this favorable opportunity of addressing you, as the patron of general literature, and more especially of Natural Science.

It is, indeed, an elementary treatise only, which is here offered to your notice. But it is no small encouragement to those, who are anxious to promote the progress of Mineralogy and Geology, to know, that these branches of knowledge receive the patronage and attention of such, as have, like yourself, devoted a large portion of life to the cultivation and improvement of deeper and more abstruse sciences.

Accept, Dear Sir, for your friendship, both to myself, and the College, with which I am connected, these sincere expressions of gratitude and respect,

from your much obliged
and humble servant,

PARKER CLEAVELAND.

Bowdoin College,

Nov. 8, 1816.

[page iv]

Systematic works on Mineralogy, which have been more or less used in preparing this volume.

Elements of Mineralogy. By RICHARD KIRWAN, 2 vols. 2d edit. London 1794.

Traité de Minéralogie. Par le citoyen HAUY, 5 tomes, Paris, 1801.

Traité Elémentaire de Minéralogie, suivant les principes du Professeur Werner. Par A. J. M. BROCHANT, 2 tomes, Paris, 1800, 1803.

System of Mineralogy. By ROBERT JAMESON, 3 vols. Edinburgh, 1804, 1805, 1808.

Tableau Méthodique des Espèces minérales. Par J. A. H. LUCAS, Paris, 1806.

Traité Elémentaire de Minéralogie, avec des applications aux arts; ouvrage destiné a l'enseignement dans les Lycées Nationaux. Par ALEXANDRE BRONGNIART, 2 tomes, Paris, 1807.

Tableau Comparatif des resultats de la crystallographie et de l'analyse chimique, relativement à la classification des Mineraux. Par M. l'Abbé HAUY, Paris, 1809.

Abbreviations, sometimes used in this volume.

KIRW. KIRWAN. BRONG. BRONGNIART.
BROCH. BROCHANT. WERN. WERNER.
JAM. JAMESON.
Introd. Introduction.
Spec. grav. Specific gravity.
Geolog. sit. Geological situation.

[page v]

PREFACE.

THE subjects of Mineralogy and Geology have but recently received any considerable degree of attention in this country. Even at the present time, these interesting studies, and often profitable pursuits, are confined to a number comparatively small.—It is, however, undoubtedly true, that the progress of Mineralogy has been much retarded by the want of suitable means of becoming acquainted with the elements of this study.

All, who are engaged in mineralogical pursuits, perceive the need of an introductory or elementary treatise in the English language, neither too brief, nor too much extended. such a work is peculiarly important for all persons, while attending lectures on mineralogy and geology. Indeed, being a portable volume, it is convenient for those, who, while travelling, are inclined to devote an occasional attention to these subjects, with a view either to increase their knowledge, or relieve the todiousness of the journey.

But, to supply that, which is so obviously wanted, or, in other words, to furnish a suitable elementary work on mineralogy and geology is an undertaking, attended with some peculiar difficulties. These difficulties arise from the nature of the subject, and from the diversity of opinipns, which already exist on these subjects.—It is, therefore, proper for the writer here to state his general views and plan.

Minerals may be divided into species and arranged according to their external characters alone, or according to their true composition, as far as that is known. Hence have arisen two, distinct, mineralogical schools; viz. the German, which regards Professor WERNER, of Freyberg, in Saxony,

[page] vi

as its founder—and the French, which looks chiefly to the Abbe HAUY, as its author.

In the system of Werner, minerals are divided into species and arranged, according to the external characters. In the system of Haüy, the true composition of minerals is considered the basis of arrangement, although the crystalline characters are, in fact, principally employed—with the belief, however, that arrangements, founded on the crystalline characters and true composition, are never at variance. In the description of minerals, Werner depends almost entirely on an accurate enumeration of all the external characters. Haüy, on the other hand, employs only the most important of the external and chemical characters, relying chiefly, however, on the crystalline form and structure, where these can be observed.—Hence it results, that, in many cases, Werner attaches to certain differences of external character a degree of importance, which Haüy does not admit;—hence also the number of species, in the arrangement of Werner, is much greater than in that of Haüy.

It has already been remarked, that minerals may be divided into species and arranged according to their external characters, or according to their chemical or true composition, as far as that is known. It is, in fact, these two methods, which, in comparison, ought to be opposed to each other. The crystallographical method of Haüy is only a modification of the chemical method, which it acknowledges as its basis; but it can never be of universal application, for some minerals are destitute both of crystalline structure and form.

In regard to the systematic works on mineralogy, which have proceeded from the German and French schools, they undoubtedly possess peculiar excellencies, with some peculiar defects intermixed. The German school seems to be most distinguished by a technical and minutely descriptive language; and the French, by the use of accurate and scientific principles in the classification or arrangement of minerals.

[page] vii

Many of the writers of the two schools appear to have indulged an undue attachment to their favorite and peculiar system, and have hereby been prevented from receiving mutual benefit; the one being unwilling to adopt what is really excellent in the other.—But it is believed, that the more valuable parts of the two systems may be incorporated, or, in other words, that the peculiar, descriptive language of the one may, in a certain degree, be united to the accurate and scientific arrangement of the other.

This union of descriptive language and scientific arrangement has been effected with good success by BRONGNIART in his system of mineralogy—an elementary work, which seems better adapted both to interest and instruct, than any, which has hitherto appeared. The author of this volume has, therefore, adopted the general plan of Brongniart, the more important parts of whose work are, of course, incorporated with this.

It is respectfully requested by the writer, that those persons, who, like himself, may have received their first ideas on mineralogical subjects from the writers of the German school, would carefully and candidly examine Chap. iii of the Introduction on the systematic arrangement of minerals; and that they would particularly attend to the distinction, which is made in Articles 176, 197, and 198 of the same Introduction, between those properties of minerals, which may be used as the basis of arrangement, and those, which may be safely employed in description only.

In the Introduction, all the external characters of minerals are enumerated, and accompanied, when necessary, by explanatory remarks. The very interesting and important subject of crystallography is also explained with as much minuteness, as is consistent with the nature of an elementary work.

But, as the limits, assigned to this volume, would not permit a particular notice of all the secondary forms of crystals, I have endeavored to give those general views of the

[page] viii

primitive form and structure of the crystals under each species, which may enable the student to refer the various secondary forms to their proper nucleus. In addition to this, the most common secondary forms, and sometimes those, which are most rare, or most complex in their structure, are particularly described, and often explained by the assistance of diagrams.—It is extremely important to possess correct, general ideas of the form and structure of the perfect crystals of each species; for, without such knowledge, it would often be impossible to recognise those forms, which are incomplete, or irregular in regard to the number or extent of their faces, &c.

In the list of Localities, subjoined to each species, I have intermixed brief, geological notices, whenever it was practicable.—Of foreign localities some of the most important only are selected.

In regard to American localities, several difficulties have attended this first attempt to collect them; and, although I have many acknowledgments to make to those mineralogists, who have kindly assisted me in the collection, the list is still incomplete. But I have reason to place great confidence in the accuracy of those, which are given; for most of them have been furnished expressly for this Volume. Bruce's Mineralogical Journal, v. 1; a paper by S. Godon in the Memoirs of the American Academy, v. iii; and another by Dr. Adam Seybert, of Philadelphia, in the Medical Museum, v. v. are almost the only printed authorities, which I have employed,

Among those gentlemen, to whom I am under obligations for lists of localities and geological notices, not before published, are Drs. H. H. Hayden and E. Debutts, and R. Gilmor, esq. of Baltimore—Messrs. C. I. Wister and S. W. Conrad, of Philadelphia—Prof. Bruce and Col. G. Gibbs of New York—Professor Hall, of Middlebury College, Vt.—and Professor Silliman, of Yale College, Connecticut. These authorities are generally cited, when used.—To Dr.

[page] ix

Hayden and Professor Silliman I am under peculiar obligations.

The names of the species, Subspecies, and varieties are, in most cases, accompanied by notes, containing the synonyma of Werner, Haüy, Kirwan, Jameson, Brochant, and Brongniart. Wherever the German names of Werner differ from those, found in Jameson's Mineralogy, they are copied from the Tableau comparatif, &c. of Haüy, who took them from a late edition of Karsten's Mineralogical Method. It should be remarked, that, when synonyma from any of the aforementioned authors are wanting in a note, it is not to be inferred, that those authors have not mentioned that particular mineral.

In preparing this volume, the author has made indiscriminate use of whatever appeared to him most important in the more recent systematic works on mineralogy; among which are those of Kirwan, Haüy, Brochant, Jameson, Lucas, and Brongniart. The titles and editions of these works have already been mentioned, p. iv. The foregoing authors are seldom cited, except in regard to some facts, which are uncommon, or whose existence, as universal facts, is still doubtful. —Whenever the Tableau comparatif of Haüy differs from his Traité de Minéralogie, in consequence of additions, corrections in the measure of angles, &c. &c. the Tableau has been uniformly employed. Hence, in most cases, where the name of Haüy is annexed to an assertion, the reference is to the Tableau comparatif.

The works of Humboldt, Spallanzani, and other modern travellers, various Reviews, and literary Journals have also furnished something toward this volume. In many cases, however, to abridge as much as possible, I have barely mentioned the author's name, without the title of his work, although I am sensible, that some inconvenience attends this practice.

Some authors, whose works I have not seen, are cited on the authority of Brongniart, Edinburgh Review &c. The

b

[page] x

analyses of Kirwan are, in general, those, which were published in Nicholson's Journal.

To pursue, with pleasure and advantage, the studies of mineralogy and geology, some previous knowledge of natural philosophy and conchology is important; but an acquaintance with the general principles and nomenclature of chemistry is a necessary prerequisite.

This preliminary knowledge of chemistry is, indeed, easily attainable; but, for the convenience of those, to whom the nomenclature of chemistry may not be familiar, a vocabulary of chemical terms is subjoined to this volume.

It will be seen by the reader, that the United States have furnished not only some new varieties, belonging to species already known, but also a few species of minerals entirely new, The rocks of this country seem also to offer some aggregates, not heretofore named or described.

An acquaintance with simple minerals, or with Mineral. ogy in the more limited sense of this word, is a necessary prerequisite, to the study of Geology. To the student, therefore, who has acquired this preliminary knowledge only, we may apply the lively remark of Haüy in the Preliminary Discourse of his Mineralogy;—'il n'a pas encore vu la nature, mais il a recu des yeux pour la voir.'

[page xi]

CONTENTS.

This table relates only to the contents of the Introduction to the study of Mineralogy, extending from p. 1 to 87, and the Introduction to the study of Geology, from p. 586 to 597. For other and more particular contents, see the general Index, at the close of the volume.

INTRODUCTION TO THE STUDY OF MINERALOGY.

Page.
CHAP. I. DEFINITIONS AND PRELIMINARY OBSERVATIONS, 1
CHAP. II. PROPERTIES OF MINERALS, 4
SECT. I. Crystallography, ib.
Crystallization and crystals, 5
Primitive forms, 8
Nature of mechanical division, 9
Forms of the integrant particles, 12
Structure of secondary forms 14
Goniometer, 21
Description of crystals, 22
Nomenclature of crystals, 27
SECT. II. Physical or External Characters, 36
Color, 37
Changeable colors, or chatoyement, or play of colors; irised colors, 41
Lustre, 42
Transparency, ib.
Refraction, ib.
Form, 44
Surface, 46
Unctuosity, 47
Coldness, ib.
Smell, ib.
Taste, 48
Adhesion to the tongue, ib.
Soil or stain, ib.
Streak, bi.
Distinct concretions, 49

[page] xii

Flexibility, 49
Sound, 50
Cohesion, ib.
Hardness, ib.
Fracture; and structure, as indicated by fracture, 51
Frangibility, 55
Shape of fragments, 56
Tenacity, ib.
Magnetism, ib.
Electricity, 57
Phosphorescence, 59
Specific gravity, 60
SECT. III. Chemical Characters, 62
Fusibility, 63
Action of acids; and other tests, 65
CHAP. III. SYSTEMATIC ARRANGEMENT OF MINERALS, 66
SECT. I. General principles of Arrangement, ib.
SECT. II. Arrangement of Minerals, according to the system of Werner, 69
SECT. III. Arrangement of Minerals, according to their chemical composition, or constituent parts, 73
SECT. IV. Description of Minerals, 81
CHAP. IV. NOMENCLATURE OF MINERALS, 84
Tabular View of Simple Minerals, 86
INTRODUCTION TO THE STUDY OF GEOLOGY.
Sect. 1. General Remarks, 586
Sect. 2. General view of the Structure of the exterior crust of the Earth 588
Sect.3. Geological Systems, 591
Sect. 4. Veins, 594
Sect. 5. Strata and beds, 596
Sect. 6. Mineral Formations, 597
Sect. 7. Wernerian arrangement of Rocks, ib.

[page 1]

INTRODUCTION

To

THE STUDY OF MINERALOGY.

CHAPTER I.

DEFINITIONS AND PRELIMINARY OBSERVATIONS.

1. THE extensive field and the numerous objects, which Natural History presents for our observation, render systematic arrangement and division of labor absolutely necessary. By these means each individual is enabled to direct his attention to some particular class of bodies, with advantage to himself and the public; and to pursue his favorite path in natural science without that confusion and perplexity, which the multiplicity of objects would otherwise produce.

2. Natural bodies may with great propriety be divided into two extensive classes; organic and inorganic.

3. Organic bodies have a peculiar structure, which consists in the possession of certain organs, on the proper action of which they depend for increase and perfection. This class embraces animals and vegetables; the former of which is distinguished from the latter by possessing the power of voluntary motion.

4. Inorganic bodies, on the contrary, possess neither life, nor the power of voluntary motion; they are entirely destitute of organic structure, and suffer change from the influence of external agents only. In this class we find minerals, and adopt the following definition.

5. Minerals are those bodies, which are destitute of organization, and which naturally exist within the earth, or at its surface.*

6. Mineralogy is that science, which has for its object a knowledge of the properties and relations of minerals, and enables us to distinguish, arrange, and describe them.

7. The writers of the Wernerian school usually divide mineralogy into the following five branches.

* The term fossil is usually appropriated to those organic substances, which have become penetrated by earthy or metallic particles; thus we say fossil shells, fossil bones, fossil wood, &c. Sometimes however the alteration, which these bodies have undergone in the mineral kingdom, is very slight. But the consideration of fossils belongs more particularly to geology.

1

[page] 2

Oryctognosy (οζνχτος γνωσις), which consists in the description of minerals, the determination of their nomenclature, and the systematic arrangement of their different species. It coincides very nearly with mineralogy in its modern acceptation.

Chemical mineralogy, which describes the chemical properties, and ascertains the constituent parts of minerals.

Geognosy (γη γνωσις), which investigates the structure, position, and relative situation of minerals, as they exist in the earth; and indeed every thing, which regards the mineralogical constitution of the crust of this globe.

Geographical mineralogy, which informs us what minerals are found in any particular section of the globe, and in what manner they there exist. It bears the same relation to a portion of the earth, that geognosy does to the whole.

Economical mineralogy, which considers minerals with reference to their various uses in the arts, medicine, &c.

The two branches, which have just been defined under the names of oryctognosy and geognosy, involve some important distinctions, and require further elucidation. But the names themselves, having been unnecessarily introduced into the English language from German writers, will, in this treatise, yield precedence to the terms Mineralogy and Geology.

8. The distinction between the two branches, of which we have just spoken, is intimately connected with a division of minerals into two kinds; simple or homogeneous, and compound or heterogeneous. The words simple and compound do not here relate to chemical composition, but merely to the different appearances, which these two classes of minerals respectively exhibit to the eye.

9. Simple minerals appear uniform and homogeneous in all their parts. They do in fact usually contain several different elementary principles; but these are so intimately combined and similarly blended in every part, as to exhibit the aforementioned uniformity of appearance.

10. Compound minerals, on the other hand, more or less evidently discover to the eye, that they are composed of two or more simple minerals, which either merely adhere to each other; or, as is sometimes the case, one appears imbedded in the other. Compound minerals are frequently called aggregates or rocks.

11. Now it is the simple minerals only, with which mineralogy, in the present acceptation of this term, is concerned. It is only this portion of minerals, which it undertakes to describe and arrange. The description of compound minerals or aggregates, including their mutual relations, &c. constitutes the science of geology.

[page] 3

12. We shall conclude this chapter with a few observations on the connexion of mineralogy with other sciences; its rank, as a distinct branch of science; and the utility of mineralogical and geological researches.

13. It is not unfrequentfy necessary to call in the united aid of philosophy, chemistry, and mineralogy to obtain a complete investigation of the properties of a single mineral. In the examination of the same body they differ from each other by observing that body from different points of view, and by taking cognizance respectively of different sets of properties. The two last of these sciences, however, are the most intimately connected.

It is but a few years since mineralogy could with any propriety claim the rank of a science; and for this claim she is principally indebted to the discoveries of chemistry. But, as if elated by her own rapid progress, she has, in several instances, refused to acknowledge the assistance, derived from chemistry. The truth is, both sciences necessarily concur to furnish us with the knowledge and description of minerals.

A chemist may ascertain the ingredients, which enter into the composition of a given mineral; but he cannot inform us what he has analyzed, nor describe the subject of his experiments, without the assistance of mineralogy. On the other hand, a mineralogist may detail every external character of a mineral; he may give it a name, and describe some of its relations to other minerals; but he cannot inform us what it contains, nor indeed designate some of its most essential and important characters without the aid of chemistry. Their connexion will more strikingly appear in a subsequent chapter on the classification of minerals.

It is further to be remarked, that no inconsiderable share of chemical knowledge is a necessary prerequisite to render mineralogical pursuits either pleasant or advantageous.

14. From a superficial view of minerals in their natural depositories, at or near the surface of the earth, it would hardly be expected, that they could constitute the object of a distinct branch of science. Nothing appears further removed from the influence of established principles and regular arrangement, than the mineral kingdom, when observed in a cursory manner. But a closer inspection and more comprehensive view of the subject will convince us, that this portion of the works of nature is by no means destitute of the impress of the Deity. Indications of the same wisdom, power, and benevolence, which appear in the animal and vegetable kingdoms, are also clearly discernible in the mineral.

To be convinced, that the mineral kingdom affords suitable objects for scientific research, we need but glance our eyes on those singular

[page] 4

properties of phosphorescence, electricity, magnetism, and double refraction, which some minerals possess, and more especially on that striking modification of the laws of affinity, which results in the production of those regular, beautiful, geometrical solids, called crystals.

But whatever progress may hitherto have been made in mineralogical pursuits, every new advance has opened a wider and more interesting prospect. The science is still in its infancy, and in many of its paths can proceed only with a faltering and uncertain step.

15. The general view of mineralogy, which we have already given, will offer to the minds of many sufficient inducements to the cultivation of this branch of knowledge. It may also be remarked, that several arts and manufactures depend on mineralogy for their existence; and that improvements and discoveries in the latter cannot fail of extending their beneficial effects to the aforementioned employments. In fine the study of mineralogy, whether it be viewed as tending to increase individual wealth to improve and multiply arts and manufactures, and thus promote the public good; or as affording a pleasant subject for scientific research, recommends itself to the attention of the citizen and scholar.

CHAPTER II.

PROPERTIES OF MINERALS.

16. THE description of minerals and their arrangement in systematic order must result from an investigation of their properties. These properties consist in certain relations, which minerals bear to our senses, or to other objects. Some of them are discoverable by mere inspection, or, at most, require some simple experiment to be made upon the mineral to ascertain its hardness, structure, &c. but without producing any important change in its natural state; while others cannot be observed without a partial, or complete decomposition of the mineral. All these properties, when employed for the purpose of discriminating minerals, are usually called characters. We hence have a twofold division of the properties or characters of minerals into physical and chemical. Of the various characters, which these two divisions comprehend, the most important will be described in the present chapter.

SECTION 1.

Crystallography.

17. Of the physical properties of minerals no one is so important in itself, and extensive in its influence and application, as that, by which crystals or regular solids are produced. To investigate and describe these solids is the object of crystallography, and constitutes without doubt the most interesting branch of mineralogical research.

[page] 5

Crystallization and Crystals.

18. Crystallization, in the most limited extent of the term, is that process, by which the particles of bodies unite in such manner, as to produce determinate and regular solids. But it is equally true, that those minerals, which possess a foliated or fibrous structure, are the products of crystallization under circumstances, which have rendered the process more or less imperfect, and prevented the appearance of distinct and regular forms.

Let a quantity of muriate of soda (common salt) be dissolved in water, and permit the solution to evaporate by a moderate heat; the particles of the salt will separate from the water, unite, and form little cubes, which float on the surface, till their increased weight causes them to fall through the liquid. These cubes are called crystals. Other substances, when permitted to crystallize, also exhibit regular solids, but of a different form. Thus the emerald presents the form of a hexaedral prism, and the garnet that of a dadecaedron with rhombic faces.

19. The ancients believed crystallized quartz (rock crystal) to be water, congealed by exposure to intense cold; and accordingly applied to it the term χζνσταλλος, which signified ice. Hence the etymology of the word crystal. Now, as a beautiful regularity of form is one of the most striking properties of crystallized quartz, the name crystal has been extended to all mineral and other inorganic substances, which exhibit themselves under the form of regular, geometrical solids.

20. A crystal may therefore be defined an inorganic body, which, by the operation of affinity, has assumed the form of a regular solid, terminated by a certain number of plane and polished faces. The corresponding faces of all crystals, which possess the same variety of form and belong to the same substance, are inclined to each other in angles of a constant quantity. This constancy of angles remains even in those cases, where the faces themselves, from some accidental causes, have changed their dimenions or number of sides. Transparency, though many crystals possess it in a greater or less degree, is not a necessary property. But plane surfaces, bounded by right lines, are so essential to the crystalline form, that their absence decidedly indicates imperfection in the process of crystallization. The lustre and smoothness of the faces may also be diminished by accidental causes.

21. The property of crystallizing is by no means confined to a small number of bodies. Nearly all the different species of simple minerals, and some inorganic bodies of vegetable and even animal origin, such as sugar, camphor, and spermaceti have been seen in a crystallized state. Most of the aforementioned substances are also capa-

[page] 6

ble of exhibiting a variety of forms. It is exceedingly probable, that many other natural bodies, not hitherto observed in the state of crystals, would, under favorable circumstances, undergo a similar process.

22. The limits, prescribed to this introduction, will not permit many remarks on crystallization, as a chemical process. It will be recollected, that affinity is of two kinds, homogeneous and heterogeneous; the former of which unites particles of the same kind; the latter, particles of different kinds. Now it is evident, that the production of a crystal essentially depends on the action of homogeneous affinity.

Solution in some fluid, as water or caloric, is a necessary prerequisite to crystallization. By solution the particles of the body to be crystallized are reduced to a state of minute division, separated from each other, and permitted to move in the solvent with perfect freedom. As solution takes place by the action of heterogeneous affinity, it is evident, that so long, as this continues to act with undiminished force on the particles of the dissolved body, no crystallization can be effected. It is therefore necessary to diminish the force of heterogeneous affinity, and cause the dissolved particles to approach each other, still permitting them to move freely and moderately among themselves. This may sometimes be effected by simple cooling, as in the case of metals; but to crystallize other substances, as most of the salts, slow evaporation and subsequent cooling are necessary.

It is obvious from the preceding remarks, that, to produce perfect crystals, the solvent should be free from external agitation, and sufficient in quantity to permit the particles to move, and to arrange themselves in the requisite order without disturbance. But, when these conditions are not complied with, an imperfect crystal, or only a fibrous or foliated mass is produced. Indeed from the frequent absence of some of the requisite conditions, large and perfect crystals are somewhat uncommon. The effects of a disturbed crystallization will be subsequently noticed.

23. It is evident, that the geometrical forms, which crystals exhibit, must depend on regularity of form in the particles, which compose these crystals, and on a determinate arrangement of these particles, at the moment of combination. The particles, of which we now speak, and which are undoubtedly the same, into which the body is reduced by solution, are called integrant particles. But we know that mere solution does not produce decomposition. Hence there are in bodies two kinds of particles; integrant and elementary.

24. Integrant particles are the smallest particles, into which a body can be reduced without destroying its nature; that is, without decomposing it.

25. Elementary or constituent particles are the final results of

[page] 7

chemical analysis. They are the elements, of which integrant particles are composed. Thus, while the latter remain invariable in the same body, the elementary particles must vary with the progress of chemistry.

Let a portion of the natural compound of sulphur and iron, called sulphuret of iron or pyrites, be as minutely divided, as is possible, without producing decomposition, and we shall, obtain the integrant particles; each particle, although invisible and excessively small, will be perfectly similar in its composition to the original mass, and will be really a portion of pyrites. But, if the same mass of sulphuret of iron be decomposed, we shall have its elementary particles, consisting of sulphur and iron. Possibly the sulphur and iron may both prove to be compounds; but this will not affect the integrant particles of sulphuret of iron.

In bodies really simple the integrant and elementary particles are evidently the same. It is also undoubtedly true, that the elementary particles of bodies must possess a regularity of form, which is constant in the same simple substance.

26. From the preceding observations it must be obvious, that a mineral is an assemblage of similar particles; and that it is formed, and increases in size merely by the juxtaposition of these similar, integrant particles. It depends on no interior mechanism, like organic bodies, for its growth; but is enlarged in its dimensions by the application of successive layers of particles.

27. Both theory and observation induce us to believe, that the integrant particles of the same substance possess the same form and dimensions. Now it is obvious, that, if these similar particles always combined in the same manner, all the crystals of any given substance would exhibit the same form. This however is far from being the case. It is true, indeed, there are many bodies, which have a determinate form, under which each of them most frequently appears. Thus muriate of soda usually presents a cube; the emerald, a hexaedral prism.

28. But the same species of minerals often presents itself under very different forms, equally regular and well defined. Sulphuret of lead (galena) appears at one time in the form of a cube, at another in that of an octaedron. Carbonate of lime can exhibit a rhomb, a hexaedral prism, and a dodecaedron with triangular or pentagonal faces. Indeed most bodies have several different forms, under which they occasionally appear.

29. Frequently the different solids, which the same substance produces, have no apparent resemblance. But, as all the particles of the same substance have the same form, it is undeniable, that this

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striking difference of form, observable in the crystals of any one substance, must depend entirely on a difference of arrangement in the integrant particles. Thus the cubic particles of the sulphuret of iron can so arrange themselves, as to produce sometimes a cube, sometimes an octaedron, and sometimes a solid, contained under twenty triangular faces.

30. Again, different substances sometimes crystallize under the same form. Fluate of lime, muriate of soda, and the sulphurets of iron and lead all occasionally appear in cubes.

But, notwithstanding this variety and apparent confusion, every thing is regulated by established laws. The different crystalline forms which any one substance is permitted to assume, are limited to a certain number; and the most dissimilar varieties, belonging to the same substance, do in a certain sense originate from one common point, which is the primitive form.

31. In illustrating the theory of crystallization, it will be necessary to describe the primitive forms of crystals and the methods of obtaining them; to ascertain the forms of integrant particles; to show in what manner secondary forms are constructed on the primitive, and to investigate the laws of their formation.

Primitive forms.

32. Every substance, when crystallized, has a particular form, which it actually exhibits, or on which, as a basis, all the other varieties of existing forms, which belong to that substance, depend. Thus, if we examine the various crystals of the carbonate of lime, we shall find them either in the form of a rhomb, under given angles constantly the same, or containing within them a similar rhomb, as a nucleus. This rhomb may be extracted from the crystal, which contains it, by a certain operation, and is called the primitive form of the crystals of carbonate of lime. All the other forms, which this substance presents, are called secondary forms.

33. It is on the primitive, as a substratum, that the various secondary forms are constructed by different arrangements of the integrant particles. Sometimes the primitive form is entirely concealed within the secondary, while, in other cases, some of its original faces are still visible; but its angles, edges, or bases are modified by additional faces.

34. The primitive form is found to be invariable, and to give a constant measure of its angles in all the crystals of the same substance. Thus all the secondary forms of the garnet are reducible to a dodecaedron, whose sides are rhombs, inclined to each other at an angle of 120°, which is its primitive form. If the fluate of lime do not pre-

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sent a regular octaedron, whatever form it actually exhibits may be reduced to an octaedron, for that is its primitive form.

The same nucleus is often extracted from secondary forms, which differ exceedingly from the primitive and from each other. Of the truth of this remark the crystals of carbonate of lime furnish striking instances. Some substances are almost always found under some one of their secondary forms, and seldom or never exhibit their primitive, as a natural crystal.

Nature of mechanical Division.

35. The primitive forms of crystals can be ascertained only by mechanical division. This process, sometimes called cleavage by lapidaries, consists in separating thin layers or slices from the sides, edges, or angles of a crystallized substance in a given direction. Many crystallized substances are very obviously composed of thin plates or laminæ, which by careful operation may be separated from each other, without presenting the appearance of a fracture. The planes, in which these laminæ are applied to each other, are called the natural joints of a crystal or crystallized mass. It is at these joints only, in the direction of the laminæ, that mechanical division can be effected.

In some minerals the natural joints are very obvious, while in others they are nearly or quite imperceptible; even in the same crystal the joints in one direction are often much more easily perceived, than in another. In examining many crystals it is necessary to employ the bright light of a candle, by the reflection of which from the faces of the laminæ the direction of the joints may be discovered.

36. This division is best effected by applying a thin, sharp instrument of steel to the natural joints of the mineral, and causing it to enter by a very delicate percussion. Sometimes, indeed, a gentle and well directed percussion is sufficient without an instrument of steel, especially when an edge or solid angle is to be removed. But, in other cases, it is necessary to heat the mineral red hot, and plunge it into cold water, which produces fissures in the direction of the natural joints.

37. The faces of the crystal or nucleus, obtained by mechanical division, as well as those of the separated laminæ, are plane and smooth, possessing a greater or less degree of polish; and are thus easily distinguished from the surfaces, which a common fracture produces, and which never exhibit all the aforementioned properties.

38. Many crystals are not susceptible of this kind of dissection This frequently arises from too great brittleness; sometimes from other causes, but in no instance from any thing, which appears incon-

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sistent with the general theory of the structure of crystals. But, when the primitive form cannot be obtained by mechanical division, it may often be inferred with considerable probability from the secondary forms by calculation. The striæ or channels, sometimes observed on crystals, may often assist in the determination of the primitive forms.

38. The nature of mechanical division will be best illustrated by an example.

Let a b c d e f g h (Pl. I, fig. 1.) be a hexaedral prism of carbonate of lime. Let a knife be applied to one of the sides of the prism, suppose t u f g, in the direction of the line s r, not far from the edge t u, and parallel to it; let the knife be so inclined, as to make an angle of 45° with the face of the crystal. By gentle blows with a hammer a segment will be separated from this edge of the crystal, leaving on the prism a smooth, polished, trapezoidal face m v r s, inclined both to the base and the side of the prism in an angle of 135°. If a similar attempt be made on the next edge u d, it will not succeed; either no impression will be made on the crystal, or a mere fracture will be produced.

Proceed to the third edge d c, and from this may be removed a segment altogether similar to the one removed from the edge t u; the trapezoidal face, remaining on the crystal, will be equally smooth, and inclined both to the base and side of the prism in the same angle of 135°. Pass to the fourth edge c b, which is parallel to the first edge t u, but no separation can be effected. Apply the instrument, as before directed, to the fifth edge b a, parallel to u d, and here another segment is obtained, leaving a smooth surface. Attempt a division on the sixth edge a t, and nothing but a fracture will be produced.

Proceed now to the other end of the prism. Let the first attempt be made to remove the edge g f, parallel to the edge t u, first operated upon at the other extremity of the prism. Nothing can be here obtained, but a fracture. Repeat the attempt on the next edge f e, parallel to the edge u d, which, at the other extremity, refused to be separated. A trapezoidal face i l o p, entirely similar to the preceding faces, obtained by division, will here be produced. Pass round the prism; the alternate edges n y and h g will submit to a division, while the other edges e n and y h will be found refractory.

From an examination of the prism, thus far dissected, it appears, that only the alternate edges at each end yield to a division; viz. the first, third, and fifth edges, at one extremity, and the second, fourth, and sixth edges, at the other extremity, counting from the side, whose edge was first separated. It further appears, that the edges, which, at one end of the prism, are capable of being removed by me-

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chanical division, correspond to those, which, at the other end, prove refractory. The section i l o p is parallel to the section, supposed to be made on the edge a b; and the four remaining sections are also parallel, taken two and two.

Mechanical division, thus far effected, has converted the prism into a solid, contained under fourteen faces. The remainder of each side of the prism is a pentagon; the remaining surface of each base is a triangle; and, by the removal of the edges, six new trapezoidal faces are produced.

Let the division be continued by sections, parallel to those already made. It is evident, that the bases of the prism must gradually diminish, till they entirely disappear, and a new solid (Pl. I, fig. 2.) is obtained. This solid is a dodecaedron, exhibiting twelve pentagonal faces. Six of these faces, of which s r i O w is one, are remaining portions of the original sides of the prism; and the other six, of which A I r s E is one, have resulted from the division.

Continue the removal of laminæ from the crystal in directions parallel to the preceding. The six pentagons, which, in the last figure, terminated the solid, remain the same; but the lateral pentagons gradually diminish in length, till they are converted into triangles. The solid is still a dodecaedron (Pl. I, fig. 3.), but it is now bounded by six pentagons and six triangles; see the faces A I r s E, &c. and s r O, &c.

One step more will close the process. Continue to separate layers from the crystal, as before, till the six lateral triangles vanish. No part of the surface of the original solid is now visible. Instead of a prism, we have a rhomb A B E K (Pl. I, fig. 4.), bounded by six equal and plane rhombs. This rhomb is the primitive form of crystallized carbonate of lime. All the other varieties of form, belonging to this substance, though exceedingly numerous and different from each other, yield, by mechanical division, a nucleus, perfectly similar to the preceding, both in form and the measure of its angles.*

39. In the same manner, if the eight solid angles a c d b, &c. (Pl. I, fig. 5.) of a cubic crystal of fluate of lime be removed by a knife, placed parallel to the diagonals of the faces, and inclined at an angle

* The reader will find the preceding example of mechanical division strikingly illustrated, by preparing a six-sided prism of soft wood, or, what is still better, of a potatoe, and dividing it in the manner already described for obtaining a rhombic nucleus. Indeed the structure of crystals should always be studied with the assistance of models, some of which should be composed of separable parts to illustrate the interior arrangement of the laminæ. See Traité de Minéralogie par le Cen. Haüy; also Elements of Crystallography, after the method of Haüy, by Fredrick Accum.

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of about 54½°, the same number of polished, triangular faces, of which e f g is one, will be produced. By continuing to remove laminæ, parallel to the first section, the sides of the cube entirely disappear; and an octaedron e i f g h (Pl. I, fig. 6.) with triangular faces is obtained, as the primitive form.

40. The primitive form is always divisible in directions parallel to all its sides. But such a division can only diminish its size; it can never change its form. A cube, however frequently divided by sections of equal laminæ, parallel to its sides, would remain a cube. Hence we have a good distinction between primitive and secondary forms. The latter are never divisible in directions, parallel to all their sides; whereas primitive forms are always divisible in directions, parallel to all their sides, and frequently also in other directions.

41. The number of primitive forms at present known is six; viz. a parallelopiped; including the cube, rhomb, and all other solids, contained under six faces, which are parallel, when taken two and two; a regular tetraedron; an octaedron with triangular faces; a regular hexaedral prism; a dodecaedron, whose faces are rhombs; and a dodecaedron, whose faces are isosceles triangles.

42. Were there as many different primitive forms, as there are distinct species of minerals, we should be enabled very easily to distinguish different substances by this character alone. Still however the aforementioned six solids, by a variation in their angles, dimensions, &c. are capable of furnishing a very considerable number of distinct, primitive forms. Thus the rhomb may vary in its angles in different species, as in the carbonate of lime and the tourmaline; the two pyramids, which compose the octaedron, may vary in the shape of their bases; and in the prismatic forms the base may be a square, rhomb, &c. and the ratio between the sides of the base and the height of the prism may vary indefinitely.

43. Some of the primitive forms, however, are common to several different substances. Muriate of soda and the sulphurets of lead and iron have a cube; fluate of lime, the spinelle, diamond, and the red oxide of copper, &c. have a regular octaedron.

Further it should be remembered, that the same form is sometimes primitive in one substance and secondary in another. Thus the cube, just mentioned as the primitive form of the sulphuret of lead, is one of the secondary forms of the fluate of lime.

Forms of the integrant Particles.

44. Mechanical division is not limited to the discovery of primitive forms only. These forms are still capable of division, and the ultimate result is the form of an integrant particle. We have already

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remarked (40), that the primitive form is always divisible in directions parallel to all its sides. But, if divided in this manner, it is evident its form would not be changed; and could we reduce it so minutely, that any further division would involve a decomposition in substances not really simple, we should then have obtained an integrant particle; but its form would be precisely the same, as that of the primitive crystal.

45. But, if the primitive form be also divisible in any direction or directions, not parallel to any of its sides, it may evidently be resolved into solids, whose forms are different from that of the primitive. This is in fact the ease with some of the primitive forms. Take, for example, the primitive form of the staurotide, which is a right prism (Pl. I, fig. 7.), whose bases a b c d and l m n o are rhombs. If this be divided by a plane, passing through d b and o m, the shorter diagonals of the bases, we shall obtain two triangular prisms, which may be further divided in directions, parallel to their sides, but in no other. We must therefore conclude, that all the integrant particles of the staurotide possess the form of a triangular prism.

46. Even in cases, where the primitive form permits no division, except in directions parallel to its sides, the integrant particles will sometimes be found to possess a form, unlike that of the primitive. The phosphate of lime furnishes an example. Its primitive form is a regular hexaedral prism. Let a b c d e f (Pl. I, fig. 8.) be one of the bases of this prism. If a division be made by removing laminæ in directions, parallel to the three alternate sides a b, c d, e f only, the solid will be reduced to a triangular prism g h i, which, being incapable of division, except in directions parallel to its sides, is the form of an integrant particle of the phosphate of lime. In the figure, the lines of division are extended over the whole base, for the purpose of rendering it obvious to the eye, that the hexaedral prism is an aggregate of a certain number of integrant particles in the form of triangular prisms.

47. Only three forms of integrant particles have hitherto been discovered. They are the three most simple, geometrical solids, viz. a tetraedron; a triangular prism; and a parallelopiped, including all solids of six sides, parallel two and two.

48. It is not to be understood, that integrant particles can be actually obtained by mechanical division. These particles are infinitely small in reference to our senses; we can neither perceive them, nor even name their real magnitude. But it is certain, that, however small, they must have some form; and it is believed, that their true form may be ascertained by the methods already described.

49. From these three forms of integrant particles proceed, by different modes of combination, the aforementioned six primitive forms

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of crystals (41). The preceding examples of the staurotide and phosphate of lime show hew two different forms, a right prism with rhombic bases, and a regular hexaedral prism, may be composed of integrant particles, having the form of triangular prisms.

50. It has been already remarked (27), that all the integrant particles of the same substance undoubtedly possess the same form and dimensions. Now, as integrant particles have but three forms, it would seem, that the same form must be common to many different substances. It is true, that, in some instances, different minerals have integrant particles of precisely the same form in all respects. Both muriate of soda and sulphuret of lead have a cube.

But it appears from the results of mechanical division, combined with calculation, that, in a large number of the different species of minerals, each species has integrant particles, whose form is peculiar to itself. It may then be asked, how can it be said, that the number of forms is only three. The varieties however, which these three forms are capable of producing, will be obvious, if we consider how many modifications the angles of the same form may undergo, and the various proportions, which may be made to exist between the dimensions of different faces of solids, bearing the same name. Thus the rhomb may vary indefinitely in its angles; the base of the four-sided prism may be a square, or a rhomb, the latter of which may also exhibit a great variety of angles; the base of the triangular prism may be isosceles or equilateral; and the ratio between the sides of the base and the height of the prism may serve to distinguish particles, which in other respects possess the same form.

51. This constancy of form in the integrant particles of the same substance is a character of very considerable consequence in the examination of minerals. It often enables us to recognise a mineral, which, by accidental causes, may have its usual characters very much altered or disguised. For amidst the various coloring matters and other accidental ingredients, which are often found in different individuals of the same substance, its integrant particles and the nucleus of its crystals retain the same form.

Structure of secondary Forms.

52. Having pointed out the method of analyzing crystals by mechanical division, we are now to examine their synthesis; or to inquire in what manner the integrant particles arrange themselves around the nucleus to produce secondary forms. These forms may be supposed to arise from the successive application of laminæ of integrant particles to the faces of the primitive crystal. These laminæ form a decreasing series, beginning with the layer first applied to the

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nucleus; and each succeeding layer is somewhat less in extent, than that, which immediately precedes it. This decrement of the laminæ is produced by successively abstracting one range or more of integrant particles from the sides or angles of each layer. These abstractions may be made on all the sides at once, or on all the angles, or only on some one or more of them.

The planes, in which these laminæ of superposition are applied to each other, are always parallel to the faces of the nucleus, and constitute, as we have seen (35), the natural joints of the crystal. It seems then, that the integrant particles first combine to produce the primitive form, and are then so arranged around this nucleus, as to produce the secondary forms.

53. It is important to remark, that even in those crystals, whose integrant particles are tetraedrons or triangular prisms, these particles are so arranged in the interior of the crystal, that, if taken in groups of two, four, six, or eight, they constitute parallelopipeds; so that in fact in every secondary form, the decrements may be supposed to be effected by abstracting ranges of little parallelopipeds. Thus it is obvious (Pl. I, fig. 8.), that any two contiguous triangles compose a rhomb, which may be viewed as the base of a parallelopiped.

54. There are four kinds of decrements, sometimes called laws of decrements.

Decrements on the edges; in this case the ranges of particles are abstracted from the edges of the laminæ in directions, parallel to the edges of the nucleus.

Decrements on the angles; here the abstraction of particles is made from the angles of the laminæ, parallel to the diagonals of the faces of the nucleus.

Intermediate decrements; these are made parallel to lines, intermediate between the diagonals and edges of the nucleus.

Mixed decrements; these take place, when the number of ranges subtracted is greater than unity, and, at the same time, the height or thickness of each layer is greater than the height or thickness of a single integrant particle; thus the decrement may be made by two ranges of particles in breadth, and three ranges in height.

Of these four laws the first and second are by far the most common.

55. The structure of secondary forms in best explained by one or two examples.

Let the cube a b c o l f g (Pl. I; fig. 9.) be the given nucleus, on which a secondary form is to be constructed, according to the first law of decrement. Let this cube be composed of 4913 cubic particles. Each face of the primitive, as a b c o, will exhibit 289 of these small cubes, and of course each side of this face will present 17 cubic particles. Let L,

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M, N, O, P, R, S, T (Pl. I, fig. 10.) be laminæ, composed of cubic particles, each cube being equal to one of those, contained in the nucleus. Each of these laminæ is successively diminished by the abstraction of one row of particles from all its sides; so that the number of particles, contained in each side, forms the decreasing series 15, 13, 11, 9, 7, 5, 3, 1. In this series the common difference is two, because one range of particles is taken from each side of each lamina; there will of course be eight laminæ, the last being a single cube only.

Let the lamina L (fig. 10.) be applied to the face a b c o of the primitive form (fig. 9.), so that the letters r, s, t, u, at the angles of this lamina, shall correspond with the same letters on the face of the nucleus. The sides of this lamina will be parallel to the edges a b, b c, &c. of the cube; but the lamina itself will evidently be less, than the face, on which it is deposited, by one row of particles on each side.

In a similar manner let the other laminæ be successively applied ever each other, with their edges parallel to those of the first lamina. This series of layers, terminating with a single cube, will evidently form a four-sided pyramid a b c d (Pl. I, fig. 11.) with triangular faces. By a similar process five other equal and similar pyramids may be raised on the remaining five faces of the primitive cube. This will give a solid, bounded by twenty four triangular faces. Now each of these faces is equally inclined to the face of the nucleus, because the rate of decrement is the same in all the pyramids. Consequently, any two of these triangular faces, as d b c and e b c, belonging to two contiguous pyramids, lie in the same plane; and, uniting at their bases, form the rhomb b d c e. But, as there are twenty four triangular faces, thus united two and two, the secondary form will be a dodecaedron, bounded by twelve rhombs.

It must also be obvious, that if the six solid angles d, e, h,&c. of the dodecaedron be removed by mechanical division, a cubic nucleus will remain.

56. In the crystal, which we have just constructed, it will be perceived, that the decrements form re-entering angles, and the edges of the laminæ projecting angles, so that the sides of the pyramids do in fact resemble the steps of a stair. But in the real crystal, which we suppose to have the same structure, the faces appear perfectly plane and smooth. This apparent difficulty however will instantly vanish, when we consider, that the real cubes, which compose the crystal, are infinitely small in reference to our senses, and consequently the abstraction of one or two rows of particles is imperceptible. Hence the smoothness and uniform appearance of the new faces.

The effects however of these decrements are not always invisible.

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It is not very uncommon to find the faces of secondary crystals, exhibiting striæ or little channels in the direction of the decrement, as on some trapezoidal garnets. This circumstance, although arising from imperfection in the process of crystallization, forms a striking proof in favor of the theory we are now illustrating, and sometimes may assist to determine the form and position of the nucleus. Some caution however is requisite in employing this character, for it is possible, that striæ may appear on secondary forms in directions, which do not correspond to those of the decrements, and indeed they may sometimes be observed on the primitive form.

57. The new faces on this dodecaedron are usually somewhat less brilliant, than those of the primitive cube. The reason of this will appear, when we reflect, that in the primitive we look directly upon the faces of the integrant cubes; whereas in the secondary form we view the edges of the same cubes; for the faces of this dodecaedron are really composed of an infinite number of edges of laminæ.

58. When the process of crystallization ceases before this dodecaedron is completed, the secondary form presents eighteen faces, of which six are squares and parallel to the sides of the primitive cube, and the remaining twelve are hexagons, parallel to the sides of the secondary dodecaedron. Or the crystal may be described as a cube, truncated on all its edges.

59. In the preceding example the rate of decrement was supposed to be one row of particles from the four sides of each of the successive laminæ. But, instead of one row, there may be two, three, or more rows of particles, subtracted from the sides of each layer. In these cases it is evident the altitude of the pyramids would be diminished, and the several pairs of contiguous, triangular faces would not lie in the same plane. The solid thus produced would consequently have twenty four triangular faces.

60. The decrements, of which we have hitherto spoken, are supposed to affect only the breadth of the laminæ, while their height or thickness remains the same, that is, equal to the height of one of the integrant cubes. But there are cases also, in which the height or thickness of each lamina of superposition may be equal to the height of two or more ranges of particles, while the breadth is diminished by one range only. The former of these is called a decrement in height; the latter, a decrement in breadth.

Sometimes these two decrements combine in the same crystal. Sulphuret of iron exhibits a dodecaedron with pentagonal faces, derived from a cubic nucleus by decrements both in height and breadth. On two opposite sides of each pyramid the decrements are made by two rows of particles in height and one row in breadth, and on the

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other two sides by two rows in breadth and one in height. But these decrements are so combined, that each pentagonal face is in fact composed of two faces, belonging to contiguous pyramids, but lying in the same plane; one of these two faces results from a decrement of two rows of particles in height, and the other from a decrement of two rows in breadth.

61. We shall close this account of the structure of crystals by an example of decrements on the angles.

Let A B C D (Pl. II, fig. 1.) be the upper base of the primitive form, which is supposed to be a cube, containing 729 smaller cubes. This face of the nucleus will exhibit the faces of 81 of these cubic particles, and each side of this face will present the edges of 9 particles. If these little cubes be considered as forming rows, which pass diagonally over the face, as from D to B, it is evident they would touch each other by their edges only, and not by their faces.

Let the lamina (Pl. II, fig. 2.) be so applied to the face A B C D (fig. 1.), that the points a′, b′, c′, d′ in fig. 2 shall be directly over the points a, b, c, d in fig. 1. It is evident, that the squares A a, B b, C c, D d in fig. 1 will be left uncovered by this lamina, thus forming a decrement of one cube, at each angle, parallel to the diagonals of the face. It is also evident, that one range of particles, contained between Q & V (fig. 2.), will project beyond the edge A B (fig. 1.) of the primitive cube; in the same manner the other borders G F, I L, & N 0 (fig. 2.) will extend one range of particles beyond the other edges B C, C D, & D A of the primitive. These projections are necessary to enable the laminæ of superposition completely to envelop the nucleus, and prevent the appearance of re-entering angles. Hence, although the decrement alone determines the form, those parts of the crystal, not affected by the decrement, increase.

Apply the second layer (fig. 3.), so that the points a″, b″, c″, d″ shall correspond to the points a′, b′, c′, d′ in fig. 2. This second layer leaves uncovered a second row of cubes at each angle, as O, E, S, Q and V, T, M, G, &c. which evidently produces a second decrement on each of the angles (fig. 1.), parallel to the diagonals of the face A B C D. It will also be perceived, that this layer extends itself by one cube on each side A, G, L, K beyond the borders Q V, G F, &c. of the preceding layer.

From an inspection of the figures it will appear, that the laminæ are at first octaedral, but afterwards become squares, as in Jig. 3; from this period they decrease by the abstraction of one row of particles from each side, as in the third lamina (fig. 4.)

Let now the several laminæ (fig. 4, 5, 6, 7, 8, 9) be successively applied over each other in the order indicated by corresponding let-

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ters, as already shown in regard to the first and second laminæ. This series will terminate with the single cube (fig. 9.), and a quadrangular pyramid will be erected on this face. But, the laminæ having at first increased and then decreased, each face of the pyramid will be a quadrilateral L Z Q C (Pl. II, fig. 10.), formed by the union of two triangles at their bases. We shall consequently have twenty four similar and equal quadrilaterals, formed upon the six faces of the primitive cube. All these new faces form equal angles with that face of the nucleus, on which they stand. Consequently the three quadrilaterals, about any one solid angle of the primitive, are in the same plane, and, by their union, constitute an equilateral triangle I Z N, as in Pl. II, fig. 11. Now, as there are twenty four quadrilaterals, united three and three in one plane, the secondary crystal is contained under eight equilateral triangles, and is a regular octaedron; the centre of each face corresponds to each of the solid angles of the nucleus. Sulphuret of lead furnishes an example of this structure.

62. In the case of decrements on the angles, the laminæ, which compose the secondary faces, do not present their edges to view, as in the former example (57) of decrements on the edges; for here the solid angles of the integrant cubes meet the eye. The faces of this secondary octaedron are therefore really composed of an infinite number of angular points, which, on account of their extreme minuteness, exhibit a smooth surface.

63. Had the process of crystallization, in the present example, closed before the several pyramids had reached their vertices, the secondary form would have been that of a solid with fourteen faces; six of them being squares, parallel to the sides of the cube, and the remaining eight being parts of the faces of the unfinished octaedron.

64. The four laws of decrements already noticed (54), when we consider the numerous modifications, to which they are subject, will appear amply sufficient to produce that vast variety of secondary forms, which has been observed. Thus these decrements may take place on all the edges, or all the angles at once; or only on some of the edges, or on some of the angles; they may consist uniformly of one, two, or three ranges of particles; or they may vary from one angle or from one edge to another; they may exist at the same time on the angles and edges; in fine, two different laws of decrement may be successively applied to the same angle or edge.

It is seldom, that decrements take place by more than two ranges of particles; yet, within these limits, it appears from calculation, that carbonate of lime may assume 2044 different forms; and, if the calculation extend to decrements by three and four ranges of particles, the same substance may have 8,388,604 distinct forms.

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65. To assign the causes of the preceding modifications, or even of secondary forms in general, is, in the present state of our knowledge, impossible. No doubt some of them may be found in the nature of the solvent, and its various densities, &c. The presence of foreign ingredients, or even an undue proportion of one of the principles of the crystallizing body, may have considerable influence on the arrangement of the particles. It is certain, however, that the causes of a particular secondary form are often quite extensive. For it is frequently the case, that secondary crystals of any given substance, taken from the same vein or repository, or even from the same range of mountains, have the same form; while crystals of the same substance, taken from another place, exhibit a secondary form of a different kind, but uniform in that particular repository.

66. We cannot indeed demonstrate that secondary forms are actually produced in the manner, which the theory supposes.* It is however no inconsiderable argument in its favor, that all calculations, founded on it, give results perfectly conformable to observed facts. The quantity of an angle, obtained by calculation, is verified by actual measurement on the crystal. The theory can determine what forms it is possible for the same body to assume; and of course enables us to say of any particular form, it does, or it does not belong to a given substance; or that this substance can or cannot assume a given form. We are hereby furnished with some important assistance in the discrimination of crystallized minerals, viz. an appeal to the forms and structure of their crystals. In fine, this theory is in fact a very interesting application of the prinoiples of geometry to the analysis and synthesis of various solids. It shows us, that a crystalline structure is to minerals in some degree what organization is to vegetables.

67. The theory, we have just considered, does indeed extend only to the structure of the crystal, which is to be considered, as an aggregate of similar particles, having a determinate arrangement; it presumes not to explain the mode of formation.

It may however be remarked, that it is not necessary to suppose, that the primitive form always reaches the size of that, which we extract by mechanical division, before the application of the laminæ of superposition. Indeed we find very minute crystals equally perfect

* It can hardly be necessary to state, that mineralogy is indebted to the Abbé Haüy, of Paris, for the system of crystallography here given; more especially for the actual discovery of primitive forms, the details, which relate to secondary forms, and the application of this theory to a great proportion of the crystals hitherto observed. Bergman and Romé de Lisle had previously drawn some of the outlines.

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in their structure with those of the same kind, that are larger. Is it not then possible, that the secondary form may be often completed soon after the commencement of crystallization, and afterwards increase without changing its form?

Goniometer.

68. It has already been remarked (20), that crystals, which possess the same form, and belong to the same substance, give a constant measure of their angles; it is hence true, that crystals of the same form, but belonging to different substances, may, in most instances, be distinguished by the measure of their angles, which, though constant in the same substance, is different in different substances, even when possessing the same form. It must then be a matter of great importance to ascertain with accuracy the quantity of any required angle. The importance of such measurements will be more striking, when we consider, that the same substance sometimes presents crystals, which fall under the same general name, but which are produced by different decrements, and differ in the measure of their angles, by which alone, however, they must be discriminated. Thus the carbonate of lime yields different secondary forms, which come under the name of a rhomb. Indeed different forms sometimes so nearly resemble each other, that they can hardly be distinguished by the eye, as in the case of a very obtuse rhomb and a cube.

69. This accurate measurement of crystals is, in a great degree, effected by a very simple instrument, called a goniometer (Γωνια Мετρον), and invented by M. Carangeau. It consists of a brass semicircle a b d (Pl. II, fig. 12, A.), graduated into 180°. A thin plate of brass extends from d to a. The centre c of this brass plate is made the centre of motion of two steel arms g d and k i, which, at the extremities g and k, are reduced to a point, that they may more conveniently be applied to a crystal; and, for the same reason, both arms are made to slide on the pin, which confines them at the centre. By being thus enabled to shorten the arms at pleasure, the inconvenience, arising from the gangue or adjoining crystals, may be avoided; sometimes also the brass plate extends only from d to the centre, and the quadrant a b is made to fold back occasionally on b d, that it may not interfere with adjoining crystals.

Now, if the two inner edges of the steel arms, near the points g and k be carefully applied to the planes of two contiguous faces of a crystal, the arms being held perpendicular to the edge, formed by these two faces, we shall evidently obtain the angle, which the two aforementioned faces make with each other; for it is equal to its vertical angle, and measured by the arc, contained between the two arms, at their extremities i and d.

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The arms of the goniometer are sometimes distinct from the semicircle, as in Pl. II, fig. 12, B. The measurement is effected in the manner already described; and the arms are then applied to the semicircle to ascertain the angle. This mode is convenient in very acute angles.

The goniometer, invented by Dr. Wollaston, appears to be capable of great accuracy in its measurements. It may be called an optical goniometer; for the angle is determined by rays of light, reflected from those two faces of the crystal, which contain the angle. It consists of a vertical wheel or circle with a graduated circumference. The axis of this wheel is perforated in a horizontal direction, and through this perforation passes a moveable axis, to which the crystal is attached. When the position of the crystal is so adjusted by this moveable axis, that one of the sides, containing the angle to be measured, reflects its light to the eye, the circle is turned, till the other side is brought into the same position; and hence the inclination of these two faces is measured by the arc, through which the zero or index of the vertical circle has passed.

This goniometer must be peculiarly useful in cases, where the side of the crystal, or the surface of the fracture is imperfect; for the most minute portions of those laminæ, which are parallel to each other, though not in the same plane, reflect the light at the same moment.

70. Hitherto in our remarks on crystallization we have supposed the results to be perfect crystals. But the numerous and frequent imperfections, which crystals exhibit, clearly indicate a very considerable degree of disturbance in the process of their formation. This disturbed crystallization is productive of various modifications in the shapes of crystals, or even entirely prevents the appearance of the crystalline form. Sometimes this disturbance manifests itself by giving an undue extension to some of the faces, while others are scarcely perceptible; so that the crystal sometimes appears to have been compressed in certain directions. Sometimes the edges are rounded and the angles blunted; while, in other instances, the faces of the crystal present a convex or concave surface.

In cases, where the crystalline form has entirely disappeared, a fibrous or lamellar structure of the mass may still indicate, that the mineral has been formed by a very disturbed crystallization. The particular names, by which those crystallized substances, which present no regular form, are designated, will be given in the section on external characters, under the article imitative forms (105).

Description of Crystals.

71. For the purpose of describing and distinguishing minerals

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crystallography furnishes two kinds of characters. One is derived from the actual forms of crystals; the other from the internal structure, and may obviously be extended to laminated masses, not possessed of regular forms.

As the actual forms of well defined crystals furnish important characters, we shall now attend to the modes of describing them.

72. Crystals may be described, either by the assistance of a diagram, or by employing certain well defined terms, capable of conveying an adequate idea of the solid intended. The use of a diagram is attended with many obvious advantages. It enables us to refer with ease to a particular angle or side. Indeed when the form is very complex, mere description is tedious, even when sufficiently intelligible; whereas a figure conveys at once a correct, general idea of the form of the crystal. In all cases, however, the exact quantity of the most important angles should be mentioned; or of so many of them, at least, as may be necessary to prevent mistake.*

73. If a crystal exhibit the form of any geometrical solid, known by a particular name, as a cube, or a regular tetraedron, or octaedron, it is easily described; it is sufficient to name it. But, when a definite idea of the form of a crystal cannot thus be conveyed, some other method must be employed. And probably no mode is attended by so many advantages, as that, in which a clear, short, and technical description of the form, including accurate measures of the most important angles, is combined with a diagram.

74. For accurate definitions of the terms, now generally employed in the description of crystals, mineralogists are much indebted to the celebrated Werner. This mode of description is founded on certain assumed principles, and essentially consists in supposing the crystal to possess what is called a predominant form; and that this predominant form has undergone certain alterations, till it has acquired the actual form, intended to be described.†

* Some mineralogists designate the angles of crystals, as right, acute, or obtuse, and qualify the two last by some general terms, expressive of the degree of obliquity. But it appears from previous remarks (68), that this can assist but little in discriminating forms, which much resemble each other. Two crystals may exhibit in certain parts very obtuse angles, and yet these angles may uniformly differ by a certain quantity, insensible to the eye.

† It is important to premise, that this method of describing the forms of of crystals is, in general, entirely artificial; that the assumption of certain predominant forms has no relation whatever to the primitive form, or the manner, in which crystals are actually formed; and that the alterations, supposed to be made in these predominant forms, are not real; for a crystal, viewed as a whole, always increases during the period of its formation, whereas this method supposes certain subtractions to be made from the magnitude, which the crystal once possessed.

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By the predominant form of a crystal is intended that geometrical form, to which the given crystal most approximates. Thus the solid (Pl. II, fig. 13.) most resembles a cube; but it has lost a segment from each of its solid angles, and from each of its edges; or each edge and each solid angle is said to be replaced by one face. The solid (Pl. II, fig. 17.) most resembles a prism; but its extremities exhibit pyramids. In the two preceding examples a cube and four-sided prism are respectively the predominant forms. The appearance of a crystal may be still more removed from that of the predominant form by further alterations.

75. The number of predominant forms may be reduced to six; an icosaedron with triangular faces; a dodecaedron with pentagonal faces; a hexaedron, or solid with six equal faces; a prism; a pyramid; and a table, by which is intended a very short prism. In describing these solids and their various modifications, the faces, edges, and solid angles must receive attention.

76. Many solids admit a distinction both of their faces and edges into lateral and terminal.

In crystals of a prismatic form the lateral faces are the sides of the prism, as M, M (Pl. II, fig. 14.); and the lateral edges are those formed by the meeting of any two lateral faces, as the edge a b in the same figure.

The terminal faces of prismatic crystals are their bases, sometimes called the upper and lower base, as P, P in fig. 14; and the terminal edges surround the bases or terminal faces, as a c, c d in the figure last mentioned.

If the crystal have a tabular form (Pl. II, fig. 15.), P is a lateral face, and a b a lateral edge. And in the same crystal M, M are terminal faces, and c d a terminal edge.*

A pyramid is said to have a base, and lateral faces; and its lateral edges all meet at the vertex. An octaedron is sometimes considered a double four-sided pyramid, having a common base at the junction of the two pyramids. The vertices of a double pyramid are also called its summits; and a rhomb is sometimes viewed, as a double three-sided pyramid, whose summits are the two opposite, solid an-

* This mode of distinguishing the faces and edges of tabular crystals is altogether unnecessary. A table, as just observed, is only a very short prism; and its several parts may be denominated in the same manner, as those of a longer prism. This distinction between lateral and terminal faces does not extend to the two first named predominant forms.

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gles, which are formed by three equal plane angles. So also the pyramidal terminations of a prism are called its summits.

When all the faces of a prismatic crystal are not equal, they are sometimes alternately wide and narrow; and sometimes two opposite faces are equally wide or narrow.

77. We are now to notice the several alterations, to which the predominant form may be subjected. These are three; truncation, bevelment, and acumination or termination. By each of these supposed alterations new faces are produced on the crystal; and their inclination to the contiguous faces may be measured by a goniometer.

78. Truncation. This alteration supposes a segment to be cut off or separated from the predominant form. A truncation may be applied either to an edge or a solid angle of a crystal, and will evidently leave a face more or less large in place of the edge or angle, as a, a and b, b (Pl. II, fig. 13.), where each edge and each solid angle of the cube is replaced by one small face. A truncation is said to be oblique, when the new face does not make equal angles with all the contiguous faces.

79. Bevelment. A bevelment may be applied to a lateral or terminal edge, or even to a terminal face, or a solid angle. It supposes the removal of two contiguous segments from the edges, angles, or terminal faces of the predominant form, thereby producing two new faces, as r, r (Pl. II, fig. 16.), inclined to each other at a certain angle and forming an edge; in this figure the cube is bevelled on all its edges. This new edge is sometimes situated obliquely, when referred to the edge or face, on which the bevelment is made. When a terminal face is bevelled, the two planes may stand either on the lateral faces or lateral edges. A second bevelment is sometimes applied to the edge, produced by the first, thereby forming four new faces, instead of two.

The degree of alteration, produced in the predominant form by truncation or bevelment, may be expressed in a general manner by saying slightly or deeply truncated or bevelled.

80. Acumination or termination. When three or more new faces are produced in the manner aforementioned, and these all unite in one point or line, a termination or acumination is said to exist. This alteration may be applied to a terminal face, as in the pyramidal termination a d b c (Pl. II, fig. 17.); or to a solid angle, as a, a, a (fig. 18.), where each solid angle of the cube is terminated by three faces. The faces of a termination, which is applied to a terminal face, may correspond to the lateral faces or the lateral edges of the predominant form; and the edges, produced by these terminating

4

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faces, are called the lateral edges of the termination. Sometimes two opposite faces of a pyramidal termination are so much wider than the others, that the pyramid terminates in an edge, instead of a point, and is said to be cuneiform.

81. When a crystal is supposed to stand on one of its bases, or to have its axis vertical, or indeed to rest in any other given position, its faces and edges may be conveniently designated, as horizontal, vertical, or oblique.

82. Grouping of crystals. Two or more crystals are often found attached to each other in groups more or less regular. In a few cases, indeed, these groups have much regularity in their structure and appearance. Sometimes they are composed of two crystals, which partially penetrate each other, or simply adhere by two faces similarly situated on both crystals. Sometimes two prisms intersect each other at constant angles, either right or oblique.

Other groups exhibit the appearance of two halves of the same crystal, so applied to each other, that, while one half is supposed to remain at rest, the other half, without being separated from the former, seems to have performed some part of a revolution in the common plane of intersection.

In some cases that half, which is supposed to revolve, seems to have passed through only one sixth of the circumference of a circle; in others it has described a semicircle, so that its position is inverted in regard to that half, which remains fixed. To this inversion of one half the Abbé Haüy has given the name hémitropie (hemitropy), which is designed to indicate, that one segment of the crystal has turned through half the circumference of a circle; and the crystal, thus produced, he designates by the epithet hémitrope. Such crystals are also called double or twin crystals.

These hemitrope or twin crystals, as well as those, which penetrate or intersect each other, may almost always be easily recognised by the re-entering angle or angles, which they present; for such angles never appear on simple crystals. Those parts of the crystal directly opposite to these re-entering angles will, of course, exhibit projecting edges or angles. In Pl. II, fig. 19. is an octaedral crystal of spinelle, which is supposed to be bisected in the plane of the dotted hexaedron, which appears in the interior. If, while the lower half remains fixed, the upper half be supposed to revolve in the aforementioned plane, through one sixth of a circle, the crystal (fig. 20.) will be produced. Feldspar and oxide of tin exhibit hemitrope crystals, as will be seen under those articles. In some minerals more than two single crystals are regularly grouped.

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Most frequently, however, groups of crystals are quite irregular. In this case, they are described, as far as practicable, by comparing them to some known body, which they resemble. Thus these groups may be fascicular, like a bundle of rods, or scopiform, like a broom, being in both cases composed of small crystals diverging from a centre; they may also resemble a rose or a sheaf. Sometimes the crystals aggregate in rows, and constitute acicular or columnar groups. In fine the groups may be globular, pyramidal, &c.

All these various adhesions of crystals must arise from a greater or less degree of disturbance in the process of their formation.

83. Size of crystals. As the size of crystals may vary from that of several inches in some of their dimensions, till their form becomes indeterminable without the aid of a microscope, it is of some consequence, that their general size should be stated.

Nomenclature of Crystals.

84. The importance of a systematic nomenclature in any branch of science is extremely obvious; and chemistry has already presented a striking instance of the truth of this remark. It must also be evident, that numerous advantages would result from a similar nomenclature in crystallography; especially when we consider the imme se variety of crystalline forms, which the mineral kingdom presents, and the importance of being able, without the labor of description, to designate any particular variety of form by some name or epithet, which may indicate the form itself, or the general structure, or some peculiarity of form or structure. The attempt, of which an account is now to be given, has been made by the celebrated Haüy.

The original names will be employed with an explanation annexed, and, in many cases, a reference to figures; for the analogy of our language does not appear to justify a literal translation of many of the terms of this nomenclature.* Indeed mineralogy already presents many uncouth and barbarous terms unnecessarily introduced into the English language by a literal translation of words belonging to foreign languages.

It may, however, be remarked, that many of the terms of this nomenclature may be easily understood without a knowledge of the French language, and may with great propriety be adopted, as English words, by a slight alteration of the orthography.

85. Primitif or Primitive, added to the name of the species, always denotes the primitive form of the crystals of that species. Thus zircon primitif.

* See Elements of Crystallography, after the Method of Haüy, by Fredrick Accum. London; 1813.

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86. The secondary forms of crystals may be considered under six different points of view.

I. Secondary forms, considered in regard to the modifications, produced in the primitive form, by a combination of the faces of the latter with those, which result from the laws of decrement.

Thus a crystal may be called

Pyramidé, when the primitive form is a prism, and, in the secondary form, is terminated at each extremity by a pyramid, having as many faces, as the prism has sides.

Prismé, when the primitive form is composed of two pyramids united base to base, and, in the secondary form, these pyramids are separated, and a prism is interposed. Thus zircon prismé; (Pl. III, fig. 34).

Semi-prismé, as in the preceding, except that the interposed prism has only half as many sides, as there are edges at the common base of the two pyramids.

Basé, when the primitive form is a rhomb, or is composed of two pyramids united base to base, and, in the secondary form, the summits of the rhomb or double pyramid are truncated by faces perpendicular to the axis of the crystal.

Epointé, when all the solid angles of the primitive form are truncated, each by one face. Thus strontiane sulfatée (sulphate of strontian) epointée; (Pl. III, fig. 6).

Bisépointé, triépointé, quadriépointé, when each solid angle of the primitive form is replaced by two, or three, or four faces. Thus analcime triépointée; (Pl. IV, fig. 21).

Emarginé, when all the edges of the primitive form are truncated, each by one face.

Bisémarginé, triémarginé, when each edge of the primitive form is replaced by two, or three faces.

Périhexaèdre, when the primitive form is a prism of four sides, and, in the secondary form, is converted into a prism of six sides by the decrements; or, in other words, is truncated on two of its lateral edges.

Périoctaèdre, péridécaèdre, péridodécaèdre, when, as in the preceding, a four-sided prism is converted into a prism of eight, or ten, or twelve sides. The term péridodécaèdre is also employed, when the primitive form is a regular six-sided prism, and, in the secondary form, has each of its lateral edges truncated by one face.

Raccourci (shortened), when the primitive form is a prism, whose bases are rhombs, and, in the secondary form, each of the two lateral edges, contiguous to the longer diagonals of the bases, is truncated

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by one face; in consequence of which the crystal appears diminished in length.

Rétréci (narrowed), when the primitive form is the same as in the preceding, but, in the secondary form, each of the two lateral edges, contiguous to the shorter diagonals of the bases, is truncated; in consequence of which the crystal appears diminished in breadth. Thus baryte sulfatée (sulphate of barytes) rétrécie; (Pl. III, fig. 2).

87. II. Secondary forms, considered by themselves, and merely as geometrical forms.

A crystal may be called

Cubique, when it exhibits a cube, as a secondary form.

Cuboïde, when the form differs very little from a cube. Thus chaux carbonatée (carbonate of lime) cuboïde; (Pl. III, fig. 15).

Tétraèdre, when the crystal presents a regular tetraedron, as a secondary form.

Octaèdre, when it presents an octaedron, as a secondary form.

Prismatique, when the form is a right or oblique prism, whose sides are inclined to each other at an angle of 120°.

Dodécaèdre, when the surface of the crystal presents twelve triangular, quadrangular, or pentagonal faces, all equal and similar, or whose plane angles possess only two different measures. Thus zircon dodécaèdre; (Pl. III, fig. 35); also cuivre gris (gray copper) dodécèdre; (Pl. IV, fig. 40).

Icosaèdre, when the crystal is bounded by twenty triangles, of which twelve are isosceles and eight equilateral. Thus fer sulfuré (sulphuret of iron) icosaèdre; (Pl. V, fig. 7).

Trapézoïdal, when the surface is composed of twenty four trapeziums, all equal and similar. Thus grenat (garnet) trapézoidal; (Pl. IV, fig. 14).

Triacontaèdre, when the crystal is bounded by thirty rhombs. Thus fer sulfuré (sulphuret of iron) triacontaèdre; (Pl. V, fig. 8).

Ennéacontaèdre, when the surface presents ninety faces.

Birhomboïdal, when the surface is composed of twelve rhombic faces, which, being taken six and six and prolonged in idea, till they intercept each other, would form two different rhombs.

Trirhomboïdal, when, as in the preceding, three different rhombs would be formed. Thus chabasie trirhomboïdale; (Pl. IV, fig. 22).

Biforme, when the crystal embraces a combination of two remarkable forms, as the cube, rhomb, octaedron, dodecaedron with rhombic faces, &c.

Triforme, when, as in the preceding, three forms are concerned. Thus cobalt arsenical triforme; (Pl. V, fig. 24).

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Cubo-octaèdre, when the crystal presents a combination of the two forms, indicated by the name, viz. a cube and octaedron.

Cubo-dodécaèdre, cubo-tétraèdre, when, as in the preceding, the forms are a cube and dodecaedron, or a cube and tetraedron. Thus fer sulfurè (sulphuret of iron) cubo-dodécaèdre; (Pl. V, fig. 6).

Trapézien, when the lateral planes are composed of trapeziums, situated in two ranges between the two bases. Thus baryte sulfatée (sulphate of barytes) trapézienne; (Pl. III, fig. 3).

Ditétraèdre, when the form is a tetraedral prism with diedral summits. Thus fer arsenical (arsenical iron) ditétraèdre; (Pl. V, fig. 4).

Dihexaèdre, dioctaèdre, when the form is a hexaedral prism with triedral summits, or an ootaedral prism with tetraedral summits. Thus topaze dioctaèdre; (Pl. III, fig. 25).

Didécaèdre, didodécaèdre, when the crystal is a decaedral prism with pentaedral summits; or a dodecaedral prism with hexaedral summits. Thus diopside didodécaèdre; (Pl. IV, fig. 26).

Trihexaèdre, when the surface exhibits three ranges of faces, placed one above the other, each range containing six faces.

Tétrahexaèdre, pentahexaèdre, eptahexaèdre, trioctaèdre, tridodécaèdre, when, as in the preceding, the crystal presents certain ranges of a given number of faces, as indicated by the several names respectively.

Bigéminè, when the crystal exhibits a combination of four forms, which, taken two and two, are of the same kind.

Amphihéxaèdre, when the faces of the crystal, counted in two different directions, give two hexaedral outlines, or are found to be six in number.

Sexdécimal, when a prism, or the middle part of a crystal, has six faces, and the two summits, taken together, ten faces; or the reverse. Thus feldspath sexdécimal; (Pl. IV, fig. 7).

Quadridécimal;, octodécimal, sexduodécimal, octoduodécimal, déciduodécimal, octosexdécimal, sexoctonal, &c, when, as in the preceding, a prism or the middle part of a crystal, and the two summits have the number of faces, indicated by the several names respectively. Thus feldspath quadridécimal; (Pl. IV, fig. 6); also corindon (corundum) octoduodécimal; (Pl. III, fig. 29); also plomb carbonate (carbonate of lead) sexoctonal; (Pl. V, fig. 15).

Péripolygone, when a prism has a great number of sides.

Surcomposé, when the form is very complex. Thus fer sulfurè (sulphuret of iron) surcomposé; (Pl. V, fig. 10).

Antiennéaèdre, when there are nine faces on two opposite parts

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of the crystal. This form appears in a variety of the tourmaline, in which each summit has nine faces, and the prism twelve sides; whereas the prism usually has nine sides.

Prosennéaèdre, when there are nine faces on two adjacent parts of the crystal. This form also belongs to a variety of the tourmaline, in which the prism has nine sides and one of the summits nine faces.

Récurrent, when the faces of the crystal, being counted in annular ranges from one extremity to the other, furnish two different numbers, which succeed each other several times, as 4, 8, 4, 8, 4.

Eguidifférent, when a different number of faces is presented by the prism and by each summit; and these three numbers form a series in arithmetical progression, as 6, 4, 2. Thus amphibole (hornblende) equidifférent; (Pl. IV, fig. 30).

Convergent, when the series of numbers, taken as in the preceding variety, is rapidly convergent, as 15, 9, 3.

Impair, when a different number of faces is presented by the prism and by each summit; but the three numbers follow no law of progression. Thus tourmaline impaire; (Pl. IV, fig. 3).

Hypéroxyde (acute to excess), which is a name given to a variety of carbonate of lime, embracing a combination of two acute rhombs, of which however one is much more acute, than the other; (Pl. III, fig. 21).

Sphéroïdal, when it is bounded by several 'convex faces, as one variety of the diamond, which has forty eight convex faces; (Pl. IV, fig.34).

Plan-convexe, when, as in a variety of the diamond, some of the faces are plane, and others curved.

88. III. Secondary forms, considered in regard to certain faces or edges, remarkable by their position, or relative situation.

Thus a crystal may be called

Alterne, when on two parts, an upper and lower part, it presents faces, which alternate among themselves, but which correspond with each other, when the two parts are compared.

Bisalterne, when, as in the preceding case, the alternation takes place not only between the faces on the same part, but also between those on the two parts.

Bibisalterne, when there is on both parts two sets of bisalterne faces. Thus mercure sulfuré (sulphuret of mercury) bibisalterne; (Pl. IV, fig. 39).

Annulaire, when a hexaedral prism has six, or an octaedral prism eight marginal faces, disposed in a ring about each base; or when, these prisms are truncated on all their terminal edges.

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Monostique, when a prism of a given number of sides has on the margin of each base a range of faces of a different number from that of the sides; these faces may be all marginal, or some may be marginal and others may replace the solid angles; or they may be viewed as truncations of the terminal edges and solid angles. Thus topaze monostique; (Pl. III, fig. 26); also epidote monostique; (Pl. IV, fig. 16).

Distique, when, instead of one range, as in the preceding variety, there are two ranges of faces about each base.

Subdistique, when two of the faces, disposed in the same range about each base, are surmounted by two additional faces, which seem to constitute the beginning of a second range.

Plagièdre, when a crystal has faces situated obliquely, or in a slanting direction.

Dissimilaire, when two ranges of faces, situated one above the other towards each summit, have a want of symmetry. Thus epidote dissimilaire; (Pl. IV, fig. 17).

Encadré, when a crystal has faces, which form a kind of frame about the faces of a more simple form, already existing in the same species.

Prominule, when a crystal has edges, which contain a very obtuse angle, and of course project but little.

Zonaire, when the crystal has about its middle part a range of faces, which form a kind of zone.

Apophane (manifest), when certain faces or certain edges present some useful indication for discovering the position of the nucleus, which it would otherwise be difficult to determine.

Emoussé (blunted), when there are faces, which intercept and apparently blunt certain edges or angles, which, without these faces, would be more projecting than the other edges or angles.

Contraeté, a name applied to a dodecaedral variety of the carbonate of lime, in which the bases of the terminating pentagons suffer a kind of contraction, in consequence of the inclination of the lateral faces.

Dilaté, a name applied to another variety of the dodecaedral carbonate of lime, in which the bases of the pentagons, which terminate the crystal, suffer a kind of dilation, in consequence of the inclination of the lateral faces; (Pl. III. fig. 20).

Acutangle, a term employed to designate a hexaedral prism of carbonate of lime, which has its solid angles truncated by very acuteangled triangles.

Defective, a name particularly applied to a variety of the borate

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of magnesia, in which four of the solid angles of the primitive cube are truncated, each by one face, while the opposite solid angles remain untouched.

Surabondante, a name applied to another variety of the borate of magnesia, in which each of the solid angles of the cube, which were untouched in the preceding variety, is terminated by four faces; (Pl. III, fig. 24).

89. IV. Secondary forms, considered in regard to the laws of decrement, on which they depend.*

A crystal may be called

Unitaire, when its form is produced by a single decrement of one range of particles. Thus feldspath unitaire; (Pl. IV, fig. 5).

Bisunitaire, triunitaire, quadriunitaire, when there are two, or three, or four decrements by one range of particles. Thus epidote bisunitaire; (Pl. IV, fig. 15); also pyroxene (augite) triunitaire; (Pl. IV, fig. 28).

Binaire, when the secondary form depends on one decrement by two ranges of particles.

Bibinaire, tribinaire, when it depends on two, or three decrements, each by two ranges of particles, according to the names respectively. Thus chaux carbonatée (carbonate of lime) bibinaire; (Pl. III, fig. 18).

Ternaire, biternaire, when the secondary form is produced by one, or two decrements, each by three ranges of particles, according to the names respectively.

Unibinaire, when there are two decrements, the one by one range, and the other by two ranges of particles. Thus staurotide unibinaire; (Pl. III, fig. 30).

Uniternaire, when one of the two decrements is by one range of particles, and the other by three ranges. Thus titane siliceo-calcaire uniternaire; (Pl. V, fig. 35).

Binoternaire, when, of the two decrements, one is by two and the other by three ranges of particles. Thus fer oligiste (specular oxide of iron) binoternaire; (Pl. V, fig. 11).

Equivalent, when the exponent or index of one decrement is equal to the sum of the exponents of the other decrements. Thus chaux sulfatée (sulphate of lime) équivalente; (Pl. III, fig. 11).

Soustractif, when the exponent, which relates to one decrement,

* By the term exponent, employed in this division, is intended the number, which indicates how many ranges of particles are subtracted in the several decrements. In mixed decrements the exponent is a fraction, of which both terms are greater than unity; the numerator expresses the decrement in breadth, and the denominator the decrement in height.

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is less by unity, than the sum of the exponents of the other decrements.

Additif, when the exponent of one decrement exceeds by unity the sum of the exponents of the other decrements.

Progressif, when the exponents form a series of numbers in arithmetical progression, as 1, 2, 3. Thus fer oligiste (specular oxide of iron) progressif; (Pl. V, fig. 13).

Disjoint, when the decrements differ much from each other, as from 1 to 4 or 6.

Partiel, when some part of the primitive form remains without decrements, while other parts, similarly situated, undergo them. Thus cobalt gris (gray cobalt) partiel; (Pl. V, fig. 25).

Soudouble, when the exponent of one decrement is half the sum of the other exponents. Thus axinite soudouble; (Pl. IV, fig. 11).

Soutriple, souquadruple, when the exponent of one decrement is only one third, or one fourth the sum of the other exponents.

Doublant, when one of the exponents is twice repeated in a series, which would otherwise be regular.

Triplant, quadruplant, when one of the exponents is three, or four times repeated in a series, which would otherwise be regular.

ldentique, when the exponents of two simple decrements are equal to the terms of the fraction, which express a third and mixed decrement in the same crystal.

Isonome (equality of laws), when the exponents, which mark the decrements on the edges, are equal; and also those, which denote the decrements on the angles. Thus cuivre sulfate (sulphate of copper) isonome; (Pl. V, fig. 3).

Mixte, when the form results from a single mixed decrement.

Pantogène (originating from all its parts), when every edge and every solid angle undergoes a decrement. Thus baryte sulfatée (sulphate of barytes) pantogène; (Pl. III, fig. 4).

Bifère, when each edge and each solid angle suffers two decrements.

Entouré, when there are decrements on all the edges and on all the solid angles about the base of a prismatic nucleus.

Opposite, when one decrement is made by one range of particles, and another decrement is intermediate.

Synoptique, when the laws of decrement in any given crystal offer a kind of synopsis of the laws, which operate in the formation of all the other secondary crystals of that species, or at least the greater part of them.

Rétrograde, which is a name applied to a variety of the carbonate

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of lime, whose form depends chiefly on two mixed decrements; and the faces thence resulting seem to retrograde, that is, they appear to be thrown backward toward that side of the axis, which is most removed from that face, where the decrements commence.

Ascendant, when all the laws of decrement have an ascending direction, setting out from the angles or lower edges of a rhombic nucleus.

90. V. Secondary forms, considered in regard to certain geometrical properties, which they present.

Thus a crystal may be called

Isogone (equality of angles), when the faces, which exist on certain parts, differently situated, form among themselves equal angles. Thus tourmaline isogone; (Pl. IV, fig. 2).

Anamorphique (inverted form), when the crystal cannot be placed in its most natural position, without apparently inverting that of the nucleus. Thus stilbite anamorphique; (Pl. IV, fig. 20).

Rhombifère, when certain faces of the crystal are true rhombs, although, from the manner, in which they are connected with the contiguous faces, they do not, at first view, appear to be regular figures. Thus quartz rhombifère; (Pl. III, fig. 36).

Equiaxe, when the secondary form is a rhomb, whose axis is equal to that of the primitive form, which is also a rhomb. Thus chaux carbonatée (carbonate of lime) equiaxe; (Pl. III, fig. 13).

Inverse, when the secondary form is a rhomb, whose edges contain angles equal to the plane angles of the primitive form, which is itself a rhomb, and whose plane angles are equal to those, contained by the edges of the primitive rhomb. Thus chaux carbonatée (carbonate of lime) inverse; (Pl. III, fig. 14).

Métastatique (a transfer), when the secondary crystal has some of its plane angles and some of those, formed by the inclination of its faces, equal to certain angles of the nucleus, which are thus in a certain sense transferred to the secondary form. Thus chaux carbonatée (carbonate of lime) métastatique; (Pl. III, fig. 16).

Contrastant, which is a name applied to a very acute rhomb of carbonate of lime, whose angles, when compared with those of the variety equiaxe, undergo an inversion, similar to, that described in the variety inverse; in consequence of which certain parts of the crystal are made to resemble a very obtuse rhomb, thus producing a kind of contrast in the same crystal.

Persistant, a name applied to a variety of carbonate of lime, in which certain faces are intercepted by the contiguous faces in such manner, that they preserve the same measures of their angles, which

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they would have had without being thus intercepted; these angles may however have different relative positions.

Analogique, when the form presents many remarkable analogies. Thus chaux carbonatée (carbonate of lime) analogique; (Pl. III, fig. 22).

Paradoxale, when the structure presents singular and unexpected results.

Complexe, when the structure is rendered complicate by uncommon decrements; as when some are mixed and others intermediate.

91. VI. Secondary forms, considered in regard to certain peculiar properties.

Thus a crystal may be called

Transposé, when it is composed of two halves of an octaedron, or of two portions of some other crystal, of which one seems to have turned upon the other through a space equal to one sixth of the circumference of a circle. Thus zinc sufuré (sulphuret of zinc) transposé; (Pl. V, fig. 23).

Hémi-trope, when it is composed of two halves of the same crystal, of which one half seems to be inverted in regard to the other; see art. 82. Thus feldspath hémi-trope; (Pl. IV, fig. 8).

Rectangulaire, a name applied to that variety of the staurotide, composed of two prisms, which cross at right angles.

Obliquangle, a name applied to another variety of the staurotide, in which the two prisms cross at an angle of 60°. (Pl. III, fig. 31).

sexradiée, a name applied to that variety of the staurotide, composed of three prisms, which cross in such manner, as to exhibit the six radii of a regular hexagon.

Cruciforme, a name applied to a variety of the harmotome, composed of two prisms, intersecting each other, and producing a kind of cross. (Pl. IV, fig. 23).

Triglyphe, when the stræ on the surface of the crystal, being viewed on three faces, which unite about the same solid angle, have three different directions, all perpendicular to each other. Thus fer sulfuré (sulphuret of iron) triglyphe; (Pl. V, fig. 5).

Géniculé, when the crystal consists of two prisms, which unite at one extremity, so as to form a kind of knee. Thus titane oxidé (red oxide of titanium) géniculé; (Pl. V, fig. 31).

SECTION 2.

Physical or External Characters,

92. The properties of minerals are somewhat numerous, and fall under the cognizance of two distinct branches of science; hence the

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twofold division, already mentioned (16), into physical and chemical properties or characters. But, as the physical characters of minerals may be ascertained by mere inspection, combined in some instances with a simple experiment, they have generally received the name of external characters; to describe which is the object of this section.

93. Whenever those properties, which are named in the description of bodies, exist in different degrees in different substances, it becomes peculiarly important, that the language employed should be accurate. Now this is remarkably the case in regard to the external characters of minerals. The same character, when viewed in different minerals, often presents very nice grades of distinction. Even different individuals of the same species not unfrequently possess the same property in various degrees. These remarks will be sufficiently illustrated by referring to the numerous degrees of hardness, lustre, &c. and more especially to the almost innumerable varieties of color, observable in the mineral kingdom.

It must hence be obvious, that great precision and accuracy of language are absolutely necessary in describing minerals by their external characters. Each term must be well defined, and carefully employed, so that it may always convey the same definite idea.

94. For the appropriate language, now generally employed to express the external characters of minerals, we are indebted to the celebrated WERNER, Professor of Mineralogy, at Freyberg, in Upper Saxony. In the following arrangement of these characters, no other principle is regarded, than to pass from those, which may be observed by mere inspection, to others, requiring more or less of experiment.

Color. Smell. Hardness.
Changeable colors. Taste. Fracture.
Lustre. Adhesion to tongue. Frangibility.
Transparency. Soil. Shape of fragments.
Refraction. Streak. Tenacity.
Form. Distinct concretions. Magnetism.
Surface. Flexibility. Electricity.
Unctuosity. Sound. Phosphorescence.
Coldness. Cohesion. Specific gravity.

1. Color.

95. This property, although one of the most striking, is by no means the most characteristic. Its real importance, however, will be best ascertained by examining its sources.

First, in many minerals the coloring matter is both accidental and variable; and arises from the presence of metallic oxides, particularly

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those of iron and manganese. Now these oxides may exist in different proportions, or with different degrees of oxidation; either of which would produce a variation in the color, or at least in the shade of the color of different varieties, belonging to the same species. Hence zircon may be gray, green, blue, red, yellow, or brown; quartz may be white, gray, brown, yellow, green, red, &c. and all these colors are further diversified by various shades. Now in these and similar cases it is evident, that but little reliance can be placed on color alone. It may indeed be true, that most minerals usually exhibit some one or two of the colors belonging to them; it may even be true, that some minerals present but one color, yet this one may assume a variety of shades. It is hence obvious, that, when the color depends on some accidental ingredient, it can only increase the probability, that the mineral under examination belongs to this or the other species. The preceding remarks apply to the colors, which appear on most of the earthy compounds and of the earthy and alkaline salts. The coloring matter may actually be extracted from some saline minerals, and every other property remain the same.

But, secondly, the color sometimes depends on the nature of the mineral, and is produced by light reflected from its essential, component parts. Here it is a character of very considerable value. This is the case with most of the ores of the metals, and with some combustibles.

96. We shall now notice the varieties of color, and the terms employed in describing them.

Fundamental colors. Of the various colors eight are assumed, as fundamental. These are snow white; ash gray, the color of woodashes; velvet black; Berlin or Prussian blue; emerald green; lemon yellow; carmine red, a high red, like that of vermillion; and chesnut brown. All other colors are considered, as intermixtures of two or more of these; and are expressed by combining the names of the two principal colors, of which the intermixture is supposed to consist, as greenish white, or by referring to some well known substance, whose color is nearly uniform, as blood red. When a color is compounded of any two colors, which have received distinct names, and seems to be intermediate between them, it is described by saying, that the predominant color inclines to or passes into the other, according as it exhibits less or more of that other color.

Varieties of white.* Snow white; reddish white; yellowish

* In the explanations, annexed to many of the varieties of color, the additional shade is supposed to be mingled with the fundamental color, unless the contrary be expressed.

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white; silver white, which has a slight tinge of yellow with a metallic lustre; grayish white; greenish white; milk white, which has a slight tinge of blue; tin white, which is nearly the preceding with a metallic lustre.

Varieties of gray. Lead gray, which has a slight tinge of dark blue with a metallic lustre; bluish gray; smoke gray, which has a shade of brown; pearl gray, which has a very slight tinge of violet blue; greenish gray; yellowish gray; ash gray; steel gray, which has a shade of blue and a metallic lustre.

Varieties of black. Grayish black; iron black, which is a dark grayish black with a metallic lustre; velvet black; pitch black, which contains a little brown; raven black, in which a shade of green is perceptible; bluish black.

Varieties of blue. Indigo blue, which is very dark; Berlin or Prussian blue; azure blue, which is dark with a slight tinge of red; violet blue, which has a strong tinge of red; plum blue, which is a dark reddish blue; lavender blue, which contains a little reddish gray; smalt blue, which is azure blue, rendered pale by an intermixture of white; sky blue, which is pale, with a tinge of green.

Varieties of green. Verdigris green, which has a shade of blue; sea green, which is paler than the preceding; mountain green, which is pale and grayish; emerald green; apple green, which has a tinge of white; grass green, which is lively, but has a strong tinge of yellow; blackish green; leek green, which is dark and contains a little brown; pistachio green, which has a shade of brownish yellow; asparagus green, which is paler, than the preceding; olive green, which is a pale grass green, with a strong shade of brown; oil green, which is paler and has more yellow than pistachio green; canary or siskin green, which is a pale yellowish green.

Varieties of yellow. Sulphur yellow, which is pale and has a shade of green; brass yellow, which is the preceding, with a shade of gray and a metallic lustre; straw yellow, which is sulphur yellow, containing much white; bronze yellow, which is brass yellow, mingled with gray; wax yellow, which has a shade of reddish brown; honey yellow, which is sulphur yellow, tinged with brown; lemon yellow; gold yellow, which differs from the preceding by its metallic lustre only; ochre yellow, which has a strong shade of brown; wine yellow, which has a shade of brownish red; isabella yellow, which is brownish yellow, with a slight tinge of red; orange yellow, which has a shade of red.

Varieties of red. Aurora red, which has a strong shade of yellow; hyacinth red, which is tinged with brownish yellow: brick red.

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which is paler, than the preceding; scarlet red, which has a very slight tinge of yellow; blood red, which is nearly a pure red, but tinged with a little dark brown; flesh red, which is paler, than the preceding; copper red, which is nearly flesh red with a tinge of yellow and a metallic lustre; carmine red; cochineal red, which has a shade of bluish gray; crimson red, which has a strong shade of blue; columbine red, which is darker, than the preceding; rose red, which resembles cochineal red, but is pale; peach blossom red, which is a pale reddish white, with a slight tinge of blue; cherry red, which is crimson red with a strong shade of dark brown; brownish red, which is a blood red, shaded with brown.

Varieties of brown. Reddish brown; clove brown, which is dark with a very slight tinge of red; hair brown, which is the preceding with a shade of gray; broccoli brown, which is hair brown with a tinge of blue; chesnut brown; yellowish brown; pinchbeck brown, which is the preceding with a metallic lustre; wood brown, which results from a mixture of yellowish brown with a large portion of gray; liver brown, which has a shade of gray; blackish brown.

The various intensities of the same color are denoted by the terms dark or deep, light or pale.

It is always to be understood, unless the contrary be expressed, that the color of a mineral is observed on the interior surface, exhibited by a fracture recently made, and that the mineral is in an unaltered state.

When minerals are perfectly clear and transparent, having no perceptible color, they are said to be limpid, or colorless.

97. Arrangement of colors. Some minerals present two or more colors differently arranged. The collocation of these colors is expressed by the terms dotted, veined, clouded, striped, or zoned, &c.

98. Tarnished colors. The surface of a mineral often exhibits very different colors from those, which appear in the interior, and is said to be tarnished. This tarnish usually arises from the action of moisture or air on some metallic matter, contained in the mineral, or investing its surface. When more than one color is present, the tarnish is described by referring to some well known appearance, which it more or less resembles, as the neck of a dove, the tail of a peacock, the rainbow, tempered steel, &c. hence it is denominated columbine, pavonine, irised, &c. These tarnishes are frequent on some of the ores of copper and iron; and the alteration of color sometimes extends to a considerable depth.

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2. Changeable colors, or chatoyement, or play of colors; irised colors.

99. The appearances, denoted by the above terms, are altogether distinct from a tarnish, although the latter may sometimes appear irised. They are exhibited by minerals in their purest state, and depend on a peculiar incidence and reflection of light. We notice both changeable and irised colors in the same article, because they are often produced in a similar manner; and for the former, which is the most beautiful, we have mentioned the French term chatoyement, because it is expressive, and because there is no word in English, by which it may be translated. This term alludes to those mutable and shining colors, which appear in the eye of a cat, when observed in the dark; similar appearances may be seen on certain varieties of silk.

A mineral is said to exhibit changeable colors, or a chatoyement, when different collections of colors alternately appear and disappear, according to the varying position of the mineral, in regard to the incident light. This is a striking property in that variety of quartz, called cat's eye, in the precious opal, and particularly in some varieties of feldspar.

In other cases most of the colors of the iris or rainbow appear; and, although moveable, do not change, but present the same appearance, on whatever part of the mineral they may be observed. Crystallized quartz and carbonate of lime exhibit this property.

The preceding colors may exist near the surface, or rise from the interior; and are sometimes confined to two opposite parts of a crystal.

The exhibition of changeable and irised colors, when the latter is not merely a tarnish, appears in most cases to be produced by light, reflected from the sides of numerous and very minute fissures, which traverse certain minerals. These fissures sometimes proceed from a partial decomposition and slight separation of the laminæ, in which case the fissures will all lie in the direction of the natural joints of the mineral; in other cases the mineral is traversed by fissures in all directions, as in the precious opal.

In some instances these peculiar appearances seem to arise from irregularity in the relative position of some of the integrant particles, or even from the total absence of some of these particles; little cavities are hereby produced, from whose sides the light is variously reflected, and, during its passage to the eye, becomes refracted.

According to Bournon, when these little cavities are near the surface and lie in the same plane, a pearly light is reflected.

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3. Lustre.

100. The lustre of a mineral depends on its disposition to reflect light more or less copiously. It must of course be variously modified by the shape, position, and density of the integrant particles. The lustre of the internal surface, discovered by breaking the mineral, is always intended, unless external lustre be expressly mentioned. We perceive not only different degrees, but different kinds of lustre. The degree of lustre is distinguished by the following terms; splendent, when perceptible in full day light at a great distance, as in highly polished metals; shining, when it is weak at a considerable distance, but strong, when the object is near the eye, as in most crystals; glistening, which is not perceptible, unless near, as in some silks; glimmering, when only a few shining points appear, even when the mineral is held very near to the eye.

The kind of lustre is made known by comparing it with that of some familiar objects. Hence it may be vitreous, waxy, resinous, pearly, adamantine, or metallic. Minerals, having no lustre, are said to be dull.

4. Transparency.

101. This well known property needs no definition. According to the quantity of light transmitted, the transparency will be variable; and its different degrees are denoted by the following terms;* transparent, when objects may be distinctly perceived through the mineral; semitransparent, when objects may be perceived, but not distinctly; translucent, when light evidently passes, but objects cannot be distinguished; translucent at the edges, when light passes through the edge only. If no light pass through any part of a mineral, it is said to be opaque.

Some minerals, nearly or quite opaque, become more or less transparent by being plunged in water, and are said to be hydrophanous. This phenomenon depends on the imbibition of water, and will be more fully explained.

5. Refraction.

102. It is well known, that, when a ray of light passes obliquely from one medium to another of different density, it is refracted, or bent from its original direction. Still the image of any object, seen through a refracting medium, usually appears single. There are,

* Some writers denote the different degrees of transparency and lustre by the numbers 4, 3, 2, 1, the number 4 indicating the highest degree in each character.

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however, some transparent minerals, which have the remarkable property of causing objects to appear double; that is, they present two images of any object, seen through them. In this case it is evident, that the ray must be divided into two portions after entering the refracting medium, and that each portion presents an image of the object.

As this property depends on the nature of the mineral, and not on any accidental circumstances, it must be a distinctive character of very considerable value. Different opinions have been given on the cause of this phenomenon; it has indeed exercised the abilities of Huyghens and Newton, nor is it by any means certain, that it is yet well understood.

We have room only for some general remarks on this character, and to point out the mode of observing it.

This property was first observed in that variety of carbonate of lime, sometimes called Iceland spar; and few minerals exhibit it in so striking a manner. Let a black line be drawn on white paper, and viewed through two opposite and parallel surfaces of a rhombic crystal or fragment of the aforementioned substance so placed, that the longer diagonals of the two opposite faces shall be parallel to the line on the paper. Two distinct and separate lines will appear, the one being somewhat above the other. If now this rhomb be made to revolve, the two images or lines will approach each other, till they coincide in the direction of their length, but in such manner, that the extremity of one image extends a little beyond that of the other. This coincidence takes place, when the shorter diagonals of the aforesaid faces become parallel to the given line. The experiment is in some respects more striking, when a circle is employed, instead of a line.

It appears probable, that all substances, possessed of this property, have a limit, at which the two images coincide. The quantity of the refraction is measured by the angle, contained between the two portions of the divided ray.

In some minerals the double refraction is very great, and easily observed. Often however it cannot be perceived without difficulty; the two images are very near, and apparently touch or penetrate each other, and are scarcely distinguishable, except at their borders. It is often necessary to view the object through two sides of a crystal, which are naturally inclined to each other, or so cut by a lapidary. Thus to observe double refraction in crystallized quartz, the ray to be refracted must be made to pass through one side of the prism, and the opposite face of the pyramid, which terminates the prism.

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The distance between the two images is, in general, proportional to the quantity of the angle, contained between the two inclined faces; and, when other things are equal, it is proportional to the thickness of the medium.

This character may frequently be observed by holding the mineral near the eye, and looking through it at a pin, held by the point, at some distance on the opposite side, the face being directed toward a window. If the pin be successively placed in various positions, there will be one, in which two images of the pin will be seen, parallel to each other, and usually irised.

Or it may be observed in the following manner. Make a very small puncture in a card or piece of pasteboard; and, having closely applied the card to that side of the crystal most distant from the eye, look through the crystal and the puncture at a candle, placed at some distance from the eye in a dark room. The two images are quite distinct.

It seems hardly necessary to suggest the important use, to which this character may be applied. As it can be noticed with equal ease after a mineral has been deprived of its native appearance by a lapidary, it may enable us to discriminate minerals, in which other characters cannot be observed.

6. Form.

103. This is a very important character in the description of minerals. The varieties of form may be included under three general divisions, viz. regular, imitative, and indeterminate or amorphous.

104. Regular forms. These all arise from a crystallization, which is attended with but little or no disturbance; and have already received sufficient attention in the first section of this chapter.

105. Imitative forms. The form of a mineral is said to be imitative, when it is not regular, and, at the same time, has sufficient resemblance to any other body to be denominated by the name of that body. These forms are either the results of a very disturbed crystallization; or they may be mere concretions, formed under circumstances, which have entirely prevented the appearance of a crystalline form or structure. The following are the most common; viz. lenticular, resembling a convex lens—this form may be conceived to arise in some cases from the disappearance of the edges and angles of a crystal, thereby producing a convexity of surface; cylindrical—sometimes produced by the rounding of the edges of a prism; acicular, like a needle—minerals, possessing this form, are sometimes in very minute prisms, and sometimes in very small pyramids much

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elongated; filiform or capillary, resembling a thread or a hair; stalactical, resembling an icicle—stalactites are generally produced by the filtration of water, containing earthy, saline, or metallic particles, through the poros or crevices of other minerals—sometimes also they are formed on the floors of caverns by the dropping water, and in this case are often called stalagmites;* tubular, which is more or less cylindrical and hollow; dentiform, like teeth, presenting short and often crooked cones; coralloidal, resembling a branch of coral; dendritic, branching like a tree or shrub; reticulated, like a net; nodular, in small lumps; globular—this form may sometimes arise from a crystal, whose edges and angles are rounded, or it may be produced by an aggregation of prismatic crystals or fibres; botryoidal, like a bunch of grapes; reniform or mammillary, in the form of a kidney—it presents elevations, resembling segments of a sphere, but the eminences are more flat than in the botryoidal form; tuberous—it presents elevations less regular, than the preceding, and separated by intermediate depressions; cellular—the cells have various forms and are separated from each other by thin plates or laminæ—they are often produced by the impression of crystals, and present regular forms, as cubic, hexangular, &c; perforated, when a mineral exhibits numerous round holes, like a sieve; corroded, presenting numerous cavities, as if eaten by a worm; vesicular, having cavities, which resemble bubbles of air in ice; ramous or entangled, composed of slender branches of filaments, intermingled in various directions; specular, having the even, polished surface of a mirror; also in leaves, plates, scales, or membranes.

106. Incrustations. These are deposites, made in the form of a crust, sometimes on other minerals, and frequently on the surface of bodies, belonging to the vegetable kingdom; sometimes also they invest the sides of cavities, situated in the interior of certain bodies. The latter appearance may often be observed in tubes, through which water, containing calcareous particles, has been running for a long time. Sometimes the crust is left empty by the removal of the body, whose form it has taken. This may happen, when crystals of carbonate of lime are incrusted by quartz. Incrustations are most frequently calcareous or siliceous, and their structure is sometimes a little crystalline.

107. Geode. This is an incrustation, whose form is, in general, nearly spherical. Its interior is sometimes empty, and, in this case, the sides of the cavity are often lined with crystals. Sometimes it

* For a particular account of the manner, in which stalactites and stalagmites are formed, see the species carbonate of lime.

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contains a solid, moveable nucleus; and is sometimes filled with an earthy matter different from the envelope.

108. Guhr. This is a loose, earthy deposit from water, and may be siliceous, calcareous, &c.

109. Pseudomorphous bodies. These bodies have received their present form in cavities, which true crystals, or some other substances, either animal or vegetable, had once occupied. When the form has been taken from cavities, once occupied by crystals, it is by no means difficult to distinguish the pseudomorphous or false from the true crystal. The edges and angles of the former are seldom well defined; their surfaces are frequently rough and unpolished; and they never submit to mechanical division in any direction. Quartz and steatite furnish crystals of this kind.

Sometimes the form has been derived from the interior of a shell, and is a true model of the animal, which once occupied it; and sometimes it is a faithful imitation of the trunks and branches of vegetables. It hence appears, that many petrifactions are strictly pseudomorphous bodies.

In some cases it is probable, that the particles of the pseudomorphous body have found the cavity entirely empty; in others they have perhaps entered, as the original substance has gradually disappeared.

110. Indeterminate or amorphous forms. When the form of a mineral is neither regular nor imitative, it is called indeterminate, or the mineral is said to be amorphous.

If a mineral form a part of an aggregate or compound rock, and its different portions be less than a hazel nut, it is said to be disseminated in the aggregate; but, if it exist in portions not less than a hazel nut, it is said to occur massive.

The term massive is also employed to denote those varieties of certain minerals, which, though indeed crystallized, do not present a regular form, but occur in masses more or less large, having a crystalline structure. Whenever used in this treatise, it is to be understood in the latter sense.

When a mineral occurs in loose, detached portions, it may be in grains, or in angular or rounded fragments.

7. Surface.

111. By this is intended the external surface of minerals, and also that of their distinct concretions, when separated. The internal surface, or that brought to view by a fracture, will be noticed under a distinct article. The most common varieties of external surface are the following; viz.

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uneven, presenting small and irregular elevations and depressions; granulated, when the little elevations on the surface are rounded, like shagreen; rough, when the asperity is discoverable by feeling, rather than by sight; smooth; drusy, when the surface is covered with minute crystals, often somewhat grouped; striated, when it is marked with small channels or furrows.

The last variety of surface is far more important, as a character, than any of the others; for these striæ, as we have already remarked (56), when found on secondary crystals, not unfrequently indicate the direction of the laminæ, applied to the primitive form.

The direction of the striæ is to be noticed in description. Thus in reference to the face of a crystal, the striæ may pass longitudinally, transversely, or diagonally, all on the same face being supposed parallel. In some substances, not regularly crystallized, the striæ are irregular.

8. Unctuosity.

112. Certain minerals, when the finger is passed over their surface, or applied to their powder, feel as if they were coated with some unctuous or greasy substance. The sensation is, in general, easily distinguished from that, which is excited by mere smoothness of surface. It is often an important character in discriminating minerals; and its existence in a mineral, when reduced to powder, is to be particularly noticed. Most minerals, however, especially when in powder, feel dry or meager.

9. Coldness.

113. Little use can be made of this character. It has been remarked, that siliceous minerals feel colder than those, which are calcareous, both possessing the same temperature; and that combustibles feel less cold than most other minerals.

10. Smell.

114. This character can be observed in but few minerals. When, however, it does exist, it generally indicates the nature of the mineral, or, at least, of some of its principal ingredients. The odor of a mineral may be bituminous; sulphureous; alliaceous, like that of garlic; empyreumatical, like that of burnt substances; earthy or argillaceous, like that of moistened clay; bitter; or fetid, like that of sulphuretted hidrogen gas.

In some cases the odor is constantly exhaled. In other instances it is necessary to develop it by very slightly moistening the mineral, as with the breath; or by friction; or by the application of heat.

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11. Taste.

115. This property supposes at least a partial solubility of the mineral in water or saliva, and belongs to a part of those bodies, called salts. The terms, employed in describing the different tastes, are those in common use. Thus the taste may be saline; astringent; sweetish; cool; bitter; or urinous. Sometimes the taste, excited by the first impression on the tongue, is a little different from that, which soon follows; hence a kind of compound taste results.

12. Adhesion to the tongue or lip.

116. The adhesion of a mineral to the tongue or lip depends on its disposition to imbibe moisture. In some instances, when the tongue is too moist for the experiment, the adhesion to the lip is still very sensible. Its degree may be noted by the terms strong; moderate; slight, &c. Aluminous or argillaceous substances furnish striking examples of this property.

In some cases, where little or no alumine is present, this adhesion appears to arise from a partial decomposition of the mineral, which, by losing its water or some other ingredient, becomes filled with minute pores; and these pores absorb moisture on the principle of capillary tubes. Such is probably the cause of the adhesion sometimes observed in calcedony, flint, and other siliceous substances. This explanation is confirmed by the fact, that, when the same bodies are reduced to powder, they lose their absorbent power, and do not adhere to the tongue.

13. Soil or Stain.

117. Some minerals, when rubbed on white paper or other light colored substances, leave a trace, more or less distinct. In some cases merely a soil or stain is produced; in other cases a trace is left sufficiently definite for the purpose of writing. It should be observed, whether the color of the trace be similar to that of the mineral; or dissimilar.

14. Streak.

118. By the streak of a mineral is understood the appearance, which arises from scratching it with a hard, sharp instrument, as the point of a knife. The streak is said to be similar, when its color, or rather that of the powder produced, is the same with the color of the mineral; and dissimilar, when its color varies from that of the mineral.

The lustre of thè streak may also be compared with that of the mineral.

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This character, though very simple and easily observed, is often of very considerable value. It is well known, that many minerals, when reduced to powder, present a different color from that, which they exhibit in portions of any sensible magnitude. It is also known, that the same mineral, though presenting different colors in its natural state, may, when reduced to a fine powder, uniformly exhibit but one color. This is certainly the case with a number of minerals. Hence in description, the color of the powder, obtained by trituration, should be mentioned; especially if the color belong to the nature of the mineral, and is not dependant on any accidental ingredient. The powder, produced by scraping the mineral, is perhaps never so fine, as that obtained by trituration.

15. Distinct concretions.

119. Some minerals appear to be composed of certain distinct portions, more or less large, united to each other by the intervention of a very delicate seam, but with a less force than that, which unites the minuter particles of each concretion. Hence these distinct concretions are usually separable at the aforementioned seams without producing a fracture in the more strict sense of that term. When, however, their union is so strong as to prevent a separation from each other, their form may be discovered, either by the directions of the seams, or by the different relative positions of the concretions themselves. Each concretion may be said to be bounded by its own surface, as distinguished from the surfaces produced, when a real fracture is made.

The shape of the concretions may be referred to one of the three following kinds; viz.

granular—these may be round, or angular, large, coarse, small, or fine; lamellar—these may be straight or curved, thick or thin;— columnar—these may be large or small, straight or curved, parallel, diverging, or promiscuous, and sometimes cuneiform.

In some minerals this character might with propriety be described, as presenting a particular kind of structure.

16. Flexibility.

120. This well known property is easily observed. Very few minerals possess it naturally. It is to be particularly noticed, whether the flexibility be accompanied with elasticity, that is, whether the mineral have the power of restoring itself to its former position, after being bent.

Some minerals by the gradual application of heat may be rendered flexible; while others lose this property by exposure to heat, and

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regain it, when moistened. See further remarks on this character under the article, granular limestone.

17. Sound.

121. To discover the existence of this property, which is rare, the mineral must be struck or bent. Some minerals, when struck, give a clear and almost metallic sound, which dwells for a moment on the ear; others, when bent, give repeated and almost constant cracks.

The production of these sounds depends much on the tabular form of the mineral. Thus the Chinese employ small and thin tables of certain minerals, as bells or musical instruments.

18. Cohesion.

122. According to the various degrees, in which this property exists, minerals are described as solid; friable or earthy; or fluid.

19. Hardness.

123. This property, although liable to a little variation in minerals of the same species, from partial decomposition or the presence of some accidental ingredient, still constitutes an important character. It may often of itself discriminate minerals, that occur together and much resemble each other. It is evident, however, that it is only the relative hardness, which can be described.

Hardness is that property in a body, which enables it to resist, more or less, the impression of another body; and must depend on the strength of cohesion between the integrant particles. In saying this, however, a careful distinction must be made between the cohesion of integrant particles, and that aggregation of small grains, by which the larger masses of many minerals are formed. With the cohesion of these grains the real hardness is often very little connected. This is evident in the case of certain sandstones, the grains of which are sufficiently hard to scratch steel, although the mass itself will not strike fire with steel, in consequence of its friability.

Different modes of observing the hardness of bodies have been employed. One method depends on the application of a file or a knife, and the property, which some minerals possess of giving sparks with steel.

Thus a body is said to be

extremely hard, when it receives no impression from a file; very hard, when a file produces but little effect; hard, when it yields to a file without difficulty, but still strikes fire with steel; semihard, when it does not give fire with steel, and yields a little to a knife;

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soft, when it is easily cut by a knife, but receives no impression from the finger nail; very soft, when it is easily impressed by the finger nail.

It must be evident, however, from the preceding remarks on the friability of certain sandstones, that a greater or less power of giving fire with steel cannot accurately indicate the hardness. It is also true, that, in cutting or scraping a mineral with a sharp instrument of steel, the apparent hardness will in part depend on the greater or less degree of cohesion between the grains or minute parts, of which the body is composed.

124. It is perhaps a more definite method of ascertaining the different, degrees of hardness to determine in what order minerals impress or scratch each other; and in this way the hardness of a mineral in the state of grains or a powder may be discovered. According to this method minerals must be arranged under several divisions. Thus the first division may comprehend all minerals, capable of scratching crystallized quartz, a substance possessing a very uniform degree of hardness. The different substances, which compose this division, are to be so arranged, as far as practicable, that each preceding substance may be understood to scratch that, which follows it. The second division may exhibit a similar arrangement of those minerals, which are inferior in hardness to the precedeing, but still capable of scratching some particular kind of glass.*

Crystallized carbonate of lime may form the basis of a third division; and the last division may contain those minerals, properly arranged, which are inferior in hardness to carbonate of lime.

20. Fracture; and structure, as indicated by the fracture.

125. To denote that character of a mineral, which is derived from its structure, many writers have employed the term fracture; meaning thereby the appearance of the surface, produced by a fracture. Indeed the terms fracture and structure are sometimes indiscriminately used. But, although the fracture in many instances discovers the structure of the mineral, there are several epithets, employed to describe certain fractures, which cannot with propriety be applied to the structure. We have therefore placed both terms at the head of this article, and shall endeavor to point out the appropriate use of each.

126. The structure of a mineral undoubtedly depends on the

* In some cases after rubbing a mineral on glass, it is important to wipe the glass with a wet cloth, to determine whether the trace, which may be perceived, do not arise from particles of the mineral, adhering to the glass.

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shape, size, and arrangement of the minute parts, of which it is composed. These minute parts may have the shape of little plates, or laminæ; or they may resemble fibres; or they may be in grains of no determinate form. The size of these laminæ, fibres, and grains may vary indefinitely, and their arrangement may be more or less regular.

Now it is evident, that any mineral, composed of fibres, arranged in a given order, may be said to have a certain structure, which actually exists in it, whether the mineral be broken, or remain entire. In this example we should say the structure is fibrous. If this mineral be broken, the fibres will appear, forming the two separated surfaces; but the fracture has not produced the fibres.

Let us now suppose another mineral to be broken, and, as is frequently the case, let the surface of the fragments exhibit little splinters, projecting above the surface, but adhering to the mineral by one of their extremities. It would be hardly correct to say, that this mineral has a splintery structure; these splinters did not preexist in the mineral; they were produced by the fracture, that is, the given mineral has a splintery fracture. Still however every mineral must have some structure; and the disposition of any substance to exhibit splinters on the surface of its fracture must ultimately depend on its structure, whatever that may be.

In the former of the two supposed cases we may indeed say, that the fracture is fibrous, meaning the surface, produced by the fracture, though in truth the fibres belong to the structure. But in the latter of these cases, although the splintery appearance of the fracture depends on the structure, we cannot with propriety substitute the word structure in the place of fracture, and say that the structure is splintery.

We shall now describe the various fractures and structures, observed in minerals.

127. Splintery fracture. The fracture is called splintery, when the surface, produced by breaking a mineral, is nearly even, but exhibits little splinters or scales, somewhat thicker at one extremity than the other, and still adhering to the surface by their thicker extremities. That part of the splinter or scale, which projects above the surface of the mineral, becomes very thin at its extreme edges, and hence permits a little light to pass. By this light the splinters become visible, and may be distinguished as coarse or fine.

Even fracture. This scarcely needs a remark. The surface produced is nearly plane, having no perceptible inequalities.

Conchoidal fracture. A fracture is said to be conchoidal, when its

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surface exhibits concave depressions, and convex elevations, as if it had been impressed by a shell. These cavities and elevations may be perfectly or imperfectly conchoidal; they may be large or very small; and the cavities may be deep or flat. Some varieties of this fracture are with great propriety said to be undulated. When the cavities are imperfect and small, this fracture gradually passes into the following.

Uneven fracture. This exists, when the surface, produced by the fracture, exhibits numerous inequalities. The elevations on this surface are usually sharp or angular, somewhat abrupt, and irregularly arranged. According to their size, the fracture is said to be coarse or fine grained uneven. It passes into the following.

Earthy fracture. The surface of this fracture is rough, the elevations and depressions being very minute. Minerals, which present this fracture, have probably been formed by precipitation from some fluid, in which they were minutely divided and suspended, rather than dissolved. Dry or indurated clay often exhibits this fracture.

Hackly fracture. This is peculiar to metals. It. is not easily distinguished by the eye, but may be discovered by attempting to pass the finger over its surface, from which very fine and sharp points seem to project and impede the progress of the finger.

No one of the preceding fractures clearly indicates the structure.

128. Fibrous structure; or fracture. This fracture obviously brings to view the structure of the mineral (126). It presents a surface, composed of fine threads or fibres. Sometimes these fibres are too minute and delicate to permit a measurement of their breadth; indeed they are sometimes so very minute and closely applied to each other, that the mineral appears compact, except in being marked with very delicate striæ. From this extreme, their breadth gradually increases, till it becomes capable of being measured, and is sometimes so great, that this fracture may be viewed, as passing into the foliated. Their comparative breadths or sizes may, however, be sufficiently distinguished by the terms broad or narrow, coarse or fine, or capillary.* Their direction may be straight or curved. Their

* The fracture here described is often divided into two kinds. When the fibres are too small to be measured, it is called a fibrous fracture; and when they become broader, the fracture is said to be radiated. The distinction however does not appear to be important, nor useful. They are equally fibres in both cases, and their comparative breadths may be sufficiently indicated by the terms already mentioned. If greater accuracy be requisite in regard to the broader fibres, their average breadth may be estimated or actually measured.

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relative position may be parallel or diverging; and in the latter case the fibres may be radiated, diverging on all sides from a common centre, or fascicular, like a bundle of rods confined at one extremity, or promiscuous.

The broader fibres are frequently separable from each other, and often terminate in a crystal, which causes them to appear pointed. Indeed minerals, having a fibrous structure, are always the result of a disturbed crystallization.

129. Foliated or laminated structure; or fracture.* This fracture discovers the structure. It appears in minerals, composed of thin plates or laminæ. When such minerals are broken, the fracture exhibits laminæ, having smooth, shining or polished surfaces, like the surface of a crystal. In fact, minerals, having a foliated fracture, are the result of crystallization; and, when they are divided or separated in the direction of their laminæ, it can hardly be called a fracture; it is really a mechanical division of a crystallized substance (37).

Several particulars are to be noticed in regard to this fracture. The magnitude of the laminæ may vary from very large to very small. In some cases a single plate extends through the whole mass; in others the plates appear like very minute scales, not easily discernible, except by the reflection of light from their polished surfaces. The direction of the laminæ may be straight; curved; undulated; or indeterminate, that is, lying irregularly in various directions. Sometimes a number of plates unite in the same point, like the petals of a flower.

The most important circumstance, connected with this fracture, is the direction or directions, in which it can be made; or in other words, the directions of the natural joints of the mineral, for it is at these only, that a cleavage or mechanical division can be effected (35). In some minerals there is but one direction, in which their component laminæ can be so separated, as to exhibit a smooth, shining surface. Other minerals may be divided in two, three, or more directions. But in all cases, where the mineral can be thus divided in two or more directions, it is exceedingly important, that the angles, which the laminæ form with each other, should be accurately measured. This measurement renders mechanical division even in

* The terms foliated—laminated—lamellar or lamellated are all employed to express this structure. The first may be viewed as the most general, and as indicating nothing in regard to the size of the foliæ or laminæ. The second is usually applied to minerals, composed of large laminæ; and the third to those, whose laminæ are small.

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masses, which have not a crystalline form, an important character in determining the nature of the mineral.

The fracture, of which we are speaking, is said to be perfectly or imperfectly foliated, according as the plates separate with more or less ease, and exhibit a surface more or less smooth and polished. Sometimes the foliæ appear only on certain parts of the surface, and cause it to glimmer.

130. Slaty structure; or fracture. Minerals, which exhibit this fracture, are composed of somewhat thick and extensive layers; but the surfaces of the layers are not smooth and polished, as in minerals, having a foliated fracture. They split only in one direction. In fine, this fracture appears in substances not crystallized, whereas the foliated belongs to minerals more or less perfectly crystallized.

When minerals appear to be composed of different layers, which do not, however, easily separate from each other, their structure is rather stratified, than slaty.

131. Granular structure; or fracture. When a mineral is composed of grains, either large or small, but still visible to the eye, as in sandstone, its structure may be called granular. Such minerals are sometimes described as composed of granular, distinct concretions (119). When the grains become invisible to the eye in consequence of their minuteness, the mineral is said to have a compact texture; such is that of jasper.

132. In minerals not crystallized the fracture may be made in any direction, provided natural seams be avoided. In minerals of a prismatic form, it should be stated, whether the fracture be longitudinal or transverse; for these are often different. Thus a prismatic crystal of hornblende may be mechanically divided in the direction of its axis, that is, its longitudinal fracture is foliated; whereas its transverse or cross fracture is uneven.

21. Frangibility.

133. This property can be described only in general terms; or by comparing one mineral with another in this respect. Thus a body may be very tough; tough; moderately tough; brittle or very brittle.*

* Much confusion arises from the distinction, which some writers make between brittle and fragile. By opposing brittle to ductile, and tough to fragile, they have been led to say, that certain bodies were brittle, but not fragile. If these distinctions are necessary in the description of a mineral, termsless ambiguous ought to be employed.

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22. Shape of the fragments.

134. When a mineral of a moderate size receives a heavy blow, it usually separates into a number of fragments, which are commonly very irregular in their shape. Sometimes, however, these fragments exhibit a form more or less regular; and, when the substance is crystallized, the particular form results from the arrangement of the laminæ, which compose the mineral. Such fragments may be cubic, rhombic, trapezoidal, tetraedral, &c. Even fragments somewhat irregular may sometimes be designated as cuneiform, splintery, tabular, &c. The sharpness or bluntness of the edges of irregular fragments, and the comparative lustre of different faces of regular fragments may also be noticed.

23. Tenacity.

135. It is in consequence of possessing this property, that certain substances permit themselves to be drawn into wire, or flattened under a hammer; in the former case the substance is ductile; in the latter, malleable. A mineral is sometimes said to be ductile also, when it may be moulded between the fingers, or cut into slices. It is called sectile, when, being cut with a knife, the separated particles do not fly away, but remain on the mass.

24. Magnetism.

136. It is well known, that two north or two south poles of a magnetic needle repel each other, when brought near; and, on the contrary, that a north and south pole attract each other in a similar situation. Hence any mineral, which, being alternately presented to the two poles of a magnetic needle, attracts the one and repels the other, is said to be magnetic, or to possess polarity.

If a small needle of pure iron be alternately presented to the two poles of a magnet, it will be attracted by both poles; because the magnet produces in that end of the iron needle, which is nearest to itself, a polarity contrary to its own. On removing the iron, however, its magnetism disappears.

Hence to determine whether a given mineral possess magnetic polarity, it is often necessary to employ a needle, which has a very feeble magnetic power; for, if the power of the needle be in a great degree superior to that of the mineral presented, each extremity of the needle may produce in the mineral a polarity, contrary to its own, and consequently attraction only will appear at both poles.

Although the property of magnetism belongs only to nickel, cobalt, and iron, and not indeed to all the ores of iron, yet, from the

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frequent intermixture of magnetic iron in other minerals, there is very often occasion to notice this property. A delicate needle is superior to a magnetic bar for detecting the existence of magnetism.

25. Electricity.

137. It will be recollected, that there are two kinds of electricity, which are called positive and negative, or vitreous and resinous, according as they are produced by exciting smooth glass, or any resinous substance. It will also be recollected, that, when two bodies possess the same kind of electricity, whether positive or negative, they repel each other; but, if one possess positive electricity and the otaer negative, they attract each other.

A considerable number of minerals may be rendered electric by friction with the hand or woollen cloth; and, when thus excited, they are capable of attracting light bodies, or of moving a delicate electrometer.

138. Among the minerals, which are capable of exhibiting electric properties, there are a few, which acquire electricity by being heated, either by simple exposure to a fire, or by immersion in hot water. But those minerals, which are excited by heat, acquire, at the same time, both positive and negative electricity; but so separated, that, on whatever part of the mineral the positive may appear, the negative will be found on the part diametrically opposite. Thus if positive electricity appear on one side, or at one extremity of a crystal, negative electricity will exist on the opposite side, or at the other extremity. And it is very remarkable, that, in crystallized minerals, excitable by heat, the opposite parts of the crystal, on which the two electricities appear, are almost always different from each other in their configuration, or number of sides, although similarly situated in reference to the crystal itself. Thus if it be a prismatic crystal of tourmaline, and If the two electricities appear at the two extremities or summits of the prism, these two summits will differ from each other in the number or situation of their sides.* Most frequently that part of the crystal, which possesses positive electricity, presents the greater number of faces. On the contrary, it is usually the case, that, when a crystal does not become electric by heat, the opposite parts are similar. Some-

* The different configuration of the opposite parts of a crystal, exhibiting the two kinds of electricity, has been supposed to be a uniform fact. But more extensive observations seem to show, that it is not always the case. Some tourmalines from Pegu and Ceylon, which give both electricities, appear to have both summits perfectly regular and similar. Another exception appears in the dodecaedral crystals of the borate of magnesia. (Bourron)

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times certain angles or faces possess positive electricity, while the opposite angles or faces exhibit negative.

139. It may be stated as a general fact, with very few exceptions, that stones and salts, possessing a considerable degree of purity, and having their surfaces polished, acquire positive electricity; but, if their surfaces are not smooth and polished, they may acquire negative electricity, as is the case with rough glass.

Combustibles, the diamond excepted, become negatively electric by friction. The diamond, whether polished or unpolished, always becomes positive.

Ores are usually conductors of electricity, with the exception of some metallic salts, which become positive by friction.

140. For observing the electricity of minerals the electrometer (Pl. I, fig. 12.) is the most convenient instrument. In this figure a b is a needle of copper, terminated at each extremity by a small ball, and moving very easily on a pivot at the centre. At c the instrument has a metallic base. If a mineral, which has been excited, either by friction or heat, be presented near to one of the balls, the needle turns, whether the electricity be positive or negative; and the force of the electricity may be estimated by the distance, at which the needle begins to move.

To determine which kind of electricity a mineral possesses, the needle must previously be electrified, either positively or negatively; which may be done in the following manner. Let the instrument be insulated by placing it on d, a plate of glass or resin. Having excited a tube of glass, or a stick of sealing wax, place one finger on the metallic base c of the electrometer, and then bring the excited glass or sealing wax e within a small distance of one of the balls of the needle. When the needle is sufficiently electrified, first withdraw the finger, and then remove the glass or sealing wax. If now an excited mineral be presented to the needle, they will repel or attract each other, according as they possess the same or opposite kinds of electricity. But, as the electricity of the needle is known, that of the mineral may be determined.

To ascertain the electric poles, or those parts of a crystal, which possess contrary electricities, let a thread of silk about one fourth of an inch in length be connected to one extremity of a rod of sealing wax, which must then be excited. To this thread of silk, which of course is negative, let the sides, angles, or summits of the mineral under examination be successively presented; and the attraction or repulsion observed will indicate those parts of the crystal, where the two electricities reside.

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141. Sealing wax, when rubbed by most minerals, becomes negative. There are, however, a few minerals, of which the sulphuret of molybdena is one, which, being rubbed on sealing wax, communicate to it positive electricity. In these experiments both the wax and mineral should possess smooth surfaces of considerable extent.

142. The power of conducting electricity, possessed by some minerals, may enable us to detect the existence of metallic matter; for this purpose the mineral must be insulated and connected with an electrified conductor. It must however be remembered, that carbon is also a good conductor of the electric fluid.

The power of acquiring electricity by heat, the comparative facility, with which minerals become excited by friction, and the comparative strength of their electricities, often constitute important characters for determining the nature of minerals, even when cut and polished. Thus chrysoberyl may be distinguished from adularia by the great facility, with which the former is excited.

26. Phosphorescence.

143. A body is said to phosphoresce, when it shines with a feeble light, unattended by any sensible heat. Some minerals exhibit this property, when rubbed against each other, or when scratched by any other hard body; and a few phosphoresce even when brushed by a feather. Others must be reduced to a coarse powder, and projected, in a darkened room, on a shovel or other body, heated but very little below redness. Sulphuret of zinc may be examined, as an example of phosphorescence by friction, and the fluate or phosphate of lime, by heat. Some minerals phosphoresce, when melted by the blowpipe. This appearance is considered by Vauquelin, as indicating the presence of lime.

This property does not appear to be essential to those minerals, in which it exists; for in those species, which most uniformly phosphoresce, there are certain varieties, which refuse to yield this light. Thus the variety of phosphate of lime, called asparagus stone, does not phosphoresce; and certain dark blue fluates of lime from Cumberland, England, yield no light whatever. (BOURNON.)

The color of the light is variable, being green, blue, yellow, reddish, &c. and may even change during the experiment according to the degree of heat or some other circumstance.*

* In a paper, communicated to the National Institute of France in 1810, by M. Dessaignes, it is asserted, that, when bodies phosphoresce by an increase of temperature, the color of the light is always blue, unless altered by the presence of iron.

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144. In general, phosphorescence more frequently appears in minerals possessing color, than in those, which are limpid or colorless. And perhaps the most interesting circumstance, attending this property of minerals, is the connexion between the phosphorescence and the color of the mineral; particularly when the former is developed by the action of heat. In this case, as the light diminishes, the color gradually disappears; and, when the color has entirely departed, the phosphorescence ceases. (BOURNON.)

To secure a proper degree of heat in these experiments, it is perhaps best to heat a shovel, till it becomes red; and, having entered a dark room, let the mineral, in a state of powder, be projected on the shovel immediately after the redness disappears.

The time, during which equal quantities of different minerals continue to phosphoresce, is variable. Thus phosphate of lime loses its color and phosphorescence much sooner than fluate of lime.

27. Specific gravity.

145. The specific gravity of a body is its weight, compared with that of another body of the same magnitude. Thus, if a cubic foot of water weigh 1000 ounces, and a cubic foot of iron 7000 ounces, their comparative weights or specific gravities are as 1000 : 7000, or as 100 : 700, or as 10 : 70, or as 1 : 7.

It is well known, that, when a body is immersed in water, it is in some degree supported by the water, and consequently loses part of its weight. This loss of weight is also known to be precisely equal to the weight of a quantity of water, of the same magnitude, as that of the body immersed. If then we weigh a body in air, we have its absolute weight; if we weigh the same body in water, we have the absolute weight of a bulk of water equal to that body; for it is equal to the weight, which that body loses in water. We hence have the absolute weight of two different bodies of equal bulk; and the ratio of these weights is the ratio of their specific gravities.

For convenience, however, the weight of a given bulk of some substance must be assumed, as a standard or unit, with which to compare the weight of the same bulk of all other bodies. In this case one number is always sufficient to express the specific gravity of a body, because the standard unit is understood.

For the purpose of a standard, distilled water is usually employed, a cubic foot of which weighs 1000 avoirdupois ounces. This, we have already seen, may be called 1000, or 100, or 10, or 1, adding decimals as far, as necessary. If we assume 1, as the standard, the following proportion will give the specific gravity of all bodies heavi-

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er than water;—as the weight, which a body loses in water, is to its absolute weight, so is 1 to the spec. grav. required. If the mineral be lighter than water, add the weight, which is necessary to make it sink in water, to its weight in air, and then say, as this sum is to its weight in air, so is 1 to the spec. gravity.

146. On the preceding principles is founded the method of taking specific gravities by the instrument, commonly called Nicholson's Portable Balance (Pl. II, fig. 21).

The body of this instrument is a hollow cylinder of tinned iron, of which each extremity a and b terminates in a cone. From the vertex of the upper cone a small stem of brass a c rises perpendicularly, bearing on its upper extremity a small tin cup d. From the vertex of the lower cone is suspended a similar cup e, attached to a cone of lead underneath it, as a ballast. Both the cups may be removed, when the balance is not in use.

When this instrument is placed in a vessel of water, a portion of the cylinder ought to swim above the surface of the water. The tin cup d is then to be loaded with weights, till the instrument sinks so far, that the surface of the water may exactly coincide with a mark near f on the brass stem. The quantity, necessary to make the instrument sink thus far may be marked on the cup, as a given quantity for future use. Suppose this quantity to be 600 grains, which may be called the balance weight, and will serve for taking the specific gravity of any substance, whose absolute weight is not greater than that of the balance weight.

To ascertain the specific gravity of a mineral, place it alone in the upper cup, and add weights, till the mark on the stem coincides with the surface of the water; and suppose this to be 210 grains. Subtract the 210 grains from the balance weight of 600 grains; and the remaining 390 grains is the absolute weight of the mineral in air. Let the mineral be now removed to the lower cup; but, as it weighs less in water, than in air, the mark on the stem will rise a little above the surface of the water. Additional weights must now be placed in the upper cup, till the mark on the stem again coincides with the surface of the water. Suppose this to be 80 grains, which will of course be the weight of a quantity of water precisely equal in bulk to the mineral. We now have the absolute weights of equal bulks of water and of the mineral; then say, as 80 : 390 :: 1.000: 4.875, the spec. gravity.

If the mineral under examination be lighter, than water, it must be confined, when weighed in the lower cup; and the weight of whatever confines it is to be regarded, as belonging to that of the instru-

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ment. In other respects the process is the same, as the preceding. But, as the mineral is lighter than water, it is evident the second term of the proportion will be less than the first.

If the mineral very sensibly absorb water, which fact may be discovered by the gradual sinking of the instrument, after the specimen is placed in the lower cup, although no additional weight is put into the upper cup, the weight of the water imbibed must be ascertained by again weighing the mineral in air; and is then to be added to the first term of the proportion.

Some minerals are rapidly dissolved in water. In such cases some other fluid, as oil of turpentine, may be employed; or the water may be previously saturated with a portion of the same salt, whose specific gravity is to be taken.*

147. The spec. gravity of minerals, belonging to the same species, often varies a little, either from the accidental mixture of coloring matter or other foreign ingredients, or from a more or less intimate combination of the component parts. But, notwithstanding these variations, the character drawn from the spec. gravity is exceedingly useful. For by taking the mean spec. grav. of several specimens of the same species in a state of as great purity, as can be procured, something like a standard of spec. grav. for every species may be obtained. In crystallized minerals, not obviously impure, the variation from the mean, will probably be within the limits of one fiftieth above or below. In substances not crystallized it must be greater, especially in certain species of ores.

SECTION III.

Chemical Characters.

148. The characters to be described in this section are called chemical, because it is the business of chemistry to discover and examine them. They are all to be ascertained by experiments, which produce a partial decomposition of the mineral, or a separation of its integrant particles. In most cases these characters are exceed-

* The preceding experiments are supposed to be made with distilled water at the temperature of about 62° Fahr. But, when common water, at a different temperature, is employed, the true spec. grav. of the mineral in distilled water, at the proper temperature, must be determined by calculation; for the method of which, reference may be made to treatises on hydrostatics.
But in those cases, where the greatest precision is not requisite, rain water, at a temperature near to 62°, will give results sufficiently accurate.
Fluid minerals are few in number and rare. For methods of obtaining their specific gravity, reference may be made, as above.

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ingly important; more especially when the properties, on which they depend, belong to the nature of the mineral, unaffected by any accidental circumstance. Their number is indeed considerable, though but very few are commonly employed; and these depend on very simple experiments, easily performed, and requiring very little apparatus. A complete analysis of the mineral is not included in the characters, of which we now speak.

1. Fusibility.

149. When the fusibility of a mineral is mentioned, it is always to be understood, that the flame is supported by atmospheric air, unless the contrary be expressed. For, when oxigen gas is employed, many minerals, usually called infusible, are easily melted.

In order to derive the greatest benefit from the fusibility of minerals, as a distinctive character, the precise temperature, at which they melt, when in a state of purity, as well as the results of their fusion, ought to be known. The most common method of ascertaining the temperature is by Wedgewood's Pyrometer; but this instrument, not always uniform in its results, involves the use of a forge, which it may not always be convenient to employ; it is also difficult to inspect the process on account of the great heat.

150. The most convenient and useful method of examining the fusibility of minerals is by the blowpipe. It is true we do not here discover the temperatures, at which fusion takes place; we have, however, the advantage, not only of inspecting the different products of fusion, but also of observing the manner of fusion, that is, the various appearances, which minerals present, while melting. Even these appearances are often very characteristic, and greatly assist in determining the nature of the mineral.

The blowpipe is an instrument too well known to require a minute description. The tube should be composed of two different materials, as metal and wood, Or metal and ivory, to prevent the communication of heat to the fingers and mouth. The flame, which is directed by the blowpipe towards the mineral, assumes the form of a cone, whose sides, however, are not very well defined. But within this flame appears a second conical flame, well defined, and of a blue color; and it is at the vertex of this second cone, that the greatest heat exists. In many cases it is expedient to heat the mineral at the vertex of the outer cone, before it is exposed to the intense heat of the blue flame.

151. Much depends on the size of the fragment to be melted, and on that of its support. It is essential, that the fragment should be

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extremely small, never exceeding a grain of pepper; otherwise a part of it will be without the focus of heat, and may prevent a complete fusion by cooling that part, which is within the focus.

Various methods, depending on the nature of the mineral, must be employed for supporting the fragment before the flame. Very small forceps will be sufficient, when the mineral has but little fusibility. For substances easily fusible a small platina or silver may be employed. It is important, that these metallic supports should be very small, that they may not absorb too much caloric. When metallic oxides are to be reduced, a piece of very compact charcoal forms the best support. A small cavity is made in the charcoal, in which even minerals in a state of powder may be conveniently examined, especially if the cavity be partly covered by another piece of charcoal.

152. Minerals, while exposed to the action of the blowpipe, exhibit very different appearances, which, being directly before the eye, are easily observed, and should be minutely described. Sometimes their color is changed, or entirely disappears. Some minerals decrepitate, others split or exfoliate, when exposed to the flame. Some indurate and contract their bulk; others effervesce, or, rising in little blisters, melt with intumescence. It is also important to notice the vapor or odor, which may escape during the experiment; even the color, which some minerals communicate to the flame, is to be regarded.

153. The degree of fusion, and the results obtained, are to receive attention. On some minerals the blowpipe produces no effect whatever; others are partially fused; and others again melt with great ease.

The results of fusion may depend in some degree on the intensity or continuance of the heat, as well as on the nature of the mineral. Some minerals by the action of the blowpipe are merely softened, and alter their shape a little; or, if the substance be in loose grains, they become agglutinated. Others are converted into a kind of porcelain, in which only a few points are vitrified. Some melt into a slag, which is a compact substance, containing metallic matter; others yield a tumefied mass, or are reduced into a scoria, which is light and porous; and others give an enamel, which has a vitreous aspect, but is not transparent; sometimes the enamel is only superficial.

Many minerals, when melted, yield a globule of perfect glass, which, in different substances, has various colors, and possesses different degrees of transparency. Both enamels and glasses are sometimes porous or vesicular.

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When minerals contain foreign ingredients, their fusibility and the appearance of the product may be much altered.

The greatest heat of the blowpipe, according to Kirwan, never exceeds 130°, on Wedgewood's Pyrometer; but Brongniart extends it to nearly 150° on the same scale.

154. The compound blowpipe, sometimes mentioned in this treatise, is a very ingenious and valuable instrument, invented by Mr. Robert Hare, of Philadelphia. In this instrument the heat arises from the combustion of a united stream of hidrogen and oxigen gases; and there is scarcely any substance, not combustible, which it does not melt. Professor Silliman, of Yale College, was early associated with Mr. Hare in his experiments, and has since greatly extended them. See Bruce's Min. Journal, vol. i.

155. Certain substances, called fluxes, are sometimes added to the fragment under examination to promote its fusion; and by their assistance many minerals, otherwise infusible, may be melted. There are some cases, however, in which the mineral, although not really melted, unites with the flux, in which it appears to be minutely divided and suspended, or even dissolved. It is to be remembered, that the appearances of the mineral during fusion, and also the results of fusion are variously modified by the action of fluxes. The same flux becomes differently colored by different minerals; and different fluxes receive different colors from the same mineral.

One of the fluxes most commonly employed with the blowpipe is the sub-borate of soda (borax). In some cases the color, communicated to the flux by metallic oxides, may assist in determining the kind of metal present.*

2. Action of acids; and other tests.

156. In most cases it is best to employ either the nitric or sulphuric acid. The only apparatus for these experiments is a piece of glass; and nothing is more convenient, than the crystal of a watch. A small fragment of the mineral is to be placed in the glass, and a

* It is sometimes necessary to operate on larger masses, than can be exposed to the flame of a blowpipe. In this case recourse may be had to a crucible, placed in a forge, which, on some accounts, is preferable to a wind furnace. And although the greatest heat of a common forge does not exceed 125° W. yet, by means of a large bellows, heavily loaded, the heat may be raised to 168° W. When the hearth of the forge has become heated by a previous experiment, the greatest heat may be obtained in less, than half an hour. It is often proper to examine the ores of metals in a crucible, making use of suitable fluxes; especially when an opinion is to be formed concerning the expediency of working such ores in the large way.

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sufficient quantity of acid poured on to cover it. If the acid have any action on the mineral, it is then to be observed, whether the solution take place quietly, or with effervescence; and, when a gas arises, its properties are to be noticed. In some cases the solution is complete; in others a residue is left; and sometimes the solution is gelatinous. It is also to be observed, whether a mineral lose its color by solution, or communicate color to the solvent; whether it dissolves, when in grains of a sensible magnitude, or only when reduced to a fine powder; in fine, whether the solution can be effected at the common temperature of the air, or only by the assistance of heat.

Liquid ammonia may in certain cases be employed with advantage, as a test. In fact, the chemical characters may be indefinitely multiplied, according to the nature of the mineral. Some, not here noticed, will be mentioned under the minerals, which exhibit them.

CHAPTER III.

SYSTEMATIC ARRANGEMENT OF MINERALS.

SECTION I.

General principles of arrangement.

157. THE same reasons, which require a distribution of Natural Science(1) into different branches, render subdivisions and systematic arrangement in each branch peculiarly important and useful. Indeed without a systematic arrangement of facts, these branches of knowledge could not be considered sciences; for every science involves a knowledge not only of facts, but of the mutual relations, which exist between these facts; and these relations are the basis of scientific arrangement. Hence to obtain a knowledge of the science of mineralogy, we must examine the properties of minerals, compare them with each other, and, according to the results of this comparison, establish a systematic arrangement.

158. Such arrangements have already been successfully effected in Zoology and Botany. The subdivisions, most commonly employed in those two kingdoms, are the following, descending from the larger to the smaller; viz. class, order, genus, species, and varieties. Of these divisions the species is undoubtedly the most important, and ought to be first formed.

159. In arranging a system of bodies our attention must be directed to the differences as well, as resemblances, which exist between the bodies to be arranged. Thus, if we compare certain plants, for

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example, we shall find them to resemble each other in most of their properties, although in some less important properties they may differ. If we neglect those properties, in which they differ, and confine our attention to the points of resemblance only, we can form these plants into one group, which is called a species; and all other plants, possessing the properties, which are common to this group, will belong to the same species. The differences, which exist between the plants, belonging to this group, may be employed in subdividing the species into varieties.

Let several groups or species be formed according to the same principle. If now we compare certain groups or species of plants, we shall perceive them to agree in some properties, while in others they are unlike. Abstracting the attention from those properties, in which these species differ, and regarding their resemblances only, we can form them into one group, which is called a genus. Here the points of resemblance characterize, the genus, and those of difference, the species. By similar comparisons and abstractions we may proceed to establish orders and classes. It must be evident, however, that the properties, employed to form the species, are more numerous, than those, which determine the genus; and thus continue to diminish, as we ascend to the higher divisions.

160. The same general principles, so far as they are applicable, ought undoubtedly to be employed in arranging the mineral kingdom. But here difficulties arise, which do not exist among animals nor vegetables. These difficulties originate from the inorganic nature of minerals, and make their appearance at the very foundation of the arrangement viz. in forming the species.

161. Could we satisfactorily determine what constitutes a species in mineralogy, little difficulty would remain in forming the other divisions. Deprived of organization, a mineral has not the power of reproducing another like itself. In organized bodies, on the contrary, this power of reproduction preserves all the species perfectly distinct, however nearly they may resemble each other in their general properties. Further, in bodies possessing organic structure, one species can never pass into another by imperceptible degrees; whereas minerals, being formed merely by the juxtaposition of their parts, and being continually subjected to the influence of external agents, during the period of their formation, are frequently contaminated by substances, foreign to their true composition; and individuals of different species are thus made to approach indefinitely near to each other in their appearance and properties. It must hence be obvious, that no small difficulty attends the determination of the species in

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mineralogy; and accordingly we find, that different opinions have been entertained, and different methods employed.

162. So great in fact has been the diversity of opinions on this subject, that scarcely any two persons have adopted precisely the same division of minerals into species. But, neglecting the minor and unimportant differences between the various methods of arranging minerals, we may reduce them to two, which may be called the mineralogical and chemical methods; the former depending chiefly on the external characters of minerals, the latter on their chemical composition.

Some indeed have employed the structure and form of crystallized substances, more particularly the form of their integrant particles, as the leading principle of the arrangement. It is perfectly obvious, however, that this principle is limited in its application, for all minerals are not crystallized. But its results coincide very remarkably with those, obtained by the chemical method. Indeed the Abbé Haüy, who first directed the attention of mineralogists to this method of arrangement, has, by examining the structure and form of some crystallized minerals, in a certain degree anticipated the results of analysis.

163. In that, which we call the Mineralogical method, the species is determined by the external characters. Hence, those minerals, which possess the same external characters, are supposed to belong to the same species; and consequently, if two minerals differ in their external characters, they must be referred to different species, although the results of analysis should declare both minerals to be the same substance.

164. In the Chemical method the species is determined by the true composition of the mineral, so far as that can be ascertained. Hence, if the composition of two minerals is known to be the same, they are supposed to belong to the same species, although their external characters should be more or less different.

165. It must however be remarked, that, in the present state of our knowledge, neither of these two methods can be rigidly adopted, and thus each preserved perfectly distinct. Even those, who depend most on the use of the external characters in arranging minerals, are, in many cases, evidently guided by chemical principles. And, although these methods so materially differ in principle and in some parts of the resulting arrangement, still there are many points, in which they coincide, that is, a large number of species are the same in both methods. This coincidence results from the fact, that minerals, which possess similarity of composition, generally exhibit a re-

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semblance in their external characters. This, however, is not always the case.

166. As each of the aforementioned methods of arranging minerals has received the support of very respectable mineralogists, it is proper to give the outlines of both, whichsoever may be adopted as our guide in the following work. In describing that method, which depends essentially on the use of the external characters, our attention will be confined to the system of Professor Werner, as it has been delineated by his pupils. In stating the principles of the chemical method, there will be occasion to refer to the arrangement of minerals by the Abbé Haüy.

SECTION II.

Arrangement of minerals, according to the system of Werner.

167. The Wernerian arrangement of minerals is, in a certain degree, a mixed method. But, as the species, the most important division, is determined almost uniformly by the external characters, it cannot with propriety be denominated a chemical method, although its divisions may not unfrequently correspond with chemical results. The basis of the Wernerian system, as stated by Professor Jameson, an intelligent mineralogist, who has attended the lectures of Werner, is "the natural alliances and differences, observable among minerals." (Jameson's System of Mineralogy i, Introd. p. xxiii.) These alliances and differences are there said, on the authority of Werner, to depend on the quality, quantity, and mode of combination of the constituent parts. But it is expressly asserted by Prof. Jameson (Introd. p. xxiv), that Werner "does not pretend, that his arrangement shall always correspond with the experiments of the chemist; for it is only when chemical results agree with the natural alliances of the mineral, that he gives them a place in his system." It is also said (p. xxv of the same Introd.), that "a chemical oryctognosy, in so far, as it stands in opposition to the natural alliances, observable among minerals, must be rejected;" and it is added (p. xxxvi), that the greater number of species in the mineral kingdom have been "arranged solely by agreements and differences in the external characters." The preceding authority is sufficient, it is conceived, for asserting, that the Wernerian arrangement essentially depends on the use of the external characters; and the system itself, in many parts, affords indubitable evidence of the same fact.

The divisions and subdivisions, introduced by Werner into the mineral kingdom, are the following, taken in a descending series; viz. class, genus, species, subspecies, and kind.

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168. The number of classes is four; viz. earths and stones; salts; combustibles; and ores. This division was first introduced by Cronstedt about the middle of the last century.

169. Each class is subdivided into genera. In most cases the genera are determined by the earth, or salt, or combustible, or metal, which is supposed to be either the predominant, or characteristic ingredient. It will be noticed, that a distinction is here made between the predominant and characteristic ingredient. It is indeed commonly the case, that the characteristic ingredient, or that, which is most effective in producing the peculiar characters of the mineral, is also predominant in quantity. But there are some minerals, which do not appear to be characterized by that ingredient, which is present in the largest proportion. This distinction is undoubtedly important; and could we, in cases of minerals, composed of several earths, estimate the relative energies as well, as the relative quantities of the different ingredients, we might ascertain what is essential to the true composition of such minerals.

170. The first or earthy class contains nine genera. Seven of these are determined by the predominant or characteristic earth; viz. the zirconian, siliceous, aluminous, magnesian, calcareous, barytic, and strontian genera. They, however, exhibit a number of anomalies. Thus sapphire is placed in the siliceous genus, although it is nearly pure alumine; and opal, which, in some varieties, does not contain a particle of alumine, is nevertheless referred to the aluminous genus.

But sapphire and opal are thus arranged in perfect consistence with the true principles of this system. For the fact appears to be this; a certain number of external characters, which siliceous minerals usually exhibit, being assumed as generic characters, or as a type of the genus, every mineral, possessing these characters, whether it contain any silex or not, is arranged under the siliceous genus.

We have mentioned seven of the genera, belonging to the first class; the remaining two are introduced into the earthy class, merely in consequence of possessing certain external characters, and in direct opposition to their true composition. One of these is the diamond genus, composed of pure carbon, and belonging to the class of combustibles. The other is called the hallite genus (from the Greek άλς, a salt), because the minerals, which it contains, resemble native salts; and they are in fact true salts.

171. The second class, salts, is divided into four genera; viz. carbonates; nitrates; muriates; and sulphates of the alkalis, earths, and metallic oxides. But the term salts is here to be understood in

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a much more limited sense, than when employed by chemists. It includes only those salts, which have some taste and a considerable degree of solubility in water.

172. Combustibles, which form the third class, are also divided into four genera; viz. sulphur; bitumen; graphite; and resin.

173. The class of ores contains as many genera, as there are distinct metals, found in the state of an ore.

In forming and naming most of the genera, even in this system, mineralogists have been more or less guided by chemical principles, whatever deviations may exist in the arrangement of certain species. In forming the metallic genera an attention to the constituent parts of minerals is unavoidable; for, were these genera to be established by external characters, independent of chemical analysis, the various species of ores, belonging to the same metal, would not always be collected into the same genus. Indeed several species of ores would undoubtedly be arranged among earthy minerals. Thus no one, relying on external characters only, would associate carbonate of lead with the other ores of that metal, nor even place it in any metallic genus.

174. The genera are subdivided into a greater or less number of species; and these, as before remarked(167), are determined almost uniformly by the use of the external characters. It is true, indeed, that Werner, in the introduction to his treatise on External Characters, says, that all minerals, which differ essentially in their chemical composition, ought to form different species; and that those, which do not differ essentially in their composition, belong to the same species. This principle, however, is indefinite, and in many cases entirely useless in establishing the species, unless we are informed what constitutes an essential difference in chemical composition. Indeed the aforementioned principle seems to be practically admitted only on the supposition, that the external characters are always a true index of the chemical composition; and, of course, that all essential differences in composition are clearly indicated by corresponding differences in the external characters. For, whenever the external characters and chemical composition are at variance, the species is determined solely by the external characters. The truth of this will appear by referring to the two species Apatit and Spargelstein of Werner; both of which are phosphate of lime, and really constitute but one species, although somewhat different in their external characters. Gypsum and selenite are in a similar situation.

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When the species is extensive, it is subdivided into subspecies; and these are often further divided into kinds.*

175. A careful examination of this system will render it extremely probable, that its author has, in some instances, supposed his distinctions to be formed by external characters alone, while, though perhaps unconscious of the fact, he has been in a great degree guided by the sure light of chemistry. In many instances, however, no one will deny, that the distinctions depend on external characters alone.

In favor of this system it is urged, that the use of the external characters enables us in a moment, almost by a glance of the eye, to ascertain the species, to which a given mineral belongs; and also to describe that mineral in a very concise manner, but, at the same time, so accurately, that another person may recognise it. It is also asserted, that, by enumerating every external character, a complete picture of the mineral, or rather of the species, to which it belongs, is presented to the view; and that the aggregate of external characters, exhibited by a given species, can never be found in a mineral of a different species, although a number of the characters, included in that aggregate, may be common to both species.

On the other hand, it is objected to this system, that the method, which it employs for determining the species, is not scientific, being founded on principles both arbitrary and variable; and that consequently different species are often formed without any specific difference. It is also objected, that, although the aggregate of external characters be presented in description, no discrimination is made between those, which are specific and distinctive, and those, which are not so. Hence the most unimportant characters appear in the description of equal value with those, which are really distinctive, and the reader is of course unable to characterize the species. It is further objected, that those, who adopt this system, so rigidly avoid all experiment, that, in their descriptions, they do not avail themselves of all the advantages in their power. Thus they express the hardness of minerals very indefinitely, as pretty hard, &c.; they give the specific gravity of bodies by estimation, saying middling heavy, &c. instead of obtaining it by experiment; and they decline a measurement of the angles of crystals, although this measurement would render the crystalline form and structure characters of the first importance.

It is obvious, that some of the preceding objections, though perfectly just, and true in fact, do not necessarily attach themselves to the

* In the earthy class certain species, having a general resemblance, are often collected into families.

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system, as they have no connexion with the divisions and arrangements, which it proposes.

SECTION III.

Arrangement of minerals, according to their chemical composition, or constituent parts.

176. We are now to direct our attention to that arrangement of minerals, which is designed to be strictly chemical. But, in order the more accurately to estimate the merits of the chemical method, it must be remembered, that our only object, at present, is to establish a systematic arrangement, or classification of minerals, on certain fixed principles.—To describe a mineral in such manner, that it may be easily recognised and referred to its place in a system already formed, is a distinct object; and permits the use of those properties of minerals, which would be insufficient to determine the arrangement itself. The mode of describing minerals will constitute the subject of the next section.

177. We have already remarked, that the species, the most important division, ought to be first formed.

It must be extremely obvious, that those minerals, which most resemble each other, belong to the same species. We are then to inquire what constitutes the most perfect resemblance between two or more minerals. Can similarity of color, form, fracture, hardness, &c. constitute a resemblance so perfect, as that, which arises from identity of composition? Or can a difference of color, form, fracture, &c. establish so important a distinction between minerals, as that, which is produced by dissimilarity of composition? Would not two minerals, both composed of phosphoric acid and oxide of lead, in the samè proportion, belong to the same species, although the color of one should be brown, and that of the other green? Would not two minerals, composed of phosphoric acid and lime, in the same proportion, belong to the same species, although the forms of their crystals, essentially the same, should exhibit different modifications? In fine, can properties, liable to numerous variations from trivial and accidental causes, be supposed to establish the identity of two or more minerals with that degree of evidence, which is afforded by a well ascertained similarity in composition? We hesitate not to answer these questions by saying, that the true composition of minerals ought to be the basis of arrangement; and by this only ought the species to be established. This only can give permanence of character to the species. The composition of a mineral, that is, the ingredients proper and essential to its composition, may remain unaffected by the accidental presence

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of certain foreign ingredients, which materially change several of the external characters.

178. Hence a species may be thus defined; a collection of minerals, which are composed of the same ingredients, combined in the same proportions.

179. But, granting that identity of composition constitutes the best specific character of minerals, are we sufficiently well acquainted with the composition of minerals to employ it, as the principal character, in the determination of the species? Is chemical analysis, in the present state of our knowledge, sufficiently accurate and perfect for this purpose? To this it may be answered, that the various species of alkaline and earthy salts, some species of combustibles, and almost every species among the ores of the metals can be limited and established by their well known composition. Difficulties may sometimes arise from the presence of foreign ingredients; but they are not of sufficient importance nor extent to affect the general principle of arrangement.

180. There remains, however, one class of minerals, composed chiefly of different earths, combined in various proportions, such as garnet, feldspar, &c. whose composition is not yet sufficiently understood, to be employed, as the basis of specific or even generic arrangement. This extensive class of minerals is really involved in some very peculiar difficulties. Analysis can indeed inform us what earths are present in these minerals, and in what proportions; but it has not yet been able to discover in what manner these earths are here combined, nor to distinguish between those ingredients, which are essential to the composition, and those, which are not, and which may in fact be considered as accidentally present.

Some minerals, which strongly resemble each other in their physical or external properties, and which, judging by these characters, evidently belong to the same species, do, however, when analyzed, widely differ in their composition. Others, on the contrary, possessing very different external characters, appear to be composed of nearly the same ingredients, combined in proportions very nearly the same.

181. This singular difficulty in regard to earthy minerals undoubtedly arises from two sources; one of which is the degree of imperfection still attached to the present modes of analysis. The other source, and probably the most extensive in its influence, is our inability to determine what ingredients are essential in a compound; or rather which one, two, or more of its ingredients may be most influential in producing its physical properties. We have

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already noticed(169) a distinction between a predominant and characteristic ingredient. This principle is undoubtedly important in its application to the present case. Some one or two of the ingredients of a compound mineral, although present in but a small proportion, may be much more powerful in determining the peculiar characters of that mineral, than another ingredient, which exists in a much greater quantity. It is indeed very probable, that certain earths may be almost always present, in small quantities, in a mineral, and yet not essential to the composition of that mineral. These various intermixtures, unessential to the species, may be supposed to have arisen, at the moment of the formation of the mineral, from the various and complicate affinities, existing between the several earths and their compounds. Foreign ingredients may have thus been interposed, or essential ingredients made to exist in excess.

Hence, perhaps, the reason why different crystals of the same substance yield to mechanical division with very different degrees of ease. Hence also one cause of the different results of analysis in minerals of the same species. Hence also it appears, that, notwithstanding the numerous though often trivial differences in these results, there may still be a unity of composition in each species. Hence also it is obvious, that, in analyzing minerals, an attention to their gangue or matrix is important; for this may have furnished accidental ingredients, or caused essential principles to exist in excess.—It ought here to be remarked, that the difficulties, which have resulted from diversity of analysis in minerals, supposed to belong to the same species, are gradually disappearing in consequence of the progress of chemistry. This progress is clearly evinced by the discovery of new earths and metals; and also by the detection of alkalis in many minerals, where, till lately, those substances were not suspected to exist.

182. It must be obvious from the preceding observations, that, until the analysis of earthy minerals becomes more decisive, some other mode or modes must be employed for determining the species. But, whatever these modes may be, they ought to employ those characters only, which depend on the nature or true composition of minerals. In many cases of crystallized minerals the species may be determined by the form of the integrant particles; for these forms undoubtedly depend on the elementary particles or true composition. It is the adoption and extension of the principles just stated, which constitute the peculiar traits of the system of mineralogy by the Abbe Haüy. This principle and its application require a more particular illustration.

183. In the section on crystallization(24) we have already defin-

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ed an integrant particle; and shown in what manner its form may frequently be ascertained by mechanical division(44). It was there remarked, that it is known from observation, that, in a large number of species of minerals, each species has integrant particles of a form peculiar to itself(50). But it must be distinctly noticed, that, in some instances, different species do certainly possess integrant particles of precisely the same form and relative dimensions, although differing in other properties.

It may, however, undoubtedly be assumed as a universal principle, that every species of minerals has integrant particles, whose true composition is peculiar to that species. In other words, no two really distinct species of minerals can be found, whose integrant particles exhibit the same form and agree in their composition; for, if their forms be the same, their composition and many of their physical properties will differ.

184. It hence appears, that an integrant particle in the mineral kingdom corresponds to an individual among animals, or vegetables. As each plant, abstracted from its individual qualities, is a representative of all the plants, belonging to the same species, and of the species itself, so an integrant particle represents the species, to which it belongs. The integrant particles of the same species possess the same composition, the same form and other physical properties; and an aggregate of these particles, whether it be crystallized or amorphous, would exhibit the mineral in a pure state, and possessing all the essential properties, which belong to that species.

We therefore conclude, that, in cases, where the results of chemical analysis are not satisfactory, the form and some other physical properties, which are essential to the integrant particles, may furnish us with specific characters, on which very great reliance may be placed in determining that composition, which characterizes the species. Indeed the history of the Arragonite justifies us in saying, that suck irreconcilable differences of structure and other important properties may exist between two minerals, whose composition, in the present state of analysis, appears to be the same, as to render it proper to suspend a decision in regard to such minerals.

185. The preceding view of the nature, or properties of the integrant particle does not, perhaps, differ from that, given by the Abbé Haüy in his Treatise on Mineralogy. But although he admits, that it belongs to chemical analysis to establish the basis of arrangement, yet, in determining the species, he appears to be governed chiefly by the form of the integrant particles, except in those cases, where different species have integrant particles of the same form. Hence he de-

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fines a species, a collection of bodies, whose integrant particles are alike, and composed of the same principles, united in the same proportions. The latter clause of the definition he adds for the purpose of including those cases, in which integrant particles of different species bave the same form.*

186. The form of the integrant particle is indeed dependant on the true composition of the mineral, and is unquestionably, in many instances, a very important character to indicate what is essential to that composition. But the acknowledged fact, that some species, really distinct, have integrant particles of precisely the same form, proves that the character, derived from the form of the integrant particle, being less general, ought to be subordinate to the true composition. It is hence obvious, that the form of the integrant particle can never be adopted, as a universal standard, for establishing the species among minerals.

187. Further, it is by no means evident, that certain minerals, which have never been seen crystallized, do not constitute really distinct species, and are in fact only a mixture of several species. We have remarked, that every species has integrant particles, whose composition, and very frequently, whose form and some other physical properties, are peculiar to that species, and would, if well understood, distinguish it from every other species. But, would not the integrant particles of a mineral remain the same in their real nature, whether regularly arranged in a crystal, or collected into an amorphous mass? In order that minerals may crystallize, they must be placed in certain circumstances, favorable to this process. Now we find some minerals have crystallized much less frequently than others. And where is the inconsistency in supposing, that some species of minerals seldom or never crystallize? We do not indeed know all the circum-

* Notwithstanding the great reliance, which M. Haüy places on the form of the integrant particle, he has remarked in his Tableau Comparatif, that he does not consider a knowledge of the form of the integrant particle indispensable to the admission of a mineral to the rank of a distinct species, provided its composition be well ascertained, and found to be different from that of any known species. And it was under these circumstances that he first introduced the chromate of iron, as a distinct species.
It appears, that M. Haüy's first object in forming his system of crystallography was to unite different crystallized varieties of the same species about one common point, as a nucleus or primitive form; and he was thus almost necessarily led to form a classification of crystallized minerals. But, however perfect this system may be in regard to the laws, by which various secondary forms are derived from the same primitive form, it is not, even by its celebrated author, supposed equally competent to establish a mineralogical method.

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stances, under which minerals were placed at the time of their formation; but is it not perfectly consistent to believe, that the presence of certain earths, not essential to the species, may, by their counteracting affinities, prevent crystallization? This we know to be sometimes the case in mixtures of certain salts. It is true, the number of supposed species, which has never been seen crystallized, is indeed small. But, if they are really distinct species, their claims to that rank ought to be asserted, although they have never been permitted to delight our eyes by their regularity of form.

188. It is unnecessary to describe the genera, orders, and classes, which exist in the system of the Abbé Haüy; for they are strictly chemical as far, as the present state of the science permits, and, of course, do not materially differ from the arrangement, employed in this treatise.

189. It may be useful here to recapitulate the principles, we have endeavored to establish for a scientific arrangement of minerals, and to make some additional remarks on the subject.

1. The true composition of minerals is the only sure criterion for determining the species, and, when known, should be employed in all cases.

2. When the composition of minerals is entirely unknown, or but imperfectly understood, other characters, depending more or less on the composition, must be employed. Of these the more important are undoubtedly derived from the crystalline form and structure; the latter of which may be extended to foliated masses, not possessed of a regular form; for these often easily yield to mechanical division. Indeed a careful attention to crystalline characters may sometimes remove apparent difficulties in the results of analysis.

3. The form of the integrant particle may often be employed with great advantage; but this alone cannot be relied upon with certainty, because the same form is sometimes common to different species; and hence, if two minerals are found to have integrant particles of the same form, the other properties of these minerals, examined in a state of purity, must agree, in order to establish the identity of the two substances.

4. When minerals, whose ingredients are capable of combining in various proportions, are crystallized, the form of the integrant particle may be of great use in limiting the species.

5. The form of the integrant particle, and the primitive form of crystals may be employed with advantage to distinguish what ingredients, found in a mineral, are unessential to the species; for whatever can be added to a mineral, or taken from it, without affecting

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these forms, may be considered foreign or not essential. The siliceous carbonate of lime (calcareous sandstone of Fontainbleau) affords a striking instance of a mineral greatly contaminated by a foreign substance, without affecting the form of the integrant particle.

6. When analysis is wanting, much benefit may be obtained from the primitive forms of crystals in establishing the species; for it is worthy of notice, that, when two or more crystals, belonging to different species, have the same primitive form, their other physical characters are, in general, strikingly different; as in the case of spinelle and magnetic oxide of iron. Indeed the primitive form may, in many instances, be employed instead of that of the integrant particles.

7. The structure and actual forms of secondary crystals are also important, provided the various angles of the crystal be accurately measured.*

8. When all assistance from analysis or the crystalline form is denied, the species must be determined by a well chosen aggregate of those external characters, such as structure, fracture, hardness, &c. which depend most intimately on the nature of the mineral. It is however to be understood, that, in all cases, where the composition is unknown, the species are to be considered provisional, till the progress of chemistry shall enable us to reexamine them.

190. The number of species, whose composition is not well known, even if it were greater than it is, ought not to be offered as an objection to the principles, we have just stated, for establishing the species. An objection of this kind would be saying, that, because we have not sufficient light on every object, it should be rejected in cases, where it shines with the greatest clearness. Neither can any difficulty or confusion arise from adopting a method somewhat mixed, depending in different parts on different principles. For so far, as the method is mixed, it arises from an imperfect knowledge of the true composition of certain minerals; and there is reason to believe, that the provisional species will gradually disappear, either by becoming well established, or by being associated with other species.

191. The preceding principles, it is believed, will enable us to limit and determine every species of simple minerals with as much accuracy, as the present state of our knowledge will permit. They embrace not only well crystallized minerals, but those, which are imperfectly crystallized, or which exist in foliated masses, destitute of

* The nature of amorphous minerals, whether granular or compact, may often be ascertained by their intimate connexion with well defined crystals, or even with laminated masses of the same substance. Of this, epidote furnishes an important illustration.

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regular form; they extend not only to amorphous minerals in a state of purity, but also to those, whether crystallized or amorphous, which are more or less contaminated by foreign ingredients. For it must be remembered, that a systematic arrangement is not designed to embrace those minerals, which are merely compounds of different species. Difficulties may sometimes arise in determining whether a given mineral is only a mixture of different species, or whether it belongs to some distinct species, but is greatly contaminated by other minerals.

192. We are now briefly to state the manner, in which the higher divisions are formed. Here also chemistry is to be our guide; for the genera, orders, and classes are to be determined, as far as may be, by the composition of minerals, or by some of their chemical properties.*

193. A genus will therefore be composed of certain species, which possess some common ingredient, and resemble each other in their chemical properties. In selecting the common ingredient, a preference should be given to that, which is most fixed and permanent. Thus all minerals, which are composed of lime, united to an acid, will form one genus, characterized by a common earth, and receiving its name from that earth.

194. An order will then be composed of certain genera, whose bases resemble each other in their nature. Thus all the earths have certain common properties, in which they resemble each other. Hence all those genera, which have for their base an earth, united to an acid, will form one order, which embraces the earthy salts. It is also to be understood, that the chemical properties of the different genera, united in the same order, should be similar.

195. A class is formed by the union of several orders. But it must be evident from the general principles of arrangement, that the relations, which unite orders into classes, must be more abstract and general, than those, which exist between the several species of a genus, or the several genera of an order. The relations, which characterize the classes, will be sufficiently explained in the subjoined tabular view of minerals.

196. The species, when necessary, may be divided into subspecies, varieties, and even subvarieties; but these subdivisions are determined chiefly by the external characters. By these means we are

* It may be said, that the arrangement here proposed is not strictly chemical, because the alkalis and earths are not considered as metallic oxides; but, at present, it would be neither expedient nor convenient to place the alkaline and earthy minerals in the class of metals.

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enabled to preserve a scientific arrangement, and, at the same time, to subdivide an extensive species, and to descend to any degree of minuteness in description, which the importance or utility of the species may require. The following general principles will determine the divisions into subspecies, &c.

1. The presence of any ingredient, not essential to the species, but which, nevertheless, produces a considerable change in the specific gravity, fusibility, or other important properties of the mineral, may be the basis of a distinction into subspecies.

2. Different structures and different degrees of cohesion between the particles are often found in minerals of the same species, and require divisions into subspecies or varieties. Thus, if only specific characters were given, it would be almost impossible to recognise all the varieties of carbonate of lime, sometimes finely crystallized, sometimes stalactitic, sometimes in a state of powder, and sometimes exhibiting a structure, which is granular, fibrous, or compact. But, by forming a number of subspecies and varieties, every important diversity of appearance in the species may be noticed.

3. Subspecies and varieties may sometimes be founded on particular colors, when these colors, although arising from ingredients unessential to the species, are sufficiently constant. Sometimes the difference of color, which appears in minerals of the same species, is produced by different coloring matters, and may be employed for subdividing the species.

SECTION IV.

Description of minerals.

197. It has already been remarked(176), that the description of a mineral, for the purpose of enabling any one to recognise it and refer it to its true place in a system, already formed, permits the use of those characters, which would be insufficient to establish a mineralogical method. Hence, in describing a mineral, we may employ every character, whether physical or chemical, which can afford some important assistance in distinguishing that mineral from those, which belong to other species, and in conveying an accurate idea of its appearance.

198. It must be perfectly obvious, that whatever is employed in establishing the species should, in itself, be of universal application; such is the true composition of minerals. But it is equally obvious, that any character, which almost uniformly belongs to a particular species, will be useful in describing and distinguishing that species. It is hence evident, that all those external characters, such as form,

11

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hardness, structure, &c. which depend more or less intimately on the composition of the mineral, are to be employed in description. Even those characters, which arise from the presence of superfluous or unessential ingredients, if their occurrence be sufficiently uniform, are of important use. Hence the very frequent appearance of a particular color may furnish a strong presumption, that the mineral in question belongs to a certain species. Much assistance may also be derived in some crystallized minerals from the frequent assumption of a particular form by some one species; or from certain peculiarities of form, arising from truncation or bevelment, &c.

199. The primitive form of the crystal, when it can be ascertained, is by no means to be omitted in description. This character, however, is incapable of universal application; for a large proportion of minerals are most frequently found either amorphous, or so imperfectly crystallized, that mechanical division is with difficulty applied. And, in regard to many minerals, much experience and practical skill are requisite to discover the natural joints and dissect a crystal with sufficient degree of accuracy; more especially to obtain the form of the integrant particles.

But a measurement of the angles of a crystal, whether those, formed by the inclination of contiguous faces to each other, or the plane angles of the faces, may be easily and accurately effected, and constitutes a very important and useful character. For, in any given species, all the crystals, belonging to the same variety of form, have their corresponding faces inclined to each other in angles of a constant quantity. This measurement is often particularly useful in cases, where certain faces of a crystal have taken an undue extent, and where other deviations from the usual form have been produced. Thus in hexaedral prisms of quartz, terminated by six-sided pyramids, the mutual inclinations of the faces remain the same, however much the prism may be compressed, or the faces of the pyramids unduly extended.

200. It is extremely important, that the characters, used in describing minerals and referring them to their proper species, should be susceptible of easy and expeditious application. Hence the advantage of employing certain chemical characters, and also those external characters, which can afford a satisfactory degree of evidence.

But the various external characters, which may be usefully employed in description, ought not to be indiscriminately detailed. On the contrary, those, which are most important, distinctive, and characteristic, should be particularly designated, either by being placed first in the description, or by being collected into a distinct paragraph.

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Hereby a pupil will save time and labor, and may avoid many perplexities.

201. Another character, peculiarly important to the practical mineralogist, and which ought never to be omitted in description, remains to be mentioned. This is called the geological character, and depends on particular associations, existing among minerals. It appears from observation, that certain minerals often occur together; while others, on the contrary, have seldom or never been found associated. Further, some minerals have a particular gangue or repository, in which they are contained. Thus the staurotide (granatit of Werner) is most usually found in a micaceous slate.

The greater number of simple minerals are found in compound rocks or aggregates. But the nomenclature and description of these compounds belong to geology, and will be given at the close of this volume. A very few general remarks will be sufficient to explain the geological characters, employed in the following descriptions.

202. Those minerals, which fall under the cognizance of geology, may be divided into five classes.

1. The first class contains the primitive or primary rocks, such as granite, gneiss, micaceous slate, certain limestones, &c. These rocks are chiefly composed of various simple minerals, irregularly crystallized, and aggregated without the intervention of any cement. They never contain organic remains of animals or vegetables. When connected with rocks, belonging to a different class, they occupy the lowest place, in reference to the centre of the earth. They are therefore supposed to have been first formed, and have accordingly received the name of primitive rocks.*

2. There exists another class of rocks, less distinctly the result of crystallization than the preceding, in part composed of mechanical deposites, and sometimes containing petrifactions. This class, to which belong graywacke, certain varieties of greenstone and limestone, &c. lies over the primitive rocks, when both classes occur together, and is called the transition class.

3. The third class is composed of those, which are called secondary rocks. These are always situated over or above the primitive or transition rocks, and often abound with organic remains or petrifactions. They appear to be chiefly mechanical deposites from water; in this class we find sandstones, and certain varieties of limestone.

4. Alluvial substances constitute the fourth class. They consist

* For an explanation of the word formation, as applied to extensive deposites of minerals, see remarks on geology, at the close of this volume.

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of clay, sand, pebbles, &c. and are evidently produced in a great degree by the disintegration of the preceding classes.

5. Volcanic productions form the fifth class.

CHAPTER IV.

NOMENCLATURE OF MINERALS.

203. The nomenclature of most minerals is at present so incumbered with synonyma, that it has become extremely perplexing to the student. He is hereby reduced to the alternative of perpetually recurring to books, or of loading the memory with several names, taken from the various languages, in which modern works on mineralogy have appeared. These remarks may be illustrated by the example of epidote. This mineral, which is called epidote by Haüy, is named pistazit by Werner, thallite by Lemetherie, akanticone by Dandrada, delphinite by Saussure, glassy actynolite by Kirwan, arendalit by Karsten, glasiger strahlstein by Emmerling, la rayonnante vitreuse by Brochant; &c. This is indeed an extreme case, and few other minerals have received so many synonyma.

We are not only deluged with various names given to the same mineral, but, in some cases, confused by the application of the same name, by different writers, to substances perfectly distinct. This multiplication of names is, in many cases, altogether unnecessary; and sometimes, when a new name has been substituted for one already existing, the former has been found equally objectionable with the latter. In all cases, where the chemical nomenclature cannot be applied, it would perhaps be a good general rule to permit the mineral to bear the name, given it by its discoverer.

204. By some writers the chemical nomenclature has been employed as far, as practicable; but most of the names, by which minerals are known, have been derived from the name of the place, where they were first observed; or from the name of the discoverer; or from the prevailing color, or some other characteristic property of the mineral. Sometimes the allusion of the name to the property is very obscure, and sometimes very trifling; see the names grammatite, analcime, chabasie, &c.* When the composition is unknown, those names, which are altogether unmeaning in regard to any property of the mineral, are perhaps the least objectionable; for they certainly cannot lead to error.

* See Traite de Minéralogie par le Cen. HAUY, tome 3, pp. 176; 180; and 227.

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205. In this treatise, the chemical nomenclature will be employed to designate the species in all cases, where the composition of the mineral is supposed to be sufficiently understood; it will, however, be accompanied by some familiar, mineralogical name, when such name exists, and by synonyma from some of the most valuable modern writers. But many of the aforementioned species embrace important varieties, which it is necessary to distinguish. This is peculiarly the case with the carbonate and sulphate of lime. Now these varieties must be distinguished either by the addition of certain modifying epithets to the name of the species, or by some single name. The latter mode is more simple and convenient for general use, and is probably attended with fewer objections, than the former. We shall, therefore, whenever it is practicable, distinguish subspecies and varieties by mineralogical names already in use and well known.

In a few instances, a single species, as determined by the composition, is divided by Werner, according to the external characters, into two or more species; and distinct, mineralogical names have been imposed on each. These names may be retained in the chemical method to designate subspecies or varieties. This is the case with the species, phosphate of lime; it is divided by Werner into two species, apatit and spargelstein, which are merely varieties, but which it is useful to distinguish. Many obvious advantages will result from retaining these names already in use, and employing them for the purpose just mentioned. Thus sulphuret of arsenic contains two subspecies, the red and the yellow, which have long been known and distinguished by the names realgar and orpiment; and there does not appear any sufficient reason for their disuse.

206. It cannot with propriety be objected, that the giving of distinct names to the subspecies and varieties will too much incumber the memory. For something must be remembered; and in cases, where a significant appellation is unknown, or would be inconvenient, the shortest name is undoubtedly to be preferred. It would indeed be a fortunate circumstance, if mineralogists would agree to designate minerals by some common nomenclature. But, while a systematic and significant nomenclature of all minerals cannot be formed; and while respectable mineralogists continue to establish the species by external characters alone, and studiously avoid the use of the chemical nomenclature in those cases, where it is applicable, every mineralogist must be acquainted with mineralogical names.

It is certainly convenient, at least for the purpose of conversation, to be able to designate a mineral by a single name. But, if names are given to species only, it will be necessary to employ description,

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or, at least, one or two epithets to distinguish any particular variety, of which we wish to speak.

207. The names of earthy minerals, whose true composition is not well known, and where consequently the chemical nomenclature is inapplicable, will, in general, correspond with those employed by Kirwan and Jameson, which are probably most familiar in this country, and are in most cases preferable to those of the Abbé Haüy. There must, however, be a number of deviations from their nomenclature. Some minerals, now known, are not mentioned by the two former writers. Other deviations necessarily arise from the late accurate and scientific researches of Haüy and other French mineralogists, who have shown, that, in some instances, minerals really distinct have been collected into one species. Two or more new species will hence arise, and must retain the names, they have received. In other cases it appears, that minerals, which really belong to the same species, have been separated, and must again be united. These new associations and separations cannot fail of producing some degree of confusion in the nomenclature; but the true interests and progress of the science ought not to be sacrificed to so trifling an inconvenience.

TABULAR VIEW OF SIMPLE MINERALS;

according to the order, in which they are arranged and described in this work.

208. In the following tabular view of simple minerals, the divisions into species and the nomenclature of the species are perhaps as strictly chemical, as the present state of mineralogical knowledge will permit. In the class of earthy compounds an accurate division into genera is impracticable. An attempt has therefore been made to arrange the species of this class, in some degree, according to their composition, as far as that can be ascertained from the results of chemical analysis. In other words, those minerals, which most resemble each other in the results of their analysis, are collected into the same group. We are hereby enabled to determine how far those minerals, which appear to be composed of the same ingredients, united in different proportions, resemble each other in their external characters.

209. In forming these groups, the latest analyses of the most experienced chemists have been employed, and principally those made by Klaproth, Vauquelin, and Chenevix. It has also been an object to select analyses made on the purest, crystallized specimens. In general, no ingredient has been considered essential, which does not occur in at least five per cent. in specimens apparently pure; while,

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at the same time, some ingredients, which occur in greater proportions in specimens obviously impure, have been rejected as accidental. After all, it must be obvious, that this arrangement of the earthy minerals is liable to various alterations, in proportion as chemical analysis becomes more correct. The important question, which remains to be answered, in regard to the greater number of the species in the earthy class, is this; which two or more of the ingredients, mentioned in the results of chemical analysis, are essential to the true composition of each species.

In the tabular view, subspecies are distinguished from varieties by a larger type, and by their position in the column.

A number of species, recently discovered, and concerning which little is yet known, are alphabetically arranged in an appendix to the earthy class.

Those species, which have never been analyzed, are marked by an asterisk. The place of such minerals, when not contained in the appendix, is determined merely by some external analogies.—Subvarieties are not included in the tabular view; and in the descriptions are not numbered.

TABULAR VIEW.*

CLASS I.

Substances not metallic, composed entirely, or in part, of an Acid.

This class contains four orders. In the first order, the acid is free or not combined; in the second, it is combined with an alkali; in the third, with an earth or earths; and in the fourth, with both an alkali and an earth. Hence the presence of an acid, provided it be not united to a metallic base, characterizes this class.

ORDER I.

Acids not combined.

The base of the acid determines the genus. All the species in this order have oxigen, as a common ingredient, so combined with a base, as to produce an acid.

GENUS I.

SPECIES 1. Sulphuric acid.
2. Sulphurous acid.

* Those species, which are printed in Italics, have not hitherto been observed in crystals, nor even with a crystalline structure.

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GENUS II.

SPECIES 1. Muriatic acid.

GENUS III.

1. Carbonic acid.

GENUS IV.

1. Boracic acid.

ORDER II.

Alkaline Salts.

These salts are composed of an alkali, united to an acid. Hence an alkali, so combined as to form a salt, characterizes this order. Each alkali designates a genus.

GENUS I. AMMONIA.

SPECIES 1. Sulphate of Ammonia.
2. Muriate of Ammonia.

GENUS II. POTASH.

1. Nitrate of Potash.

GENUS III. SODA.

1. Sulphate of Soda.
2. Muriate of Soda.
3. Carbonate of Soda.
4. Borate of Soda.

ORDER III.

Earthy Salts.

These consist of an earth, or of earths, united to an acid. Hence an earth, so combined as to form a salt, characterizes this order. Each genus is determined by the earth it contains.

GENUS I. BARYTES.

SUBSPECIES AND VARIETIES.
SPECIES 1. Sulphate of Barytes.
lamellar
columnar
radiated
fibrous
concreted
granular
compact
earthy
fetid
2. Carbonate of Barytes.

GENUS II. STRONTIAN.

1. Sulphate of Strontian.
foliated
fibrous
calcareous
2. Carbonate of Strontain.

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GENUS III. LIME.

SUBSPECIES AND VARIETIES.
SPECIES 1. Arseniate of Lime.
2. Nitrate of Lime.
3. Phosphate of Lime.
Apatite.
Asparagus stone.
fibrous
amorphous
siliceous
4. Fluate of Lime.
Fluor spar.
compact
earthy
argillaceous
5. Sulphate of Lime.
Selenite.
massive
Gypsum.
fibrous
granular
compact
branchy
snowy
earthy
Plaster stone.
6. Anhydrous Sulphate of Lime.
sparry
compact
silico-anhydrous
7. Carbonate of Lime.
calcareous spar.
crystallized
laminated
granular
fibrous
compact
coarse grained
Chalk.
Agaric Mineral.
Fossil farina.
concreted
Pisolite.
Oolite.
calcareous sinter.
Tufa.

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SPECIES Argentine.
Silvery chalk.
magnesian
common
Dolomite.
siliceous
Madreporite.
Calp.
fetid
bituminous
ferruginous
Brown spar.
Marl.
indurated
common
Bituminous marlite.
8. Arragonite.
fibrous
coralloidal
9. Siliceous Borate of Lime.
Botryolite.

GENUS IV. MAGNESIA.

1. Sulphate of Magnesia.
2. Carbonate of Magnesia.
3. Borate of Magnesia.
4. Fluate of Magnesia.

GENUS V. ALUMINE.

1. Mellate of Alumine.

ORDER IV.

Salts with an alkaline and earthy base.

1. Alkaline sulphate of Alumine.
2. Fluate of Soda and Alumine.
3. Glauberite.

CLASS II.

Earthy compounds, or Stones.

The minerals, which belong to this class, are composed chiefly of earths, combined with each other; they frequently contain some metallic oxide, and sometimes an alkali, or acid.

Alumine, silex and fluoric acid. SPECIES 1. Topaz.
Pycnite.

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SUBSPECIES AND VARIETIES.
Alumine nearly pure. SPECIES 2. Sapphire.
perfect
blue
violet
red
yellow
limpid
Corundum.
Adamantine spar.
Emery.
Alumine and water. 3. Diaspore.
4. Wavellite.
Alumine and magnesia. 5. Spinelle.
Ruby.
Ceylanite.
Alumine and silex. 6. Fibrolite.
7. Cyanite.
8. Staurotide.
Alumine, silex and lime. 9. Chrysoberyl.
Alumine, silex and zinc. 10. Gahnite.
Ittria & silex. 11. Gadolinite.
Zirconia and silex. 12. Zircon.
Jargon.
Hyacinth.
Silex nearly pure. 13. Quartz.
common
limpid
smoky
yellow
blue
rose red
irised
aventurine
milky
greasy
radiated
tabular
granular
arenaceous
pseudomorphous
Amethyst.
Prase.
ferruginous
yellow
red
greenish
fetid
Cat's eye.

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Silex nearly pure. SPECIES Chalcedony.
common
Cacholong.
Carnelian.
Sardonyx.
Plasma.
Hyalite.
Heliotrope.
Chrysoprase.
Opal.
precious
common
Hydrophane.
Girasole.
Semi-opal.
Flint.
swimming
Hornstone.
Silicicalce.
Buhrstone.
Jasper.
common
striped
Egyptian
14. Tripoli.
15. Porcellanite.
Silex, alumine and alkali. 16. Siliceous Slate.
Basanite.
17. Petrosilex.
18. Clinkstone.
19. Pumice.
20. Obsidian.
vitreous
Pearlstone.
21. Pitchstone.
22. Spodumen.
23. Lepidolite.
24. Mica.
laminated
lamellar
prismatic.
25. Leucite.
26. Fettstein
27. Lapis Lazuli.
Lazulite.
28. Schorl.
common
Tourmaline.
Indicolite.
Rubellite.
29. Andaluzite.

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Silex, alumine, lime and alkali. SPECIES 30. Feldspar.
common
Adularia.
opalescent
aventurine
Petuntze.
granular
compact
31. Jade.
Nephrite.
Saussurite.
Axestone.
Silex, alumine and glucine. 32. Emerald.
precious
Beryl.
33. Euclase.
Silex, alumine and lime. 34. Basalt.
columnar
tabular
globular
amorphous
35. *Wacke.
36. Dipyre.
37. Scapolite.
38. Wernerite.
39. Axinite.
40. Garnet.
precious
Pyrope.
common
Melanite.
manganesian
41. Aplome.
42. Epidote.
Zoisite.
Skorza.
manganesian
43. Cinnamon Stone.
44. Allochroite.
45. Idocrase.
46. *Meionite.
47. Byssolite.
48. Prehnite.
crystallized
Koupholite.
fibrous
Silex, alumine, lime and water. 49. Ædelite.
50. Stilbite.
51. Zeolite.
mealy
Crocalite.
Needlestone.
52. *Laumonite.
53. *Melilite.

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Silex, alumine, soda and muriatic acid. SPECIES 54. Sodalite.
Silex, alumine, alkali and water. 55. Natrolite
56. Analcime.
57. Bildstein.
58. Nacrite.
59. Chabasie.
Silex, lime and cerium. 60. Allenite.
Silex, lime and iron. 61. Yenite.
Silex, lime and water. 62. Schaalstein.
63. Ichthyophthalmite.
Silex, barytes, alumine & water. 64. Harmotome.
Magnesia and silex. 65. Chrysolite.
common
Olivine.
66. Labrador stone.
Silex, magnesia and lime. 67. Tremolite.
common
fibrous
Baikalite.
68. Asbestus.
Amianthus.
common
Mountain cork.
ligniform
compact
69. Diopside.
70. Sahlite.
71. Amianthoide.
Silex, magnesia, alumine and lime. 72. Augite.
common
Coccolite.
73. Hornblende.
common
Basaltic
lamellar
fibrous
slaty
Actynolite.
common
acicular
74. Diallage.
granular
resplendent
Bronzite.
75. *Macle.

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SPECIES 76. Native Magnesia.
77. Magnesite.
Keffekil.
Argillo-murite.
Silex, magnesia and alumine. 78. Serpentine.
precious
common
79. Steatite.
common
Potstone.
80. Talc.
common
indurated
81. Chlorite.
common
slaty
foliated
Green earth.
Silex and alumine. 82. Sommite.
83. Anthophyllite.
84. Pinite.
85. Argillaceous Slate.
Argillite.
Shale.
Novaculite.
Aluminous slate.
graphic
86. Clay stone.
87. Clay.
Native Argill.
Collyrite.
Kaolin.
Cimolite.
adhesive
Potter's
Lithomarge.
Fuller's Earth.
Bole.
Reddle.
Yellow Earth.
Umber.
88. Alum stone.
Appendix.
89. *Bergmanite.
90. *Chusite.
91. *Fuscite.
92. *Gabronite.
93. *Haüyene.
94. *Iolite.
95. *Petalite.

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SPECIES 96. *Pseudo-sommite.
97. *Sideroclepte.
98. *Spinellane.
99. *Spinthere.

CLASS III. COMBUSTIBLES.

1. Hidrogen Gas.
carburetted
sulphuretted
2. Sulphur.
3. Bitumen.
Naptha.
Petrolium.
Maltha.
elastic
Asphaltum.
Retinasphaltum.
4. Amber.
5. Diamond.
6. Anthracite.
slaty
granular
conchoidal
columnar
7. Graphite.
foliated
granular
8. Coal.
cannel
slaty
coarse
9. Lignite.
Jet.
brittle
Bituminous Wood.
brown
earthy
10. Peat.
fibrous
compact

CLASS IV. ORES.

GENUS I. GOLD.

1. Native Gold.

GENUS II. PLATINA.

1. Native Platina.

GENUS III. SILVER.

1. Native Silver.
auriferous

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SUBSPECIES AND VARIETIES.
SPECIES 2. Antimonial Silver.
3. Arsenical Silver.
4. Sulphuret of Silver.
5. Sulphuretted Antimonial Silver.
brittle
6. Black Silver.
7. Carbonate of Silver.
8. Muriate of Silver.
argillaceous.

GENUS IV. MERCURY.

1. Native Mercury.
2. Argental Mercury.
3. Sulphuret of Mercury.
common
fibrous
bituminous.
4. Muriate of Mercury.

GENUS V. COPPER.

1. Native Copper.
2. Sulphuret of Copper.
pseudomorphous
3. Pyritous Copper.
variegated
4. Gray Copper.
arsenical
antimonial
5. Red oxide of Copper.
foliated
capillary
compact
ferruginous
6. Azure Carbonate of Copper.
earthy
7. Green Carbonate of Copper.
fibrous
compact
earthy
ferruginous
8. Dioptase.
9. Muriate of Copper.
sandy
10. Sulphate of Copper.
11. Phosphate of Copper.
12. Arseniate of Copper.
obtuse octaedral
acute octaedral

13

[page] 98

SPECIES
foliated
prismatic
fibrous
ferruginous

GENUS VI. IRON.

1. Native Iron.
2. Arsenical Iron.
argentiferous
3. Sulphuret of Iron.
common
radiated
hepatic
magnetic
arsenical
4. Magnetic Oxide of Iron.
Native magnet.
Iron sand.
5. Specular Oxide of Iron.
micaceous
6. Red Oxide of Iron.
scaly
Hematitc.
compact
ochrey
7. Brown Oxide of Iron.
scaly
Hematitie
compact
ochrey
8. Argillaceous Oxide of Iron.
columnar
granular
lenticular
nodular
common
Bog ore.
9. Carbonate of Iron.
10. Sulphate of Iron.
11. Phosphate of Iron.
foliated
earthy
Green iron earth.
12. Arseniate of Iron.
13. Chromate of Iron.
crystallized
granular
amorphous

GENUS VII. LEAD.

1. Native Lead.
2. Sulphuret of Lead.

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SPECIES
common
compact
fibrous
antimonial
argento-antimonial
argento-bismuthal
3. Oxide of Lead.
earthy
4. Carbonate of Lead.
crystallized
acicular
columnar
compact
black
5. Carbonated Muriate of Lead.
6. Sulphate of Lead.
7. Phosphate of Lead.
acicular
arseniated
bluish
8. Arseniate of Lead.
9. Chromate of Lead.
10. Molybdate of Lead.

GENUS VIII. TIN.

1. Oxide of Tin.
fibrous
2. Pyritous Tin.

GENUS IX. ZINC.

1. Sulphuret of Zinc.
yellow
brown
black
fibrous
2. Red Oxide of Zinc.
3. Siliceous Oxide of Zinc.
foliated
common
4. Carbonate of Zinc.
5. Sulphate of Zinc.

GENUS X. NICKEL.

1. Native Nickel.
2. Arsenical Nickel.
3. Oxide of Nickel.

GENUS XI. COBALT.

1. Arsenical Cobalt.
dull

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SPECIES 2. Gray Cobalt.
3. Sulphuret of Cobalt.
4. Oxide of Cobalt.
black
brown
yellow
5. Sulphate of Cobalt.
6. Arseniate of Cobalt.
acicular
earthy
argentiferous

GENUS XII. MANGANESE.

1. Oxide of Manganese.
radiated
compact
earthy
ferruginous
2. Sulphuret of Manganese.
3. Carbonate of Manganese.
4. Phosphate of Manganese.

GENUS XIII. ARSENIC.

1. Native Arsenic.
concreted
specular
amorphous
2. Sulphuret of Arsenic.
Realgar.
Orpiment.
3. Oxide of Arsenic.

GENUS XIV. BISMUTH.

1. Native Bismuth.
2. Sulphuret of Bismuth.
3. Oxide of Bismuth.

GENUS XV. ANTIMONY.

1. Native Antimony.
arsenical
2. Sulphuret of Antimony.
radiated
foliated
compact
plumous
3. Oxide of Antimony.
earthy
4. Sulphuretted Oxide of Antimony.

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SUBSPECIES AND VARIETIES.

GENUS XVI. TELLURIUM.

SPECIES 1. Native Tellurium.
auro-argentiferous.
auro-plumbiferous.

GENUS XVII. CHROME.

GENUS XVIII. MOLYBDENA.

1. Sulphuret of Molybdena.

GENUS XIX. TUNGSTEN.

1. Calcareous Oxide of Tungsten.

2. Ferruginous Oxide of Tungsten.

GENUS XX. TITANIUM.

1. Red Oxide of Titanium.
2. Ferruginous Oxide of Titanium.
Menachanite.
Nigrine.
Iserine.
3. Silico-calcareous Oxide of Titanium.
4. Octaedral Oxide of Titanium.

GENUS XXI. URANIUM.

1. Black Oxide of Uranium.
2. Green Oxide of Uranium.
crystallized
earthy

GENUS XXII. COLUMBIUM.

1. Oxide of Columbium.
ferruginous
Ittrious

GENUS XXIII. CERIUM.

1. Oxide of Cerium

[page 102]

ELEMENTARY TREATISE

ON

MINERALOGY.

CLASS I.

Substances not metallic, composed entirely, or in part, of an Acid.

THIS class is characterized by the presence of an acid, which may be free or not combined; or combined with an alkali; or with an earth; or with both an alkali and earth.*

ORDER 1. Acids not combined.

Twelve acids, either disengaged, or in combination with other substances, are known to exist in the mineral kingdom. They are the carbonic, phosphoric, fluoric, sulphurous, sulphuric, muriatic, nitric, boracic, chromic, molybdic, arsenic, and mellitic acids. All these, the sulphurous excepted, are usually found in combination with bases, forming native salts.

Several of the preceding acids, however, have been sometimes observed to exist native in a free state, or not combined with any base. They are the sulphuric, sulphurous, muriatic, carbonic, and boracic acids. But their occurrence in a disengaged state is very rare, in consequence of their great tendency to combine with other bodies.

These acids have perhaps never been observed in primitive earths. They never occur in large quantities; the carbonic is the most abundant. In most cases they undoubtedly arise from the decomposition of other minerals.

* If the definition of minerals already given (Introd. 5.) be rigidly applied, air and water would probably be introduced into the mineral kingdom; for they are inorganic bodies, found native at the surface of the earth. They have, in fact, no inconsiderable action upon some minerals; and this action it is important to notice, whenever it exists. But the natural history of air and water, and the investigation of their various properties undoubtedly belong to Philosophy and Chemistry.
Water, indeed, often contains various minerals in solution, and is then called a mineral water. Such waters will be noticed, as far as may be convenient, under the several substances, which they hold in solution.

[page] 103

GENUS I.

This genus contains two acids, whose base is sulphur.

SPECIES 1. SULPHURIC ACID.

The existence of sulphuric acid in a free state is extremely rare. It may always be recognised by its strongly acid taste, and by the white, insoluble precipitate, which it invariably produces in solutions of the nitrate or muriate of barytes. It has been found native both in a concrete and imperfectly liquid state. To distinguish this native sulphuric acid from sulphates with an excess of acid, recourse may be had to evaporation; in the former case little or no residue is perceived.

(Localities.) Mr. Baltassari has found this acid in a concrete state in the grottos of the volcanic mountain, Zaccolino, near Sienna. These concretions are in the form of cauliflowers, pendent from the ceiling of the grottos, and adhering to sulphate of lime, on which this acid can have no action. They are probably a compound of sulphuric and sulphurous acids. The same grottos contain sublimed sulphur and sulphurous acid.—Mr. Pictet mentions a cavern near Aix, in Savoy, from the roof of which this acid, mixed with water and a little sulphate of lime, is observed to drop.—It has also been seen by Dolomieu in many caverns of Etna.

In the United States. In New York, at Clifton Springs, in Farmington, 11 miles from Geneva, this acid is mixed with native sulphur, from which it may be extracted by water. (GODON.)

SPECIES 2. SULPHUROUS ACID.

The presence of this acid, which, when disengaged, always exists in a gaseous state, may be determined by its peculiar and suffocating odor.

(Localities.) It has been found only in volcanic countries; and most usually issuing from fissures in the lava, near volcanoes, whose eruptions it either accompanies or follows. It has also been found in certain hot springs, near volcanoes, in Italy. Although in most cases its existence in any one place is transient, depending on the activity of some neighboring volcano, it appears to be constantly disengaged from the Solfaterra, not far from Naples; and from the summit of Stromboli, &c.

GENUS II.

SPECIES 1. MURIATIC ACID.

Muriatic acid, when not united to other substances, is a gas, having a peculiar odor, and produces a white precipitate in a solution of the nitrate of silver.

[page] 104

(Localities.) The existence of native muriatic acid appears to be nearly confined to volcanic regions, where it is observed in a gaseous state near volcanoes, especially during their eruptions. Spallanzani has obtained muriatic acid from the volcanic glass and pumice of Lipari. He supposes the acid to have gradually penetrated these volcanic products, after their ejection from the volcano; for in lavas recently ejected he did not find this acid.—Not far from Valadolid, in New Spain, are springs, whose waters contain muriatic acid gas. (HUMBOLDT.)

GENUS III.

SPECIES 1. CARBONIC ACID.

This acid is sometimes found in a state of gas; and sometimes it is dissolved or rather diffused in water, with which its union is extremely feeble. A few simple experiments are sufficient to detect the presence of this acid, whether gaseous, or contained in water. Its great specific gravity, causing it to occupy the lower parts of the cavity, in which it exists, its power of extinguishing flame, and of producing a precipitate in lime water, sufficiently characterize it, when in a state of gas. To water, which has absorbed it in any considerable quantity, it usually communicates an acidulous taste. But, if other substances, contained in the same water, render this acid imperceptible to the taste, it must then be liberated by heat.

(Localities.) A knowledge of those places, in which carbonic acid has been observed, or in which it may be supposed to exist, is extremely important, on account of the deletereous effects, which are often produced on those, who are immersed in this gas. Thus, as it often exists in large quantities in mines, caverns, pits, and in some wells, it is dangerous and often fatal to descend into such places without sufficient precaution.

The existence of carbonic acid in a gaseous state is almost exclusively confined to volcanic countries, and to those, which contain certain deposites of carbonate of lime, usually called secondary limestone. In such countries it is often very abundant, occupying the lower parts of caverns, pits, fissures, &c. or even filling them entirely. Between Naples and Pozzuolo, in Italy, is the celebrated Grotta del Cane. On the floor of this cavern, or rather excavation, a stratum of carbonic acid gas, about eight inches in thickness, is constantly found. If a dog or any other animal be plunged into this stratum of gas, it soon expires. The Abbé Breislak supposes the quantity of carbonic acid, now disengaged in this grotto and its vicinity, to be much less, than it was in the time of Pliny.—Near Bolsenna, in Italy, if an aperture of

[page] 105

seven or eight feet in depth be made in the earth, this acid gas is immediately disengaged.

Mineral waters, containing Carbonic acid, are by no means uncommon among rocks or earths of a secondary or late formation, and also in volcanic countries. Those of Pyrmont and Spa in Germany, and of Châteldon and Vichy in France, are well known; at Vichy the water is warm, a circumstance rather uncommon, when it contains Carbonic acid.

In the United States several springs, impregnated with carbonic acid, have been observed. The mineral waters of Balltown, Saratoga, and New Lebanon, in the state of New York, are well known. A French chemist has obtained from 25 ounces of the Balltown water 3 times its bulk of carbonic acid gas; 31 grains of muriate of soda; 22 grains of supercarbonate of lime; 12½ grains of muriate of magnesia; 5 grains of muriate of lime; and 4 grains of carbonate of iron. The existence of a mineral water, of the composition just described, may obviously be productive of much benefit to the public.

(Remarks.) Different opinions have been expressed on the origin of this native acid. By some it is supposed to originate from the decomposition of carbonate of lime by subterraneous fires, or by some other acid, or by the action of sulphur; and by others it has been suggested, that, in volcanic countries, this acid does not pre-exist in any compound, but arises from the direct combination of oxigen and carbon.

GENUS IV.

SPECIES 1. BORACIC ACID.

Boracic acid, when pure, is concrete; and usually presents itself in the form of small, white, shining scales, which are soft and even unctuous to the finger. When dissolved in alcohol, this acid communicates to its flame a greenish tinge. It has little taste, and is sparingly soluble in water, especially when cold. When in the form of scales, its specific gravity is 1.47. (KIRWAN.) Before the blowpipe it melts into a transparent glass.

(Localities.) It is found in solution in the warm waters of several small lakes in Tuscany. According to Mr. Hoeffer, it is sometimes in the proportion of nearly nine grains to one hundred grains of water. If this be correct, its solubility must be greatly increased by the presence of other substances in the same waters; and it is in fact accompanied by several borates, and by the sulphates of alumine, ammonia, &c.—It is also found on the shores of the same lakes in a concrete state, in the form of stalactites, or small scales, or crystalline grains, of a grayish white color with yellowish spots.

14

[page] 106

A substance, found by Mr. Mascagni, near the warm spring of Sasso, in Tuscany, has, from that circumstance, received the name of Sassolin; but Klaproth has ascertained, that it contains 86 per cent. of Boracic acid.

Probably this acid will be found to exist more abundantly, than has been generally supposed. Smithson Tennant has described a specimen of concrete Boracic acid from Lipari, of a scaly, shining appearance, and slightly yellowish from contamination with sulphur. Indeed thin crust of sulphur adhered to one side. This specimen was 7 or 8 inches long, and 5 or 6 inches broad, and appeared to have been taken from a larger mass. (Geolog. Trans. v. i.)

ORDER II. Alkaline salts.

This order is characterized by the presence of an alkali, united to an acid, and forming a salt. Few of the alkaline salts ever occur in large masses; and they are very often more or less mingled with each other. They all communicate some peculiar taste to the tongue, and, when pure, are devoid of color. They often appear as an efflorescence on other substances. They are easily soluble in water, and hence are also frequently found dissolved in that fluid. This order contains three genera.

GENUS I. AMMONIA.

This alkali, when not combined, exists in a gaseous state, and has occasionally been observed in mineral waters. But in those cases it has undoubtedly originated from animal or vegetable substances. Only two species, the sulphate and muriate of ammonia, will be described under this genus. The carbonate of ammonia has, however, been found in some mineral waters. (THOMPSON.)

SPECIES 1. SULPHATE OF AMMONIA.*

This salt has a sharp and somewhat bitter taste. When triturated with pure lime, it is decomposed, and the odor of ammonia becomes perceptible. It is not acted upon by sulphuric acid; and, when heated nearly to redness, is chiefly decomposed.

It occurs in stalactites, or in crusts, or in an earthy state. Its color, from contamination with other substances, is gray or yellow of different shades.

When pure, it is composed of ammonia 14.24, sulphuric acid 54.66, water 31.10. (KIRWAN.)

* Ammoniaque sulfatée. HAUY. BRONGNIART. Mascagnin. Reoss. Vitriolic Ammoniac. KIRWAN.

[page] 107

(Localities.) It is found in the vicinity of volcanoes. Near Turin it appears on the surface of the earth. It is also found in and near certain lakes in Tuscany, adhering to the sides of fissures.

SPECIES 2. MURIATE OF AMMONIA.*

Sal ammoniac.

The sharp, urinous taste of this salt, the strong odor of ammonia, which it yields, when triturated with pure lime, and the disengagement of muriatic acid gas by the affusion of sulphuric acid, are three of its most important characters; by the last of which also it is sufficiently distinguished from the sulphate of ammonia. It is entirely volatilized by heat, rising in white fumes; and is soluble, when pure, in about three times its weight of water.

This salt usually appears in the form of an efflorescence or a crust, adhering to other substances, or in stalactical concretions. It is often in a state of powder, and completely enveloped in other minerals, particularly in lava. In this case, though imperceptible to the eye, it may be detected by trituration with lime. It has also been observed in small crystals, badly defined. Its color, arising from the mixture of foreign substances, may be gray, yellowish white, or even green, or nearly black.

Pure Muriate of ammonia is composed of ammonia 25.00, muriatic acid 42.75, water 32.25. (KIRWAN.) A specimen of the native Muriate from Bucharia yielded Klaproth 2.5 of the sulphate of ammonia.

(Localities.) This salt is found most frequently in the vicinity of volcanoes, near their craters, or in the fissures of the lava; having been sublimed from the interior of the volcano. At the Solfaterra, which may be called a half-extinguished volcano, the sublimation of this salt is very abundant. It has even been collected for use by condensing it in long tubes, placed over the apertures, from which it issues.—This mineral, according to Kirwan, has been found in the interior of Asia and Africa, at a distance from any volcanic eruptions.— In Persia it is mixed with clay or earths, or effloresces on certain rocks.—It exists also in the vicinity of the coal mines of Newcastle, Eng. and in the waters of certain lakes in Tuscany.

(Remarks and uses.) This salt, for the purposes of commerce, is obtained chiefly from Egypt, where it is manufactured from the excrements of certain animals, which feed on plants, impregnated with muriate of soda. The Muriate is sublimed from the soot, which arises

* Ammoniaque muriatée HAUY. BRONGNIART, Natürlicher Salmiack. WERNER. Natural Sal Ammoniac. JAMESON. Le Sol Ammoniac natif. BROCHANT. Sal Ammoniac. KIRWAN.

[page] 108

from the combustion of these excrements. Ten parts of soot yield three of this salt.—It is also prepared in various parts of Europe by different processes.

Muriate of ammonia is employed in medicine and the arts. In dying, it is used to heighten certain colors; in the tinning of iron and in soldering, to clean the surface and prevent oxidation. As it renders lead more brittle, it is sometimes employed in the manufacture of shot.

GENUS II. POTASH.

Only one species, the nitrate of potash, will be described under this genus. Probably three other species actually exist native. The carbonate and muriate of potash have occurred in minute quantities in some mineral waters; and the latter of these frequently accompanies the nitrate. Sulphate of potash also is said by Mr. Bowles to exist in certain parts of Spain.

SPECIES 1. NITRATE OF POTASH.*

Nitre. Saltpetre.

This salt, whether pure, or mixed with earthy or saline substances, may generally be recognised by placing it on hot coals. A vivid combustion, accompanied by a hissing noise and slight detonations, is produced by the oxigen, contained in the salt. Indeed, however minute the quantity of the salt, it discovers itself by the production of vivid points on the coal. Its taste is somewhat sharp and cooling.

It usually occurs in the form of an efflorescence or a crust; and these efflorescences appear to be composed of very minute fibres or capillary crystals.† Substances thus incrusted often have a mouldy appearance. Its color may be grayish or yellowish white, or nearly snow white.

Pure Nitrate of potash is composed of potash 51.8, nitric acid 44.0 water 4.2. (KIRWAN.) A specimen of the native Nitrate from Molfetta yielded Klaproth nitrate of potash 44.55, carbonate of lime 30.40, sulphate of lime 25.45, muriate of potash 0.20;=100.60.

(Geological situation.) Nitrate of potash is found native in all countries, where there are circumstances, favorable to its production;

* Potasse nitratée. HAUY. BRONGNIART. Natürlicher Salpeter. WERNER. Natural Nitre. JAMESON. Le Nitre natif. BROCHANT. Nitre. KIRWAN.

† This salt, when artificially crystallized, often exhibits hexaedral prisms, terminated by hexaedral pyramids, and perfectly resembling one variety of crystallized quartz, as far as the eye can determine. But in the Nitrate the faces of the pyramid form with the sides of the prism an angle of 143° 51′, whereas in the similar crystals of quartz the aforesaid angle is only 141° 40′.

[page] 109

and, although much more abundant in some countries than others, it never presents itself in very large masses. It frequently effloresces on the soil; but never exists at a greater depth, than that of a few yards beneath the surface. Sometimes also it invests the sides of caverns and fissures in calcareous rocks, which it often corrodes.

The existence of dry atmospheric air, and perhaps of animal or vegetable substances, in a state of decomposition, is requisite to the spontaneous production of Nitre. It also appears, that the presence of carbonate of lime greatly accelerates the formation of this salt; perhaps it is a necessary agent in many cases.

Native Nitre has seldom or never been found in pure clay, or in pure sand. But, if those earths, from which the Nitrate of potash has been extracted by lixiviation be replaced in their original situation, they again become impregnated with the same salt. Old walls and the vicinity of stables, &c. very often present efflorescences of Nitre.

(Localities.) One of the most remarkable localities of this salt in Europe is in the Pulo, or cavity of Molfetta, in the kingdom of Naples. This cavity, which is about 100 feet deep, contains several grottos or caverns, in the interior of which is found the Nitrate of potash in efflorescences or crusts, attached to compact limestone. When these efflorescences are removed, others appear in about a month. The soil in this cavity is calcareous, and richly impregnated with Nitre.

The Ukraine, Podolia, Hungary, Spain, Italy, Peru, and India furnish more or less of this salt for the purpose of commerce. It is in most cases extracted by lixiviating the earths, which compose the soil. —It has also been observed in the waters of certain springs in Hungary.

In the United States. The calcareous caverns, which abound in the state of Kentucky, furnish large quantities of Nitre. The earths, which exist in these caverns, and which contain both the Nitrate of potash and the nitrate of lime, are lixiviated; and the lixivium is then made to pass through wood ashes, by the alkali of which the nitrate of lime is decomposed.* After due evaporation, the Nitre is permitted to crystallize. One of the most remarkable of these caverns is in Madison County, on Crooked Creek, about 60 miles S. E. from Lexington. This cavern extends entirely through a hill, and affords a convenient passage for horses and waggons. Its length is 646 yards; its breadth is generally about 40 feet; and its average height about 10

* It appears that two bushels of ashes, made by burning the dry wood in hollow trees, contain as much alkali, as eighteen bushels of ashes, obtained from the oak.

[page] 110

feet. One bushel of the earth in this cavern commonly yields from one to two pounds of Nitre; and the same salt has been found to exist at the depth of at least 15 feet; even the clay is impregnated with nitrate of lime.

Kentucky also furnishes native Nitre under a very different form, and constituting what is there called the rock ore, which is in fact a sandstone, richly impregnated with Nitrate of potash. These sandstones are generally situated at the head of narrow vallies, which traverse the sides of steep hills; they rest on calcareous strata, and sometimes present a front from 60 to 100 feet high. When broken into small fragments and thrown into boiling water, the stone soon falls into sand, one bushel of which, by lixiviation and crystallization, frequently yields 10lbs. and sometimes more than 20lbs. of Nitrate of potash. The Nitre, obtained from these rocks, contains little or no nitrate of lime, and is said to be superior for the manufacture of gunpowder to that, extracted from the aforementioned earths.

Masses of native Nitre, nearly pure, and weighing several pounds, are sometimes found in the fissures of these sandstones, or among detached fragments. Indeed it is said, that these masses of native Nitre sometimes weigh several hundred pounds. (BROWN in Trans. Am. Philos. Soc. v. vi.; and Bruce's Min. Jour. v. i.)—Similar caverns occur in Tennessee and in some parts of Virginia and Maryland;—at Hughe's cave near Hagarstown, in Maryland, this salt has already been manufactured. (HAYDEN.)

(Artificial nitre beds.) The various sources of native Nitre are not, however, sufficient to answer the demands of chemistry and the arts. To supply this deficiency artificial nitre beds are prepared, in which are placed earths from the vicinity of inhabited buildings, old plaster, vegetable matter, &c. To these are added blood, urine, &c. After sufficient time, the earth, which remains in these beds, is lixiviated, and an impure nitre is obtained.

We have not room minutely to describe the process of manufacturing this salt; but perhaps the following simple mode of purifying the impure nitre is not generally known. It is thus given by Brongniart.

The impure nitre, previously pulverized, is to be washed three times in cold water in the proportion of 35lbs. of water to l00lbs. of the salt; taking care entirely to pour off each water, before another is added. These washings separate the greater part of the muriate of soda, and the deliquescent salts, such as nitrate of lime, &c. When thus washed, the nitre is to be dissolved in one half its weight of boiling water. On cooling, the salt begins to crystallize, and, by agitating the liquid

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during this process, extremely minute crystals are obtained. These crystals, when drained, are to be washed with 5lbs. of cold water for every l00lbs. of the salt, and then dried in a temperature of about 45°. The nitre, thus obtained, is well adapted to the manufacture of gunpowder.

(Uses.) The uses of this valuable salt in medicine, chemistry, metallurgy, and in the manufactures of gunpowder, nitric acid, &c. are well known.

GENUS III. SODA.

Four species, some of which are very important, will be described under this genus. A fifth, the nitrate of soda, probably exists native, but is extremely rare.

SPECIES 1. SULPHATE OF SODA.*

Glauber's salt.

The taste of this salt is at first saline and cooling; but it leaves an impression nauseously bitter. It is very soluble in water, and yields prismatic crystals, terminated by diedral summits. The crystals are usually irregular, and deeply striated. They rapidly effloresce in the air.

This salt occurs in an earthy state; sometimes also in efflorescences or crusts, and rarely in concretions, or in prismatic or acicular crystals. Its color is usually yellowish or grayish white.

Pure Sulphate of soda is composed of soda 18.48, sulphuric acid 23.52, water 58.00. (KIRWAN.) The native Sulphate is usually much contaminated by other salts, among which are the carbonate and muriate of soda, sulphate of magnesia, &c. The substance, found at Sedlitz, in Bohemia, and sometimes called Reussin, is composed of sulphate of soda 66.04, sulphate of magnesia 31.35, the remainder being muriate of magnesia, and sulphate of lime.

Sulphate of soda, in many of its properties, resembles the sulphate of magnesia (Epsom salt); but it is less bitter, and its solution remains apparently unaffected by the addition of an alkali, whereas a solution of the magnesian sulphate, when similarly treated, yields a Copious precipitate.

(Geological situation.) This salt is often contained in mineral waters; but, whether thus dissolved, or in an earthy state, it is found most frequently in the vicinity of springs or mines of muriate of so-

* Soude sulfatée. HAUY. BRONGNIART. Natürliches Glaubersalz. WERNER. Natural Glauber Salt. JAMESON. Le Sel de Glauber natif. BROCFAST. Glauber's Salt. KIRWAN.

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da. Its formation is, in many cases, undoubtedly to be attributed to the mutual action of muriate of soda and sulphate of magnesia.

Sometimes its efflorescences are attached to certain argillaceous slates; and sometimes they appear on the walls of brick buildings, &c.

(Localities.) Small quantities of this salt exist in most countries, especially in the colder latitudes; but it is seldom found in large masses. It is abundant in the lakes of Siberia, on the bottom of which it appears, when the temperature of the atmosphere is reduced to the freezing point of water; it is sometimes so abundant as to be collected for use.—At the foot of the Uralian mountains, near Tscheliabinsk, it effloresces on the soil in the spring of the year, but does not appear to extend far below the surface.

The Sulphate of soda, employed in medicine, is chiefly obtained during the extraction of muriate of soda from sea water, or of muriatic acid from the muriate of soda.

SPECIES 2. MURIATE OF SODA.*

Common salt.

This salt is easily distinguished by its well known saline taste. It is not unfrequently crystallized; and the primitive form, under which also it usually appears, is a cube. But it most frequently occurs in large masses, whose fracture is foliated, sometimes conchoidal, and, when recently made, presents a strong vitreous lustre. These masses are often composed of granular distinct concretions.

Sometimes also it is in capillary crystals, or in masses, composed of parallel fibres.

This salt is in general strongly translucent, and sometimes even transparent and limpid. Its color is commonly gray or white, often tinged with other colors; but it also presents certain shades of red, blue, violet, brown, green, or yellow, all arising from impurities. Its spec. gravity is 2.14.

In the fire it decrepitates. In the air it is not deliquescent, unless it contain muriate of magnesia or some other deliquescent salt. Pure Muriate of soda is composed of soda 53.00, muriatic acid 38.88, water 8.12. (KIRWAN.) The impurities, which sometimes color and contaminate the native Muriate, may be separated by solution in water.

(Geological situation.) This salt frequently occurs in large and

* Soude muriatée. HAUY. BRONGNIART. Natürliches Kochsalz. WERNER. Natural Rocksalt. JAMESON. Le Sel de Cuisine. BROCHANT. Common Salt, KIRWAN.

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extensive solid masses; and is often dissolved in the waters of certain springs and lakes. The ocean, however, is the great depository of Common Salt; for nearly one thirtieth part of its weight is Muriate of soda. Other salts, viz. the muriates and sulphates, both of magnesia and lime, exist in the waters of the ocean; so that the average quantity of saline ingredients is about½8 of the whole. This proportion is nearly the same in all latitudes.*

Muriate of soda, whether solid in mines, or dissolved in springs, occurs only among secondary rocks. But, although neither mines nor springs have been found in primitive earths, they are usually not far distant from the foot of primitive mountains.—This salt, which is usually deposited in thick, and sometimes extensive beds, may exist at the surface of the earth, or at a great depth below the soil. Sometimes also it has been deposited in regions greatly elevated above the level of the sea; and, in a few instances, is known to constitute whole mountains of very considerable elevation.

Muriate of soda is almost constantly associated with certain other minerals. Thus, with very few exceptions, it is accompanied by beds of clay, which often alternate with those of the salt. This clay is more or less impregnated with the salt, and often contains large masses of it. Other minerals, as sand, sandstone, compact, fetid, and bituminous limestone, usually accompany these deposites of Salt.

But the intimate connexion, which exists between this salt and sulphate of lime or gypsum, forms one of its most striking geological characters. Muriate of soda is in fact almost always associated with gypsum, over which the beds of this salt are usually placed, or even alternate with it. The salt, with which the gypsum is sometimes impregnated, is worth extraction.

Elephants' teeth, shells, bitumen, sulphur, &c. have been found in the various beds of minerals, which accompany this salt.

Salt springs are always connected with clay, the presence of which in fact seems necessary to the existence of these springs. And, although salt springs occur in countries, in which mines of this salt have not yet been discovered, it is extremely probable, that such mines actually exist beneath the soil, and impregnate the water. The sulphates of lime and of soda are usually found in these springs.

* There are a few exceptions to these general remarks. The Baltic is much less salt, than the ocean, and contains, when an easterly wind prevails, only 1/108 of saline matter.—The Dead Sea, in Palestine, is an exception of the opposite kind. According to Klaproth, one hundred parts contain water 57.4 muriate of magnesia 24.2, muriate of lime 10.6, muriate of soda 7.8; the last ingredient constituting about 1/13 of the whole.

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salt lakes sometimes furnish Muriate of soda, already crystallized by natural evaporation, and deposited at their edges, or on the bottom of the lake.—There is scarcely a mineral spring, which does not contain more or less of Muriate of soda.

(Localities.) It is worthy of grateful notice, that this mineral, so necessary to supply the wants of man, is almost universally distributed over the face of the globe. The following are some of its most interesting localities.

In England, near Northwich, Cheshire county, there is a rich and lucrative mine of this salt, whose beds alternate with those of clay, and commence at the depth of 35 or 40 yards below the surface. The upper bed of Salt varies from 20 to 30 yards in thickness; and the strata above it consist of clay, sandstone, and sulphate of lime. The salt is sometimes limpid and sometimes red. It is transported to Liverpool, where it is purified by solution in sea water, and subsequent evaporation; but this process does not separate the sulphate of lime. The annual produce of this mine is stated to be such, that many thousand tons are sent to those parts of the Prussian coast, most nearly adjacent to the celebrated Polish salt mines. (Edin. Rev. v. xix.)

France contains many salt springs; but no mines have been discovered.

In Spain are many salt springs; and at Cardona, in Catalonia, is a mountain of this salt. Its height is estimated at about 500 feet; and it is about 3 miles in circumference. The whole mountain forms one homogeneous mass, not stratified, and unaccompanied with sulphate of lime, unless it should be found to rest on this mineral.

Germany contains a number of mines, and abounds with springs of this salt. The salt mines of Tyrol are situated in a mountain; and are explored by excavating galleries, into which fresh water is introduced, and suffered to remain, till it is saturated.

In Hungary and Poland there appears to be an immense deposite of Muriate of soda, at the foot of the Carpathian mountains, on both sides. Indeed this mineral seems to extend with but few interruptions from the Black Sea to the Alps. The salt mine of Wieliczka, near Cracow, in Poland, has been worked since 1251; and, in 1780 had been sunk to the depth of about 900 feet; the salt commences about 200 feet below the soil. The galleries are completely dry; and the mine contains springs of both fresh and salt water. In this mine also are excavated several chapels, some of which are furnished with an altar, a crucifix, and statues, all of solid salt.

In Moldavia is a mountain of Salt, which in several parts is not covered even with soil.

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Russia obtains this salt not only from mines and springs, but also from salt lakes. In the province of Astracan are lakes, whose waters, when much concentrated, and sometimes the salt obtained from them, have a dark red color. (PALLAS.) The country near the Caspian Sea so abounds with Muriate of soda, that, in the vicinity of Gourief, the fogs, dews, and even the juices of plants become saline. (PALLAS.)

In Caramania, in Asiatic Turkey, this salt, in consequence of its hardness and the dryness of the air, is sometimes employed in the construction of buildings. (CHARDIN.)

In Africa the deposites of Muriate of soda are very abundant, and extensive. In the mountains, which form the northern boundary of the desert of Lybia, is an immense plain, covered with Common Salt. (HORNEMAN.)

In America the localities of this mineral have been but little explored. It appears, however, to exist in many places under one or both of its usual forms. In Peru are numerous mines, situated at a very great elevation above the sea; some are near Potosi. The salt is very hard, and usually of a violet color.—It has also been found in several parts of Chili, &c.

In California it is found in very solid masses; and in St. Domingo, near lake Xaraguay, it exists in a mountain.

In the United States, salt springs are numerous in several districts. These springs sometimes flow naturally, but are more frequently formed by sinking wells in those places, where this salt is known to exist, as in certain marshes, and in salt licks, so called, having formerly been the resort of wild animals to lick the clay, impregnated with this Muriate. These springs are found on the banks of the Hockhocking, Scioto, Wabash, Tennessee, Kanhaway, Great Sandy, and various other rivers, all west of the Alleghany mountains, and emptying their waters into the Ohio. They occur also in the state of New York near the Onondago and Cayuga lakes; those of Onondago rise in a marsh on the border of the lake, at some distance from hard ground; they are richly impregnated, one gallon of the water sometimes containing from ¼ to ½ a pound of the salt. Some springs, however, on the eastern waters of the Ohio are considerably richer than these.

The whole quantity of Salt, annually extracted from saline springs in the United States, undoubtedly exceeds 600,000 bushels. Of this the springs of Onondago and Cayuga alone furnish about 300,000 bushels, and the Wabash saline, which belongs to the United States, yields 130,000 bushels.

Much of the salt, employed in the arts, is obtained from saline

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springs, and especially from the sea, by evaporation, effected either by the action of the sun and the air, or by the application of fire. We have room to remark only, that the quality of the salt depends greatly on the mode of extracting it, whether by crystallization, or by a very rapid evaporation. When the solution is boiled or evaporated to dryness, the salt will, in general, be greatly contaminated by several earthy salts, particularly the muriates of lime and magnesia, which render it deliquescent.

The uses of this salt, though numerous and important, are too well known to require any particular notice.

SPECIES 3. CARBONATE OF SODA.*

Soda; in commerce.

This species embraces two varieties, differing in the quantity of carbonic acid, which they contain. One, which is the most common, is obviously in the state of a sub-carbonate; while the other appears to be a Carbonate, or perhaps sometimes contains an excess of acid. We shall embrace both varieties in one description, noting their different characters.

This salt, especially the sub-carbonate, has a warm, alkaline taste, but is not very caustic. It strongly effervesces with acids, and is very soluble in water. The sub-carbonate changes the vegetable blue to green, and rapidly effloresces, while the other remains unchanged by the air.

Like many other salts, the common variety occurs in efflorescences or crusts more or less thick, or in small flakes, or in a dry, dusty powder. But that, which is saturated with acid, sometimes appears in thick layers, having a granular texture, and sometimes in crusts, composed of acicular, translucent crystals, aggregated together and resembling fibrous gypsum. The color is grayish or yellowish white.

The pure sub-carbonate is composed of soda 21.58, carbonic acid 14.42, water 64.00. (KIRWAN.) Native specimens of this variety are always mixed with other salts, particularly the muriate and sulphate of soda and carbonate of lime. In a specimen of the Carbonate, from Sukena, Klaproth found soda 37.0, carbonic acid 38.0, sulphate of soda 2.5, water 22.5. Another from near Buenos Ayres yielded Cabral de Mello soda 24.25, carb. acid 44.25, muriate of soda 9.50, sulphate of soda 1.25, water 20.75.

* Soude carbonatée. HAUY. BRONGNIART. Natürliches mineral alkali. WERNER. Natron. KIRWAN. JAMESON. L'Alcali mineral natif. BROCHANT. This salt, called nitrum and natrum by the ancients, must not be confounded with the nitre of the moderns, which is the nitrate of potash.

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(Geological situation.) This salt appears in efflorescences or crusts on certain dry and warm soils; or on the surface of decomposing rocks; or on the walls of cellars and other damp places, especially if near the sea. It is also found abundantly in the waters of certain shallow lakes, situated in dry and flat countries. These lakes become in part or entirely dry, during the heat of summer; and this salt is deposited on their sides or bottoms.

This Carbonate is supposed by Berthollet frequently to arise from the mutual decomposition of muriate of soda and carbonate of lime, especially in warm and moist places.

Carbonate of soda is exceedingly common in mineral springs, and, in many cases, constitutes one of the principal ingredients. Hence the phrase soda water.

(Localities.) In Hungary, near Debreczin, the common variety of this salt is very abundant, both efflorescing on the soil, and deposited from lakes; large quantities are here collected for use.—At Bilin, in Bohemia, it effloresces on gneiss.

In Egypt it is plentifully found in what are called the lakes of Natron. These lakes, six in number, are westward of the Nile, not far from Terrana, in a valley, surrounded by limestone. The carbonate and muriate of soda exist together in these waters; but, when the water is diminished by natural evaporation, these salts are deposited in distinct layers, the muriate of soda being underneath. In one of these lakes, the waters on the eastern side contain only muriate of soda, while in those of the western side Carbonate of soda only is dissolved; but the two solutions do not mingle. (BRONGNIART.)

The Carbonate of soda, strictly so called, is found in the province of Sukena, two days journey from Fezzan, in Africa. It appears in crusts, composed of minute crystals, at the foot of a mountain. It is there called trona, and is transported to Egypt, Tripoli, &c.—This variety is also found near Buenos Ayres in considerable quantities. whence it has been transported to England. It there exists in stratified masses, from two to six inches thick, resting on clay, which is strongly impregnated with common salt. It has a light yellowish gray color, a granular texture, is easily broken, and does not effloresce in the air. (CABRAL DE MELLO.)

(Uses.) Large quantities of this salt are used in the manufacture of glass and hard soap. But the value of most of that, which is furnished by the mineral kingdom, is much diminished by adulteration with other salts. Indeed a large proportion of the soda, employed in the arts, is obtained by the combustion of the salsola, and other plants, growing near the sea; and is, in commerce, called barilla or kelp.

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SPECIES 4. BORATE OF SODA.*

Borax.

The characters of this mineral in its native state are almost entirely unknown. It is partially purified and crystallized in the East Indies and China, whence it is exported to Europe, under the name of Tincal. It must however undergo further purification to render it useful in the arts. During this process, which has hitherto been conducted chiefly by the Dutch, it is said to lose about 20 per cent.

When received from India, it is in the form of prismatic crystals, of very different sizes, more or less perfect, and always invested with a crust, which has apparently been produced by the application of some greasy substance to the surface of the crystal. This crust is usually of a dirty gray color, sometimes with a tinge of green or yellow; and is supposed to have been applied to prevent the salt from efflorescing.—That, received from China, differs from the preceding by being more limpid and purer.

It is unnecessary minutely to describe the characters of this well known salt in its purified state. It has an alkaline or soapy taste, and changes the vegetable blue to green; it is of course a sub-borate. It does not effervesce with acids. A specimen of tincal, analyzed by Klaproth, yielded soda 14.5, boracic acid 37.0, water 47.0;=98.5.

(Geological remarks and Localities.) This salt appears to be found at the bottom of certain lakes, or to exist in their waters, having probably been extracted by the water from contiguous earths. In some parts of Thibet it is said to have been dug from the earth in small crystalline masses. In Persia we are told it is artificially prepared, as we obtain nitre.

Asia, and particularly Thibet, is the only country, which furnishes this salt in any considerable quantity. It is said to exist in Peru, Ceylon, and Lower Saxony.

(Uses.) It is much employed, as a flux, in the examination of minerals, and the soldering of metals; but ought previously to be fused to remove its water of crystallization.

ORDER III. Earthy Salts.

These consist of an earth or of earths, united to an acid. Hence an earth, so combined with an acid, as to form a salt, characterizes this order. Many of the salts, which belong to it, exist in great abundance, and are appropriated to numerous and important uses. Some

* Soude boratée. HAUY. BRONGNIART. Borax. KIRWAN. Le Tinkal. BROCHANT.

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of them are, in common language, usually called stones. Those salts, which have an alkaline earth for their base, are here placed next to the alkaline salts.

GENUS I. BARYTES.

This genus contains only two species, the sulphate and carbonate of barytes. Although neither of these species is very abundant, the former occurs in much greater quantities, and is much more common, than the latter.

SPECIES 1. SULPHATE OF BARYTES.*

Heavy spar.

One of the most striking characters of this mineral is its great specific gravity, which varies from 4.29 to 4.50. When its structure is foliated and sufficiently regular, the laminæ easily separate in three directions, parallel to the faces of a four-sided prism (Pl. III, fig. 1.), whose bases are rhombs, having angles of 101° 32′ and 78° 28′. This prism is the primitive form of crystallized Sulphate of barytes; and any one side of the base is to the height, as 45 to 46. Mechanical division, parallel to the bases, is most easily effected. The integrant particles are triangular prisms.

Sulphate of barytes is harder than crystallized carbonate of lime, but may be scratched by fluate of lime. Some varieties are opaque; but it is generally translucent, and sometimes transparent, exhibiting double refraction. To observe the last mentioned property, an obtuse angle of one of the bases of the primitive form may be truncated, and the object observed through the new face thus produced, and also through the opposite base.

Its more common color is white, either pure, or variously tinged with yellow, red, &c. but it also presents several shades of red and gray, and sometimes of yellow, blue, green, and brown.

(Chemical characters.) This mineral is well characterized by its chemical properties, joined to its great specific gravity. When a fragment is exposed to the flame of a blowpipe, it almost always strongly decrepitates. While melting, it gives a greenish tinge to that part of the flame beyond the fragment, and is at last converted into a solid, white enamel, which, in the course of ten or twelve hours, falls into powder. If a piece of this enamel be applied to the tongue, it produces a taste, resembling that of rotten eggs; and has evidently been converted, at least in part, into a sulphuret of barytes. The

* Baryte sulfatée. HAUY. BRONGNIART. Schwer spath. WERNER. Heavy par. JAMESON. Baroselenite. KIRWAN. Le Spath pesant. BROCHANT.

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powder just mentioned, when recently calcined, shines in the dark with a reddish light, after being exposed to the rays of the sun.

When pure, it is composed, according to Vauquelin and Thenard, of barytes 75, sulphuric acid 25. But, by the analysis of Clément and Désormes, the proportions are barytes 67.82, sulph. acid 32.18. Chenevix found the proportion of earth to acid as 74 to 26; and Bucholz as 69 to 31. It frequently contains a few hundredth parts of silex, alumine, oxide of iron, and sometimes of sulphate of strontian.

(Distinctive characters.) This mineral may easily be confounded with sulphate of strontian, although the latter has a specific gravity somewhat less. But the sulphate of strontian, after fusion, never communicates to the tongue that peculiarly disagreeable taste, excited by the enamel from Sulphate of barytes. Further, the flame of the blowpipe is never colored green by sulphate of strontian, but often receives a reddish tinge.—It also resembles the carbonates of barytes and strontian; but these two salts always effervesce with diluted nitric acid, and slowly dissolve, while the Sulphate of barytes never effervesces, except from accidental impurities.—It differs from fluate of lime by its greater specific gravity, and by never phosphorescing, when merely reduced to powder and thrown on burning coals.—From some varieties of feldspar, which it resembles, a careful examination will easily distinguish it.—One variety of this Sulphate strongly resembles certain specimens of the carbonate of lead; but the latter has a greater specific gravity, a conchoidal fracture, and is blackened by the hydrosulphuret of ammonia, which has no action on the Sulphate of barytes.

This species admits a number of subdivisions, founded on diversity of form or structure, or force of cohesion, or the presence of foreign ingredients, which affect the physical characters.

Var. 1. LAMELLAR SULPHATE OF BARYTES.* This variety usually occurs in foliated masses; but not unfrequently it appears in beautiful crystals, whose surfaces, though sometimes dull, generally present a splendent and pearly lustre. M. Haüy has described sixty three modifications of the primitive form. These crystals are almost always well defined; and their magnitude is often considerable, presenting sometimes a thickness of nearly two inches. It most commonly appears in prisms, either right or oblique, having four, six, or eight sides. But these prisms are usually so short or compressed, that they assume a tabular form; and these tables or prisms are subject to numerous truncations and bevelments.

* Geradschaaliger schwerspath and saulen schwerspath. WERNER. Straight lamellar and prismatic heavy spar. JAMESON.

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Sometimes it presents the primitive form; which, in some specimens, has the solid angles, formed by the obtuse edges and the bases, truncated.—Sometimes a six-sided table (Pl. III, fig. 2.).—Sometimes also a rectangular four-sided table, with a bevelment on all its terminal or narrrow faces (Pl. III, fig. 3.).—The solid angles, formed by the edges of the bevelments on the preceding crystal, are often truncated, and sometimes also the edges of two opposite bevelments.—Sometimes its form is an eight-sided table, with a bevelment on all its terminal faces, and the edges of these bevelments truncated (Pl. III, fig. 4.).—Sometimes an oblique four-sided prism, terminated by two planes, standing on the acute lateral edges.—The preceding prism is sometimes terminated by four faces, placed on the lateral edges, and those, which stand on the acute edges, meet in a line.—It also occurs in cuneiform octaedrons.

Its structure, and of course its fracture, is foliated; its lustre shining and rather pearly. It breaks into rhomboidal fragments. When massive, it is only translucent, but the crystals are sometimes limpid and transparent. Its color is usually some variety of white or red.

A specimen from Sussex county, New Jersey, whose specif. grav. was 4.417, yielded Mr. Chilton barytes 61.34, sulph. acid 30.67, silex 3.0, alumine and oxide of iron 1.0, water 2.0, with a trace of strontian;=98.01. Another specimen, from Hatfield, Mass. whose spec. grav. was 4.28, was found by Dr. Gorham to contain barytes 58.50, sulph. acid 29.83, silex 4.0, alumine 2.0, water 3.0;=97.33.

Some specimens of this variety appear to be partially disintegrated.

CURVED LAMELLAR SULPHATE OF BARYTES.* In this subvariety the foliæ are curved, and sometimes unite in a point, like the petals of a flower; hence in some specimens the fracture has a fibrous, radiated, or even splintery aspect. Its masses, though usually amorphous, are sometimes globular or reniform; and, in some instances, different colors appear in stripes.

CRESTED SULPHATE OF BARYTES.† This is merely an aggregation of thin tables, whose edges are rounded and indented.

2. COLUMNAR SULPHATE OF BARYTES.‡ It occurs in long, acicular prisms, collected into little bundles or columnar groups, and sometimes intersecting each other confusedly; the surface is deeply and

* Krumm-schaaliger schwer spath. WERNER. Curved lamellar heavy spar. JAMESON.

† Baryte sulfatée crêtée. HAUY. BRONGNIART.

‡ stangen spath. WERNER. Columnar heavy spar. JAMESON. Baryte sulfatée bacillaire. HAUY. BRONGNIART.

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longitudinally striated, and has a pearly lustre. It is translucent, and its color is white, either pure, or tinged with yellow, &c.

This variety strongly resembles some specimens of carbonate of lead; but may be distinguished, as already mentioned.

3. RADIATED SULPHATE OF BARYTES.* It is found in roundish masses, of a moderate size, having a rough or uneven surface. This roughness of the surface appears to arise from the projecting edges of the numerous crystals, of which these masses are composed. Its fracture is fibrous, and has a resinous lustre; the fibres are broad and more or less distinctly radiate from a centre. In some specimens the fracture is foliated in certain directions. It is strongly translucent; and its color exhibits different shades of gray.

The phosphorescent property of this variety has been long known. To exhibit this property, the mineral is calcined, and reduced to powder; this powder, by means of gum water, is formed into little cylinders or cakes, which, after exposure to the light, become capable of shining in the dark.

It has been found at Monte Paterno, near Bologna, in Italy, imbedded in argillaceous marl, in which it seems to have been formed. The surface of detached masses is sometimes smooth, in consequence of their having been rolled.

4. FIBROUS SULPHATE OF BARYTES.† This variety is mentioned by Karsten. It occurs in reniform or tuberose masses, composed of diverging fibres. Its color is brown; its external lustre resinous; and its spec. grav. only 4.08.—It has been found at Neu-Leiningen, in the Palatinate.

5. CONCRETED SULPHATE OF BARYTES.‡ This occurs in reniform, undulated, or stalactical concretions. These stalactites are sometimes bent and twisted in a singular manner; and, from some resemblance to the intestines, have received the name of tripe stone. Its zones sometimes alternate with those of fluate of lime. In some tubular stalactites the cross fracture is fibrous, and the longitudinal fracture foliated. It sometimes receives a good polish.

It has been found in the mines of Saxony and Derbyshire;—also near the warm springs of Liege in fibrous concretions.

Fine specimens, found at Wieliczka, and supposed to belong to this variety, are said, on the authority of Klaproth, to be anhydrous sulphate of lime.

* Baryte sulfatée radiée. HAUY. BRONGNIART. Bologneser spath. WERNER. Bolognese spar. JAMESON.

† Baryte sulfatée fibreuse. BRONGNIART.

‡ Baryte sulfatée concrétionnće. HAUY. BRONGNIART.

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6. GRANULAR SULPHATE OF BARYTES.* It is always in amorphous masses. Its structure is granular, and the grains are usually small. Its fracture is most commonly foliated, sometimes a little splintery, and has a strongly glimmering and pearly lustre. It is feebly translucent, and sometimes of a beautiful snow white color; it is also gray, or yellowish.

According to Klaproth, it contains barytes 60, sulph. acid 30, silex 10.

It strongly resembles some granular limestones, but is easily distinguished by its greater spec. gravity.

Lamellar, granular, and compact Sulphate of barytes bear to each other relations, similar to those existing between lamellar, granular, and compact carbonate of lime.

7. COMPACT SULPHATE OF BARYTES.† This variety usually appears in amorphous masses; sometimes also nodular or reniform. Its fracture is earthy, uneven, or splintery, and is nearly or quite dull. It is opaque or perhaps translucent at the edges; and its common colors are white or gray, often tinged with yellow.

The substance, known in Derbyshire and other parts of England by the name of cawk, sometimes belongs to this variety; and sometimes, according to Kirwan, its structure is lamellar or fibrous. It is found in mines, interspersed among the ores.

8. EARTHY SULPHATE OF BARYTES.‡ This occurs in coarse, earthy particles, usually cohering a little. They feel rough; and their color is a dull white, often with a shade of yellow, &c. Their great spec. grav. however is perceptible.

It is a rare variety. Near Freyberg, in Saxony, it invests crystallized Sulphate of barytes.

SUBSPECIES 1. FETID SULPHATE OF BARYTES.§

This mineral is either compact, or has a foliated structure. By friction or the application of heat, it exhales a fetid odor, resembling that of sulphuretted hydrogen. Its color is gray of different shades; and its spec. grav. is sometimes only 2.66. (KIRWAN.)

A specimen from Andrarum, in Scania, yielded Bergman sulphate

* Körniger schwer spath. WERNER. Granular heavy spar. JAMESON. Baryte sulfatée grenue. BRONGNIART.

† Dichter schwer spath. WERNER. Compact heavy spar. JAMESON. Baryte sulfatée; compacte. HAUY. BRONGNIART.

‡ Schwer spath erde. WERNER. Heavy spar earth. JAMESON. Baryte sulfatée terreuse. BRONGNIART.

§ Baryte sulfatée fétide. HAUY. BRONGNIART.

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of barytes 38, silex 33, sulphate of alumine 22, sulphate of lime 7, mineral oil 0.3:= 100.5.

At Kongsberg, in Norway, it accompanies ores of silver.—In the United States it is found in Virginia, Albemarl Co. both lamellar and compact, of a lead gray color. (SEYBERT.)

(Geol. sit. of the species.) Sulphate of barytes, although not a rare mineral, is seldom found in large masses. It never constitutes whole mountains, and has but rarely been seen in beds. It usually occurs in veins, which may traverse primitive, transition, or secondary rocks; the veins are often large and rich in ores. This mineral frequently accompanies the sulphurets of zinc, lead, iron, copper, antimony, and mercury, and other ores. It is said to be rarer in granite, than in rocks of a later formation.

(Localities.) Sulphate of barytes is found in most countries, where mines have been worked. Very fine crystals are obtained in the mines of Hungary, Saxony, &c.

In the United States. At the lead mines of St. Genevieve, on the western bank of the Missisippi, in tabular crystals. (MEADE.)—In North Carolina, in Buncomb Co. in argillaceous slate.—In Virginia, at Austin's lead mine, on the great Kanhaway;—at Fincastle, &c.—In Maryland, at Liberty, in Frederick Co. with gray copper;—also in Washington Co.—In Pennsylvania, at the Perkiomen lead mine, 25 m. west from Philadelphia;—also in large quantities in secondary rocks at the west foot of the Blue Ridge, Bedford Co. (WISTER.)— In New Jersey, near Newton, Sussex Co. it occurs both in lamellar masses and tabular crystals; the vein traverses limestone, being inclined to the horizon at about 40°, and in its vicinity are found detached masses of the Sulphate of barytes, containing a spheroidal nucleus of chalcedony, quartz, limestone, &c. 5 or 6 inches in diameter. (CHILTON.)—Also on the west side of Paulin's Kill, not far from the locality last mentioned, is another vein of this Sulphate.—In Connecticut, at Cheshire, 15 m. north from New Haven, it occurs in foliated masses with quartz, sandstone, and the carbonates of lime and copper;—also in lamellar rolled pieces in a rivulet, passing through Berlin and Farmington. (SILLIMAN.)—In Massachusetts, at Hatfield, Hampshire Co. it exists both in tabular crystals and foliated masses; the veins are narrow at the surface, but become wider at the depth of a few feet; they traverse granite or gneiss, and are inclined to the horizon at about 40°. (GORHAM.)— Also at the lead mine in Southampton, 8 m. southwest from Northampton;—also at Middlefield, in Hampshire Co. where both the lamellar and granular varieties occur.

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(Uses.) It is sometimes employed as a flux in metallurgic operations; also in chemistry, and in some medical preparations. It is said to be a good base for water colors.

SPECIES 2. CARBONATE OF BARYTES.*

This species, like the preceding, has a very great specific gravity, varying from 4.29 to 4.33. Its structure is usually fibrous; its longitudinal fracture is shining and intermediate between fibrous and foliated, but its cross fracture is undulated, uneven, or splintery, with a resinous lustre, less shining than that of the former fracture.

This mineral is usually in small, fibrous masses. Its crystals are rare, generally imperfect, and attached to the same substance in a massive state. They are commonly six-sided prisms, terminated by six-sided pyramids, the vertices being often truncated. M. Haüy has described three modifications of the primitive form, which is a rhomb slightly obtuse. It is sometimes in concretions, or in an earthy state.

It is strongly translucent, and usually of a light yellowish gray color, sometimes whitish, or with a tinge of green. Its hardness is about equal to that of the preceding species.

(Chemical characters.) It effervesces, and, if pure, entirely dissolves in diluted nitric or muriatic acid. When nitric acid is employed, a white deposite usually appears, while the solution is going on. Before the blowpipe it decrepitates, and easily melts into a kind of enamel; but does not lose its carbonic acid.

When pure, it is composed, according to Klaproth, of barytes 78, carbonic acid 22. The native specimens are sometimes contaminated with a little alumine, carbonate of strontian, &c.

(Distinctive characters.) Its effervescence and solution in diluted acids distinguish it from the sulphates of barytes and strontian.— It has a greater spec. grav. than carbonate of strontian; and further, if a small quantity of the solution of Carbonate of barytes in nitric acid be added to alcohol, it gives to the flame of the latter a yellowish tinge; whereas, if carbonate of strontian be treated in a similar manner, a purple flame is produced. The same distinction may be observed by burning paper, previously dipped in these solutions.

(Geological situation and Localities.) Carbonate of barytes was discovered at Anglesark, in Lancashire, England, by Dr. Withering, in honor of whom it has been called Witherite. It is a rare mineral, and has been found only in small quantities. At Anglesark it is contained principally in the upper part of a vein of sulphuret of lead,

* Baryte carbonatée. HAUY. BRONGNIART. Witherit. WERNER. Witherite. JAMESON. Barolite. KIRWAN. La Witherite. BROCHANT.

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traversing sandstone, &c. and accompanied by sulphate of barytes, &c. It here occurs in spherical masses, whose surfaces are covered with little projections, arising from the union of pyramids, which terminate the prisms, of which these balls are composed.—In Styria it is sometimes in an earthy state, investing crystals or masses of the same substance.

(Remarks.) Its action on the animal system is extremely powerful; operating in doses of a few grains, as a fatal poison to dogs. The native Carbonate is much more powerful, than the artificial, when received into the stomach; for the latter in large doses excites vomiting only, but is not fatal.

GENUS II. STRONTIAN.

This genus, like the preceding, has only two species, the sulphate and carbonate of strontian, which, in most of their characters, resemble the salts of barytes. There is, indeed, a remarkable similarity between the two sulphates, and between the two carbonates of barytes and strontian.

SPECIES 1. SULPHATE OF STRONTIAN.*

The great weight of this mineral is its most striking physical character; its spec. grav. extending from 3.58 to 3.95. The forms of its crystals closely resemble those of the sulphate of barytes, but differ a little in the quantity of their angles. We here see the importance of an accurate measurement of the angles of crystals in discriminating minerals. The primitive form, like that of the sulphate of barytes, is a four-sided prism (Pl. III, fig. 5.); its bases also are rhombs, but with angles of 104° 48′ and 75° 12′, and the ratio of one side of the base is to the height as 114 to 113. Eight secondary forms have been described by Haüy. Its integrant particles are triangular prisms.

Its hardness is a little less, than that of fluate of lime, but rather exceeds that of sulphate of barytes. It possesses double refraction.

(Chemical characters.) The blowpipe melts it, and the globule thus produced often excites a slightly sourish taste. It usually communicates to the blue flame of the blowpipe a purple or reddish tinge, more or less sensible.

A crystallized specimen from Sicily yielded Vauquelin strontian 54, sulphuric acid 46. In the fibrous variety from Pennsylvania Klaproth found strontian 58, sulph. acid 42.

(Distinctive characters.) This mineral may be distinguished

* Strontiane sulfatée. HAUY. BRONGNIART. Celestin. WERNER. Celestine JAMESON. La Célestine. BROCHANT.

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from the carbonates of strontian and barytes by the effervescence and solution of the two last in nitric acid, especially if diluted. Sometimes, however, effervescence appears in the Sulphate of strontian in consequence of the intermixture of carbonate of lime, but it soon ceases.—To distinguish this salt from the sulphate of barytes, see the last named species.

Var. 1. FOLIATED SULPHATE OF STRONTIAN.* It occurs both massive and regularly crystallized. Its crystals are usually four or six-sided prisms, variously modified, and terminated by 2,4, or 8 sided summits, but less frequently compressed into tables, than those of the sulphate of barytes. Among its more common forms is an oblique four-sided prism, terminated at both extremities by four faces, standing on the lateral edges; two of these faces meet in a line, and contain an angle of 104° 48′.—Very frequently the preceding crystal has its obtuse lateral edges truncated, thus becoming a six-sided prism (Pl. III, fig. 6.). The crystals are often long and slender, and collected into fascicular groups; their surface has a strong lustre, but they are seldom transparent. When massive, it is only translucent.

The fracture is foliated and glistening; and the color is some shade of blue, or milk white, and sometimes gray, or reddish.

This variety is abundant near Bristol, England.—Very fine crystals are obtained from Sicily, where they occur in cavities in beds of native sulphur, which alternate with those of sulphate of lime.

2. FIBROUS SULPHATE OF STRONTIAN.† It presents itself in fibrous masses, composed of acicular prisms or fibres, applied to each other, usually parallel, but sometimes diverging. In one direction its fracture is sometimes foliated. It is more or less translucent; and its color varies from sky blue to bluish gray, or even milk white. It is said to lose its color in cabinets. (JAMESON.)

This variety is rare. It sometimes occurs in thin beds or layers, like fibrous gypsum, its fibres being perpendicular to the sides of the bed.

In the United States it has been found near Frankstown, in the Bald Eagle mountain, Huntingdon Co. Pennsylvania, where it is said to exist in layers about one inch thick between the strata of a brownish gray slate; its color is a fine light blue. (SEYBERT.) Sulphate of strontian is supposed to have been found in small quantities in gneiss, near Baltimore; but the writer knows not of which variety.

* Blättriger Celestin. WERNER. Foliated Celestine. JAMESON. Strontiane sulfatée cristallisée. BRONGNIART.

† Fasriger Celestin. WERNER. Fibrous Celestine. JAMESON. Strontiane sulfatée fibreuse. HAUY. BRONGNIART.

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SUBSPECIES 1. CALCAREOUS SULPHATE OF STRONTIAN.*

This subspecies is found in masses usually spheroidal and compressed, and frequently of the size of a man's head. In the interior they are often divided into prisms by interstices, which are sometimes lined by small crystals of the same substance. It has a dull, splintery fracture, a yellowish or bluish gray color, and is usually opaque.

It has been found only at Montmartre, near Paris; and is imbedded in argillaceous marl. It contains nearly 9 per cent, of carbonate of lime.—To the eye it often much resembles compact limestone.

The geological situation of this species is not much known. It is in many cases accompanied by sulphur and sulphate of lime.

SPECIES 2. CARBONATE OF STRONTIAN.†

The specific gravity of this species varies from 3.40 to 3.67. It usually appears in masses, composed of diverging fibres, which are often in the form of fascicular groups. The fracture, perpendicular to the direction of the fibres, is uneven or splintery, with a resinous lustre. It also occurs in hexaedral prisms, or in acicular crystals, grouped in the cavities of massive Carbonate of strontian.

It is a little harder than carbonate of barytes; is more or less translucid; and its usual colors are greenish or yellowish white, or nearly apple green.

(Chemical characters.) It communicates a purple or reddish purple color to the flame of the blowpipe; and, when gently heated by this instrument, it swells and sends out minute filaments, of which the extremities only are melted. The fragment itself is infusible, but loses its color. In nitric acid it dissolves with effervescence; and paper, when dipped in this solution and dried, burns with a purple flame.

It is composed, according to Klaproth, of strontian 69.5, carbonic acid 30.0, water 0.5. By the analysis of Dr. Hope the proportions are strontian 61.21, carb. acid 30.20, water 8.59.

(Distinctive characters.) This mineral strikingly resembles the carbonate of barytes; but the latter has a greater spec. gravity, does not send out filaments before the blowpipe, and easily melts without Changing the color of the flame.

(Localities.) This mineral was first discovered at Strontian, in Scotland, in a vein traversing gneiss; it is there accompanied by sul-

* Strontiane sulfatée calcarifère. HAUY. Strontiane sulfatée terreuse. BRONGNIART.

† Strontiane carbonatée. HAUY. BRONGNIART. Strontianit. WERNER. Strontiane. JAMESON. Stronthianite. KIRWAN. La Strontianite. BROCHANT.

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phuret of lead, carbonate of barytes, &c. Humboldt has since brought it from Peru; but it is a rare mineral.

It does not possess those poisonous properties, which belong to the carbonate of barytes. (BROCHANT.)

GENUS III. LIME.

This genus embraces nine species, some of which are extremely abundant, and important in their uses. It will be recollected, that the term salt is applied to minerals of a certain composition, independent of physical characters. Hence it is, that many salts in this genus exhibit the properties of those substances, usually called stones.

SPECIES 1. ARSENIATE OF LIME.*

The physical characters of this mineral will hardly enable one to distinguish it. It has hitherto been found in acicular crystals or fibres, which are commonly united either in bundles, or in mammillary or globular masses, or in crusts. The fibres diverge, and sometimes radiate from a centre. It is easily broken, and the fracture has a silken lustre. The more distinct crystals are translucid. Its true color is milk white or snow white; but, from the presence of arseniate of cobalt, its surface is very frequently violet or reddish white. Its spec. gravity is 2.64.

(Chemical characters.) It is insoluble in water; but dissolves in nitric acid without effervescence. Before the blowpipe the arsenic acid is volatilized with the odor of arsenic, but the lime remains pure. Klaproth has obtained from it lime 25.00, arsenic acid 50.54, water 24.46.

(Distinctive characters.) From carbonate of lime it is distinguishable by the blowpipe, and its want of effervescence in nitric acid. —From the white oxide of arsenic, by its insolubility in water, and partial volatility.

(Localities.) It is a rare mineral, and has been seldom observed. Near Wittichen in Suabia, it is disseminated in the fissures of granite, and is accompanied by the arseniate of cobalt, and the sulphates of lime and barytes.

SPECIES 2. NITRATE OF LIME.†

The taste of this salt is sharp and bitterish. It is found native in

* Chaux arseniatée. HAUY. BRONGNIART. Arsenik blüthe. WERNER. Arsenic Bloom. JAMESON. Pharmacolite. BROCHANT.

† Chaux nitratée. HAUY. BRONGNIART. Nitrated calx. KIRWAN.

17

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efflorescences, or in delicate needles, often united in little silken tufts, or in a state of powder, disseminated in earths.

It is very deliquescent, and extremely soluble in water. On burning coals it slowly melts, and slightly detonates, as it dries, during which it loses its acid. The powder, remaining after calcination, does not attract moisture from the air, and is phosphorescent in the dark.

It is composed of lime 32.00, nitric acid 57.44, water 10.56. (KIRWAN.)

From nitrate of potash it may be distinguished by its taste and deliquescence.

(Geological situation.) This salt almost always accompanies the nitrate of potash; and, like that salt, is daily formed, when circumstances are favorable. Hence it is often found efflorescing on walls, in caverns, near stables, &c. and on calcareous rocks, especially if in the vicinity of decomposing vegetables. The earths of calcareous caverns are often richly impregnated with this salt. It sometimes exists in mineral waters.

In the United States, it is abundant in the calcareous caverns of Kentucky, &c. (See nitrate of potash, for this locality.)

SPECIES 3. PHOSPHATE OF LIME.*

This species, though perfectly well characterized, embraces several varieties, some of which exhibit physical characters, not common to the whole species. When crystallized, which is most frequently the case, its forms are prismatic, and present either a six-sided prism, or some modification of that form. Indeed its primitive form is a regular hexaedral prism, in which one side of the base is to the height nearly as 10 to 7. Seven secondary forms have been described by Haüy. Its integrant particles are equilateral, triangular prisms. (Introd. 46.)—It is a little harder than fluor spar, but does not strike fire with steel. Its spec. gravity usually lies between 3.02 and 3.21. Most of its varieties phosphoresce, when their powder is thrown on hot coals.

(Chemical characters.) In the nitric and muriatic acids it dissolves slowly, and without effervescence, or barely with the extrication of a few bubbles. Sometimes, however, foreign ingredients cause the earthy variety to effervesce a little. Before the blowpipe it is infusible.

The first variety (Apatite) yielded Klaproth lime 55, phosphoric

* Chaux phosphatée. HAUY. BRONGNIART. Phosphorite. KIRWAN.

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acid 45. In the second variety (Asparagus stone) Vauquelin found lime 54.28, phosphoric acid 45.72.

(Distinctive characters.) Its solubility in acids and inferior hardness may serve to distinguish it from the chrysoberyl, tourmaline, topaz, chrysolite, beryl, emerald, and some varieties of quartz, all of which it sometimes more or less resembles, especially the emerald, beryl, and chrysolite.—From carbonate of lime it differs by its greater hardness and want of effervescence in acids;—and it does not, like the fluate of lime, when its powder is thrown into warm sulphuric acid, yield a gas, capable of corroding glass, unless from the accidental presence of a small quantity of that salt.

Var. 1. APATITE.*JAMESON. This variety, usually in crystals, sometimes presents a low six-sided prism, the primitive form.—The lateral and terminal edges, and even the solid angles of this prism are subject to truncation.—Sometimes all the edges are truncated (Pl. III, fig. 7.); the new lateral faces, produced by truncation, are often longitudinally striated, and the terminal edges are sometimes very deeply truncated. The prisms are generally short, and sometimes even tabular.

Its fracture, parallel to the base, is foliated, but, in the direction of the sides, it is uneven, or imperfectly conchoidal. It is translucent, sometimes almost opaque, and sometimes nearly or quite transparent and limpid. This mineral exhibits a great variety of colors, belonging to white, green, blue, yellow, red, violet, or brown, variously shaded and intermixed. On burning coals its powder phosphoresces.

The same gangue, which contains the crystals, often embraces grains or small granular masses, having a crystalline structure, but nearly or destitute of a regular form.

The Apatite occurs in veins, or is disseminated in granite, gneiss, or other primitive rocks. It is associated with quartz, feldspar, fluate of lime, garnets, the oxides of iron, tin, &c.

(Localities.) In the United States, the Apatite is not uncommon. In Maryland, near Baltimore, it exists in grains or hexaedral prisms in granite; its color varies from bluish green to lemon yellow. (GILMOR.)—In Pennsylvania, in various parts of the state, particularly in the granite and gneiss of Germantown, accompanied by the beryl, garnets, schorl, &c. it is both crystallized and massive, and often of a grass green color. (WISTER.)— In New York, at Anthony's

* Apatit. WERNER. Chaux phosphatée Apatite. BRONGNIART. The name of this variety is from the Greek,απαταω, to deceive; it having often been mistaken for other minerals.

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Nose, on the Hudson, in greenish yellow crystals, in pyrites. (WOODBRIDGE.)—In Connecticut, at Milford Hills, near New Haven, in imperfect, pale green crystals, in granite. (SILLIMAN.)—In Maine, at Topsham, pale green crystals of Apatite, often badly defined, but phosphorescing strongly on hot iron, are disseminated in granite; they are seldom found more than 3 or 4 inches below the surface of the granitic mass, which also abounds with garnets.*

2. ASPARAGUS STONE.† JAMESON. The name of asparagus stone has been given this variety in consequence of its so frequently exhibiting an asparagus green color. It is distinguished from the Apatite partly by its color, partly by its crystalline form, and more particularly by its want of phosphorescence on hot coals. It sometimes presents the primitive form, either perfect, or with truncated lateral edges, but most frequently the hexaedral prism is terminated by six-sided pyramids, whose faces correspond with the sides of the prism, and form with them an angle of 129° 14′; sometimes the lateral edges are truncated. These prisms are usually longer than those of the Apatite. It is sometimes in small crystalline masses without a regular form.

Its longitudinal fracture is often more distinctly foliated, than that of the Apatite, and its cross fracture sometimes less so. It is translucent, and frequently transparent. Beside asparagus green, it presents other shades of green, or is greenish white, or nearly gray, brownish, bluish, &c.

It is somewhat remarkable, that its powder does not phosphoresce on burning coals. It has however been observed, that the artificial phosphate of lime never phosphoresces.

(Localities.) This variety is found abundantly near Cape de Gate, in the province of Grenada, in Spain; its gangue is a decomposed stone, concerning which mineralogists are not agreed.—It is found near Vesuvius, mixed with idocrase.—Near Arendal, in Norway, it exists in crystals or small masses, of a brownish, or greenish blue color, in primitive rocks; these crystals have been called Moroxite.

In the United States, this variety is found in gneiss at Germantown, Pennsylvania; it is in hexaedral prisms, sometimes truncated on the lateral edges, but more frequently it is destitute of a regular form; its color is bluish green, sometimes gray; and on burning coals it does not phosphoresce. (GODON.)

* The writer is not confident, that some of the abovementioned localities do not belong to the next variety.

† Spargelstein. WERNER. Chaux phosphatée Chrysolithe. BRONGNIART.

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3. FIBROUS PHOSPHATE OF LIME. This variety, still rare, is sometimes in masses, composed of delicate fibres, collected into groups, and radiating from a centre. It is phosphorescent.

The supposed phosphate of lime, found at Dyce in Aberdeenshire, in masses, composed of pale greenish white, delicate fibres, having a silken lustre, and phosphorescing on hot coals, is said by Cabral de Mello to be composed of sulphate of lime 76.0, silex 17.0, magnesia 2.67, water 2.0, oxide of iron 2.33. (Nich. Jour. v. 36.)

4. AMORPHOUS PHOSPHATE OF LIME.* This variety has most commonly an earthy aspect; and occurs in masses more or less solid, whose surface often presents mammillary projections. Its fracture is nearly or quite dull, and is sometimes earthy, sometimes uneven, and sometimes imperfectly foliated. It is opaque; and its color is grayish or yellowish white, often diversified by spots or zones of a yellowish or brownish tinge. Its powder phosphoresces on burning coals with a very beautiful, greenish yellow light. It is phosphorescent even by friction in the dark.

According to Pelletier, it contains lime 59, phosphoric acid 34; the remainder being small quantities of the fluoric, carbonic, and muriatic acids, with a little silex and oxide of iron. Possibly these foreign ingredients may sometimes render it fusible.

It is found near Truxillo, in Estramadura, Spain, where it is deposited in beds, intermingled with quartz, and constitutes whole hills.

SUBSPECIES 1. SILICEOUS PHOSPHATE OF LIME.†

This differs from the preceding varieties by giving fire with steel. It occurs in porous masses, whose fracture is earthy, granular, or a little foliated. Its color is gray, shaded with violet. On hot iron it phosphoresces strongly.

It is found in certain tin mines of Bohemia.

SPECIES 4. FLUATE OF LIME.‡

The more common variety of this mineral may be easily recognised by the striking beauty of its colors, and the form and perfection of its crystals. But the most distinguishing characters of this earthy salt are found among its chemical properties.

Although sometimes amorphous, it is most commonly crystallized;

* Chaux phosphatée terreuse. HAUY. BRONGNIART. Phosphorit. WERNER. Phosphorite JAMESON.

† Chaux phosphatée silicifère. HAUY. BRONGNIART.

‡ Chaux fluatée. HAUY. BRONGNIART. Fluss. WERNER. Fluor. KIRWAN. JAMESON. La Fluor. BROCHANT.

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and the primitive form of its crystals is a regular octaedron, which may easily be obtained by mechanical division. (Introd. 39.) Thirteen secondary forms have been described. Its integrant particles are probably regular tetraedrons. Unlike most of the other calcareous salts, it has seldom or never occurred under any imitative form.

It may be scratched by iron, but is harder than crystallized carbonate of lime. Its spec. gravity varies from 3.09 to 3.20. When reduced to powder, and placed on hot coals, it almost invariably phosphoresces with a very beautiful light, commonly of a greenish or violet color. (Introd. 143.) It also shines in the dark by the friction of two pieces against each other.

(Chemical characters.) If sulphuric acid be poured on this mineral in a state of powder, and slightly heated, white fumes appear, having a pungent smell, and possessing the peculiar property of corroding glass. These fumes are fluoric acid, and, in connexion with the physical characters, will almost always enable us easily to determine the presence of Fluate of lime. It is insoluble in water. Before the blowpipe it usually decrepitates, and melts into a whitish, transparent glass.

According to Klaproth, it is composed of lime 67.75, fluoric acid 32.25.

From the carbonate and sulphate of lime it is easily distinguished by its greater hardness, and its chemical characters.

Var. 1. FLUOR SPAR.* JAMESON. (Foliated Fluate of lime.) This variety, though sometimes massive, is almost always regularly crystallized. Its crystals most frequently present the form of a cube, often perfect, and sometimes truncated on all its edges by planes, which form with the sides of the cube an angle of 185°.—Sometimes a bevelment is applied to the edges of the cube.—Sometimes all the solid angles of the cube (Pl. III, fig. 8.) are truncated; if the triangular planes a, a, produced by truncation, do not touch each other, the faces b, b are octagonal; if those planes touch only, as in the figure, the faces b, b become squares; but, if the truncating planes intersect, they then become hexangular, while the faces b, b remain squares. The structure of this crystal is easily explained. The cube is here a secondary form, constructed around an octaedral nucleus. But, the de-crements having ceased before the cube was completed, the crystal remains a cubo-octaedron, having six faces parallel to those of a cube, and eight faces parallel to those of an octaedron. The incidence of a on b is 125° 16′.—The dodecaedron with rhombic faces, and the prim-

* Fluss spath. WERNER. Chaux fluatée spathique. BRONGNIART.

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itive octaedron, sometimes truncated on all its edges, are among the rarest forms of this mineral.

These crystals are almost always extremely well defined, and often very large; the cube in some cases presenting a face of several square inches. Their surface is generally smooth with a strong lustre. They are often variously grouped.

Its fracture is always foliated, though sometimes imperfectly, and has usually a shining, vitreous lustre. The crystals easily yield to mechanical division, the laminæ separating in four directions, parallel to the faces of a regular octaedron. Its fragments are either tetraedral or octaedral, resulting from the directions of the natural joints just mentioned. Its transparency is extremely variable; most frequently perhaps it is strongly translucent, but many of its crystals, especially the cubes, are transparent.

Its colors are uncommonly numerous; and, by the beauty, which they confer on its specimens, deserve attention. It is sometimes limpid, but most frequently presents some variety of white, gray, violet, blue, green, yellow, red, brown, or black. Different colors often meet in the same specimen, and are arranged in spots, zones, &c. Certain varieties, from resemblance in color, have been called false gems; thus there is the false amethyst, sapphire, emerald, &c.

Some varieties of this Fluate are rendered interesting by the color of their light, while phosphorescing. One, of a violet color, from Siberia, when placed on burning coals, does not decrepitate, but shines with an emerald green light; it has hence received the name of Chlorophane.

Another interesting variety, from Siberia, of a pale violet color with greenish spots, is made to shine, when in small fragments, with a whitish light, by the heat of the hand only; at 212° Fahr. its phosphorescence is green, and with a still stronger heat it becomes blue. But in all cases, when phosphorescence ceases, the color of the mineral has disappeared.

MASSIVE PHOSPHATE OF LIME. This subvariety is not uncommon; it has a foliated fracture, and is the result of crystallization. Its masses are often composed of distinct concretions, sometimes granular; and sometimes they are prismatic and intersected by others in the form of zones.

Very fine crystals are obtained in Derbyshire, England; indeed this mineral is sometimes called Derbyshire spar. Rose colored octaedrons have been found near Mont Blanc.

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2. COMPACT FLUATE OF LIME.* This variety, which is rare; always occurs in compact masses, whose fracture is even, imperfectly conchoidal, or a little splintery, with a feeble, resinous lustre. It is more or less translucent; and its usual colors are gray, greenish gray, or brown, sometimes diversified by other colors in spots.

It often resembles certain varieties of compact limestone or petrosilex.

3. EARTHY FLUATE OF LIME.† This is in friable masses, composed of small grains, which are sometimes arranged in parallel layers. Its color is greenish white, or has a tinge of violet.

SUBSPECIES 1. ARGILLACEOUS FLUATE OF LIME.‡

This has been found crystallized in cubes, opaque, and of a gray color, near Buxton, in England. These crystals contain considerable quantities of ferruginous clay, which however has not affected the form. They are sometimes corroded.

(Geol. sit. of the species.) Fluate of lime almost always occurs in veins. It has however been observed in beds; and, in a few instances, appears to enter into the composition of primitive rocks. (BRONGNIART.) These veins are obviously of different ages. In the most ancient, this mineral is associated with ores of tin; while in those, which appear to be more recent, it is connected with the sulphurets of lead, zinc, iron, and copper. These sulphurets, especially that of iron, are often disseminated in masses of Fluate of lime, or traverse them in a zigzag direction, and, by their metallic lustre, contribute much to the beauty of certain specimens. The veins are often very large, and composed almost entirely of Fluate of lime. In addition to metallic substances, however, it is often associated with quartz, the carbonate and phosphate of lime, sulphate of barytes, &c.—In Derbyshire, veins of Fluate of lime traverse compact limestone, containing shells. At Oxford, England, is a bivalve shell, lined with imperfect crystals of Fluate of lime. (KIDD.)

(Localities.) In the United States. Mr. Bradbury, an English naturalist, has found it, both limpid and violet, apparently in rolled pieces, on the banks of the Missouri. (SILLIMAN.)—In Virginia, near Woodstock or Miller's town, Shenandoah Co. in small, loose masses in the fissures of a limestone, containing shells. (BARTON.) —In Maryland, on the west side of the Blue Ridge, with sulphate of

* Chaux fluatée compacte. HAUY. BRONGNIART. Dichter Fluss. WERNER. Compact Fluor. JAMESON.

† Chaux fluatée terreuse. HAUY BRONGNIART. Fluss crde WERNER.

‡ Chaux fluatée aluminifère HAUY. BRONGNIART.

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barytes. (HAYDEN.)— In New Jersey, near Franklin Furnace, in Sussex Co. disseminated in lamellar carbonate of lime, and accompanied with mica and carburet of iron;—also near Hamburg, in the same Co. on the turnpike to Pompton, in a vein of quartz and feldspar. (BRUCE.)—In New York, near Saratoga springs, in limestone; it is nearly colorless and penetrated by pyrites.—In Vermont, at Thetford.—In Connecticut, at Middletown, in a vein, and is accompanied by the sulphurets of lead, zinc, and iron. (BRUCE.)—In Massachusetts, at the lead mine in Southampton, where it is imbedded in sulphate of barytes, or granite; its colors are green, purple, &c.—In New Hampshire, at Rosebrook's Gap, in the white Mountains, in small, detached pieces. (GIBBS.)

(Uses.) It is sometimes employed as a flux for certain ores; and hence the name of Fluor. In some places, particularly in Derbyshire, it is cut into plates, vases, &c. for ornamental purposes, and polished; it is sometimes extremely beautiful. It also furnishes the fluoric acid, which has recently been employed with advantage for engraving on glass. (See Bruce's Min. Jour. v. i. p. 33.)

SPECIES 5. SULPHATE OF LIME.*

Gypsum.

The examination of this mineral is interesting in many respects, particularly on account of its uses in agriculture and the arts. It is often in amorphous masses; and not unfrequently in crystals, whose primitive form is a four-sided prism (Pl. III, fig.9.), whose bases are parallelograms with angles of 113° 8′ and 66° 52′; the sides of the base and the height of the prism are as the numbers 12, 13, 32. Of this nucleus, which is easily obtained, five modifications have been observed. The integrant particles have the form of the nucleus.

It possesses double refraction, which must be observed in the manner already prescribed for sulphate of barytes. In hardness it is inferior to crystallized carbonate of lime, for, in general, it may be scratched even by the finger nail. Its spec. gravity usually lies between 2.26 and 2.31; but is sometimes as low as 1.87, according to Kirwan.

(Chemical characters.) By the blowpipe it may be melted, though not very easily, into a white enamel, which, in a few hours, falls into powder. If the fragment is crystallized, it not only whitens instantly and becomes brittle, but very easily exfoliates in one direction. In order, however, to melt these laminæ, the flame should play in the di-

* Chaux sulfatée. HAUY. BRONGNIART. Gypsum. KIRWAN.

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rection of the laminæ against their edges, and not perpendicularly to their surface. These different effects, according to the different directions of the flame, are supposed by Haüy to arise from the great length of the integrant particles, compared with the dimensions of their bases; for the laminæ are composed of an indefinite number of these little prismatic solids, which must necessarily cohere more strongly in the direction of their length or sides, than in that of their bases. It does not effervesce with acids, unless it be impure. It is soluble in about 500 times its weight of water. It does not burn to lime.

Sulphate of lime is composed of lime 32, sulphuric acid 46, water 22. (BERGMAN) It is sometimes contaminated by small quantities of carbonate of lime, alumine, silex, and oxide of iron.

(Distinctive characters.) Its inferior hardness, together with its chemical characters, will serve to distinguish it from the carbonate, phosphate, and fluate of lime.

The different structures and the extent of this species require a number of subdivisions.

SUBSPECIES 1. SELENITE.* JAMESON. (Foliated Sulphate of lime.)

Though always crystallized, it occurs both in foliated masses, and in regular crystals. One of its most simple forms is a tabular solid or low prism, whose bases are rhomboidal with angles of 126° 52′ and 53° 8′, and whose narrow sides are all bevelled by trapezoidal planes, which, on two opposite sides, are inclined to each other in an angle of 143° 53′, but, on the other two sides, in an angle of 110° 36′.— This crystal is sometimes elongated (Pl. III. fig. 10.), and then assumes a prismatic form, having six sides, but all the angles remain the same.—Sometimes the preceding crystal is terminated by four planes (Pl. III, fig. 11.).—There is also a prism with eight sides, terminated by four-sided summits. The trapezoidal faces of the preceding crystals are in general longitudinally striated.

The crystals of Selenite are frequently united, or collected into groups of various forms. Sometimes a hemitrope is formed; and sometimes large crystals are penetrated by smaller.

The geometrical beauty of the crystals is often much impaired by the bluntness of their edges and angles, and the convexity of their faces. This convexity is often so great, that the crystal becomes lenticular; and two lenticular crystals frequently unite in such manner as to form a re-entering angle on one side. Sometimes these lenses are grouped in the form of a crest, or like the petals of a rose, or in stars, &c.

* Chaux sulfatée Selenite. BRONGNIART. Fraueneis. WERNER.

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Its fracture is foliated, shining or splendent, and sometimes pearly. The laminæ separate in three directions, parallel to the sides of the primitive form, but most easily in the direction of the bases; when thin, they are flexible, but not elastic, like mica; they break into rhomboidal fragments. Though sometimes translucent, it is most commonly transparent. Some specimens are limpid, but its color is usually white, either pure, or with shades of gray or yellow, and may be reddish, violet, brown, &c. The surface is sometimes irised, or pearly.

Var. 1. MASSIVE SELENITE.* This variety is in masses, whose structure is laminated, or sometimes only lamellar. The laminæ are often large and transparent, easily yielding to mechanical division. Sometimes they are arranged in clusters or radiate from a center. As they become smaller they constitute masses, which gradually pass into granular gypsum, to which they have the same relation, as calcareous spar to granular limestone.

The laminæ of Selenite have sometimes a specular surface, extremely beautiful.

ACICULAR SELENITE. This is found in acicular crystals, particularly in old mines, or in volcanic countries, and appears to be of recent formation.

(Geological situation.) The crystals of Selenite are very often disseminated in beds of clay or marl. But their color does not appear to have been affected by that of the clay or marl, except in a few cases, where the coloring matter has obviously entered by filtration. When massive, and sometimes when in crystals, Selenite is associated with extensive beds or strata of gypsum, and sometimes with carbonate of lime, &c. In a few instances it has been observed in veins, with sulphuret of lead, in primitive rocks.

SUBSPECIES 2. GYPSUM.†

The term Gypsum, though sometimes extended to the whole species, is more frequently appropriated to those varieties of Sulphate of lime, which have a fibrous or granular structure, being the result of a confused crystallization, and to those, whose texture is compact, or earthy.

Var. 1. FIBROUS GYPSUM.‡ Its fibres are parallel and often curv-

* This includes a part of the blettriger Gips of Werner, and the foliated Gyps of Jameson.

† Gips. WERNER. Gyps. JAMESON. Chaux sulfatée Gypse. BRONGNIART.

‡ Fasriger Gips. WERNER. Fibrous Gyps. JAMESON. Chaux sulfatée fibreuse. HAUY. Chaux sulfatée Gypse fibreux. BRONGNIART.

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ed. Though sometimes coarse, they are often fine and delicate, glistening with a pearly or satin lustre; some specimens, like a mirror, reflect the flame of a candle. In some cases the fracture is foliated in one direction. It is sometimes in stalactites or concretions.— It is usually translucent, and its colors are white or gray, often more or less shaded with yellow, red, &c. sometimes in spots or veins.

It most frequently occurs in thin beds or layers.

2. GRANULAR GYPSUM.* This is a common variety. It occurs in masses, having a granular structure; but the grains are extremely variable in their size. Sometimes, when the grains are very small, it is friable, like certain sandstones.

Its fracture is both granular and foliated with a moderate lustre. Its fragments are translucent, sometimes at the edges only; and its color is some variety of white, gray, or red, or even of yellow, green, brown, or black, or is spotted, &c.

This variety often strongly resembles granular limestone, but may be distinguished by its inferior hardness, which permits it to be scratched by the finger nail.

According to the size of its foliæ or grains this variety passes, on the one side, into massive Selenite, and, on the other, into the following variety.

3. COMPACT GYPSUM.† This is found in compact masses of a fine grain, whose fracture is even, or splintery, and nearly or quite dull, or sometimes a little foliated. It is nearly opaque, and its colors are commonly white or gray, sometimes shaded with yellow, red, &c. or variously mingled. Its spec. gravity is sometimes only 1.87. (KIRWAN.) It is sometimes in concretions.

Compact Gypsum, and some varieties of granular Gypsum are employed in sculpture and architecture under the name of alabaster. The same name is also given to certain varieties of carbonate of lime. It may be well to employ the terms gypseous and calcareous alabaster.

4. BRANCHY GYPSUM.‡ This rare variety occurs in little branches, singularly curled or twisted, and collected into little tufts. M. Brongniart supposes it to be formed, like the coralloidal variety of the arragonite. It is found near Matlock, in Derbyshire, &c.

* Blættriger Gips. WERNER. Foliated Gyps. JAMESON. Chaux sulfatée Gypse compacte. BRONGNIART.

† Dichter Gips. WERNER. Compact Gyps. JAMESON. Chaux sulfatée compacte. HAUY. Chaux sulfatée Gypse compacte. BRONGNIART.

‡ Chaux sulfatée Selenite rameuse. BRONGNIART.

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5. SNOWY GYPSUM.* This is found in small, reniform or flattened masses, which have the aspect of snow. They are composed of very minute plates or spangles, and are easily reducible to powder. These little plates are snow white and pearly, resembling white talc; but they are not unctuous to the touch, like talc, and are more easily melted.

It is found in masses of Sulphate of lime; and sometimes adhering to lenticular crystals of selenite, as at Montmartre, near Paris. It may perhaps arise from the disintegration of massive selenite, at least in some cases.

6. EARTHY GYPSUM.† This undoubtedly results from the disintegration of some of the preceding varieties. It is composed of dusty or scaly particles, which resemble those of meal or chalk, and soil the finger a little. These particles are dull, and slightly cohering in small masses. Their color is gray or white with a tinge of yellow.

It is found in the cavities or fissures of other varieties of Gypsum, and also in those of other rocks in the vicinity of Gypsum. It appears to be of daily formation, being produced by the agency of rain water; for it is found more plentifully in wet than in dry seasons. It is a rare variety.

SUBSPECIES 3. PLASTER STONE.‡ (Plaster of Paris.)

This would not be entitled to a distinct notice, were it not for the foreign ingredients, which it contains, and which, in many instances, greatly improve it, as a cement. In order to render calcined Sulphate of lime a good cement, there must be present a certain quantity of quicklime. But the mineral, of which we now speak, sometimes contains the proper quantity of carbonate of lime to constitute a good cement after calcination. Hence it slightly effervesces with acids. Sometimes also it embraces clay or sand, which injures it as a cement. —Its texture is earthy or granular with coarse grains, and sometimes foliated. It is sometimes white, but it also presents various shades of other colors, arising from the presence of oxide of iron. At Montmartre, near Paris, it is yellowish.

(Geol. sit. of Gypsum.) This mineral, next to carbonate of lime, is more abundant, than any other earthy salt. It is sometimes depos-

* Chaux sulfatée niviforme. HAUY. Chaux sulfatée Gypse niviforme. BRONGNIART.

† Gips erde. WERNER. Gyps earth. JAMESON. Chaux sulfatée terreuse. HAUY. Chaux sulfatée Gypse terreux. BRONGNIART.

‡ Chaux sulfatée grossière. BRONGNIART. Chaux sulfatée calcarifère. HAUY.

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ited on the sides of primitive mountains at a considerable elevation; sometimes in vallies; and sometimes it constitutes whole hills, or exists in extensive strata at the surface of the earth, or at a great depth below.

There appears to be several distinct formations of this species, well characterized by their relative situation and accompanying minerals. In other words, Sulphate of lime is found among primitive, transition, and secondary rocks.

The oldest formation, or primitive Gypsum, is found resting on primitive rocks, or even contained within them. It is most frequently granular, sometimes lamellar, usually white, and often much resembles granular limestone. It is sometimes mixed with mica, talc, feldspar, &c. but never embraces clay, marl, nor remains of organic beings. This formation has been found in several parts of the Alps, between strata of mica slate, or gneiss, sometimes alternating with them, and accompanied by limestone, or hornblende slate.

Another formation of Gypsum appears to belong to transition rocks. It is sometimes associated with gray-wacke slate; (Von BUCH.) and, according to Brongniart, it often covers carbonate of lime, being frequently connected with the fetid limestone. But it is not obvious, where the last mentioned author draws his line of distinction between transition and secondary rocks; and it must be confessed, that the later transition and the older secondary rocks, when belonging to the same mineral species, do sometimes pass into each other by imperceptible shades.

But, in most cases, Sulphate of lime is undoubtedly of secondary or late formation. It occurs near the foot of primitive mountains or in vallies; and sometimes under plains, or forming hills of a moderate elevation, often at a great distance from primitive mountains. Its beds, either horizontal or inclined, are often very thick and not distinctly stratified. It is associated with compact limestone, which is often fetid; also with sandstone, muriate of soda, and almost always with strata of clay or marl, with which it usually alternates.—It has also been found in compact limestone, not associated with marl.

Quartz, borate of magnesia, garnets, arragonite, large masses of sulphur, and even hornstone, and fragments of compact limestone are sometimes imbedded in Gypsum. But this mineral is rarely connected with metals or coal.

Organic remains of fish, birds, and quadrupeds, and also of the vegetable kingdom sometimes occur in secondary Gypsum; but they are generally more abundant in the beds of marl, which separate those of Gypsum, or alternate with them. In this marl, shells are often found, though seldom in Gypsum.

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Secondary Gypsum undoubtedly exhibits several distinct formations, deposited at different periods of time, and capable of being marked by peculiar geological characters; but numerous observations are still wanting to complete our knowledge of its natural associations.

It is sometimes found lying immediately upon that, which is supposed to be the oldest secondary limestone. The beds of this Gypsum are frequently covered by a variegated sandstone; they contain both granular and compact Gypsum, mixed with selenite, and frequently alternate with fetid limestone. It is not unfrequently accompanied by muriate of soda, for its connexion with which, see that article.

Other deposites of Gypsum are found resting on this variegated sandstone just mentioned, or even alternating with it, and, at the same time, are covered by shell limestone. They contain both granular and fibrous Gypsum, often alternate with clay and marl, and are obviously of more recent formation, than those, which lie under the variegated sandstone.

Both the preceding formations are common in Germany.

Another formation of secondary Gypsum, apparently more recent, than either of the preceding, has been observed in the vicinity of Paris, and perhaps in one or two other places. This interesting deposite rises, in several instances, into small hills, of which Montmartre is the best known. It lies immediately over horizontal strata of a coarse grained shell limestone, and hence materially differs from the preceding formation, which lies underneath the same kind of limestone; it farther differs by not alternating with sandstone, and by not being fibrous.

This formation at Montmartre is not purely gypseous, but is composed of alternate strata of Gypsum, clay, and marl. The Gypsum is in fact divided into three principal masses by these marly strata; and each mass is further subdivided by thin strata of clay and marl. The highest of these three masses is peculiarly interesting. Its homogeneous beds discover a tendency to divide into prisms, altogether similar to those of basalt. Here also are found the skeletons and scattered bones of birds and unknown quadrupeds, also bones of tortoises, and a few shells, belonging to fresh water fish. Among the remains of quadrupeds are skeletons of mammiferous animals, which are unlike any now known to exist, and which do not occur in the lower masses. These organic remains are more solid and better preserved in the Gypsum, than in the marl.

Immediately on this Gypsum rest strata of marl, containing petrified trunks of palm trees, and some fresh water shells. It is hence evident, that this formation of Gypsum has been deposited from fresh water.

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Gypsum is sometimes found in efflorescences or concretions in volcanic countries.

In fine, Sulphate of lime is more or less disseminated in almost every soil. Hence it is frequently dissolved in the waters of springs and wells. Such waters are said to be hard, because they decompose solutions of soap, the acid of the Sulphate combining with the alkali of the soap.—It exists also in sea water.

(Localities.) It is unnecessary to cite any foreign localities of this mineral in addition to those, mentioned in the geological remarks. It occurs abundantly in Nova Scotia; but its geological situation the writer has been unable to ascertain.

In the United States. In Virginia, Sulphate of lime occurs near Abingdon, on Holstein river—also in fibrous masses near Preston's salt works. (SEYBERT.) In Maryland, in small quantities near Baltimore—and fine crystals of Selenite are found in the alluvial soil on Chesapeak Bay. (HAYDEN.)—In New Connecticut, at Poland, Trumbull Co. in fine crystals, resembling those from Oxford, England. (SILLIMAN.)—Near Niagara Falls, both Selenite and Gypsum occur in connexion with fetid limestone;(MITCHILL.) this Gypsum is sometimes snow white and granular.—In New York, Sulphate of lime is very abundant in several parts of the State, particularly in Onondago and Madison counties; also in the vicinity of Cayuga lake, whence, in 1812, 6000 tons of Gypsum were exported to Pennsylvania; (BECK.)—near Onondago it is sometimes laminated and specular, and the Gypsum of that vicinity has usually a dark color, sometimes nearly black; it is sometimes fibrous;—at Sullivan, the Gypsum is either brownish or white;—in the vicinity of Saratoga springs, Sulphate of lime is said to exist in limestone.—In Massachusetts, in small quantities at Milton, near Boston.

(Uses.) Sulphate of lime, particularly Gypsum, has been employed in several countries, as a manure for dressing the soil, and appears to be useful both on sandy and clayey soils. Its action on the soil, or the plant, is not yet perfectly well explained; but it probably operates in some degree, as a stimulant. In many parts of the United States it has been found an important article of manure in the cultivation of grasses, roots, and grain.

Sulphate of lime, both Gypsum and Selenite, is employed in the imitative and ornamental arts. We have already noticed the use of compact and granular Gypsum under the name Alabaster. It is, however, less durable and less valuable, than marble, for works in statuary.

This mineral, when deprived of its water of crystallization by cal-

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cination, constitutes plaster; and this plaster, when mixed with a certain quantity of quicklime, forms a good cement. But the finer kinds of plaster, especially that obtained by calcining selenite, being reduced to powder, and mixed with gum water, are employed for casting statues and busts in moulds, for taking impressions of medals, &c. and for stuoco and other ornamental works. In the stucco, various colors, previously ground in water, are introduced. All these works, when dry, are susceptible of a polish.

The temple of Fortune, called Seja, appears to have been built with some variety of sulphate of lime. It had no windows, but transmitted a mild light through its walls. (Pliny L. 36. c. 22.)

SPECIES 6. ANHYDROUS SULPHATE OF LIME.*

It is not many years, since the characters of this mineral, as a distinct species, were well established. It now appears, that a total absence of the water of crystallization is essential to this salt; and hence it is called anhydrous.†

It scratches crystallized carbonate of lime, and of course is considerably harder than the common sulphate of lime; indeed it is not very easily scratched by fluate of lime. When its structure is foliated and regular, the laminæ easily separate in three directions, at right angles to each other, thus giving a prism, whose bases are parallelograms, of which the sides are as 13 to 16. This primitive solid, which is nearly a cube, is further divisible into triangular prisms, showing the form of the integrant particles. Its spec. gravity is from 2.92 to 2.96.

(Chemical characters.) Before the blowpipe it does not whiten and exfoliate, like the preceding species, but the edges of small fragments are converted into a friable, white enamel. Its varieties are not equally fusible, and it is sometimes necessary to make the flame play on the edges of small fragments.

According to Vauquelin it is composed of lime 40, sulphuric acid, 60; Klaproth and other chemists have obtained similar results.

This substance sometimes absorbs water by exposure to the air, and passes to the state of a common sulphate of lime; and is then called epigene by Haüy. During this change, it is rendered more tender, its texture becomes less foliated, or nearly compact, and its specific gravity is reduced, sometimes to 2.31. The same specimen is sometimes only in part anhydrous, the other part having imbibed water.

* Chaux anhydro-sulfatée. HAUY. Chaux sulfatine. BRONGNIART. Muriacit. WERNER. Bardiglione. BOURNON.

† From the Greek Аνυδρος.

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Var. 1. CUBIC SPAR.* This variety occurs both in lamellar masses, and in crystals, whose usual form is a rectangular four-sided prism, differing little from a cube, and having its lateral edges sometimes truncated. The two opposite, broader faces of this prism often have a strong, pearly lustre.

Its structure and fracture are very distinctly foliated; its lustre Strong and often pearly; if, however, the fracture be not made in the direction of the natural joints, it is granular or uneven. It is more or less translucent, and sometimes limpid; its usual colors are milk white, or gray, sometimes with shades of yellow, red, or violet.

In the salt mines of Hall, in Tyrol, it is mingled with muriate of soda.—It sometimes accompanies sulphuret of lead, or magnetic iron. At Segeberg, in the Duchy of Holstein, it sometimes contains the borate of magnesia.

2. ANHYDRITE.† JAMESON. This variety scarcely differs from the preceding, excepting in its structure. It occurs in masses more or less compact, whose fracture is splintery and partly foliated, in consequence of interspersed laminæ; sometimes also its structure is fibrous. It is translucid, sometimes in small fragments only; and its colors are smalt blue, bluish white, milk white, gray, or violet red.

In the salt mines of Wieliczka, it is found mammillary, and in stalactites, which are often twisted, and were formerly supposed to be sulphate of barytes.

SUBSPECIES 1. SILICO-ANHYDROUS SULPHATE OF LIME.‡

Its structure is granular, much resembling that of some marbles. On hot iron it phosphoresces with an orange colored light. It is translucent at the edges, and its color is gray, sometimes with bluish veins. Its spec. grav. is 2.87.

It is easily fusible by the blowpipe, and contains 8 per cent. of silex.

This subspecies is found at Vulpino, near Bergamo, in Lombardy. It receives a good polish, and is employed as marble.

SPECIES 7. CARBONATE OF LIME.

On some accounts, this is the most interesting species, which the mineral kingdom contains. It exists more abundantly, than any oth-

* Wurfelspath. WERNER. Cube spar. JAMESON. Chaux sulfatine spathique. BRONGNIART.

† Anhydrit. WERNER. Chaux sulfatine compacte. BRONGNIART.

† Chaux anhydro-sulfatée quartzifère. HAUY. Chaux sulfatine quartzifère. BRONGNIART.

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er simple mineral, and is by some supposed to constitute one eighth part of the exterior crust of the globe. In fact, calcareous minerals, belonging to this species, are every day produced; arising either from the disintegration of Carbonate of lime, which had previously existed in the mineral kingdom, or proceeding from the decomposition of calcareous substances, once attached to animals. This mineral surpasses all others in the facilities, which it affords for the study of crystallography, by the frequent occurrence of its crystals, the diversity of their forms, the regularity of their structure, and the ease, with which they yield to mechanical division.

This species presents an unusual number of varieties, differing exceedingly from each other in their external characters. Hence, in many cases, it is necessary to depend chiefly on the chemical characters. It exists not only in extensive, amorphous masses, and under almost every imitative form, known in the mineral kingdom, but very frequently in crystals.

These crystals permit an easy separation of their component laminæ; and mechanical division obtains for the primitive form a rhomb (Pl. III, fig. 12), that is, a solid, whose sides are rhombs, having their two acute angles 78° 28′, and their two obtuse angles 101° 32′. The faces of this rhomb are inclined to each other at angles of 75° 31′ and 104° 29′.* Its integrant particles have the same form, according to Haüy; but Bournon says they are triedral pyramids with inclined bases.—In some hexaedral prisms the primitive rhomb is visible to the eye, its summits touching the terminal faces of the prism.

Carbonate of lime is harder than sulphate of lime, but may always be scratched by iron, and usually by fluate of lime. When pure and crystallized, its specific gravity varies from 2.68 to 2.74. When transparent, it possesses the property of double refraction in a high degree, which may be observed by looking through two parallel faces of a rhomboidal crystal or fragment at a black circle, drawn on white paper.

Phosphorescence is not essential to this species; but some varieties phosphoresce, either by projecting them in powder on burning coals, or by friction, or indeed by both methods.

(Chemical characters.) Carbonate of lime is soluble in nitric acid; and, by the escape of the carbonic acid, more or less effervescence is produced; some varieties, however, effervesce very slowly. Before the blowpipe it decrepitates, and, if pure, is perfectly infusible; but, by a strong heat, its carbonic acid is driven off, and quick-

* According to Dr. Wollaston, the angle last mentioned is 105º 05′.

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lime or pure lime, whose taste is well known, remains.—It is insoluble in pure water; but, if the water contain carbonic acid, it dissolves a small quantity of this mineral.

It is composed, according to the analysis of Vauquelin, of lime 57, carbonic acid 43; a little water is usually present.

(Distinctive characters.) Its greater hardness, and its effervescence in nitric acid distinguish it from sulphate of lime.—It is less hard than fluate of lime, and does not, when its powder is thrown in to warm sulphuric acid, yield a gas, capable of corroding glass.—From the zeolite it differs by the fusibility of the latter.—Like the carbonates of barytes, strontian, and lead, this mineral effervesces with nitric acid; but it differs from them by burning to lime, by possessing a less spec. gravity, and by being precipitated from its solution in nitric acid by the oxalate of ammonia.

The various structures and forms of this species, and the intermixture of foreign ingredients, more or less intimately combined, render numerous subdivisions absolutely necessary.

SUBSPECIES 1. CALCAREOUS SPAR.*

This subspecies occurs in crystals more or less regular, or in laminated masses; and may hence be divided into two varieties.

Var. 1. CRYSTALLIZED CALCAREOUS SPAR. It rarely exhibits the primitive form in distinct crystals. The Iceland spar, from the island of that name, occurs in laminated masses, very easily divisible into rhombs, perfectly similar to the primitive rhomb.

Of this nucleus or primitive rhomb Haüy has described at least 104 modifications, or secondary forms. Count Bournon has enumerated 59 modifications of the primitive form; but these modifications are variously combined, two or more of them being sometimes exhibited in different parts of the same crystal, and give rise to 616 varieties of form, of which the Count has given figures. He has also described 63 additional varieties of form, arising from a greater or less extent of the faces of the crystals. Of these various forms, more numerous than those of any other crystallized substance, we can mention but a few, and chiefly the most common.

1. A very obtuse rhomb† (Pl. III, fig. 13.), whose axis is equal to

* Kalk spath. WERNER. Calc spar. JAMESON. Chaux carbonatée pure spathique. BRONGNIART. Common spar. KIRWAN. Le spath calcaire. BROCHANT.

† A solid rhomb may be supposed to arise from two triangular pyramids, applied base to base. The two solid angles, formed by the meeting of three equal plane angles, will be the two summits or vertices of this double pyramid. Each of the other six solid angles of the rhomb is also formed by the meeting of three plane angles, of which one is equal to an angle at the summits, and the other two are each supplementary to the same angle. The rhomb is said to be obtuse or acute, according as each of the plane angles at the summits is greater or less than 90°; and its axis is a line, connecting the two summits.

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that of the primitive rhomb. Each of the plane angles at the summits is 114° 19′; and the mutual inclinations of its faces are 134° 26′ and 45° 34′. This variety is common; and, when its edges are rounded, its form is somewhat lenticular. This epithet, however, is sometimes extended to the perfect crystals. (Equiaxe. Haüy.)

2. An acute rhomb (Pl. III, fig. 14.); the plane angles of each face are 104° 29′ and 75° 31′, the latter being the measure of the angles at the summits; the mutual inclinations of its faces are 101° 32′ and 78° 28′. This form is common, and is often found in shell limestone, even in the interior of the shells. (Inverse. Haüy.)

3. A very acute rhomb, in which the plane angles at the summits are each 45° 34′.

4. A rhomb slightly acute (Pl. III, fig. 15.), and differing but little from a cube. The plane angles of each face are 87° 42' and 92° 18'. (Cuboïde. Haüy.)

5. A dodecaedron (Pl. III, fig. 16.), composed of two six-sided pyramids, applied base to base. Each face is a scalene triangle. In each half of this dodecaedron three alternate edges contain an angle of 104° 29', and the other three an angle of 144° 20'; but the more obtuse edges in one half are opposed to the less obtuse in the other half. This variety is common, and has been called hog-tooth spar. Its crystals have been seen more than a foot in length. (Metastatique. Haüy.)

6. The summits of the preceding dodecaedron are sometimes formed by three rhombic planes (Pl. III, fig. 17.), which are parallel to the faces of the inclosed nucleus. The terminating planes, at each extremity, stand on the three more obtuse and alternate lateral edges.(Binaire. Haüy.)

7. The preceding crystal (fig. 17.) is sometimes truncated on the six solid angles of the common base of the two pyramids by hexagonal faces (Pl. III, fig. 18.), so that the form assumes a prismatic aspect. (Bibinaire. Haüy.)

8. A regular six-sided prism. Two, three, or four of its sides are sometimes broader, than the other four, three, or two. (Prismatique. Haüy.)

9. A hexaedral prism with pentagonal sides (Pl. III, fig. 19.), ter-

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minated at each extremity by three pentagonal faces, which stand on alternate lateral planes, and form with them an angle of 116° 34′. The sides of this prism are sometimes so shortened, that they become isosceles triangles, and the crystal then somewhat resembles the head of a nail. This variety is common; and the summits are often so striated as to indicate the decrements. (Dodécaèdre. Haüy.)

10. Sometimes the bases of the terminating pentagons of the preceding crystal are enlarged (Pl. III, fig. 20.), thus producing an inequality in the breadth of the sides. (Dilatée. Haüy.)

Two other varieties, somewhat uncommon, are represented in Pl. III, fig. 21 and 22.*

These crystals present a foliated fracture, which has ordinarily a strong vitreous lustre; the fragments are rhomboidal. They are sometimes only translucent, or even opaque, at least in part, but are usually either semitransparent or transparent. Though often limpid, they are frequently white, sometimes tinged with yellow, &c. they are also yellowish brown, or present some shade of gray, yellow, green, red, violet, or black. Not unfrequently a play of colors appears at the surface, which is sometimes confined to the vicinity of the two summits of a rhomb.

Some crystals, especially those of a yellowish brown color, and those from bituminous or shell limestone, phosphoresce on hot iron.

2. LAMINATED CALCAREOUS SPAR. This variety is the result of a crystallization more or less confined or disturbed. The structure is always foliated. Sometimes the laminæ are very large, regularly arranged, easily separable, and often transparent; they are in fact composed of little rhombs, applied to each other by similar faces, so as to form a continuous mass in the same plane.

In other cases, the laminæ are smaller and irregularly situated; and, as their size is reduced, this variety begins to exhibit the structure of granular limestone. Most frequently it is translucent; and is usually white, sometimes tinged with yellow, &c.

(Geological situation.) Both varieties of Calcareous spar most commonly occur in veins, associated with a great variety of other minerals, as quartz, fluate of lime, sulphate of barytes, the sulphurets of lead, zinc, &c. They are found in all classes of rocks, and are

* Werner gives a general view of these crystals by referring them to three predominant forms, viz. a triangular and hexangular pyramid, both of which are usually double, and a hexaedral prism; from these he derives the other forms by truncation, bevelment, &c.
Bournon arranges them under three modifications of the primitive form, viz. rhombs, different from the primitive rhomb, prisms, and pyramids.

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very common in metallic veins. The finest crystals are obtained from cavities in veins; or from fissures, or between strata, in compact limestone.

The laminated masses are most common in veins, traversing calcareous rocks.—One variety with small laminæ, irregularly arranged, is formed by the filtration of water into cavities. But this may be distinguished from that, which belongs to older formations, by being less hard, and by being usually intermixed with compact limestone.

(Localities.) Among foreign localities Derbyshire, Iceland, and the Hartz in Saxony are particularly distinguished.

In the United States. In Kentucky, it occurs in fine, rhomboidal crystals, equal to the Iceland spar. (SEYBERT. —In New Jersey, at Schuyler's copper mine, near Newark.—In Connecticut, on Milford Hills, 5 miles W. from Newhaven, in laminated masses, penetrated with chlorite, and in rhombic crystals at the marble quarry on the same hills;—also at the lead mine in Middletown, mixed with the sulphurets of lead, zinc, &c. (SILLIMAN.)

SUBSPECIES 2. GRANULAR LIMESTONE.* JAMESON.

This subspecies is the result of a confused or irregular crystallization. Its structure is both foliated and granular. The grains are of various sizes from coarse to very fine, sometimes indeed so fine, that the mass appears almost compact. When these grains are white and of a moderate size, this mineral strongly resembles white sugar solid masses.

Its fracture is foliated; but the faces of the laminæ, which vary in extent, according to the size of the grains, are sometimes distinguishable only by their glimmering lustre. When the structure is very finely granular, the fracture often becomes a little splintery.

Both its hardness and the cohesion of its grains are somewhat variable. It generally appears to be a little harder, than calcareous spar; and, in some cases, this hardness undoubtedly depends on the presence of siliceous particles; indeed it sometimes gives a few sparks with steel. Its spec. grav. usually lies between 2.71 and 2.84.

It is more or less translucent, but, in the dark colored varieties, at the edges only. Its color is most commonly white or gray, often snow white, and sometimes grayish black. It also presents certain shades of blue, green, red, or yellow. Most frequently the colors are uniform, but sometimes variegated in spots, veins, or clouds, arising from the intermixture of foreign substances.

* Kö;rniger kalkstein. WERNER. Chaux carbonatée saccaroïde. HAUY. BRONGNIART. Foliated and Granular limestone. KIRWAN.

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Some varieties of Granular limestone are flexible, when sawn into thin slabs.

Granular limestone is sometimes a pure Carbonate of lime. (BUCHOLZ.) In a specimen of Carrara marble Kirwan found 3/100 of alumine, and a few minute crystals of quartz.

It is, in most cases, distinguishable from the Dolomite, a magnesian Carbonate of lime, by the slow effervescence of the latter in nitric acid.

(Geological situation.) Granular limestone exists in very large masses, and is almost exclusively found in primitive rocks. When thus found, it never embraces any remains of organized bodies. Sometimes, indeed, it has been observed among secondary rocks, but the shells, which it then contains, or its accompanying minerals, easily determine its relative age.

In some instances it forms the mass of the whole mountain; but more commonly it occurs in beds, which are often of very considerable extent and thickness, and sometimes more or less distinctly stratified. These beds are often contained in gneiss, mica-slate, argillite, porphyry, and greenstone; they alternate with these rocks, have the same inclination, and are undoubtedly of contemporaneous formation. Indeed this limestone is often mixed with the rock, which contains it, and even becomes one of its constituent parts. In the Pyrennees, according to Lapeyrouse, vertical beds of Granular limestone alternate with granite, and trap, or the limestone is even intermixed with those rocks.

This limestone contains various simple minerals, among which are quartz, mica, talc, garnets, tremolite, actynolite, asbestos, hornblende, serpentine, the sulphurets of lead, iron, &c. arsenical and magnetic iron, &c. The mica sometimes gives it a slaty structure.

(Localities.) There are few countries, in which Granular limestone is not found. Italy and Greece furnished the ancients with valuable quarries.

In the United States, there are numerous localities, of which we select a few. In Maryland, 9 miles from Baltimore, where it is employed to furnish marble; it is sometimes very white, semitransparent, and composed of large grains. (GILMOR.)—In Pennsylvania, in Montgomery Co. on the Schuylkill, in the town of White Marsh, &c. from 10 to 15 m. from Philadelphia; its quarries have been open several years. (CONRAD.)—In Connecticut, on the Milford Hills, 7 miles W. from Newhaven; this limestone is distinctly stratified, and its strata have the same direction with the greenstone slate, in which they are contained, and with which they sometimes alternate; it has a fine grain, and is traversed by veins of calcareous spar, and magnesian

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limestone; these calcareous strata have an extent of several miles in length by about one fourth of a mile in breadth, and, toward the eastern extremity, are mixed with serpentine, &c.—also at New Milford, Reading, Oxford, Derby, &c. often very white, with large foliæ, and frequently penetrated by crystals of tremolite. (SILLIMAN.)—ln Rhode Island, at Smithfield, where it occurs snow white, of a fine grain, translucid, and perfectly resembles the Carrara marble of Italy. (MEADE.)—In Vermont, at Pittsford, Middlebury, and various other places between the Green Mountains and Lake Champlain; at Middlebury the strata are irregular and inclined to the northwest (HALL.)—In Massachusetts, at Stockbridge, &c. in Berkshire Co.; this range of limestone extends from Stockbridge through Pittsfield, Lanesborough, &c. to Bennington in Vermont, and is thence probably continued through that state to the Michiscoui river;—in Newbury, about 2 miles from Newburyport, it occurs fine grained, with veins of precious serpentine, amianthus, &c.—In Maine, at Brunswick, in beds, which have the direction and inclination of all the stratified rocks in the vicinity, viz. from S. W. to N. E. and inclined at about 45°. The contiguous strata are somewhat variable and uncommon in their composition; sometimes they are composed of hornblende, mica, and limestone, and are perfectly fissile; sometimes of quartz and actynolite, stratified; and sometimes they form a kind of gneiss, which even passes into granite. The limestone is whitish or gray, large grained, and contains actynolite, talc, sulphuret of iron, both common and magnetic, &c.—In Thomaston, Lincoln Co. its beds have the same direction, as those of Brunswick; but the limestone is fine grained, and usually variegated with shades of gray and blue.—It occurs also in the interior of Maine, but has not been examined.

(Uses.) This, like other varieties of limestone, may be burnt to lime for preparing mortar, or employed as a flux for certain ores, particularly those, which contain alumine and silex. But it is more peculiarly appropriated to statuary, decorations in architecture, and other ornamental works, under the name of marble; it is hence sometimes called statuary marble; and also primitive marble from its geological situation.

In strict propriety the term marble should be confined to those varieties of Carbonate of lime, which are susceptible of a polish; including also some minerals, in which Carbonate of lime abounds. Among artists, however, this term is sometimes extended to serpentine, basalt, &c. when polished.

Both granular and compact limestone furnish numerous varieties of marble; but those, which belong to the fomer, exhibit a more uni-

20

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form color, are generally susceptible of a higher polish, and are hence most esteemed for statuary, and some other purposes. The uniformity of color, so common in primitive marbles, is sometimes interrupted by spots, or veins, or clouds of different colors, arising from the intermixture of hornblende, serpentine, talc, &c. &c.—Of foreign marbles we mention a few.

The Carrara marble, found in Tuscany, was highly esteemed by the ancients, and is most employed by the moderns for statuary. It is very white, sometimes veined with gray, and has a grain considerably fine.

The Luni marble, found also in Tuscany, is extremely white, and its grain is a little finer, than that from Carrara. Of this marble Dolomieu and indeed most mineralogists suppose the famous Apollo of Belvidere to be made.

The Parian marble, obtained from the isles of Paros, Naxos, &c. in the Archipelago, was much employed by the ancients. It is white, but often with a slight tinge of yellow. Its grains are larger than those of Carrara marble. The celebrated Venus de Medicis is of this marble. It is the Lychnites of the ancients, its quarries being often worked by the light of a lamp.

The Cipolin marble, anciently obtained from Egypt, is marked with greenish stripes or veins, composed of talc or mica.

The Pentelic marble, from Mount Penteles, near Athens, resembles the Parian, and is sometimes striped, like the Cipolin. Of this was made the statue of Esculapius, and many celebrated works of Athens.

Green antique marble (verde antico of the Italians) is an irregular mixture of this limestone and serpentine. The word antique is generally applied to those marbles, whose quarries are now unknown, or not explored.

In the United States are many beautiful and valuable marbles; but the state of the arts has not yet caused them to be extensively quarried, or even sufficiently explored. The following are among those best known.

Philadelphia or Schuylkill marble.* Its colors are white, or rather grayish white, either uniform, or variegated with veins or clouds of a darker color, and sometimes bluish. It is, in general, composed of large grains. This marble has been much employed for ornamental work in architecture, &c.

* Notwithstanding the efforts, which the writer has made to obtain information, he has reason to fear, that this account of American marbles is, in some instances, incomplete.

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Newhaven marble. The texture of this very beautiful marble is granular, but very fine. Its predominant colors are gray or blue, richly variegated by veins or clouds of white, black, or green; indeed the green often pervades a large mass. It takes a high polish, and endures the action of fire remarkably well. This marble contains chromate of iron, magnetic oxide of iron, and serpentine; hence it resembles the vert antique, and is perhaps the only marble of the kind hitherto discovered in America. (SILLIMAN.)

Vermont marble. It is, in general, fine grained, and sometimes nearly compact. Its quarries have been opened at Middlebury, Pittsford, &c. The marble from Pittsford is white, either pure, or shaded with gray, &c. It is conveyed by the waters of Otter Creek to Middlebury, where it is manufactured.—The Middlebury marble is sometimes of a pure white, resembling some varieties of Italian marble; but the predominating color is gray of different intensities. This marble receives a good polish, and is manufactured into tombstones, chimney jambs, window caps, &c. During the years 1809 and 1810, 20,000 feet of slabs were cut by one mill, containing 65 saws; and the sales of marble, during the same period, amounted to about 11,000 dollars. (HALL.) Some of the Vermont marbles are as white, as the Carrara marble, with a grain intermediate between that of the Carrara and Parian marbles.

Stockbridge marble, from Berkshire Co. Mass. Its grain is somewhat coarse, and its color is white, sometimes with a slight tinge of blue.—A quarry has also been opened at Pittsfield in the same county.

Thomaston marble, from Lincoln Co. Maine. It is, in general, fine grained, and its colors are often richly variegated. Sometimes it is white or grayish white, diversified with veins of a different color. But, in the finest pieces, the predominant color is gray or bluish gray, interrupted by whitish clouds, which, at a small distance, resemble the minutely shaded parts of an engraving, and, at the same time, traversed by numerous small and irregular veins of black and white. It receives a fine polish, and is well fitted for ornamental works. These quarries, considering their vicinity to navigable water, and the great beauty of the marble, will undoubtedly, in a few years, be extensively worked.

Some of the white marble of Vermont, and that, which may probably be obtained at Smithfield, in Rhode Island, more peculiarly deserve the name of statuary marble.

Flexible marble. This has been observed at Pittsford, Rutland Co. in Vermont, and at Pittsfield, &c. Berkshire Co. in Massachusetts, at the latter of which it was first discovered by Dr. Meade. According

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to the experiments of this gentleman on the Pittsfield marble, its flexibility depends on the presence of a certain quantity of moisture; for, when flexible slabs of this limestone are exposed to heat, they lose their flexibility, but immediately recover it, when plunged in water. All the marble of this quarry is not flexible; those slabs, however, which are so, exhibit this property immediately after being taken from the quarry; but the eye cannot distinguish them without experiment. —On the contrary, the flexibility of certain European limestones, which were probably Dolomites, has been supposed to be produced by the action of heat, and the consequent escape of the natural moisture of the mineral. (See Bruce's Min. Jour. v. i. pp. 93, 267.)

SUBSPECIES 3. FIBROUS LIMESTONE.*

It occurs in masses, composed of imperfect crystals or fibres. Sometimes these fibres are coarse, and feebly adhere, or are tapering toward their extremities, and hence appear partly detached from each other. Sometimes they are very delicate, firmly adhere, and thus form solid masses. These fibres, whether straight or curved, are most commonly parallel; and their cross fracture is uneven or undulated, with a resinous lustre. It is more or less translucent, and its usual colors are white or gray, often with shades of yellow, red, or green.

It has also been observed with diverging or radiating fibres; and sometimes in cellular masses, whose fibres are reticulated. (BOURNON.)—It is harder than fibrous gypsum, which it often resembles.

SATIN SPAR. This is a delicate, fibrous limestone, susceptible of a fine polish, and exhibiting the lustre of satin. Its color, often grayish, is sometimes a pale rose red. It is employed for inlaid, ornamental work.

Very beautiful specimens of satin spar are found in Cumberland Co. England. It sometimes embraces sulphuret of iron.

Fibrous limestone is usually found in veins, or between the strata of other calcareous minerals.

In the United States. In Maryland, near Baltimore. In Pennsylvania, at Cumberland valley, 15 m. from Bedford; it is amber colored and semitransparent. (SEYBERT.) In Massachusetts, at Newbury, two miles from Newburyport, near the turnpike, specimens of satin spar have been found.

* Gemeiner fasriger kalkstein. WERNER. Common fibrous limestone. JAMESON. Chaux carbonatée fibreuse. HAUY. Chaux carbonatée fibreuse massive BRONGNIART.

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SUBSPECIES 4. COMPACT LIMESTONE.* KIRWAN.

The uses and geological characters of this subspecies render it peculiarly interesting. The term compact, however, as applied to this mineral, must be received with some latitude; for, although its texture is often very close and compact, sometimes like that of wax, in other instances it is loose and earthy.

It usually occurs in extensive, solid, compact masses, whose fracture is dull, splintery, or even, and sometimes conchoidal. It is sometimes traversed by minute veins of calcareous spar, which reflect a little light; and some compact limestones are also slaty. Its hardness is somewhat variable, and some specimens, containing siliceous particles, give a few sparks with steel. Its spec. gravity usually lies between 2.40 and 2.75.

It is opaque, or translucent at the edges; its more common color is gray, often with shades of yellow, blue, &c. and indeed varying from grayish white to grayish black; it also presents certain shades of yellow, blue, brown, green, and red. These numerous colors are sometimes very lively, and frequently mingled in the same specimen in spots, stripes, veins, clouds, landscapes, &c. It is usually more or less susceptible of a polish.

It is sometimes dendritic; and these dendrites, produced by the filtration of water, containing the black oxide of iron or manganese, may be only superficial, or extend through the mass. In the latter case, the dendrites are best observed by cutting the mineral perpendicularly to the fissures, by which the water entered.

Compact limestone is seldom, perhaps never, a pure Carbonate; but contains from 2 to 12 per cent. of silex, alumine, and the oxide of iron, on the last of which its diversified colors depend. In fact, by increasing the proportion of argillaceous matter, it passes into marl. Some limestones, which effervesce considerably, are still so impure, that they melt, rather than burn to lime.

Var. 1. EARTHY COMPACT LIMESTONE.† Its texture is loose and porous, and hence this variety often absorbs a large quantity of water. Its spec. gravity, depending on its texture, is sometimes below 2.00.

Its fracture is dull, earthy or uneven, and, though sometimes fine, is usually coarse grained; indeed the mass seems to be sometimes composed of a kind of calcareous sand. It is sometimes tender and

* Gemeiner dichter kalkstein. WERNER. Common compact limestone. JAMESON. Chaux carbonatée compacte HAUY. Chaux carbonatée Marbre et compacte. BRONGNIART. La Pierre calcaire compacte commune. BROCHANT.

† Chaux carbonatée grossière. HAUY. BRONGNIART.

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friable, and sometimes solid. Its more common colors are white and gray, often with shades of yellow, brown, &c. It does not receive a polish.

(Geological situation.) It has already been remarked, that granular limestone is almost invariably characterized, as a primitive rock, by its relative situation and freedom from organic remains. As the grain becomes finer, the transparency and crystalline structure gradually diminish, and the mineral passes into a compact limestone; it then associates with a different class of rocks, and begins to contain organic remains or petrifactions.

The older varieties of compact limestone are very often found in the vicinity of primitive or transition mountains, sometimes placed against their sides, or even on their summits. They sometimes form whole mountains, or even a chain of mountains, and are often found at a great elevation, as on the summits of the Pyrennees. They occur in beds, often very thick, and usually more or less inclined. They always lie above the primitive rocks, and never alternate with them.

These older varieties of compact limestone sometimes contain, in beds or veins, the sulphurets of lead, zinc, iron, and mercury, the oxides of zinc, manganese, and iron, certain ores of copper, &c. They sometimes embrace garnets, steatite, and mica.—Petrifactions do indeed occur in all the varieties of compact limestone, but they usually increase in number and variety, as the deposite becomes more recent.

On the other hand, the most recent varieties of compact limestone appear under plains, or constitute hills or low mountains, usually at some distance from primitive mountains. They most commonly contain a great quantity of shells,* or other petrifactions.

Hills of compact limestone, seldom of a conical form, are often terminated by plains, or by rounded summits, and their sides are sometimes nearly perpendicular.

We shall describe more particularly three distinct formations; the two former of which fall among the older varieties, mentioned in the preceding general remarks.

One of these formations appears to belong to the intermediate or transition class of rocks. The limestone of this formation is always more or less compact, or, if in any degree granular, extremely fine grained. Its fracture is splintery or conchoidal; and its fragments have more translucency at the edges, than those of secondary limestone. Its colors are remarkably variegated; and it often contains

* The shells, which exist in limestone, may be composed of carbonate of lime; or have a siliceous crust, enveloping the calcareous part; or be entirely siliceous.

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white veins of calcareous spar. Its beds, frequently very thick, and indistinctly stratified, are often deposited directly upon argillite or other primitive strata, and sometimes alternate with gray-wacke slate, amygdaloid, hornblende, or greenstone. It sometimes contains organic remains of ammonites, belemnites, corallites, &c.

The formation next to be mentioned is decidedly secondary. It is distinctly stratified; its beds or strata, which vary much in thickness, are seldom horizontal, often greatly inclined, and frequently waved or twisted, still remaining parallel to each other. It often rests upon red sandstone, and is, at the same time, covered by gypsum. It sometimes alternates with clay, marl, or bituminous marlite, impregnated with ores of copper; but is seldom connected with coal.

It contains sulphate of barytes, calcareous spar, and beds of fetid limestone. It also embraces small tuberose masses of hornstone and flint, intimately united with the limestone, and sometimes arranged in beds. Petrified fish, gryphites, ammonites, and other organic remains are common in this formation, but usually less numerous than in shell limestone.—In Peru it is often traversed by veins of silver ore.

Another formation of secondary limestone, more recent than the preceding, is called coarse or shell limestone. This is found in hills with rounded summits, or resting beneath the surface of a level country. Its strata, sometimes very thin, are commonly horizontal, and not waved, like those of the preceding formation. They frequently alternate with marl, clay, sandstone, and sand, with the last of which they are often contaminated. Hornstone and flint under various forms appear also in this formation.

It is sometimes bituminous; but coal and metallic substances, the oxide of iron excepted, are extremely rare. In some instances it embraces a great variety of shells, belonging to different families, promiscuously intermingled; but frequently, in a succession of different beds, shells of the same family are found together. Sometimes the whole mass is only an aggregation of shells.

Shell limestone sometimes rests on gypsum. In other cases, as in the vicinity of Paris, it rests on a bed of clay, which separates it from chalk; and it is there covered by gypsum, belonging probably to the latest known formation of that mineral. In upper Lusatia it alternates with sandstone, and both rest on alluvial earths. (JAMESON.)

Strata of shell limestone often present rents, fissures, and caverns, which contain calcareous crystals or concretions, or argillaceous oxide of iron. These caverns are particularly remarkable for containing the bones of quadrupeds and other land animals, sometimes belonging

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to different climates and extinct species. The bones are found on the floor of the cavern, or imbedded in a limestone, which is obviously of more recent formation, than the sides of the cavern. Such caverns are found in Gibraltar, and Dalmatia on the Mediterranean, &c. No human bones, inclosed in minerals, have yet been observed.* (CUVIER.)

(Localities.) Of Compact limestone, so abundantly diffused, it is unnecessary to enumerate localities. The shell limestone of England and that of France, bordering on the English Channel, probably belong to the same strata, once continuous.

It is a predominant rock in that section of the United States, contained between the Alleghany Mountains, the Lakes, and the Missisippi, as general boundaries.

(Uses.) Compact limestone is employed to furnish lime, or marble, or as a building stone. The purest white marble or limestone undoubtedly furnishes the best lime, though but little superior to that, obtained from gray Compact limestone. The calcination of limestone may be effected by wood, coal, or peat, as fuel; but the heat should not much exceed a red heat, unless the stone employed be nearly a pure carbonate.—On this subject, and the preparation of mortar we have room for but few remarks.

Count Rumford, with his usual attention to economy in fuel and in the expense of caloric, has invented an oven for preparing lime. It has the form of a high cylinder with the hearth at the side, and at some distance above the base. The combustible, placed on the hearth, burns with an inverted or reflected flame. The lime is taken out at the bottom, while fresh additions of the limestone are made at the top; and thus the oven is preserved constantly hot.

Limestone, recently dug, and of course moist, calcines more easily, than that, which has become dry by exposure to the air; in the latter case it is found convenient even to moisten the stone, before putting it into the kiln.

(Mortar.) This is known to be a mixture of slacked lime and sand, or of some ingredient equivalent to the sand; such as clay, baked hard and reduced to powder. Much depends on a due calcination of the limestone, the fineness of the sand, and a just proportion of water. The addition of small quantities of the oxides of iron

* Some human skeletons were found a few years since at Guadaloupe in a bed of hard limestone, which closely adheres to the bones. A part of one is now in the hands of Cuvier. Another, perfect from the neck to the ancles, was lately transmitted by Sir Alex. Cochrane to the British Muséum (Christian Observer, Feb. 1814.)

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and manganese renders the mortar more solid, and capable of becoming hard under water. Some limestones contain the oxide of manganese, and yield a lime, which becomes brownish by exposure to the air; and is often called meagre lime.*

If a suitable quantity of quicklime in powder be added to a mortar, prepared with one part slacked lime and three parts sand, very great solidity will be produced. Similar advantages may be obtained by employing the least possible quantity of water, or by the addition of pounded bricks, or puzzolana, a volcanic product. Indeed most varieties of trap or greenstone, when pulverized, having been previously heated red hot and plunged into water, may be employed with great advantage in the preparation of water proof mortar for piers, docks, &c. (SILLIMAN.) In constructing the Eddystone lighthouse Mr. Smeaton employed meagre lime 2 parts in bulk, pure sand 3 parts, and trass, a pseudo-volcanic product, 1 part. A compact limestone, found near Boulogne, yields lime, capable of being formed into very good mortar without addition; it contains carbonate of lime 73, silex 15, iron 7, alumine 5. (DRAPPIER.)

Compact limestone is also an important article of manure, for which purpose the shell limestone is generally preferred. Sometimes the stone is only pulverized; in other cases it is calcined. It has however been found by experiment, that those varieties of limestone, which contain magnesia, are injurious to vegetation, when applied after calcination. These magnesian limestones may generally be known by their slow effervescence in acids.

(Secondary marbles.) Compact limestone, more particularly that, which belongs to the older formations, furnishes many beautiful varieties of marble, employed in the arts. Their colors, though sometimes uniformly grey, yellow, red, or black, are usually much variegated.

In addition to the marbles, furnished by granular and compact limestone, there are others composed of a calcareous breccia. Their colors appear in spots, are well defined, and do not pass into each other. In fine, some minerals, which, when polished, are known under the name of marble, appear to be only indurated, calcareous marl.

Black marble is frequently colored by bitumen, which it discovers, when heated or rubbed; it also gives a white lime.

Some marbles contain a large proportion of shells, and to these are indebted for much of their beauty. Of these the most beautiful is the Lumachella marble from Bleyberg in Carinthia. The ground is gray

* Meagre lime, when formed into mortar, requires less sand, than the other varieties. When limestone, containing manganese, is melted with twice its weight of nitre, a greenish trace remains on the sides of the crucible.

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or brownish; but it contains fragments of shells, having a pearly lustre, sometimes irised, and sometimes reflecting an orange red, or green, or blue light.

Another interesting variety of marble is sometimes called Florence marble, from having been found near that city. Its color is usually yellowish gray, marked with various figures of a brownish or darker yellow, which exhibit a representation of houses, towers, and in fact of a city in ruins, with clouds and sky in the back ground. (Marbre ruiniforme. HAUY.) All this pleasing illusion, however, depends on the distance of the view.

The substances, employed in polishing marble, are, in general, sandstone or emery with water, followed by filings of lead and tin putty, or, if the marble have a light color, by pumice, and a mixture of calcined bones and alum.

White marbles, which have become yellowish or otherwise sullied, may be cleaned by washing them with diluted oxymuriatic acid.

Very few marbles, belonging to compact limestone in the United States, are yet known. In Pennsylvania at Aaronsburg, in Northumberland Co. is a black marble, containing white specks, like the Kilkenny marble. (MEASE.)—In New York, at Marbletown in Ulster Co. a similar marble is found (Rees' Cyclop.);—also at Granville in Washington Co. a black marble is wrought;—a similar marble, containing shells, is found in the vicinity of Ticonderoga.

SUBSPECIES 5. CHALK.* KIRWAN. JAMESON.

This well known substance is always amorphous, with a dull, earthy fracture. It may always be scratched by the finger nail; it is rough to the touch, soils the fingers, and writes. It adheres a little to the tongue. It is opaque and usually white, sometimes with a tinge of yellow; it also occurs gray or brown. Its spec. grav. varies from 2.25 to 2.66.

Chalk is very nearly a pure carbonate of lime, containing minute quantities of alumine and oxide of iron. It seems to have been deposited from a state of suspension, rather than solution in water.

(Geological situation.) Chalk is never found associated with primitive earths. It may rise into hills of considerable elevation, or appear many yards below the surface of a level country. It occurs in thick beds, seldom distinctly stratified, in most cases nearly or quite horizontal, but sometimes highly inclined or nearly vertical.

Beds of chalk almost always contain flint in masses of a moderate size, globular, cylindrical, tuberose, vesicular, &c. These mass-

* Kreide. WERNER. Chaux carbonatée crayeuse. HAUY. Chaux carbonatée craie. BRONGNIART. La Craie. BROCHANT.

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es of flint are not promiscuously scattered, but usually arranged in numerous, parallel beds, in which, however, they do not lie contiguous to each other. The exterior of the flint is usually incrusted, or even penetrated by chalk.

Chalk also contains shells, among which are belemnites, echinites, &c. These shells are very often siliceous, and frequently the cavity itself is filled with a siliceous deposite. A piece of wood, well preserved, has been found in the chalk of Hampshire, Eng. (BOURNON.)

Chalk is often mixed with sand; but neither coal, nor any metallic substance, excepting the sulphuret or oxide of iron, has been found in it.

In the vicinity of Paris the chalk is situated under shell limestone, from which it is separated by a bed of clay. It contains many organic remains, which are not found in the shell limestone above it; and seems to be peculiarly characterized by the belemnite. When connected with shell limestone, the chalk is perhaps always underneath.

In the isle of Wight is an elevated ridge of hills, extending nearly E. & W. and composed of strata of chalk nearly vertical, or forming with the horizon an angle of 60° or 80°; the lower beds do not contain flint. Underneath this chalk is found marl and calcareous sandstone, with subordinate beds of chert, limestone, clay, and carbonized wood. (Webster's paper before the Geolog. Society.)

(Localities.) Chalk is abundant in Upper Normandy, Champagne, and Picardy in France, extending into the Netherlands. In England it prevails in the counties of Kent, Sussex, Hampshire, Berkshire, Wiltshire, &c. It is found in Poland;—also on the islands of Rugen and Zealand in the Baltic.—In Antrim Co. Ireland, it is sometimes covered by basalt. (BOURNON.)

(Uses.) Its uses are considerably numerous. It furnishes white crayons, and a base for water colors in painting. It furnishes Spanish White, to prepare which the chalk is reduced to powder, and agitated in a large quantity of water. When the sand has subsided, the water is poured off and permitted to rest, till the chalk is precipitated.

SUBSPECIES 6. AGARIC MINERAL.* KIRWAN.

It is composed of very minute particles, feebly cohering, fine or soft to the touch, and soiling the fingers. Its texture is spongy, and

* Bergmilch. WERNER. Rock milk. JAMESON. Chaux carbonatée spongiouse. HAUY. BRONGNIART. Lait de montague. BROCHANT.

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hence it usually swims for a moment, when placed on water. Its color is white, either pure, or tinged with yellow, &c.—It is a very pure carbonate of lime.

Agaric mineral undoubtedly proceeds from the gradual disintegration of other varieties of carbonate of lime; and is deposited from water in the cavities or fissures of other calcareous rocks.

Var. 1. FOSSIL FARINA.* This variety differs but little from that just described, and has probably a similar origin. It appears in thin, white crusts, light as cotton, and very easily reducible to powder. These crusts are attached to the lateral or lower surfaces of beds of shell limestone, &c.

SUBSPECIES 7. CONCRETED CARBONATE OF LIME.

Calcareous concretions exhibit some diversity of structure, and an uncommon variety of imitative forms, resulting from the peculiar circumstances, under which they have been produced. Their structure is usually more or less crystalline. Sometimes they are compact, or porous. Frequently they appear in the form of a crust, and sometimes they are amorphous. But, in almost all cases, they are more or less obviously composed of a series of successive layers, nearly or quite parallel, whether straight, undulated, or concentric,

Var. 1. OOLITE.† This variety always occurs in globular or spheroidal masses, usually very small, but varying from the size of a poppy seed to that of a pea. These globules appear to be composed of a compact, calcareous nucleus, invested by concentric layers, variable in thickness. These layers, often perceived with difficulty, have in most cases a compact texture. The nucleus is sometimes detached, leaving its place empty. (BOURNON.)

The Oolite has a dull fracture, which appears to be splintery. It is nearly or quite opaque, and its color is brown, reddish brown, or yellowish gray.

These globules are almost always united by a calcareous cement; and the beds or masses, thus formed, are found connected with rocks of recent formation, more particularly with shell limestone and calcareous sandstone; sometimes also with compact limestone, or even with gypsum.

(Remarks.) The older mineralogists supposed these globules to be the petrified roes of fish; and hence the name roestone. Dauben-

* Chaux carbonateé pulverulente. HAUY. BRONGNIART.

† L' Oolite. BROCHANT. Chaux carb. Oolithe. BRONGNIART. Chaux carbonatée globuliforme. HAUY. Roogenstein. WERNER. Roestone. JAMESON. Oviform limestone. KIRWAN. The name Oolite is derived from the Greek Ωον, an egg, and ∧ιθος, a stone.

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ton and others suppose them to be limestone, granulated by attrition with water. This opinion, however, is inconsistent with the concentric layers, of which their exterior appears to be composed. The existence of these layers is denied by some, and indeed the closeness of the texture often renders it difficult to distinguish them.

2. PISOLITE.* This variety occurs in globular or spheroidal concretions, usually about the size of a pea, though sometimes larger. These concretions are composed of distinct, concentric layers, and almost invariably contain a grain of sand, or some other foreign substance, as a nucleus. The Pisolite is nearly or quite opaque, and has a dull fracture. Its color is usually white, often dull, or with a shade of yellow, &c.

These concretions, sometimes detached and scattered, are more frequently united by a calcareous cement. Thus united, they form masses of various sizes, and also continuous beds, which are sometimes covered by alluvial deposites.

The Pisolite has been found chiefly near the warm springs of Carlsbad in Bohemia, and the baths of St. Philip in Tuscany.

(Remarks.) The structure of the Pisolite and the situation, in which it is found, seem to indicate the mode of formation. The particles of sand, or nuclei of these concretions, were probably raised and suspended by an agitated, or rotatory motion of the waters of certain springs or streams, strongly impregnated with calcareous particles. These particles were then deposited around the floating nuclei, which, being thus incrusted with a series of layers, became sufficiently heavy to fall through the fluid.

3. CALCAREOUS SINTER.† This variety embraces most of the imitative forms of carbonate of lime, and may be stalactical, tuberose, reniform, globular, cylindrical, tubular, branched, or in large, undulated masses, &c. But, under all its forms, it is composed of a series of successive layers, concentric, plane, or undulated, and nearly or quite parallel. These layers, however, in some cases are not distinct, unless the mass be large.

The structure of these concretions is more or less crystalline, according to the different circumstances, under which they were formed. The fibrous structure most frequently occurs; and the cross fracture of the fibres, though often foliated, is, in some cases,

* La Pisolite. BROCHANT. Chaux carb. concret. Pisolithe. BRONGNIART. Erbsenstein. WERNER. Peastone. JAMESON. Chaux carb. globuliforme. HAUY. The term Pisolite is derived from the Greek Πισον, a pea, and ∧ιθος, a stone.

† Kalksinter. WERNER. Cale sinter. JAMESON. La Stalactite calcaire. BROCHANT.

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undulated or uneven. These differences, however, of the cross fracture are united by imperceptible shades.

STALACTITE.* These stalactites, particularly when small, are most frequently conical or cylindrical. But when larger, they become irregular, their surface being tuberose, undulated, &c. and sometimes even branches appear. Their external surface is commonly rough, often coated with minute crystals. In some instances a well defined crystal terminates the stalactite; in other instances a protuberance appears near the extremity, forming a kind of cap, resembling a mushroom, &c. When these conical stalactites are short and large, they unite and appear reniform.

Their fracture, sometimes foliated, is commonly fibrous, with diverging or radiated fibres, having a moderate lustre; sometimes the texture appears compact and the fracture splintery. They are usually more or less translucent; their most common color is white, either pure, or tinged with gray, yellow, or brown; and they occasionally exhibit shades of green, red, blue, &c.

(Mode of formation.) Stalactites are evidently formed by the filtration of water, containing calcareous particles, through pores or fissures in the roofs of those caverns, which are frequent in limestone. The water, having percolated through the roof, there remains suspended in drops. Evaporation commences at the exterior of the drop, and the calcareous particles are deposited on the roof of the cavern in the form of a little ring, which extends by degrees, till a small tube is produced. The bore of this tube is, in most cases, gradually diminished by successive deposites, till it becomes entirely closed, and the stalactite then increases by concentric layers, applied to the exterior. Thus cylinders or cones more or less regular are produced, and sometimes so enlarged, that they unite with each other.

Tubular stalactites. Sometimes the initial tube just described does not become obstructed, but passes longitudinally through the axis of the stalactite. Such stalactites sometimes have a uniform thickness, like a quill. Their structure is distinctly foliated; sometimes the laminæ extend through the diameter of the cylinder, but still present the cavity of the tube in the place of the axis.

STALAGMITE.† (Alabaster.) While the stalactite is forming, a part of the water drops from the unfinished stalactite on the floor of the cavern, or trickles down the sides, and thus produces those cal-

* The terms stalactite and stalagmite are derived from the Greek Σταλαζα, to drop.

† Chaux carb. concret. Albâtre. BRONGNIART. Chaux carb. concrete. stratiforme. HAUY.

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careous concretions, called stalagmites; and, when large, they often bear the name of alabaster. These concretions, when attached to the sides of the cavern, are merely plates or thin crusts. But, on the floor of the cavern, they often form large masses, sometimes rising, till they meet the stalactites, pendent from the roof, and extending in all directions, till the whole cavern is nearly or quite filled.

These deposites are essentially composed of parallel layers, almost always undulated, and conformable to the surface of the soil, on which they rest. Sometimes large protuberances are formed, and indeed a great variety of imitative forms are produced even by the spray or scattered drops from the surface of the growing stalagmite. Hence, with the assistance of a lively imagination, the observer may perceive in these caverns almost any object, which he pleases; hence the glowing and luxuriant descriptions of the travellers, who have entered them, especially with the light of a candle.

These concretions may have a foliated, fibrous, or granular structure; and their parallel layers may, in general, be distinguished by a difference of density, or translucency, or color. Their color is seldom a pure white, but more frequently presents a shade of yellow, red, or brown, arranged in undulating or concentric stripes, or in spots.

(Geological situation.) We hardly need remark, that calcareous sinter is found only in fissures, or in caverns, often very large, which so frequently exist in calcareous rocks. Certain springs, however, whose waters contain carbonate of lime, often form deposites, which may be referred to this variety.

(Localities.) Among the more remarkable foreign localities of calcareous sinter are the grotto of Antiparos in the Archipelago, Bauman's cave in the Hartz, Pool's Hole in Derbyshire, the caves of La Balme in Savoy and of Auxelle in Franche-Comté.

In the United States are many caverns of a similar nature. Among these are Madison's cave, on the north side of the Blue Ridge, and Wier's cave, about 15 miles from Staunton, Augusta Co. both in Virginia; —also Hughes' cave, in Washington Co. Maryland.

(Uses.) When any of these concretions, but more particularly the stalagmite, becomes large and is susceptible of a good polish, it is employed in the arts under the name of alabaster or calcareous alabaster. And, although this alabaster and marble are composed of the same ingredients, it is not, in general, difficult to recognise the former by its parallel layers, and the arrangement of its colors already mentioned.

A very singular mode of manufacturing calcareous alabaster have

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been invented by Dr. Vegni, and employed at the hot baths of St. Philip in Tuscany. This water, impregnated with carbonate of lime, is made to fall, in very minute drops, into hollow moulds, representing various works in bas relief. After a few months a very beautiful, white deposite is produced, sufficiently hard, and faithfully exhibiting the bas relief.

4. CALCAREOUS TUFA.* This substance is deposited from water under circumstances very unfavorable to crystallization; often indeed from water in rapid motion. It is, in fact, chiefly an earthy precipitate, and is sometimes almost destitute of solidity. It is seldom compact, but usually in porous, cellular, or corroded masses, whose surface is often undulated. Its fracture is dull, earthy, or uneven, and seldom gives indications of a foliated or fibrous structure. It is nearly or quite opaque, and usually gray, often with a shade of yellow.— It has a low but variable specif. gravity, and its hardness and solidity are much increased by exposure to the air.

Tufa is impure, and often contains sand, leaves, mosses, and other vegetables, fluviatile shells, and even the horns and bones of animals. It sometimes resembles indurated mortar, or is in branches, &c.

(Geological situation.) Calcareous tufa, though sometimes in large masses, is found in alluvial earths and never at a great depth below the surface. It is sometimes deposited from rain water, which has washed calcareous substances.

A tufa of a fine grain, porous or nearly compact, is sometimes found immediately under the soil, or under beds of clay or marl, in vallies, surrounded by calcareous mountains, whence it has originated. It often contains fluviatile shells, and sometimes marine shells, brought from the mountains.

(Uses.) It is sometimes sufficiently hard to be employed as a building stone. The city of Pasti in Italy is said to be built with a tufa. The travertino of the Italians, of which the churches and other monuments of Rome are constructed, is by some supposed to be tufa, while by others it is referred to compact limestone.

CALCAREOUS INCRUSTATIONS.† These are a kind of tufa. They are found investing the exterior of other bodies, and thence derive their form. Among the substances thus incrusted are other minerals, organic bodies, particularly those belonging to the vegetable kingdom, and the interior of tubes or cavities. Hence the interior of certain aqueducts becomes gradually incrusted, and eventually filled by

* Kalk tuff. WERNER. Calc tuff. JAMESON. Chaux carb. concret tuf. BRONGNIART.

† Chaux carb. concret. incrustante HAUY. BRONGNIART.

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calcareous deposites from the water, which passes through them; of which there is a striking example in the waters of Arcueil, near Paris.— Hence in the formation of calcareous geodes, the cavity is generally incrusted before the production of those crystals, which often render their interior extremely beautiful.

Vegetables even of the most delicate texture, when immersed in waters, containing carbonate of lime, become incrusted, but still preserve their form perfectly distinct in every branch. Hence the origin of the osteocolla, to which has been attributed the property of facilitating the union of a fractured bone. It is in fact the incrusted stem of a vegetable, and somewhat resembles the bone of an animal; for the stem itself becomes decayed, leaving a cavity or blackish line.

Carbonate of lime is sometimes pseudomorphous, having been moulded in the cavity of a shell, or some other substance. Of this the ammonite (cornu Ammonis) is an example.

SUBSPECIES 8. ARGENTINE.* KIRWAN.

This mineral has a laminated or rather slaty structure. Its laminæ or layers, often curved or undulated, are seldom perfectly parallel; but their surface has almost always a pearly lustre, somewhat shining. According to Bournon, these laminæ are composed of minute rhombs, whose summits are so deeply truncated perpendicularly to the axis, that only a very thin portion of the rhomb remains. Indeed this mineral sometimes presents the primitive rhomb. It is translucent, at least at the edges; and its color is white, shaded with gray, green, or red. It is easily broken; and its spec. grav. is 2.64. (KIRWAN.)

It is nearly a pure carbonate of lime, often containing a little oxide of iron or manganese. (BUCHOLZ.) Hence, at a red heat, it often becomes reddish brown.

It is found in primitive mountains. In Saxony it exists in limestone, associated with chlorite and the sulphurets of lead and zinc.

1. SILVERY CHALK.†KIRWAN. This occurs in small masses, more or less friable, composed of lamellæ or scales, shining with a pearly lustre; sometimes its particles scarcely cohere. The scales, which compose this variety, are conjectured by Bournon to be truncated rhombs, similar to those of argentine, but irregularly arranged.

It is soft, or rather like silk, to the touch; opaque; and of a

* Schiefer Spath. WERNER. Slate Spar. JAMESON. Chaux carb. nacrée. HAUY. Chaux carb. nacrée argentine. BRONGNIART. Le Spath schisteux. BROCHANT.

† Schaum erde. WERNER. Foaming earth. JAMESON. Chaux carb. nacrée tarqueuse. BRONGNIART. L'ecume de terre. BROCHANT.

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pearly white color, sometimes with a slight tinge of yellow or green. It is found in secondary calcareous mountains in cavities, or adhering to the limestone.

SUBSPECIES 9. MAGNESIAN CARBONATE OF LIME.*

This mineral, while dissolving in nitric acid, produces, in most cases, a very moderate effervescence; sometimes indeed scarcely visible, unless the mineral be reduced to powder. And by this peculiarity, in connexion with some of its physical characters, it may generally be distinguished from the other subspecies of carbonate of lime. Some varieties, however, effervesce rapidly in nitric acid; and, in this case, unless some of the physical characters be sufficiently decisive, recourse must be had to some chemical experiment to ascertain the presence of magnesia.—It is harder, than calcareous spar; indeed some of its varieties strike fire with steel, but probably from the presence of quartz.

It presents two varieties, which resemble each other more closely in composition, than in external characters. A crystallized specimen of the common variety from the Tyrol yielded Klaproth carbonate of lime 52, carbonate of magnesia 45, oxide of iron 3. In a specimen of the Dolomite from St. Gothard he found carbonate of lime 52, carbonate of magnesia 46.50, oxides of iron and manganese 0.75;=99.25. It appears that specimens from different localities yield different proportions of the two earths.

Var. 1. COMMON MAGNESIAN LIMESTONE.† (Bitter Spar.) This variety is often in regular crystals, whose primitive and secondary forms are the same, as those of calcareous spar.‡ Most of its crystals, however, are rhombs, sometimes truncated, and sometimes with rounded edges.—It occurs also in amorphous lamellar masses, whose structure sometimes presents granular distinct concretions.

Its fracture is foliated, and its foliæ have a shining or splendent lustre, more pearly than that of calcareous spar. It is very sensibly harder, than calcareous spar, and sometimes scratches even fluate of lime. Its spec. grav. varies from 2.48 to 3.00. (BOURNON.) It is translucent, at least at the edges, and its crystals are nearly semitransparent. Its usual colors are grayish or yellowish white, pale yellow, or yellowish brown.

* Chaux carbonatée magnesifère. HAUY. Chaux carbonatée lente. BRONGNIART.

† Rautenspath. WERNER. Rhomb-spar. JAMESON. Chaux carb. lente Picrite. BRONGNIART. Le Spath magnesien. BROCHANT.

‡ According to Dr. Wollaston the greatest angle of the mutual inclination of the faces of the primitive rhomb in the magnesian carbonate is 106° 25′.

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This variety appears to pass by imperceptible shades into the Dolomite, to which it has the same relation, as calcareous spar to granular limestone.

(Geological sit. and Localities.) It is sometimes found in chlorite slate, steatite, serpentine, &c. accompanied by asbestus, tremolite, &c.

The Magnesian limestone of England, which occurs in large masses or even in beds, is, by Bournon, referred to this variety. At Matlock in Derbyshire, Magnesian limestone, sometimes containing shells, is incumbent on horizontal strata of shell limestone. (TENNANT.) In the United States. In Pennsylvania, 13 miles from Philadelphia. In Connecticut, near Newhaven, it occurs with asbestus, &c. in serpentine. (SILLIMAN.)

MIEMITE. This subvariety, sometimes in crystals, and sometimes in masses with a radiated structure, has a pale, greenish color. It has been found at Miemo, in Tuscany.

2. DOLOMITE.* KIRWAN. JAMESON. The structure of the Dolomite is always granular. The grains, though a little variable in size, are usually very fine; they differ also very much in their cohesion, the mass being sometimes solid, and sometimes very friable, even between the fingers. In fact, its texture and general appearance often much resemble those of granular limestone with fine grains. Its fracture has a glimmering lustre.—Some varieties are phosphorescent in the dark, both by friction and on a heated shovel.—It is sometimes flexible, when sawn into thin slabs. Its spec. grav. is about 2.85. It is translucent at its edges; and its color is white, either very pure, or tinged with gray, yellow, or red.

As its effervescence in nitric acid is usually feeble, this circumstance will, in such cases, serve to distinguish it from certain granular limestones.

(Geological sit. and Localities.) This variety is often found in primitive or transition mountains, forming large masses, beds, or veins. Hence its beds sometimes alternate with mica slate, or are in contact with fetid limestone. Near Varalla in Italy it exists in a vein, traversing granite. (NAPIONE.)

It sometimes contains talc, tremolite, and mica, the last of which often gives it a slaty structure. It also embraces magnetic oxide of iron, and the sulphurets of iron, zinc, arsenic, &c.

In the United States. In New York, near the city, it occurs large grained, and sometimes with indications of a foliated structure. It is not phosphorescent; and contains tremolite. (BRUCE.)—In Connecticut, at

* Dolomit. WERNER. Dolomie. BROCHANT. Chaux carb. magnes. granulaire. HAUY Chaux carb. lente Dolomie. BRONGNIART.

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Washington, Litchfield Co. in very beautiful, white masses, fine grained, and resembling loaf sugar; it is so friable, that it crumbles between the fingers, and may be ground in a common flour mill; it contains the tremolite. This Dolomite effervesces rapidly with nitric acid; and is employed in the manufacture of mineral waters, one quart of its powder yielding a barrel of carbonic acid gas by heat, and two thirds of a barrel by sulph. acid—also at the Milford Hills, near Newhaven, mixed with quartz and tremolite. (SILLIMAN.)

(Remarks.) Magnesian limestones, when calcined and spread on land as a manure, are injurious to vegetation. This fact was ascertained by Smithson Tennant from observations, made near Doncaster, &c. in England. It does not appear, that this limestone is injurious, when applied before calcination.

SUBSPECIES 10. SILICEOUS CARBONATE OF LIME.*

This mineral, at first view, so much resembles a sandstone, that it has sometimes been called by that name. But its chemical characters and crystalline form establish its claim, as a subspecies of carbonate of lime. It is crystallized in rhombs, or presents itself in mammillary concretions, or in amorphous masses. Although its structure appears granular, its fracture presents shining spots by the light, reflected from its crystallized laminæ. It is sometimes sufficiently solid to give fire with steel, and is sometimes friable. It is opaque, and grayish white; its spec. gravity is 2.6.

In nitric acid, its calcareous part, about one third of the whole, dissolves with effervescence.

(Geolog. situation and Localities.) Its crystals are found, either solitary or in groups, in certain cavities, existing in beds of calcareous sandstone. When these cavities, usually filled with sand, are in part empty, it is sometimes the case, that one half of the crystal, in the state of a pure carbonate of lime, projects into the cavity, while the other half of the same crystal is siliceous.—These crystals seem to be formed by the filtration of water, containing carbonate of lime, into the aforementioned cavities. But the particles of sand are merely enveloped by the carbonate of lime, and do not prevent it from assuming one of its proper forms.

This mineral has been found only at Fontainbleau and Nemours in France. In the same vicinity also is a siliceous limestone, which is often cavernous; and the sides of its cavities are sometimes invested with siliceous stalactites, or crystals of quartz.

* Chaux carbonatée quartzfère. HAUY. BRONGNIART. Sometimes called crystallised sandstone of Fontainbleau.

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SUBSPECIES 11. MADREPORITE.* BROCHANT.

It is found in large, rounded fragments, composed of numerous, small prisms, nearly cylindrical. These prisms are parallel, or diverge from different centres.† Their cross fracture is conchoidal or even, and glistening with a resinous lustre. It is opaque; and its surface is dark grayish brown, but its cross fracture is nearly black.

It contains carbonate of lime 63, silex 13, alumine 10, oxide of iron 11;=97. (SCHROLL.) The same result was obtained at the School of the Mines.

It is found in the valley of Rüssbach, in the Saltzburg, but has never been seen in situ.

SUBSPECIES 12. CALP.‡ KIRWAN.

This mineral is found in large, compact masses, intersected by veins of white calcareous spar. Its fracture is very fine splintery, even, or a little conchoidal, and dull, excepting where laminæ of the calcareous spar are intermixed. It is opaque; and its color is bluish black, or dark grayish blue; but its streak is white. When moistened by the breath, it exhales an argillaceous odor. Its spec. gravity is 2.68. It is easily divisible into large tabular masses or parallel-opipeds.

It effervesces with acids; and, when calcined, becomes yellowish, and falls into thin plates, but does not burn to lime; it even melts at 130° W. into a black glass. It contains carbonate of lime 68, silex 18, alumine 7, bitumen 3, iron 2;=98. (KNOX.)

It passes into compact limestone and indurated marl. It is very abundant in the vicinity of Dublin, Ireland, where it is employed, as a building stone.

SUBSPECIES 13. FETID CARBONATE OF LIME.§

The most striking character of this subspecies is the fetid odor, which it exhales, when scraped with a hard, sharp pointed body. This odor, which appears to arise from sulphuretted hidrogen gas, is urinous, or more often like that of putrid eggs. It usually occurs in masses, either compact, or having a granular or foliated structure; its fracture, of course, is various, often earthy, and sometimes fine

* Madreporstein. (DE MOLL.) Chaux carbonatée Madréporite. BRONGNIART.

† Hence its name, from a supposed resemblance in its structure to certain Madrepores.

‡ Chauz carbonatée Calp. BRONGNIART.

§ Chaux carbonatée fetide. HAUY. BRONGNIART. Stinkstein. WERNER. Stinkstone. JAMESON. Swine stone. KIRWAN. La pierre puante. BROCHANT.

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splintery, conchoidal, or foliated, at least in certain parts. It is nearly or quite opaque and destitute of lustre. Its ordinary colors vary from gray to grayish black, brown, yellowish brown, &c.

It has also been found in grouped prisms, capable of mechanical division.

Before the blowpipe it loses its odor, and by calcination yields good lime. It is often a little bituminous. (BOURON.)

(Geolog. situation and Localities.) Its geological characters are similar to those of compact limestone. It forms large beds, or even whole mountains. It is sometimes associated with the oldest formations of secondary gypsum, and is often traversed by veins of calcareous spar.

In the United States. In Maryland, it is abundant on the Alleghany Ridge.—In New York, in Dutchess Co.—also in the vicinity of Niagara Falls, and Lake Ticonderoga.

SUBSPECIES 14. BITUMINOUS CARBONATE OF LIME.*

This substance is well characterized by the bituminous odor, which it exhales, when rubbed or heated. This odor is more offensive, than that of common bitumen, arising perhaps from a mixture of sulphuretted hidrogen, or some animal matter. Its color, which is black or brown, arises from the bitumen. It is sometimes compact with a dull, earthy or conchoidal fracture, and sometimes its structure is foliated. By friction it acquires negative electricity. By the application of heat it loses both its color and odor.

This mineral is found among secondary rocks, and sometimes in small quantities in the vicinity of coal.

(Localities.) In the United States. In Connecticut, near Middletown, it is black, and traversed by veins of white calcareous spar, and satin spar, and presents distinct impressions of fish; when once ignited, it continues to burn with a bright flame. (SILLIMAN.) It also occurs in a few other places in the U. States.

(Uses.) It is sometimes polished as a marble; indeed it forms, most of the black marbles. In Ireland it is sometimes employed, as a combustible. It burns to lime with less fuel, than common limestone.

SUBSPECIES 15. FERRUGINOUS CARBONATE OF LIME.†

Its color is dark gray; but is unequally diffused, the centre of a crystal being often darker than its summits, which are sometimes semitransparent. Its lustre is considerable, but not pearly. It

* Chaux carbonatée bituminifère. HAUY. BRONGNIART.

† Chaux carbonatée ferrifère. HAUY.

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strongly scratches limpid carbonate of lime, and its spec. grav. is 2.81. Its crystals easily yield the same primitive form, as the pure carbonate, and one of its secondary forms is an acute rhomb, with truncated summits.

It does not blacken by the action of fire, and is fusible by the blowpipe into a black glass, attracted by the magnet. When reduced to powder, it slowly dissolves in nitric acid with a slight effervescence. (HAUY.)

According to Vauquelin it contains much oxide of iron and a little silex.

In the environs of Saltzburg it is found in sulphate of lime.

SUBSPECIES 16. BROWN SPAR.* JAMESON.

This substance is best distinguished by its chemical characters. Its structure and fracture are usually foliated, and the laminæ have a pearly lustre more or less shining, and sometimes almost metallic. The exterior also presents the same pearly appearance, unless prevented by partial decomposition.

Its crystals resemble those of calcareous spar; but their planes are often curved, or their form is lenticular, or their thin edges are sometimes bent up, like those of a hat. Sometimes very minute rhombic crystals are so intimately grouped, that the mineral presents a scaly appearance.

It occurs also in laminated masses, sometimes globular, reniform, or cellular. It has also been observed with a fibrous texture.

It is a little harder than calcareous spar, but seldom so hard, as magnesian limestone. Its spec. gravity varies from 2.83 to 3.00. (BOURNON.) It is more or less translucent, at least at the edges, and the crystals are sometimes semitransparent. Its color is white or gray, either pure, or tinged with yellow or red; it also presents several shades of red, and is sometimes brownish, &c. The lighter colored varieties best exhibit the pearly lustre; but in proportion as the iron and manganese increase, its colors appear, and its pearly lustre diminishes.

(Chemical characters.) Before the blowpipe it becomes yellowish, or dark brown; even exposure to the air darkens its colors in consequence of the combination of oxigen with its metallic ingredients. It undergoes the same changes of color in nitric acid, in which it dissolves, though in most cases with but little effervescence, and produces a yellowish solution.—In this mineral the oxides of iron and man-

* Braun Spath. WERNER. Chaux carbonatée brunissante. BRONGNIART. Chaux carb. ferro-manganesifère. HAUY. Sidero calcite. KIRWAN. Le Spath brunissante. BROCHANT.

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ganese are always present, but in variable proportions from 4 to 10 or 15 per cent.—By an increase of its metallic ingredients it obviously approaches sparry iron ore, from which it is often difficult to distinguish some specimens of Brown spar.

(Geological sit. and Localities.) Brown spar most frequently occurs in metallic veins, accompanied by quartz, the carbonate and fluate of lime, the sulphurets of lead, zinc, iron, copper, silver, &c. Sometimes it appears in groups of little crystals, attached to other substances.

In the United States. In Pennsylvania, on Conestoga Creek, 9 miles from Lancaster, with adularia. (CONRAD.)

SUBSPECIES 17. MARL.* KIRWAN.

It has already been remarked, that compact limestone, by an increase of argillaceous matter, passes into Marl; and hence the same specimens have by different mineralogists been referred both to marl and compact limestone.†

Marl is essentially composed of carbonate of lime and clay in various proportions. But some marls are more or less indurated, while others are friable and earthy. In some the argillaceous ingredient is comparatively small, while in others it abounds and furnishes the predominant characters. The calcareous and argillaceous marls unite by imperceptible degrees, and the latter sometimes pass into clay. Marl frequently contains sand, and some other foreign ingredients.

It must hence appear impossible to establish distinct varieties; and accordingly some have divided marls into calcareous and argillaceous; others into indurated and earthy. For several reasons we adopt the latter division, and shall notice the former under the chemical characters and uses.

Var. l. INDURATED MARL.‡ KIRWAN. JAMESON. The hardness of this Marl is inconsiderable. In most cases it may be scratched by the finger nail, and may always be easily cut by a knife. It has a dull aspect, like chalk or clay, often with a few glimmering spots, arising from sand or mica. Its fracture, usually earthy, may also be splintery, conchoidal, or slaty. It is opaque; and its color is commonly gray, often shaded with yellow, brown, or black, &c. Shades of green and yellowish brown are not unfrequent in argillaceous marls. Its spec. gravity usually lies between 2.3 and 2.7.

* Mergel. WERNER. Marne. BRONGNIART. Argile calcarifère. HAUY. La Marne. BROCHANT.

† Some of the marlites of Kirwan belong to this intermediate class, while others may be referred to compact limestone.

† Verhærteter mergel. WERNER. La Marne endurcie. BROCHANT.

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Compact marls are sometimes traversed by fissures, dividing them into prismatic columns, resembling those of basalt; and, like those, they are sometimes articulated. The sides of these fissures are sometimes rendered brown, or even dendritic, by the filtration of metallic oxides.

(Chemical characters.) It is a character of all solid marls to disintegrate or crumble by exposure to the atmosphere, usually in the course of one year, but sometimes a longer period is requisite. This diversity of time depends on the nature of the marl, and its greater or less solidity.—The same changes generally take place in a very short time, when Marl is immersed in water, with which it forms a short paste. It however crumbles more easily, and forms a more tenacious paste, in proportion as it becomes more argillaceous. It is always more or less easily fusible.

All marls effervesce with acids, sometimes very briskly, and sometimes feebly, according to their solidity, and the proportion of carbonate of lime, which may vary from 25 to 80 per cent.; indeed in the argillaceous marls it is often much less. A little mica, as well as sand, is often present.

When the calcareous part of Marl is dissolved by an acid, the residue is composed chiefly of clay; but clay is a compound of silex and alumine in various proportions, and hence the nature of the marl will also vary according as the siliceous or aluminous ingredient of the clay may preponderate.—Marls acquire but little hardness in the fire, unless they are very argillaceous.

Ludus Helmontii. This name is given to orbicular masses of calcareous marl, usually from one to 18 inches diameter, whose interior presents numerous fissures or scams, which divide the mass into irregular prisms. These fissures are usually lined or filled by some crystallized substance, as calcareous spar or quartz, which have undoubtedly entered by filtration.—These masses are usually found in beds of Marl.

Marly Geodes. These are cavities of various forms, whose interior is often garnished with crystals of carbonate of lime. As the walls of these cavities are usually more compact, than the surrounding marl, the geode easily separates.

2. EARTHY MARL.* KIRWAN. JAMESON. This variety differs from the preceding by being more or less friable, or even loose; but they gradually pass into each other. Like the indurated marl, it may be either calcareous or argillaceous; it sometimes greatly resembles clay, but may be distinguished by its effervescence in acids.

* Mergel erde. WERNER. La Marne terreuse. BROCHANT.

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(Geol. situation and Localities.) Marl, like clay, belongs both to secondary and alluvial earths, where it occurs in masses, or in beds. Hence it may alternate with compact limestone or gypsum, or with sand or clay. It contains various organic remains, as shells, fish, bones of birds and of quadrupeds; and sometimes vegetables. The organic remains are numerous and extremely interesting in the marly strata, recently examined by Cuvier and Brongniart in the vicinity of Paris.—Earthy marl sometimes lies immediately under the soil, and may, at least in many cases, have resulted from the disintegration of indurated marl.

Marl is found more or less in most countries. In New Jersey, it is abundant, particularly in Monmouth and Burlington Counties. In the latter Co. it is greenish, contains sulphate of iron, and shells, and in one instance the entire skeleton of a shark has been found in this marl. (WOODBRIDGE.)—In New York, in Orange and Ulster Cos. it sometimes contains large fossil bones. (ARNELL and MILLER.)

(Uses.) The most general and important use of Marl is that of a manure for the improvement of the soil. The fertility of any soil depends in a great degree on suitable proportions of the earths, it contains; and whether a calcareous or argillaceous marl will be more beneficial to a given soil may be determined with much probability by the tenacity or looseness, moisture or dryness of that soil. It is hence obvious, that to employ marls judiciously, the farmer should be in some degree acquainted with the chemical properties or constituent parts of the marl itself, and with the ingredients of the soil.—He may, in general, determine the existence of marl by its falling into powder, when dried, after exposure to moist air. To ascertain the proportion of its ingredients, the calcareous part may be extracted from a given weight of the marl by solution in acids, and the residue, being dried and weighed, will give the quantity of clay sufficiently accurate.—Some marls do not produce their greatest effect, until several years after they have been applied to the soil.

In England the several varieties of marl are known by the names of stone marl, slaty or flag marl, clay marl, shell marl, &c.

SUBSPECIES 18. BITUMINOUS MARLITE.* KIRWAN.

This substance in its composition approaches nearer to marl, than to argillaceous slate. Its fracture is slaty; its layers are straight or curved, and the latter have very sensibly more lustre, than the former. It is opaque, and its colors are grayish or brownish black. Its spec. grav. is about 2.38.

* Bituminö;ser mergel schiefer. WERNER. Bituminous marle slate. JAMESON. Le schiste marno-bitumineux. BROCHANT.

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It effervesces with acids, in most cases strongly. Before the blowpipe it burns with a small flame, yields a bituminous odor, and melts into a black scoria. It differs from bituminous shale by its effervescence with acids.

This mineral occurs in secondary mountains. It is sometimes associated with compact limestone and red sandstone of the oldest formation, and contains pyritous copper and other ores of copper so abundantly, that it is worked as an ore of copper; hence sometimes called copper slate.

This marlite frequently contains the impressions or remains of plants and fish. These fish are most commonly in a contorted, unnatural position, those of the same species being usually together, as if collected in shoals; both of which circumstances indicate, that they perished by a sudden irruption or deposition of the mineral, which embraces them. Sometimes the scales only, and sometimes the whole fish has been converted into an ore of copper. Most frequently, however, the fish present a coaly appearance; and the bitumen of this mineral has undoubtedly arisen from the destruction of these marine animals.

Deposites of this substance are found in Italy near Verona, and in Thuringia, &c. in Germany.

SPECIES 8. ARRAGONITE.* HAUY.

Although this mineral is composed chiefly of lime and carbonic acid, yet there is reason to believe, that other ingredients are essential to its true composition. It differs from pure carbonate of lime in hardness, specific gravity, and crystalline structure. (See remarks under the chemical characters.)

The Arragonite is harder than calcareous spar, and scratches even fluate of lime; and its spec. grav. is equal to 2.91 or 2.94.—One of its most common forms is a six-sided prism, of which two opposite edges contain an angle of about 128° each; its sides are usually striated or channelled longitudinally, and are sometimes concave. The bases of this prism often exhibit lines or projecting edges, which converge towards the centre.—Another of its forms is a six-sided pyramid, elongated and cuneiform. Indeed there are not less than 13 modifications of the primitive form, which, according to Haüy, is an octaedron; but, according to Bournon, who has described 49 forms, depending on 9 modifications of the primitive, the latter is a tetraedral prism with rhombic bases.

* Arragonit. WERNER. L'Arragonite. BROCHANT. Arragone. JAMESON. Arragon spar. KIRWAN. Chaux carb. Arragonite. BRONGNIART . L' Arragonite and Chaux carbonatée dure. BOURNON.

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The prismatic crystals present natural joints parallel to their axes, and are divisible into rhomboidal prisms with angles of about 116°, and 64°; whereas those prisms, which result from the division of the cuneiform pyramids, have angles of 128°and 32°. (BOURNON.)

The Arragonite also occurs cylindrical, fascicular, reniform, coralloidal, or in amorphous, fibrous masses. Its longitudinal fracture is more or less foliated, or fibrous; but the cross fracture is uneven with a vitreous lustre, somewhat shining.

Its colors are milk white, greenish white, gray, pale yellow or violet. Some prisms have a tinge of violet in the middle, while the parts about the extremities are greenish or without color; in this case the greenish or colorless prism is penetrated nearly at right angles by another prism, having a violet color. It is translucent, and sometimes transparent as glass.

(Chemical characters.) In nitric acid it dissolves with effervescence. The analysis of no mineral has ever so much exercised the talents, exhausted the resources, and disappointed the expectations of the most distinguished chemists of Europe, as that of the Arragonite. Vauquelin and Fourcroy obtained lime 58.5, carbonic acid 41.5; and the analysis of Biot and Thenard, conducted with much ingenuity, scarcely differs from this, except in giving a little water. With these both Chenevix and Klaproth agree, in finding the Arragonite to contain lime and carbonic acid in nearly the same proportions, as in the common carbonate of lime.

If these results are correct, it is obvious, that the composition of this mineral is at variance with its crystalline structure, which does not yield a rhomb by mechanical division; thus giving to the crystals of carbonate of lime two primitive forms.

But a gleam of light has recently appeared on this subject. Kirwan in his mineralogy, published in 1794, conjectured that the Arragonite might contain strontian; and very recently Professor Stromeyer of Gottingen has discovered in this mineral between three and four per cent. of the carbonate of strontian. This discovery will very probably lead to a solution of the preceding difficulty; but it is important the analysis should be repeated by different chemists.*

Var. 1. FIBROUS ARRAGONITE.† It is in masses, composed of fibres, sometimes parallel, but usually diverging, and, in some instances, terminating in crystals.—It also occurs in reniform or globular masses, striated from the centre to the circumference.

* Dr. Wuttig, of Russia, has recently announced a mineral under the name miaszito, composed of the carbonates of lime and strontian, and most probably a variety of the Arragonite.

† Arragonite fibreux. HAUY.

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2. CORALLOIDAL ARRAGONITE.* It occurs in little cylinders, sometimes diverging from each other, and terminating in a point, or a fork, and sometimes branched, like coral. The surface, either smooth, or garnished with little crystalline points, is often very white with a silken lustre. Its texture is fibrous; and the fibres are divergent, and frequently inclined to the axis of the cylinder in an angle of about 30°. This structure clearly indicates a different mode of formation from that of calcareous stalactites.

This variety is often found in cavities in veins of sparry iron, and has hence been called flos ferri.

(Geolog. situation and Localities.) The gangue of this mineral is variable. In the province of Arragon,† in Spain, where it was first observed, it is disseminated in ferruginous clay.—In the valley of Leogang, in the Saltzburg, it is accompanied with fluate of lime, sulphate of barytes, and calcareous spar. (DE BUCH.) Minute crystals of red ferruginous quartz are implanted in the prisms of Arragonite from the Pyrennees.—At Vertaison, in France, it is in the fissures of a rock, which appears to be a basalt. (BRONGNIART.)

SPECIES 9. SILICEOUS BORATE OF LIME.‡

This mineral has recently been discovered by Esmark. It is sometimes in prismatic crystals with ten sides (Pl. III, fig. 23.), having two opposite, solid angles on each base truncated. The primitive form is a right prism, whose bases are rhombs with angles of 109° 28′ and 70° 32′. It also appears in large granular concretions, which frequently discover indications of a prismatic form; also in grains, or amorphous. The surface of the concretions is rough and glimmering.

Its hardness enables it to scratch fluate of lime, and its spec. grav. is 2.98. Its fracture is imperfectly conchoidal, shining, and nearly vitreous. Its color is white, shaded with gray or green, often very delicately.

When exposed to the flame of a candle, it assumes a dull white color, and becomes very brittle, even between the fingers. Before the blowpipe it swells into a milk white mass, and then melts into a pale rose colored glass. It is composed of lime 35.5, silex 36.5, boracic acid 24, water 4. (KLAPROTH.)

Var. 1. BOTRYOLITE.§ This variety occurs in botryoidal masses, composed of concentric layers, reddish at the exterior, but gray or

* Arragonite coralloïde. HAUY.

† Hence its name.

‡ Chaux boratée siliceuse. HAUY. Datholit. WERNER. Chaux Datholite. BRONGNIART.

§ Botryolit. DUNIN BORKOWSKI.

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yellowish gray within; or its colors alternate in narrow stripes. Its structure is fibrous with diverging and sometimes very delicate fibres.

In this variety Klaproth found lime 39.5, silex 36, boracic acid 13.5, water 6.5, oxide of iron 1;=96.5.

This species has hitherto been found only at Arendal in Norway, where it is associated with quartz, carbonate of lime, talc, magnetic iron, &c.

GENUS IV. MAGNESIA.

This genus contains four species, no one of which occurs in any considerable quantity.

SPECIES 1. SULPHATE OF MAGNESIA.*

Epsom Salt.

This salt possesses a remarkably bitter taste. Like many other native salts, it appears in efflorescences or concretions, composed of capillary fibres, and sometimes in minute prismatic crystals; also in a loose, mealy powder. Its color is usually grayish white.

It effloresces by exposure to the air, but less rapidly than sulphate of soda. It is soluble in its own weight of water at 60°, from which it may be precipitated by potash or soda; and is hereby easily distinguished from sulphate of soda. Before the blowpipe it dissolves in its water of crystallization, but is not easily fusible. When pure, it is composed, according to Bergman, of magnesia 19, sulphuric acid 33, water 48.

The Haar salz (hair salt) of Werner is probably a mixture of the sulphates of magnesia and of iron. Its taste resembles that of alum.

(Geolog. situation.) Sulphate of magnesia is very seldom found, except in a state of efflorescence, or dissolved in water. These efflorescences sometimes appear on the soil. Sometimes they exist on argillite, gneiss, and other minerals, which contain both magnesia and the sulphuret of iron, the latter of which, by the action of the air on its sulphur, furnishes sulphuric acid, which then unites with the magnesia. It may also arise from the mutual decomposition of the carbonate of magnesia and the sulphates of lime or iron.

It exists in considerable quantities in sea water; and is abundant in many mineral springs, as in those of Epsom, in England, and Sedlitz, in Bohemia.

(Uses.) It is employed in medicine, as a purgative; hence the

* Magnesie sulfatée.. HAUY. BRONGNIART. Natürliches bittersalz. WERNER. Natural Epsom salt. JAMESON. Le Sel amer natif. BROCHANT. Epsom Salt. KIRWAN.

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value of those mineral waters, which contain it. It is sometimes procured by evaporating such waters.—In other instances it is obtained from minerals, which embrace magnesia and sulphur. The sulphur is acidified by roasting and moistening the mineral; and the sulphate of magnesia, when formed, is extracted by lixiviation.—It exists also in considerable quantities in the bittern, which remains after extracting muriate of soda from sea water, from which it may be obtained considerably pure.

SPECIES 2. CARBONATE OF MAGNESIA.

A variety of minerals, containing magnesia and carbonic acid, have been observed in different places; but the acid appears to exist in proportions extremely variable, and has very probably been in part, at least, absorbed by the magnesia after exposure to the air; silex also, in greater or less quantities, is usually present. We have, therefore, with Brongniart, referred these substances to the Magnesite, a species arranged among the earthy minerals.

If any of these varieties deserve the name of Carbonate of Magnesia, it seems to be that,* discovered by Dr. Mitchell, at Robschütz in Moravia. It is found in masses, sometimes tuberose or cellular, the interior of the cells being rough. Its texture is compact or finely granular; and its fracture dull, earthy, splintery, and also conchoidal. It is soft, a little unctuous, and adheres to the tongue. It is nearly opaque, and has a yellowish gray color with blackish spots, or dendritic figures.

According to Mitchell and Lampadius, it contains magnesia 51, carbonic acid 47.4=98.4. But, according to Wondraschek, it sometimes contains magnesia 93, carb. acid 30, silex 8, water 20, lime 0.5, manganese and iron 1.5=93.

This variety was found in serpentine, and accompanied with Keffekil.

Klaproth has also analyzed a mineral from Styria, containing magnesia 48, carb. acid 49, water 3.

This salt is frequently found in mineral waters.

The magnesia of commerce is in the state of a sub-carbonate, and is often obtained by decomposing the sulphate of magnesia by an alkaline carbonate.

* Magnesie carbonatée. HAUY. Magnesie native. BROCHANT. Reine talk-erde. WERNER. Native talc earth. JAMESON. Magnesite de Mitchell. BRONGNIART.

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SPECIES 3. BORATE OF MAGNESIA.*

This mineral has hitherto been observed only in crystals, whose primitive form is a cube; and it usually occurs in cubes, variously modified. In one of its most common forms (Pl. III, fig. 24.) all the edges are truncated. Four of the solid angles, taken alternately, are also truncated, while the other four solid angles are replaced, each by four faces, of which three are usually very small, sometimes scarcely perceptible without a glass. It hence appears, that no two solid angles, viewed as the two extremities of the same axis, pássing diagonally through the cube, have the same modification.

In another form all the edges and four solid angles are truncated, while those angles, which, in the former variety, presented four faces, remain entire. It also occurs in dodecaedrons with rhombic faces, four of whose solid angles are sometimes modified by additional faces. Haüy has described 5 secondary forms.

These crystals, though sometimes nearly half an inch in thickness, are usually quite small, with smooth, shining faces; sometimes, however, the surface is rough and apparently corroded.

The most remarkable character of these crystals is the property of becoming electric, by heat, at the eight solid angles, four of which give positive electricity, and the other four, negative. The two extremities or poles of the same axis, passing diagonally through the cube, possess opposite electricities, and differ also in their form or number of faces.—In the first variety, negative electricity appears on the four solid angles, replaced by four faces each.

Their fracture is imperfectly conchoidal; they scratch glass and give fire with steel; their spec. gravity is about 2.56. They are opaque, translucent, or even transparent; and their colors are usually white or gray, sometimes shaded with yellow, green, violet, or black.

Before the blowpipe it is fusible with ebullition into a yellowish enamel. It does not dissolve in cold acids. The transparent crystals are a pure borate of magnesia; but when opaque and of a violet or blackish color, they usually contain 10 or 12 parts of lime and a little silex, alumine, and oxide of iron.

(Geolog. situation and Localities.) This is a very rare mineral. It has been found in the mountain Kalkberg, near Lunenburg, in Lower Saxony, imbedded in gypsum.—Also at Segeberg, in Holstein; in the specimens, which the writer possesses, from the latter place the cubes are imbedded in anhydrous sulphate of lime.

* Magnesie boratée. HAUY. BRONGNIART. Boracit. WERNER. Boracite. KIRWAN. JAMESON. BROCHANT.

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SPECIES 4. FLUATE OF MAGNESIA.

This substance is said to have been discovered by Dr. Bruce of New York. Its name was inserted in the Tabular view, with the hope, that the discoverer would have published a description of this new mineral in season to be here inserted.

GENUS V. ALUMINE.

SPECIES 1. MELLATE OF ALUMINE.*

The color of this very rare mineral is almost always honey yellow, sometimes a little tinged with brown. It is crystallized in octaedrons, which are sometimes truncated on all the solid angles, or only on those of the common base, thus forming a dodecaedron with rhombic faces. This octaedron, which is also the primitive form, is composed of two pyramids with square bases, and isosceles triangular faces; and the incidence of any face of one pyramid upon the corresponding face of the other is 93° 22′. It is sometimes in grains or fragments of crystals.

These crystals have smooth, shining surfaces; and their fracture is conchoidal with a strong lustre, somewhat resinous. They are brittle, and easily cut by a knife. They are more or less translucent, or even transparent, and exhibit double refraction in a much higher degree, than they would, it, with equal density, they contained no combustible. By friction they acquire a weak negative electricity, but of short duration, unless the crystal be insulated. Their spec. grav. lies between 1.58 and 1.66.

Before the blowpipe this mineral first whitens, and becomes opaque, then blackish and falls into ashes, but does not melt. It yields neither flame, smoke, nor odor. It is composed, according to Klaproth, of alumine 16, mellitic acid 46, water 38.

It differs from amber in its weak electricity, double refraction, and chemical characters.

This substance has been found chiefly at Artern, in Thuringia, either on the surface, or in the interstices of bituminous wood;—and in Switzerland with asphaltum.

* Mellite. HAUY. BRONGNIART. Mellilite. KIRWAN. Honigstein. WERNER. Honey stone. JAMESON. La Pierre de miel. BROCHANT.

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ORDER IV.

Salts with an alkaline and earthy base.

SPECIES 1. ALKALINE SULPHATE OF ALUMINE.*

Alum.

No one of the physical characters of this salt, except its astringent and somewhat sweetish taste, is of much use in determining its presence, as found native. When not enveloped in other minerals, it usually appears in efflorescences, composed of capillary crystals or fibres. Sometimes these crystals are white, and silky, parallel to each other, and perpendicular to the surface, on which they stand, and are then often called plume, or fibrous Alum; sometimes the efflorescence resembles a mould, or is in a loose powder. Native Alum also occurs in concretions or stalactites. Its white color is sometimes contaminated by shades of gray, yellow, or green.

Its crystals, artificially obtained, are usually regular octaedrons.

It is soluble in about 3/4 its weight of boiling water; and, by the addition of ammonia, yields a white precipitate of alumine. Before the blowpipe it dissolves in its own water of crystallization, and then dries into a white, spongy mass. The mean result of several specimens of the Alum of commerce from different countries, according to the analysis of Vauquelin, is alumine 10.50, potash 10.40, sulphuric acid 30.52, water 48.58. Ammonia is also common in the Alum of commerce, but rare in native Alum, which, however, is usually contaminated by other salts.

Its taste, unless greatly modified by some foreign salt, will distinguish it from sulphate of magnesia; and it does not, like the sulphate of iron, yield a black precipitate on the addition of an infusion of nutgalls.

The Haar salz (hair salt) of Werner, formerly supposed to be a variety of alum, is, according to Klaproth, a mixture of the sulphates of magnesia and iron.

Native Alum is sometimes mingled with clay and oxide of iron.† It occurs in the cavities or fissures of argillaceous slate in soft masses, a little unctuous, and sometimes tuberose or stalactical. It is opaque, and usually has a yellowish color.

(Geological situation and Localities.) Native Alum is usually found in connexion with argillaceous earths or stones, or with volcanic

* Alumine sulfatée alkaline. HAUY. Alumine sulfatée. BRONGNIART. Natürlicher alaun. WERNER. Natural alum. JAMESON. L'Alun natif. BROCHANT. Alum. KIRWAN.

† Borg butter. WERNER. Rock butter. JAMESON.

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products. Sometimes it is diffused through certain earths, turfs, or stones; but most frequently appears efflorescing in the cavities and fissures, or on the surface of certain argillaceous slates, hence called aluminous slate.

It is also found on the surface of clays, which embrace the sulphuret of iron.

This salt is not uncommon in volcanic countries, either investing certain lavas, or contained within them. Very fine specimens of fibrous Alum are found in the island of Milo, in the Archipelago, mingled with fibrous gypsum in volcanic rocks. It is found in considerable quantities at the Solfaterra, near Naples, rising in efflorescences on the soil; at La Tolfa in Italy, disseminated in an argillaceous mineral, called Alum stone.

In Scotland, at Hurlett, near Glasgow, the aluminous slate, impregnated with pyrites, constitutes the roof of a coal mine.

In the United States, native Alum has been observed in several instances, especially in Tennessee and Pennsylvania.

(Modes of obtaining Alum.) The modes of obtaining this salt are various, and dependant on the nature of the minerals, or Alum ores, from which it is extracted.

When this salt exists, already formed, in earths or friable minerals, it is extracted by lixiviation; but, if the mineral be solid, it must be previously calcined. Thus, if the Alum stone of La Tolfa be merely lixiviated, it yields no salt; but, after calcination, it becomes disintegrated by the gradual action of moisture and the heat of the sun, and then yields its Alum by lixiviation. The calcination and exposure to the atmosphere are not here necessary to acidify the sulphur; for, according to the analysis of Vauquelin, the Alum, united with a large quantity of silex, exists already formed in this stone.

But, more frequently, those minerals, which furnish this salt, are argillaceous substances, which contain pyrites, that is, sulphur united with iron, and sometimes also the potash, requisite to the formation of Alum. The sulphur is acidified either by calcination in a moderate heat, or exposure to the air, or by both methods united. The acid, thus produced, unites with the alumine of the mineral, and forms sulphate of alumine, to which, if potash be not present, either that alkali or ammonia must be added. The alkali is sometimes furnished by the addition of ashes, which contain potash, or of urine, which contains ammoniacal salts.—By the same process also the sulphates of lime, magnesia, and iron may be produced in the same ore.

When the ore or argillaceous mass is sufficiently disintegrated, the Alum is extracted by lixiviation and crystallization.

The differences, which exist between the several varieties of the

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Alum of commerce seem to depend chiefly on the greater or less quantity of the sulphate of iron, which they contain. According to Vauquelin the Roman Alum, prepared at La Tolfa, contains the least sulphate of iron; it has usually a rosy tinge. A thousandth part of iron, contained in Alum, produces a sensible effect in dying. (THENARD.)

The English Alum, of which there are manufactories in Yorkshire, &c. contains more iron than the Roman, and is often in large masses with a resinous lustre.

Roch Alum appears to have derived its name from Roccho (Edessa), an ancient city of Syria, where a manufactory of this salt was early established.

(Uses.) Alum is employed in dying to fix the color, and sometimes to heighten it. It hardens tallow, and increases the adhesive power of common paste. Wood and paper, soaked in its solution, are less combustible. It has other uses in the arts; and is also employed in medicine as an astringent, or, when calcined, as an escha-rotic.

SPECIES 2. FLUATE OF SODA AND ALUMINE.*

This very rare mineral has been found only in masses, whose fracture is foliated, with a moderate lustre. It is brittle, and sufficiently hard to scratch sulphate of lime, but is itself scratched by fluate of lime. Its color is white, sometimes grayish or milk white. It is more or less translucent; but when a small fragment is plunged in water, it becomes nearly or quite transparent, and resembles a jelly. Its spec. grav. is about 2.95.

(Chemical characters.) Its chemical characters are very remarkable. Before the blowpipe it dissolves in its own water of crystallization, almost as suddenly as ice;† it then dries, and forms a kind of scoria, which is not easily fusible. It is insoluble in water, but dissolves in sulphuric acid with the extrication of white vapors of fluoric acid.

It is composed of alumine 24, soda 36, fluoric acid and water 40. (KLAPROTH.)

It has been found only in Greenland.

SPECIES 3. GLAUBERITE. HAUY. BRONGNIART.

Anhydrous sulphate of soda and lime.

This triple salt occurs in oblique four-sided prisms with rhombic bases. It is limpid, or has a pale yellow color, and retains its trans.

* Alumine fluatée alkaline. HAUY. Alumine fluatée, BRONGNIART. Kryolith. WERNER. Cryolite. JAMESON. Cryolithe. BROCHANT.

† Hence the name Cryolite, from χρνος and λιθος.

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pareney in the air, unless it be moistened. It scratches sulphate of lime, but is less hard than carbonate of lime. When immersed in water, it appears milk white and opaque; but, when taken out, an exterior white coat soon falls to powder, and leaves the interior unaltered. Its spec. grav. is 2.73.

Before the blowpipe it splits, decrepitates, and melts into a whits enamel. It is composed of anhydrous sulphate of soda 51, anhydrous sulphate of lime 49. (BRONGNIART.)

It has been found near Ocano in New Castile, Spain, disseminated in muriate of soda.

CLASS II.

Earthy compounds, or Stones.

The minerals, which belong to this class, are composed chiefly of earths, sometimes united to an alkali. Indeed a combustible, or even an acid is sometimes present; but, in most cases, the two last mentioned substances are merely accidental. The numerous colors, which these minerals present, almost always arise from some metallic oxide.

In the determination of the species, this class presents many difficulties, arising from the present imperfection of chemical analysis. Of the various ingredients, which chemistry may find in a given mineral, we know not which are essential to the species, and, of course, cannot with certainty distinguish them from those, which are only accidentally present; nor do we know in what manner even essential ingredients were united in the mineral before analysis. (See Introd. 180, 189.)

No advantage can arise from forming genera and orders in this elass, till such divisions can be established on more scientific principles, than is practicable at present.

It is not perhaps possible, in the present state of mineralogical knowledge, to arrange the species in this class in a very satisfactory manner. The Topaz is here placed first, because in its composition it resembles the preceding class, and ought, perhaps, to be arranged in it. The other species, beginning with alumine nearly pure, as it appears in the sapphire, are thrown into groups, which are determined by a similarity of composition, according to the most recent analyses. The arrangement of the groups also is regulated by the same principle, those, which appear to have the greatest similarity of composition, being, in general, placed contiguous. One advantage at least results from this disposition of the species;—the agreement or disagreement of external characters in those minerals, which appear to have a similar composition, will be easily perceived.

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Certain minerals in this class have received the name of gems or precious stones. Their value, as articles of luxury or commerce, depends, in a great degree, on their hardness, transparency, or color. The most important are the sapphire, embracing the oriental ruby, sapphire, and topaz; spinelle; emerald; topaz; and amethyst. Sometimes also the beryl, the garnet, the hyacinth, quartz, &c. are employed in jewelry.

SPECIES 1. TOPAZ.* WERNER. JAMESON.

The Topaz may, in general, be recognised by the eye. It is almost always in prismatic crystals, which, at first view, seem to have only four sides, with rhomboidal bases. Their sides are longitudinally striated, their terminating planes smooth, and their surface has usually a high lustre. They have never been observed under their primitive form, which is an octaedron, according to Haüy, who has described ten secondary forms; from these we select a few of the more common.

The crystal (Pl. III, fig. 25.) is an eight-sided prism, with a four-sided summit. When terminated by pyramids at both extremities, which is rarely the case, the two pyramids differ from each other. Two opposite lateral edges contain each an angle of 98° 6′ two others an angle of 124° 22′ and each of the remaining four edges a very obtuse angle of 161° 16′, thus giving the crystal the general aspect of a four-sided prism.

Sometimes the pyramid, in the preceding variety, has two additional faces, which stand on the least obtuse edges, and are inclined to each other in an angle of 91° 58′ these two sides sometimes meet in a line and give the termination a cuneiform or bevelled appearance.

Sometimes the six-sided summit of the preceding variety is truncated (Pl. III, fig. 26.) by a plane, perpendicular to the axis of the prism.

Another form (Pl. III, fig. 27.) is an eight-sided prism, one summit having six, and the other ten faces.—Indeed, nearly all its forms may be referred to 8 or 12 sided prisms variously terminated, sometimes even by fifteen faces.

It is sometimes cylindrical, or occurs in laminated, or in rolled masses. Though easily broken, it scratches quartz, but is less hard, than the spinelle. Its fracture, parallel to the base of the prism, is

* Silice fluatée alumineuse, HAUY. Topaze. BRONGNIART. BROCHANT.
The name Topaz is derived from the Greek Тοπαζιον; but it is not certain, that the ancients applied this name to the mineral, which is now called Topaz.

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foliated, and more or less conchoidal in the direction of the axis. Its lustre is strong and vitreous; its refraction double; and its spec. grav. varies from 3.46 to 3.56.

Some varieties, particularly these found in Brazil and Siberia, acquire electricity by heat; the two summits possess opposite electricities, and have at the same time a different conformation. (See Introd. 188.) The Topaz from Saxony easily becomes electric by friction; and sometimes by heat. (HAUY.)

It is commonly transparent, sometimes translucent, and the milk white variety is opaque. It is sometimes limpid as quartz; but its prevailing color is yellow, often pale, sometimes tinged with red, orange, or green, and thence passing to red or a pale green, greenish blue, or greenish white and even to gray and white.

(Chemical characters.) Before the blowpipe it is infusible. By the compound blowpipe, in which the flame of burning hidrogen is urged by a stream of oxigen gas, the Saxon Topaz melts with ebullition into a white enamel. (SILLIMAN.) The yellow Brazilian Topaz, strongly heated, becomes rose red, but the Saxon Topaz, white. A mean of three analyses by Vauquelin on specimens from Saxony, Siberia, and Brazil, gives alumine 49, silex 29.3, fluoric acid 19; a little iron is sometimes present, and there was a loss of 2 in each analysis. The powder of the Topaz in the course of a few hours changes the vegetable blue to green. Does not this indicate, that its analysis is yet imperfect?

A careful examination of its comparative hardness, its specific gravity, and electric powers, will be sufficient to distinguish it from the sapphire, spinelle, chrysoheryl, and emerald, even when all these substances are deprived of their native form by the lapidary.

PYROPHYSALITHE. HISENGER and BERZELIUS. This is probably a variety of the Topaz. It is greenish white, translucid or opaque, and sometimes prismatic. On burning coals it phosphoresces in consequence of the fluate of lime, with which it is mixed.—It has been found near Fahlun, in Sweden, in granite, from which it is separated by a layer of talc.

(Geolog. situation and Localities.) The Topaz appears to belong almost exclusively to primitive rocks, and more particularly to the oldest. In Siberia, in the Uralian mountains, it is found in graphic granite, with beryl and quartz.—In Saxony and Bohemia it is found in granite, or in veins, which traverse granite, gneiss, and mica slate, with oxide of tin, apatite, &c. At Schneckenstein, in Saxony, is an aggregate of quartz, schorl, mica, Topaz, &c. hence called Topaz rock.—The red Topaz of Brazil is sometimes imbedded in quartz.—The Topaz is sometimes found in alluvial earths.

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which have proceeded from the disintegration of primitive rocks. In this manner it occurs in Aberdeenshire in Scotland, with rock crystal and beryl. An entire crystal, probably the largest ever seen, has been found in Aberdeenshire, weighing more than 7 ounces troy; and a fragment of another, weighing more than one pound. (JAMESON.)

(Uses and Remarks.) When the Topaz is without flaws and of a pure yellow, it is somewhat esteemed in jewelry. In general, the Saxon Topaz presents a pale yellow; the Brazilian a deeper yellow, sometimes tinged with red, or is entirely red; and the Siberian Topaz is usually colorless, white, pale greenish blue, or greenish white, the last of which is the predominant color of the Topaz of Scotland.*

SUBSPECIES 1. PYCNITE.† HAUY. BRONGNIART.

This mineral, though sometimes in hexaedral prisms, nearly regular, most frequently appears in long, irregular prisms or cylinders, longitudinally striated, and united, parallel to each other, in bundles. It slightly scratches quartz: and is very brittle in a direction perpendicular to the axis of the prisms. Its cross fracture is imperfectly foliated, and its longitudinal fracture more or less conchoidal, with a moderate lustre. Its spec. gravity varies from 3.51 to 3.53; and it is electric by heat. (HAUY.)—It is translucent; and its colors are usually yellowish white, straw yellow, greenish or reddish white.

Before the blowpipe it is infusible. It contains, according to Bucholz, alumine 48, silex 34, fluoric acid 17, oxides of iron and manganese 1. Vauquelin found the same ingredients, but less acid, and more alumine.

It differs from the beryl by a greater spec. gravity, and inferior hardness;—from epidote, actynolite, &c. by its infusibility.

The Pycnite has been found chiefly at Altenberg, in Saxony, in a primitive rock, composed mostly of quartz or mica.

SPECIES 2. SAPPHIRE.‡

The minerals, which belong to this species, include some of the most valuable gems, and have been, by some mineralogists, divided into several species. In fact, the several varieties, although agreeing

* Much confusion has been produced in mineralogy by placing too much reliance on color. Hence the yellow sapphire has been called oriental Topaz; the yellow emerald Siberian Topax; yellow quartz, Bohemian or occidental Topaz; smoky quartz, smoky Topaz; and the chrysolite has sometimes exchanged names with the Topaz.

† Schö;rlartiger berill. WERNER. Schorlous beryll. JAMESON. Schorlite. KIRWAN. Le beril schorliforme. BROCHANT.

‡ From the Greek Σαπφζος. Corindon. HAUY.

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in their essential and specific characters, exhibit a great diversity of external aspect.

Its hardness, greater than that of any other earthy mineral, and inferior to that of the diamond only, is one of its most obvious and distinguishing physical characters. Its specific gravity also is very high, extending from 3.71 to 4.28. It possesses double refraction; and varies from opaque to transparent. Of its numerous colors blue, red, yellow, and gray are the most common.

Though sometimes amorphous, it is very frequently in regular crystals, whose primitive form is a rhomb, slightly acute, each of the plane angles at the summits being 86° 26′. In the opaque crystals the natural joints, parallel to the faces of the rhomb, are usually very obvious; but in most of the transparent crystals, those joints, which are perpendicular to the axis of the rhomb, are the most distinct. Its integrant particles appear to be irregular tetraedrons.

Of the primitive form Haüy has described eight modifications, which, by combining with each other, still farther increase the variety of forms.

It but seldom appears under the primitive form, the summits of which are sometimes truncated perpendicularly to the axis.—Another secondary form is a regular six-sided prism, which is sometimes truncated on three alternate angles at each extremity (Pl. III, fig. 28.)— The same crystal may also be truncated on all its edges, or only on its terminal edges.—Another form is a dodecaedron, or double six-sided pyramid, two corresponding faces of which form with each other, at the common base, an angle of 139° 54′.—Sometimes the summits of this dodecaedron are truncated perpendicularly to the axis (Pl. III, fig. 29.), and, at the same time, three alternate angles at each extremity are also truncated. In fine, nearly all its secondary forms may be referred to a rhomb, a six-sided prism, or a double six-sided pyramid.

It also occurs in laminated, cylindrical, or rounded masses.

The Sapphire, though the hardest earthy substance, appears to be essentially composed of pure alumine; a little silex and oxide of iron being sometimes present. (See results of analysis under the several varieties.) It is infusible by the blowpipe.

SUBSPECIES 1. PERFECT SAPPHIRE.*

This subspecies is usually crystallized under some of the forms already mentioned, but sometimes occurs in amorphous or rounded

* Saphir. WERNER. Sapphire. JAMESON. Le Saphir. BROCHANT. Corindon hyalin. HAUY. Corindon Telesie. BRONGNIART. Perfect corundum. BOURNON. Oriental ruby, sapphire, and topaz. KIRWAN.

25

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fragments. It is easily broken; and its fracture, though sometimes more or less foliated, is usually conchoidal, splendent, and vitreous. Its hardness is a little superior to that of the following subspecies.— The perfect Sapphire is commonly more or less transparent, but sometimes only translucent. Its colors are blue, violet, red, yellow, and green, which present many intermediate shades; it also occurs limpid, or gray. The same crystal, on different parts, sometimes presents two or three different colors; or it is partly limpid, and partly colored.

The importance of this subspecies permits several subdivisions, founded on color, or the reflection of light.

Var. 1. BLUE SAPPHIRE. (Oriental sapphire.) The term Sapphire has, in the arts, been peculiarly appropriated to this variety of color. The finest specimens exhibit an azure or indigo blue. When bluish white, the Germans call it luchs saphir. Sometimes one part of the crystal is destitute of color, or different colors are separated by a limpid part. Some blue Sapphires lose their color in the fire; others remain unaltered; and others become still more blue. In one specimen Klaproth found alumine 98.5, oxide of iron 1, lime 0.5.

2. VIOLET SAPPHIRE. (Oriental amethyst.) Its color is often very lively.

3. RED SAPPHIRE. (Oriental ruby.) It is sometimes a lively and intense red, and sometimes aurora red. A specimen, analyzed by Chenevix, yielded alumine 90, silex 7, oxide of iron 1.2;=98.2.

4. YELLOW SAPPHIRE. (Oriental topaz.) This, when exposed to a strong heat, loses its color.

5. LIMPID SAPPHIRE. This, sometimes called white Sapphire, is grayish, or colorless.

CHATOYANT SAPPHIRE. (Oriental girasole.) It is sometimes translucid and nearly limpid, reflecting slight tints of blue and red; and sometimes it reflects a pearly light.

ASTERIATED SAPPHIRE. This, when cut, and viewed in certain directions, presents a very peculiar reflection of light in the form of a star, with six radü; this appearance is undoubtedly connected with the edges of the rhombic nucleus.

(Geolog. situation.) The Perfect Sapphire has perhaps never been seen in its native situation. It is found in the sand of some rivers, and in alluvial earths, at the foot of primitive or secondary mountains. It is often accompanied by zircon, garnet, magnetic iron, &c. It is also said to have been found in ferruginous clay in the crevices of primitive rocks.

(Localities.) The finest Sapphires come from Pegu and Ceylon.

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This mineral has also been found in the stream of Expailly, near Puy, in France;—and near Bilin in Bohemia.

(Uses and Remarks.) Beside its well known use, as an article of ornament, it is employed for jewelling the pallets of escapements, and the holes of wheel pivots in astronomical clocks and watches.— The red sapphire is most highly esteemed, its value being sometimes equal to that of a diamond of the same size, and estimated at above 1000 guineas. The blue has the second, and the yellow, the third rank.

Those precious stones, which are employed in jewelry, were formerly distributed into different species, according to their colors; hence all red gems, possessing a certain degree of hardness, were called rubies; the blue, Sapphires; the yellow, topazes, &c. But, as the best rubies, Sapphires, &c. came from India, they were called oriental; while other minerals of inferior value, found in Europe, and erroneously referred to the same species, as the oriental gems, chiefly because they had the same colors, were called occidental. It appears, however, that most of the oriental gems form but one species, presenting various colors, and essentially differ from those called occidental; they occur also in other countries than India. Hence the terms oriental and occidental, as applied to the same species, now designate different degrees of perfection only, without indicating the locality.

SUBSPECIES 2. CORUNDUM.*

The Corundum is sometimes in crystals, whose more common form is a six-sided prism, on the base of which concentric, hexaedral zones of different colors often appear. It also occurs in amorphous masses of a moderate size, sometimes rolled.—Its natural joints are very obvious, at least in two directions, and it is easily divisible into rhomboidal fragments; its fracture is foliated, often with a shining lustre; the cross fracture is uneven, or somewhat conchoidal.

It is opaque or translucent, and sometimes strongly semitransparent. Its colors are neither lively nor numerous; they are commonly greenish gray, flesh or deep red, yellowish, or blue; and sometimes gray, with a pearly or metallic aspect.

Its colors are usually weakened by exposure to heat. Before the compound blowpipe it is immediately fused into a gray globule. (SILLIMAN.) A specimen from the carnatic yielded Chenevix alumine 91, silex 5, oxide of iron 1.5;=97.5.

* Korund. WERNER. Corindon-harmophane. HAUY. Corindon adamantin. BRONGNIART. Imperfect corundum, BOURNON. Adamantine Spar. KIRWAN Le Spath adamantine. BROCHANT.

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Its infusibility and hardness, which is but little less, than that of the perfect sapphire, serve to distinguish it from all minerals, which it resembles in external characters.

Var. 1. ADAMANTINE SPAR.* Its color is dark brown, and its internal lustre usually very strong. It comes from China, and almost always contains grains of magnetic oxide of iron. A specimen was found by Chenevix to contain alumine 86.50, silex 5.25, oxide of iron 6.50;=98.25.

(Geological sit. and Localities.) The Corundum appears to belong to primitive rocks, and particularly to granite, into the composition of which it sometimes enters; hence scales of mica and particles of feldspar sometimes adhere to its surface. In India, the granite, which embraces Corundum, also contains fibrolite, epidote, talc, garnets, zircon, magnetic iron, &c. It is found also in Malabar, the Carnatic, and other parts of the East.—In Italy it has occurred in mica slate.—The variety, called Adamantine spar, is found in China, in a granitic rock, containing much fibrolite and magnetic iron; the iron is disseminated through its interior, whereas, in the Corundum of India, it is usually confined to the surface.

In the United States, it is by some supposed to exist in Maryland, near Baltimore;—and in Connecticut, at Haddam, in the same granite, which contains chrysoberyl, &c.

It may be employed, like emery, in polishing hard substances.

2. EMERY.† KIRWAN. JAMESON. This substance is most probably a compact variety of Corundum. It is well characterized by its great hardness, in which it equals the common Corundum; its powder is, in fact, capable of scratching or wearing down all minerals, except the diamond. Its spec. grav. is about 4.00.

It is always amorphous; its structure finely granular; its fracture uneven or splintery; and its lustre moderate, but sometimes nearly metallic.—It is opaque, or slightly translucent at the edges; and its color varies from a deep gray to bluish gray or grayish black, and is sometimes brownish. It is a conductor of electricity, and often affects the needle.

A specimen from the isle of Naxos yielded Tennant alumine 86.5, silex 3, oxide of iron 4;=93.5. In another from the island of Jersey Vauquelin found alumine 70, iron 30; but the iron appeared to be mechanically mixed, rather than combined. Indeed Emery usually contains foreign substances, which sometimes give the mass a slaty structure.

* Diamant spath. WERNER. Diamond spar. JAMESON.

† Schmirgel. WERNER. Emeril. BRONGNIART. BROCHANT. Corindon granulaire. HAUY.

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Its hardness sufficiently distinguishes it from jasper, oxide of iron, and some other minerals, which it externally resembles.

(Geolog. situation and Localities.) Emery appears to belong to primitive rocks, but its geological relations are not well known.—In Saxony it is disseminated in a bed of indurated steatite. (BROCHANT.)—In the island of Jersey, on the coast of Normandy, it is found in masses, which resemble magnetic iron, and contain small plates of mica; it gives a dark red powder.—In the island of Naxos, in the Archipelago, it exists abundantly in fragments or rolled pieces, at the foot of primitive mountains, and contains mica, magnetic iron, &c. A few other localities have been observed, but the Emery of commerce is chiefly from Jersey and Naxos.

(Uses.) This article is almost indispensable in polishing metals and hard stones. It is previously reduced to a powder by pulverizing it in a steel mill. This powder is agitated in water, in which its particles become suspended, and are then permitted to deposite themselves for a certain length of time; and by repeated washings and by suffering the deposite to go on for 15, 10, 5, &c. minutes, the powder of Emery is obtained of different degrees of fineness.

On metals it is commonly employed with oil, and on stones with water. Certain ores of iron and other substances have, in the arts, received the name of Emery.

SPECIES 3. DIASPORE. HAUY. BRONGNIART.

This mineral is but little known. It is composed of laminæ, somewhat curved, easily separable from each other, and possessing a pearly gray color, with considerable lustre. These laminæ, according to the natural joints, which they present, when examined by a light, seem to have separated in the direction of the smaller diagonals of the bases of a rhomboidal prism.—The edges or angles of its fragments are capable of scratching glass. Its spec. grav. is 3.43.

(Chemical characters.) A small fragment, placed in the flame of a candle, almost instantly decrepitates, and is dispersed in numerous little spangles. Hence its name, from the Greek Διασπϵιρω. It is composed of alumine 80, water 17, iron 3. (VAUQUELIN.)

Nothing is known of its geological situation. Its gangue is a rock, both argillaceous and ferruginous.

SPECIES 4. WAVELLITE.* BRONGNIART.

This rare mineral is sometimes in extremely minute, prismatic crystals, of an indeterminable form, collected into little tufts, or more

* Hydrargillite. DAVY.

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irregularly grouped and resembling down. These tufts are easily reducible to a very white powder.—But more frequently it appears in small, mammillary or rounded masses, often about the size of a pea, and intimately grouped; but each of these nodules or hemispherical masses is composed of fibres, radiating from a centre. The fragments of these masses scratch calcareous spar.

The Wavellite is transparent, or only translucent; its color is white, either pure, or tinged with gray, green, or yellow; and its lustre silky. Its spec. grav. lies between 2.25 and 2.70.

(Chemical characters.) This mineral before the blowpipe loses its hardness and transparency, more than one fourth of its weight, and becomes adhesive to the tongue; but does not melt. When pure, it is soluble in the stronger acids and in alkaline solutions, if assisted by heat. According to Davy it is essentially composed of alumine 70, water 30; but a little silex, lime, or oxide of iron is usually present. It appears also to contain a small portion of fluoric acid, which is sometimes sufficiently abundant, when liberated by sulphuric acid, to corrode glass. In a specimen from Barnstaple, Eng. Klaproth found alumine 71.5, water 28, oxide of iron 0.5.

This mineral is subject to spontaneous decomposition, affecting its lustre, transparency, hardness, spec. gravity, &c. indeed it is sometimes reduced to a substance, resembling clay.

(Geolog. sit. and Localities.) The Wavellite was first found by Dr. Wavell, at Barnstaple, in Devonshire, in cavities, or forming veins in an argillite.—At St. Stephen's, in Cornwall, it exists in the cavities of granite, adhering in little tufts to the quartz, or forming a stratum on its surface.—In Ireland, near Dublin, at the foot of a hill of siliceous slate, it occurs in small nodules, invested with an earthy crust, but within composed of crystalline spiculæ. (Fitton in Geolog. Trans. v. i.)

SPECIES 5. SPINELLE. HAUY. BRONGNIART.

This species, though sometimes in rounded grains, most frequently occurs in crystals, whose primitive form is a regular octaedron, composed of two four-sided pyramids, applied base to base; any two contiguous faces of which meet under an angle of 109° 28′. The Spinelle usually presents its primitive form, which, however, is sometimes more or less modified. Thus the octaedron may be elongated, and its summits cuneiform; or it may be truncated on all its edges, or only on those, which form the common base of the two pyramids. Indeed the octaedron may be so modified by these truncations, as to resemble a tetraedron, or rhomb.—Sometimes it appears in dodecaedrons with rhombic faces, and in hemitrope or double crystals (Pl. II,

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fig. 29.) with a re-entering angle. (See Introd. 82.) Haūy has described 4 secondary forms. Its integrant particles are regular tetraedrons.

The Spinelle scratches quartz, but is itself scratched by the sapphire, and is a little less hard, than the chrysoberyl. Its structure is usually foliated, with laminæ parallel to the faces of the octaedron.

Before the blowpipe it is infusible; and does not even lose its color. It appears to be essentially composed of alumine and magnesia, having the chromic acid or the oxide of iron, as coloring matters.

SUBSPECIES 1. RUBY.*

It is almost always crystallized in octaedrons, sometimes a little modified. Its color usually presents some shade of red, as scarlet, cochineal, rose, violet, cherry, or yellowish red, but is sometimes dark blue or blackish.† Its fracture, parallel to the sides of the octaedron, is foliated, but its cross fracture is more or less conchoidal; its lustre is vitreous and splendent. It is often translucent, but may be transparent, or opaque. Its spec. grav. varies from 3.57 to 3.76.

It is composed of alumine 82.47, magnesia 8.78, chromic acid 6.18;=97.43. (VAUQUELIN.) Its red color is derived from the chromic acid. Before the compound blowpipe it quickly fuses into an elliptical, red globule. (SILLIMAN.) Its color is therefore retained in the greatest heat.

It resembles some varieties of zircon; but the latter loses its color by heat, and, when both are in octaedrons, the faces of the Ruby are equilateral triangles, and those of the zircon isoscoles.—It is less hard, and less heavy, than the red sapphire, and hence may be distinguished, even when cut.—The red topaz, which the Ruby somewhat resembles, is electric by heat, and possesses double refraction.‡

(Geolog. situation.) Its geological situation is but little known. It has usually been found in the sand of certain rivers, particularly in those of the island of Ceylon, where it is accompanied by sapphire, zircon, tourmaline, Ceylanite, &c. In some specimens from India it is imbedded in calcareous spar with mica, sulphuret of iron, &c. in others it is contained in feldspar.

(Use.) When of good color, it is very highly esteemed in jew-

* Spinell. WERNER. Spinelle. JAMESON. Spinell and Balass rubies. KIRWAN. Le Spinel. BROCHANT. Spinelle Rubis. BRONGNIART.

† Among lapidaries the scarlet red is sometimes called ruby spinelle; the pale or rose red, balass ruby; and the yellowish red, rubicelle.

‡ Many substances have improperly received the name of Ruby. The red sapphire has been called oriental Ruby; the red topaz, Brazilian Ruby; a variety of red quartz, Bohemian Ruby; red fluate of lime,false Ruby; &c.

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elry, though of somewhat less value, than the red sapphire (oriental ruby.)

SUBSPECIES 2. CEYLANITE.* JAMESON.

The Ceylanite, sometimes in rounded grains, is often crystallized in octaedrons, sometimes with truncated edges; also in dodecaedons with rhombic faces, of which eight solid angles are sometimes truncated. Its spec. gravity varies from 3.76 to 3.79, being a little greater, than that of the ruby; its hardness, however, is somewhat less, but still enables it to scratch quartz. Its structure is rather indistinctly foliated; and its fracture is shining, and conchoidal, with large, smooth cavities.

It is nearly or quite opaque, and its more common color is a very dark blue or black; but its fragments, when held between the eye and the light, transmit a dark greenish light. It also presents other shades of blue, or is purple, or even greenish, or yellowish.

The Ceylanite contains alumine 68, magnesia 12, oxide of iron 16, silex 2;=98. (DESCOTILS.)

(Geolog. sit. and Localities.) It was first observed in the island of Ceylon, in the sand of its rivers, with tourmaline, &c.—At Vesuvius it occurs in greenish crystals in the cavities of certain lavas.— At Monte Somma in rocks, sometimes calcareous, sometimes composed of mica, quartz, feldspar, idocrase, &c. the Ceylanite is in octaedrons dark blue, greenish, &c.

SPECIES 6. FIBROLITE.† BOURNON.

This very rare mineral is composed of minute fibres, intimately united, and often collected into little bundles, crossing each other in various directions. When broken perpendicularly to the fibres, it appears compact and glossy. It is a little harder than quartz; and its spec. gravity is 3.21. By friction, according to Bournon, it phosphoresces with a deep red light. Some of the fibres appear to be rhomboidal prisms. Its color is white, or gray.

It is infusible by the blowpipe. It contains alumine 58.25, silex, 38, iron 0.75;=97. (CHENEVIX.)

It accompanies the corundum from the Carnatic, and from China.

SPECIES 7. CYANITE.‡ JAMESON.

This mineral is found both massive and in regular crystals. It is

* Zeylanit. WERNER. Spinelle Pleonaste. BRONGNIART. Pleonaste. BROCHANT.

† Fibrolite. HAUY. BRONGNIART.

‡ Cyanit. WERNER. Disthene. HAUY. BRONGNIART. La Cyanite. BROCHANT. Sappare. SAUSSURE. KIRWAN.

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frequently in broad or compressed six-sided prisms, with bases a little inclined; two opposite lateral edges, which belong to the primitive form, contain angles of about 103°; and of the other four edges two are about 130°, and two about 127°. Or this crystal may be Viewed as a four-sided prism, truncated on two of its lateral edges, diagonally opposite. The wider faces have usually a much stronger lustre, than those, which are narrow.

It has also been observed in eight-sided prisms, with bases either at right angles to the prism, or inclined at an angle of about 106°, or terminated by four-sided pyramids. The primitive form is a quadrilateral prism with inclined bases. The laminæ separate in three directions, and in one, the divisions are very perfect; their surfaces are more or less shining and pearly.

The crystals, often very long, are frequently grouped. Sometimes a double crystal is formed by the union of two crystals in the direction of their length, in such manner, that a cavity or re-entering angle exists in the place of one lateral edge. Sometimes the crystals intersect each other, or are collected into groups, either parallel or diverging.

It scratches glass, when the edges of its laminæ are employed, but is itself scratched by glass, acting perpendicularly to the surface of the laminæ. Its electric powers are remarkable; for the electricity, which it acquires by friction, is sometimes positive, and sometimes negative.

The massive varieties are composed of lamellæ, often very long, sometimes very narrow, sometimes curved and interlaced; and their fracture is frequently fibrous with broad, diverging fibres. Indeed these lamellæ, situated in all directions, are sometimes so intimately united, that the mass appears to be composed of large, granular concretions, or is almost compact. The lustre is always more or less pearly. Its spec. grav. lies between 3.51 and 3.62.

The Cyanite is translucent and sometimes transparent. Its prevailing color is blue,* varying from a fine Prussian blue to sky blue, or bluish white; it also occurs bluish green, pale green, yellowish, or even gray or white, and sometimes reddish. In some cases a very intense blue appears in spots or stripes, the remainder of the crystal being a pale blue, or pearly white.

(Chemical characters.) It is infusible by the common blowpipe, even when supplied with oxigen gas. But before the compound blowpipe it is instantly fused with ebullition into a white enamel. (SILLIMAN.) A specimen from St. Gothard yielded Laugier alumine 55.5 silex 38.5, lime 0.5, oxide of iron 2.75, water 0.75;=98.

* Hence its name, from the Greek, Кνωνος, blue color. 26

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Its laminæ are harder than those of talc, and scarcely unctuous or flexible;—they are not elastic, like those of mica, which they usually scratch.

(Geolog. situation.) The Cyanite is found in primitive rocks, especially in talc and mica slate, gneiss, and granite. It is frequently accompanied by garnets, staurotide, quartz, tourmaline, &c. Very fine crystals come from St. Gothard.—In Tyrol it is sometimes red. (MACLURE.)

(Localities.) In the United States. In Maryland, 20 miles from Baltimore, on the Falls turnpike; its crystals, sometimes 5 inches in length, are usually pale green, rarely blue, and imbedded in a micaceous rock; sometimes in loose masses, composed chiefly of Cyanite, connected by quartz; it is sometimes associated with staurotide, garnets, and magnetic iron;—also on the same road 7 miles from Baltimore both crystallized and massive. (GILMOR. HAYDEN.)— In Pennsylvania, in Chester Co. sometimes in masses of united crystals a foot in length, of a pale blue color; (WOODBRIDGE.)—also at Darby, in Delaware Co. of a fine blue color, in primitive rocks; (CONRAD.)—also in Philadelphia Co. near Chesnut hill, in mica slate; (SEYBERT.)—also in Montgomery Co.—In Connecticut, at Litchfield and Harwinton, in large and beautiful blue and white crystals, or in crystalline masses, in mica slate;—also in small, imperfect crystals in mica slate near Newhaven. (SILLIMAN.)—In Massachusetts, at Chesterfield, Hampshire Co. where it was discovered by Dr. Hunt of Northampton; its crystals are sometimes very fine, and its blue color is often remarkably beautiful; it is associated with garnets, quartz, &c.—In Maine, at Brunswick, in small quantities, and nearly white, in a micaceous rock.

SPECIES 8. STAUROTIDE.* HAUY. BRONGNIART.

This mineral is always crystallized in prisms, either single, or intersecting each other at given angles. Its primitive form, under which it sometimes appears, is a four-sided prism, whose bases are rhombs, with angles of 129° 30′ and 50° 30′. Its integrant particles are triangular prisms. Of its secondary forms the following are the most common.

A six-sided prism, or the primitive form, truncated on its two acute lateral edges by planes, forming with the contiguous sides angles of 115° 15′. The four planes, which form the two most obtuse lateral edges of this prism, viz. those of 129° 30′, are in general broader, than the other two; sometimes, however, these edges of

* Granatit. WERNER. Grenatite. JAMESON. BROCHANT.

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129°30′ are formed by the meeting of one wide and one narrow plane, by which the appearance of the crystal is much altered.

The preceding prism is sometimes truncated at each extremity (Pl. III, fig. 30.) on the two solid angles, which terminate the two most obtuse lateral edges; in some specimens these truncations form a bevelment, or diedral summit.

Two prisms, belonging to either of the preceding varieties, often intersect each other, sometimes at right angles, and sometimes (Pl. III, fig. 31.) at angles of 60° and 120°. In some instances one prism enters or barely traverses the other without actually intersecting it, that is, it projects on one side only.—Sometimes also three prisms decussate each other. The surface of the crystals is sometimes smooth and feebly shining, and sometimes rough and nearly dull.*

The Staurotide feebly scratches quartz, but does not easily give fire with steel. Its fracture is uneven or imperfectly conchoidal, and usually a little foliated, parallel to the axis; its lustre is moderately shining.

It is often opaque, sometimes translucent, especially in the single crystals. Its color is reddish brown, often very dark or even blackish brown, or sometimes grayish. Its spec. grav. is 3.28.

Before the blowpipe it does not melt; but its surface is converted into a kind of black frit. It is composed, according to Klaproth, of alumine 52.25, silex 27, oxide of iron 18.50, oxide of manganese 0.25=98. In another specimen Vauquelin found alumine 47, silex 30.6, lime 3, oxide of iron 15.3;=95.9. It often contains foreign minerals imbedded.

Its form and infusibility distinguish it from the garnet.

(Geolog. sit. and Localities.) The Staurotide has been found only in primitive rocks, and most frequently perhaps in mica slate. It thus occurs at St. Gothard, often accompanied by cyanite; its crystals are often translucid, and have the reddish brown color of the garnet.—In Brittany, it is in a micaceous clay, which appears to be the result of decomposition.

In the United States. In Maryland, 7 miles from Baltimore, in mica slate, sometimes with cyanite. (DF. BUTTS.)—In Pennsylvania, in Montgomery Co. on the Schuylkill, 8 m. from Philadelphia, in rocks abounding with talc; (WISTER.)—also 12 m. from Philadelphia in mica slate. (CONRAD.)—In Connecticut, at the notch of the mountain in Bolton, also in East Hartford, and Tolland, in large crystals, often forming the cross, in mica slate with garnets; (SIL-

* In general, the prisms, which intersect each other, are shorter and more opaque, than the single prisms, and their surface has usually less lustre.

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LIMAN.)—also at Harwinton in very perfect crystals in granite with cyanite. (WOODBRIDGE.)—In Maine, at Winthrop, Sidney, Hallowell, &c. At Winthrop it is very abundant in mica slate; the crystals are opaque and of various sizes, sometimes blackish brown with smooth, glistening surfaces, and sometimes brown or reddish brown with a rough surface; they frequently contain minute garnets or scales of mica. Single prisms, double prisms, crossing at right and oblique angles, and even three prisms, intersecting each other, sometimes all occur in the same small specimen.

SPECIES 9. CHRYSOBERYL.* KIRWAN. JAMESON.

This mineral ranks next to the sapphire in hardness. It possesses double refraction; and very frequently exhibits a remarkable reflection of a bluish or milk white light, which seems to play in the interior of the crystal. It often occurs in grains, or small, rounded masses, and sometimes in crystals, whose primitive form is a rectangular, four-sided prism. Its secondary forms are all prismatic. Sometimes it appears in regular six-sided prisms, often so short, that they become six-sided tables. Sometimes these prisms or tables are truncated on their terminal edges, and the crystal then assumes the aspect of an eight-sided prism (Pl. III, fig. 32.), terminated by six-sided summits; sometimes also its summits have each ten faces.

Its fracture is conchoidal or undulated, and splendent; and sometimes foliated, parallel to the axis of the prism. Its spec. grav. extends from 3.60 to 3.79; by friction it easily becoms electric.

It is more or less transparent, or only translucent. Its color is green of different shades, usually pale, or even greenish white, but, in most cases, more or less mingled with yellow.

It is infusible by the blowpipe. It contains alumine 71.5, silex 18, lime 6, oxide of iron 1.5;=97. (KLAPROTH.)

The Chrysoberyl is harder and heavier than the emerald, which it resembles, and sometimes accompanies.—It is not electric by heat, like certain topazes of a similar color.

(Geolog. situation.) This mineral has been brought from Brazil and Ceylon, but little is known of its original situation in those places.

In the United States. In Connecticut, at Haddam, on Connecticut river, the Chrysoberyl occurs in granite in six-sided prisms and six-sided tables; its color varies from greenish yellow to yellowish green. The same granite contains garnets, emerald, tourmaline, &c.

(Use.) It is sometimes employed in jewelry.

* Krisoberil. WERNER. Cymophane. HAUY. BRONGNIART. Le Chrysoberil. BROCHANT.

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SPECIES 10. GAHNITE.*

It is always crystallized in small, but very regular octaedrons, which are sometimes double, like those of spinelle. Its color is deep green or greenish black, and its fragments are translucent. It scratches quartz, and has an uneven or conchoidal fracture. Its spec. grav. varies from 4.26 to 4.69. It is not a conductor of electricity.

Before the blowpipe it is infusible; but with borax, according to Eckeberg, it gives a green glass, while hot, which becomes colorless, when cold. It contains alumine 60, oxide of zinc 24.25, oxide of iron 9.25, silex 4.75;=98.25. (ECKEBERG.) According to Vauquelin alumine 42, oxide of zinc 28, oxide of iron 5, silex 4, sulphur 17, insoluble residue 4.

It has been found at the mine of Fahlun, in Sweden, in a rock abounding with talc.

SPECIES 11. GADOLINITE.† HAUY.

This very rare mineral has usually occurred in amorphous masses of a black or brownish black color. It slightly scratches quartz, and gives sparks with steel. It is easily broken, and its fracture is conchoidal, and shining with a vitreous lustre. It acts on the magnetic needle; and has a specif. gravity of about 4.04. It is opaque, or a little translucent at the edges.—M. Haüy has an incomplete crystal of Gadolinite, which he conjectures to be a ten-sided prism.

(Chemical characters.) Its powder, when thrown into diluted nitric acid and heated, loses its color, and is converted into a yellowish gray jelly. This mineral, when suddenly heated by the blowpipe, decrepitates, and is dispersed in small fragments, which appear inflamed. If cautiously heated, however, it remains entire, but does not melt, except in certain points, which fuse with ebullition. It tinges borax yellow. It contains, according to Klaproth, Ittria 59.75, silex 21.25, oxide of iron 17.5, alumine 0.5, water 0.5;=99.50.

(Distinctive characters.) It resembles massive chromate of iron; but the latter is heavier, tinges borax green, and does not form a jelly with acids.—A comparison of its specific gravity and chemical characters with those of the black oxide of uranium and obsidian will prevent its being confounded with those minerals.

(Geolog. sit. and Locality.) The Gadolinite, so called from Dr. Gadolin, who discovered in it the new earth, Ittria, has been found only at Ytterby, in Sweden. It exists in veins of feldspar,

* Zinc Gahnite. BRONGNIART. Spinelle zincifère. HAUY. Automalite. ECKEBERG.

† Gadolinite. JAMESON. BRONGNIART. BROCHANT. Gadolinit. WERNER.

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which traverse granite, and are themselves intersected by veins of mica.

SPECIES 12. ZIRCON. HAUY. BRONGNIART.

This mineral occurs in rounded grains or fragments, or in regular crystals, which sometimes present their primitive form, viz. an octaedron (Pl. III, fig. 33.); its sides are equal and similar isosceles triangles, and inclined to each other at the common base in an angle of 82° 50′. The surface of its crystals is generally smooth, with an oily or resinous lustre. It has nine or ten secondary forms; and its integrant particles are irregular tetraedrons.

The Zircon is a little harder than quartz, and possesses double refraction in a high degree. It is more or less transparent, or only translucent. Its spec. gravity, which generally lies between 4.38 and 4.66, is sometimes 4.70. (WERNER.)

It is infusible by the blowpipe; but usually loses its color, especially the red varieties. With the compound blowpipe it melts into a white enamel. (SILLIMAN.) It is essentially composed of zirconia and silex.

(Distinctive characters.) Its infusibility, spec. gravity, strong double refraction, and the measure of its angles, when crystallized, will serve to distinguish it from the garnet, idocrase, staurotide, &c. indeed some of these characters may be observed, when it is cut and polished.

It presents two varieties, which differ a little in some of their external characters.

1. JARGON.* KIRWAN. When in distinct crystals, its usual form is a four-sided prism (Pl. III, fig. 34.), terminated by four-sided pyramids, whose faces are inclined to the sides of the prism, on which they stand, at an angle of 131° 25′. All the edges of the prism, and even those of the pyramids are subject to truncation; and the solid angles between the prism and pyramids are often replaced by two faces or bevelled. (Pl. III, fig. 38 and 39.)—It also presents the primitive form. Its fracture is conchoidal, undulated, or uneven, with a strong lustre somewhat resinous. Its colors are numerous; it presents several shades of gray, and green; and is sometimes yellowish, bluish, red, brown, reddish brown, &c. with various intermediate shades, and is even white, or limpid.

In a specimen from Ceylon Klaproth found zirconia 69, silex 26.5, oxide of iron 0.5;=96. In another from Norway he found zirconia 65, silex 33, oxide of iron 1;=99.

* Zircon Jargon. BRONGNIART. Zirkon. WERNER. Zircon. JAMESON. Le Zircon. BROCHANT.

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(Geolog. situation and Localities.) In the island of Ceylon it is found in the sand of rivers with spinelle, tourmaline, &c.—In Norway, at Frederickswarn, in an aggregate of feldspar and hornblende.—In Galloway, Scotland, in gneiss.

In the United States. In Maryland, 2 miles from Baltimore, in granite. (DE BUTTS.)—In New Jersey, near Trenton, in gneiss, with a greenish feldspar; the crystals are small four-sided prisms, terminated by pyramids, with additional faces on their edges or angles; semitransparent and of a deep brownish red color; their length is seldom more than one fourth of an inch. (CONRAD.)—In New York, at Schooley's mountain, in detached masses of granite, consisting chiefly of feldspar; a quadrangular prism, from this mountain, of a dark brown color and almost opaque, measured nearly two inches in length and one fifth of an inch on each side. (WOODBRIDGE.)—In Connecticut, at Sharon, in detached pieces of quartz; the crystals are four-sided prisms, terminated by pyramids, have a dark brown color, and rarely exceed one half an inch in length. (SILLIMAN.) It appears from the preceding details, that the Zircon of the United States belongs to primitive rocks.

(Use.) It is sometimes employed in jewelry, especially in mourning dresses.

2. HYACINTH.* KIRWAN. JAMESON. When in distinct crystals its ordinary form is a four-sided prism, terminated by four rhombic planes (Pl. III, fig. 35.), which stand on the lateral edges. Each plane angle at the summit is 73° 44′. It may be truncated on the lateral or terminal edges, or on both. When the sides of the prism are shortened and become rhombs, the crystal resembles the dodecaedral garnet, but differs in the mutual incidence of the faces.

Its structure is more distinctly foliated, and its natural joints, parallel to the primitive octaedron, more obvious, than those of the Jargon. Its fracture, which is foliated, has a high lustre. Its prevailing color is that called hyacinth red, in which the red is more or less tinged with yellow and brown; it is sometimes pale or even grayish.

Before the blowpipe it generally loses its color, but retains its transparency. A specimen from Ceylon yielded Klaproth zirconia 70, silex 25, oxide of iron 0.5;=95.5. In one from France Vauquelin found zirconia 66, silex 31, oxide of iron 2;=99.

(Geolog. situation and Localities.) It has been found in primitive rocks; but is usually taken from the sand of rivers, &c. It is

* Hiazinth WERNER. Zircon Hyacinthe. BRONGNIART. L'Hyacinthe. BROCHANT.

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thus found in the stream of Expailly, near Puy en Velay, in France, with sapphire, octaedral crystals of magnetic iron, &c.—also in the island of Ceylon, &c.

(Use.) It is sometimes employed in jewelry, even when discolored by heat.*

SPECIES 13. QUARTZ. HAUY.

This extensive and interesting species embraces numerous varieties, differing much in their forms, texture, and other external characters. And it is somewhat remarkable, that, although but few well defined, external characters apply to the whole species, most of its varieties are easily recognised.

It is sufficiently hard to scratch glass, and it always gives sparks with steel more or less plentifully, unless the mass be too brittle to sustain the blow; and in this latter case, its powder will be found rough to the touch, and sufficiently hard to scratch glass or steel. When pure, its specific gravity is about 2.63; but in certain varieties extends both above and below this term, depending on its structure, or the presence of foreign ingredients. Indeed the mean specific gravity of the whole species, derived from the two extremes, is about 2.60.

It is sometimes in amorphous masses, and sometimes in very beautiful crystals, of which the primitive form is a rhomb slightly obtuse, the angles of its faces being 94° 24′ and 85° 36′. This nucleus is seldom easily obtained, unless the crystal be previously heated and plunged into cold water. Haüy has described nine secondary forms, of which the more common is a six-sided prism, terminated by six-sided pyramids. It exhibits double refraction, which must be observed by viewing an object through one face of the pyramid and the opposite side of the prism.

(Chemical characters.) All its varieties are infusible by the blowpipe, and, if pure, it is scarcely softened, even when the flame is excited by oxigen gas. Before the compound blowpipe a fragment of rock crystal instantly melts into a white glass. (SILLIMAN.) Quartz is essentially composed of silex, sometimes nearly or quite pure; and sometimes mingled or combined with foreign ingredients, which very materially affect its external characters.

To facilitate description this species is separated into two Divisions, each of which is farther divided into subspecies and varieties.

The first division embraces those varieties, which are susceptible

* From a resemblance in color certain sapphires have been called oriental Hyacinth; certain topazes, occidental Hyacinth; and yellow ferruginous quartz, Hyacinth of Compostella.

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of crystallization, and have a fracture more or less vitreous. It in fact comprehends all, which some mineralogists include under the species, quartz.

The second division contains those minerals, which appear to be composed essentially of silex only, often equally pure, as those of the first division, but which have never been seen crystallized, nor perfectly transparent. Most of the varieties of this division have by Brongniart been collected into one species, bearing the name of silex.*

* In giving this extent to the species of Quartz, it might perhaps be sufficient to cite the authority of the celebrated Haüy. A few observations, however, may not be inexpedient. In the Introd. art. 177, &c. it was remarked, that identity of composition forms the best specific character of minerals; and that, whenever two minerals are known to be composed of the same ingredient, or ingredients, united in the same proportions, they ought to be referred to the same species, however they may differ in their external characters. According to these principles, we include under this species all those minerals, which appear to be essentially composed of silex only, or whose other ingredients appear to be accidental and foreign to the true composition. Accordingly, when analysis informs us, that the most perfect and best characterized variety of Quartz contains from 93 to 99 parts of silex; that Amethyst contains 97.5 parts of silex; that Carnelian contains 99 parts of silex; that Chrysoprase contains 96.16 parts of silex; that Opal contains 98.75 parts of silex; and, in fine, that Flint contains 98 parts of silex; the residue being in all these cases a very little alumine, lime, water, or some metallic oxide; can we, for a moment, doubt whether all these minerals belong to the same species? Is it not evident, that silex only is their essential ingredient, and that the other ingredients are merely accidental? It is true, that these adulterating and coloring ingredients sometimes exist in proportions somewhat greater, than in the preceding analyses; but even this circumstance serves to show, that they are merely adventitious; and, if in any instances, they are sufficiently uniform to establish subspecies, they cannot consistently be permitted to form specific distinctions, unless we assume external characters only, as the basis of arrangement.
Further, what two varieties of Quartz are more unlike each other, than are crystallized carbonate of lime and compact limestone, the latter of which is often contaminated with from 3 to 12 per cent. of alumine, silex, and oxide of iron? Still the last two minerals have uniformly been referred to the same species. It may indeed be said, that the analysis of minerals, composed of several different earths, does not inform us what is essential to the species. But this remark cannot apply to a mineral, evidently composed of one earth only, as in the case of Quartz. In fine, crystals of Quartz have been found adhering to flint, and imperceptibly incorporating themselves with it, in the same manner, as crystals of carbonate of lime are found attached to compact limestone. (See Introd. art. 176, 197.)

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DIVISION 1. Quartz, susceptible of crystallization, and having a fracture more or less vitreous.

SUBSPECIES 1. COMMON QUARTZ.*

This subspecies, though often in amorphous masses, is very frequently in crystals, which, in perfection and beauty, are not exceeded by those of any other mineral. These crystals rarely exhibit their primitive form, which is a rhomb.

The most common form of crystallized quartz is a six-sided prism, terminated by six-sided pyramids, whose faces correspond with the sides of the prism, and form with them an angle of 141° 40′; the mutual inclination of any two opposite faces of the same pyramid being 75° 52′. The sides of the prism are transversely striated; but the planes of the pyramids are smooth and polished. The pyramidal termination frequently appears at one extremity only.—This form is subject to numerous modifications, which greatly affect its general appearance. Sometimes the faces of the pyramids are alternately large and small;—sometimes one face of the pyramid is so much larger, than the others, that it seems to form an oblique base to the prism;—sometimes the prism is broad or compressed, and two opposite faces become so large, that the crystal resembles a table with bevelled edges;—sometimes the sides of the prism are convergent, so that the diameter at one extremity is greater, than at the other.

Not unfrequently some of the solid angles, situated between the prism and each of the two pyramids, are truncated by rhombic planes, (Pl. III, fig. 36.)—Sometimes all the solid angles, situated as aforementioned, are truncated by trapezoidal planes, obliquely placed.

Sometimes the prism is so short, that the two terminating pyramids nearly meet, and the crystal becomes a double six-sided pyramid, with its common base truncated;—or the prism entirely disappears, leaving a double six-sided pyramid (Pl. III, fig. 37.), whose faces are isosceles triangles, inclined at the common base in an angle of 103° 26′. Sometimes only one of the pyramids is distinct;—and sometimes three alternate faces, on each pyramid, are so unduly extended, that the other faces almost disappear, and the crystal appears slightly rhomboidal.

In fine, two or more of the preceding modifications sometimes meet in the same crystal. But, notwithstanding these numerous alterations, arising from the extension of some of the sides or faces at the expense of the others, the angles of mutual incidence remain unaffected.—It has been remarked, that all the specimens from the same

* Gemeiner quarz—milch quarz—berg kristal. WERNER. Common quartz—milk quartz—rock crystal. JAMESON.

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locality usually belong to the same variety of form. In some instances the crystals attain an uncommon size, their prisms having been seen nearly three feet in length and almost two feet in breadth. They are frequently many inches in length.

Quartz is sometimes in stalactical or reniform concretions, sometimes cavernous, corroded, or in plates, &c. It is often in pebbles or rolled fragments, or in amorphous masses more or less large, and sometimes composed of small, granular, distinct concretions.

Its fracture, sometimes imperfectly foliated, is usually more or less conchoidal, undulated, or splintery, and, in some specimens, uneven. Its lustre is vitreous, sometimes splendent, and sometimes only glimmering. Its spec. gravity extends from 2.58 to 2.88. It is sometimes highly transparent, and very frequently translucent, though in some cases only in thin fragments, or at the edges. It is often perfectly limpid; its more common colors are white or gray, often intermixed with yellow, orange, red, green, blue, or black; indeed it presents several distinct shades of red, yellow, green, or blue, and is sometimes black.

By friction it exhales a peculiar odor and some varieties also phosphoresce in the dark.

A specimen, analyzed by Bergman, yielded silex 93, alumine 6, lime 1. In another Gerhard found 99 parts of silex. Its powder renders the tincture of violets green. (VAUQUELIN.) Some colored crystals retain their transparency in a heat sufficient to deprive them of color.

Var. 1. LIMPID QUARTZ. (Rock crystal.*) This, which is only the most perfect variety of Quartz, has, when crystallized, received the name of rock crystal; indeed the same name is sometimes extended to colored crystals, when transparent. Limpid quartz is without color, and sometimes as transparent, as the most perfect glass, which it strongly resembles. It is however harder, than glass, and the flaws or bubbles, which it often contains, lie in the same plane, while those in glass are irregularly scattered. (BRONGNIART.)

The finest crystals are found in veins or cavities in primitive rocks, as in granite, gneiss, or mica slate; or in alluvial earths. Savoy, Switzerland, and Madagascar are most celebrated among foreign localities.

In the United States, this variety is not uncommon. In Virginia, near the North Mountain.—In Maryland, in Frederick Co. the crystals are scattered on the surface of the ground; they are perfectly transparent, with a splendent lustre, and the sides of the prisms

* Berg kristal. WERNER. Rock crystal. KIRWAN. JAMESON.

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sometimes so smooth, that the transverse striæ are not perceptible. (HAYDEN)—In Pennsylvania, in many places east of the Blue Ridge.—In New York, on an island in Lake George, in very fine crystals. (SILLIMAN.)—In Vermont, at Grafton, remarkably pure and transparent. (HALL.)

(Use.) This variety is sometimes employed in jewelry, for watch seals, &c.

2. SMOKY QUARTZ.* Objects, seen through this variety, seem to be viewed through a cloud of smoke. Its true color appears to be clove brown. It is sometimes called smoky topaz. Fine specimens have been found near Hanover, Lancaster Co. Pennsylvania. (SEYBERT.)—In Maine, at Topsham, amorphous fragments are not uncommon; and it is sometimes crystallized.

3. YELLOW QUARTZ.† Its color is a pale yellow, sometimes honey or straw yellow. It has been called citrine; also false, or Bohemian topaz.—Good specimens are brought from Carinthia.—It is found in several parts of Pennsylvania, east of the Blue Ridge. (WISTER.)

4. BLUE QUARTZ.‡ Its color is blue, or grayish blue. Its inferior hardness and specific gravity sufficiently distinguish it from the blue sapphire. It has been called false or occidental sapphire. It comes from Bohemia, Macedonia, &c.—An amorphous blue quartz is found in Chester Co. and near Abington, Montgomery Co. Pennsylvania. (SEYBERT.)

5. ROSE RED QUARTZ.§ Its color is rose red of different shades, sometimes with a tinge of yellow. It is seldom more than semitransparent, and its lustre is often a little resinous. Its color, which is supposed to arise from manganese, is said to be injured by exposure to light.—It has been called Bohemian ruby.—In Bavaria it is found in a vein of manganese, traversing granite.—In Maine, at Topsham, in loose fragments, scattered among masses of granite and gueiss.

(Use.) It is sometimes employed in jewelry, and much esteemed.

6. IRISED QUARTZ.‖ It reflects a series of colors, similar to those of the iris or rainbow. Sometimes this appearance is produced at the surface by a thin coat of some metallic oxide. Sometimes also the colors are reflected from the interior, being caused by numerous small fissures, which traverse the quartz.

* Quartz hyalin enfumé. HAUY.

† Quartz hyalin jaune. HAUY.

‡ Quartz hyalin saphirin. BRONGNIART.

§ Milch quarz. WERNER. Milk quartz. JAMESON. Quartz hyalin rose. HAUY.

‖ Quartz hyalin irisé. HAUY.

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7. AVENTURINE QUARTZ.* Its predominant color, which may be red, yellow, gray, greenish, blackish, or even white, is variegated by brilliant points, which shine with a silver or golden lustre. These shining points seem to be produced by the reflection of light from numerous fissures, or from disseminated plates of mica, or perhaps from laminæ of Quartz, interspersed through the mass. It is often found in rolled pieces; and, when the fragment is large, the centre usually exhibits very few of those reflections, peculiar to this Quartz. This variety is sometimes employed in ornaments of jewelry.

8. MILKY QUARTZ.† Its color is milk white, in some cases a little bluish; and it is nearly opaque; its fracture has sometimes a resinous lustre. It is sometimes in small crystals, but more often in large masses.—In Maryland, it occurs near Baltimore, both crystallized and amorphous.—In Pennsylvania, Chester Co. 14 miles from Philadelphia, is found an amorphous, milky quartz, which easily separates into very thin laminæ. (SEYBERT.)

9. CREASY QUARTZ.‡ Its colors are various, either light or dark, sometimes reddish, yellowish, &c. but its lustre is peculiar. Its fracture, which may be large splintery or conchoidal, appears as if rubbed with oil. Sometimes its structure is distinctly laminated.

10. RADIATED QUARTZ. It is in masses, which have a crystalline structure, and are composed of imperfect prisms, closely applied to each other, and sometimes terminating in pyramids at the surface. These prisms usually diverge a little, or radiate from a centre, and often separate with great ease.—In Maryland, this variety occurs 8 miles from Baltimore in detached masses. (GILMOR.)—In Massachusetts, at the Lead Mine, near Northampton, where it often constitutes the gangue of the ores.

11. TABULAR QUARTZ. It occurs in plates of various sizes, which are sometimes applied to each other by their broader faces. Sometimes they intersect each other, producing cells of various forms. Sometimes their appearance is pectinated, or crested, like a cock's comb.

In Maryland, this variety occurs near Baltimore.

It should, however, be remarked, that the cellular appearance of quartz is often produced in a very different manner. In this latter case it presents impressions, whose forms may be cubic, tabular, pyramidal, &c. and sometimes the cavities are altogether irregular. But these vacuities proceed from the removal or decomposition of crystals or grains of some metallic sulphuret, &c.—in fact, this decomposition may sometimes be observed, when only partially advanced.

* Quartz hyalin aventuriné. HAUY.

† Quartz hyalin laiteux. HAUY.

‡ Quartz hyalin gras. HAUY.

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12. GRANULAR QUARTZ. KIRWAN. Its structure presents small granular concretions, or grains, which are sometimes feebly united. This variety must be carefully distinguished from certain sandstones, which it sometimes resembles.—It is said to occur at Hinsdale, Berkshire Co. in Massachusetts, in large, friable masses, snow white, and much resembling sugar. It may, probably, prove important in the manufacture of glass, and certain kinds of stone ware.

13. ARENACEOUS QUARTZ.* It is in loose grains, coarse or fine, either angular or rounded, and constitutes some varieties of pure sand.—Certain sandstones appear to be composed of this quartz united by some cement; but they belong not to simple minerals.

14. PSEUDOMORPHOUS QUARTZ.† It appears under regular forms, such as cubes, octaedrons, &c. which do not belong to the species. These false crystals have been moulded in cavities, which real crystals of the fluate, sulphate, or carbonate of lime, sulphate of barytes, &c. once occupied. They are opaque, their surfaces dull, and their edges often blunted.

(Geological situation.) Common Quartz, the subspecies just described, never forms whole mountains. It is sometimes in large masses, or in beds, and frequently in extremely large veins, which, according to Dolomieu, have often been mistaken for beds. Hence are detached those loose, insulated masses, which so often occur. Humboldt mentions a mass in the Andes, supposed to be several thousand feet thick.

Veins or beds of Quartz are usually situated in primitive rocks. as granite, gneiss, mica slate, greenstone; and in the cavities of these veins, or of the rocks, which they traverse, are found the finest crystals of quartz. The whole vein may be composed of Quartz, or it may embrace various other substances. Large masses of Quartz are often traversed by fissures.

Quartz, in the form of crystalline grains, or of irregular masses of various sizes, is abundantly disseminated in granite, gneiss, mica slate, &c. of all which it forms a constituent part. It is sometimes in regular crystals, dispersed through the granite, as at Brunswick, Maine. In porphyry also it is sometimes regularly crystallized. It also occurs in carbonate of lime, anthracite, &c. It rarely exists in masses in argillite.

Among secondary rocks Quartz is found forming the greater part of many sandstones; also between strata of compact limestone, of clay, or of marl, or in geodes of marl, or imbedded in sulphate of lime, &c.

* Quartz hyalin arenacé. HAUY.

† Quartz hyalin pseudomorphique. HAUY.

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In alluvial earths it exists in the form of sand.—In fine, stalactites or crystals of Quartz are every day forming by the filtration of water, containing particles of silex, through the pores or crevices of other minerals. Hence stalactites of Quartz have, in certain mines, been found attached even to wood.

Quartz is often associated with the carbonate, and fluate of lime sulphate of barytes, and feldspar in metallic veins; indeed it exists in almost every metallic vein.

This mineral is sometimes traversed by whitish filaments of sulphate of barytes; or by crystals of actynolite; or by threads of asbestus, which give it a fibrous structure; or it is rendered nearly opaque by the presence of chlorite. It is sometimes penetrated by acicular crystals of titanium or antimony, or by plates or capillary filaments of native copper, silver, or gold.—Hornblende, schorl, epidote, garnet, magnetic iron, &c. are also among the minerals, contained in Quartz. Mica sometimes gives it a slaty structure.

In some rare instances bubbles of air, and even drops of water and bitumen have been found in Quartz.—Although common Quartz never contains any organic remains, it is sometimes crystallized in fossil wood.

(Localities.) Of a mineral so universally diffused, we shall cite but a few localities, in addition to those already mentioned. In Maryland, the hills, on which Baltimore is built, present immense quantities of pebbles of Quartz, arranged in beds of various thickness. (GILMOR.)—In Pennsylvania, 4 miles from Philadelphia, on the Schuylkill, in prisms terminated by pyramids at both extremities. (CONRAD.)—In New York, at Shawangunk mountain, where it passes into Ulster Co. this quartz is used for mill stones; (ARNELL.)—also at Lansinburgh in small, brilliant, well defined crystals;—also at Greenbush in prisms sometimes three inches in diameter with pyramids at both extremities. (WATERHOUSE.)—In Connecticut, at Washington, Litchfield Co. was found a mass of transparent Quartz now in the cabinet of Yale College; it appears to be a fragment of an immense crystal, and probably weighs between 200 and 300 pounds. (SILLIMAN.)—In Rhode Island, 12 miles north of Providence, is a hill, composed in a great measure of quartz, often crystallized. (SILLIMAN.)—In Massachusetts, at the Lead mine in Southampton, Hampshire Co. it forms the greater part of the gangue of this metallic vein, in the cavities of which it appears in crystals usually very regular, sometimes large, and often extremely beautiful; here also occurs the radiated quartz, already mentioned. (SILLIMAN.)—In Maine it is abundant, especially in the coarse grained granites, in which it sometimes forms very large masses, is often smoky, and in

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some cases beautifully impressed by the contiguous mica, or even alternates with it in very thin layers.

(Uses.) We have already seen, that certain varieties of Quartz are employed in jewelry. It is also used, especially the sandy variety, in the manufacture of glass; also in the preparation of smalt, and certain enamels.—Its appearance is sometimes much altered by introducing metallic solutions into fissures, previously formed by exposure to heat.

SUBSPECIES 2. AMETHYST.* WERNER. JAMESON.

The color of the Amethyst is most commonly violet blue, but is seldom of equal intensity through the whole mass or crystal, in some parts of which it often entirely disappears. Sometimes it has a strong shade of red, and sometimes its color passes to brown or gray, or has even a shade of green. Different colors sometimes appear in the same specimen. It most frequently occurs in crystals, whose forms are the same as those of common quartz. It is also found in rolled fragments, or in masses, composed of prismatic, distinct concretions, or rather of imperfect, prismatic crystals. These prismatic concretions exhibit transverse striæ, and at the surface of the mass, often terminate in regular pyramids; they are frequently intersected by lamellar concretions, passing in a zigzag direction. When these prisms are long, small, and very intimately united, the mass has a fibrous appearance. Its other characters are those of common Quartz.

It contains, according to Rose, silex 97.50, alumine 0.25, oxide of iron 0.50, oxide of manganese 0.25; =98.50.

(Geolog. sit. and Localities.) It is sometimes attached to the interior of geodes of agate; and is frequently found in metalliferous veins. It also constitutes veins in primitive rocks. The Uralian mountains, Murcia in Spain, and Oberstein in Germany, furnish fine specimens. A greenish variety is found in Silesia.

In the United States. In Pennsylvania, 40 miles from Philadelphia, in Chester Co. near the Lancaster turnpike, in large, transparent crystals of a rich purple; (WISTER.)—also in Delaware and Berks Counties, in transparent crystals.—In Connecticut, at Wallingford, Farmington, and Berlin.—In Massachusetts, on Mount Tom, near Northampton, in beautiful crystals. (SILLIMAN.)—In New Hampshire, at Hampton Falls, in rolled pieces.

(Use.) It receives a good polish, and is sometimes employed in jewelry, and for articles of ornament, &c. The oriental Amethyst is a sapphire.

* Quartz hyalin violet. HAUY. Quartz hyalin Amethyste. BRONGNIART. L'Amethyste. BROCHANT. From the Greek Αμϵθνστος.

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SUBSPECIES 3. PRASE.* JAMESON.

This subspecies, which is seldom crystallized, possesses all the essential characters of Quartz. Its color, which is uniformly diffused through the mass, is always green, and usually a leek or dark olive green. Its lustre is often a little resinous. When in prismatic concretions, of which its masses are often composed, they are transversely striated. Its specific grav. is 2.58. It is commonly translucent.

Prase appears to be common Quartz, colored by actynolite or epidote. But the uniform diffusion of its color distinguishes it from that quartz, which is colored by chlorite; for the chlorite either adheres, as a crust, or appears to be suspended in the interior.—In Saxony it is found in a metallic bed, accompanied by actynolite, &c.

(Localities.) In the United States. In Maryland, near Baltimore—also in Washington Co. west side of the Blue Ridge, in masses scattered on the surface. (HAYDEN.)—In Massachusetts, at Brighton and West-Cambridge, and appears to be colored by epidote. (GODON.)

(Use.) It receives a good polish, and is sometimes employed for ornamental purposes.

SUBSPECIES 4. FERRUGINOUS QUARTZ.†

This mineral is opaque, or translucent at the edges only. Its fracture is uneven, or more or less conchoidal, shining and nearly vitreous. It is sometimes in very minute and perfect six-sided prisms, terminated at both extremities by six-sided pyramids; in some cases only three faces of each pyramid are distinct. Its colors, which are usually some variety of yellow or red, and its opacity appear to depend on the oxide of iron, which it contains.

By exposure to the blowpipe, and often to the flame of a candle, it acquires magnetism.

Var. 1. YELLOW FERRUGINOUS QUARTZ. Its color is ochre yellow, sometimes mixed with brown, or with a very slight tinge of green. It is sometimes in distinct crystals; but more often in masses, which appear to be an aggregation of small crystals.

2. RED FERRUGINOUS QUARTZ.‡ Its color is blood or brownish red, or deep brown, or has a tinge of yellow. It occurs in small but very perfect crystals, and in masses, which resemble some varieties

* Prasem. WERNER. Quartz hyalin vert obscur. HAUY. Quartz Prase. BRONGNIART. Prasium. KIRWAN. La Prase. BROCHANT.

† Quartz rubigineux. HAUY. BRONGNIART. Eisenkiesel. WERNER. Iron Flint. JAMESON.

‡ Quartz rubigineux Sinople. BRONGNIART. Quartz hyalin hematoïde. HAUY.

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of jasper; but their fracture, unlike that of jasper, has a vitreous, shining lustre.

When massive, the red variety occurs in metallic veins in primitive mountains, and is sometimes penetrated by the sulphurets of iron, lead, &c. or by native gold.—At Schemnitz in Hungary it contains organic remains. (DE BORN.)—Very perfect crystals of the red variety occur in sulphate of lime near Compostella in Spain, and have been called hyacinth of Compostella.

(Localities.) In the United States. In Maryland, in Washington Co. west side of the Blue Ridge, are found small, yellowish, well defined crystals of this quartz.

3. GREENISH FERRUGINOUS QUARTZ.* It occurs in small grains of a greenish yellow color, which becomes darker before the blowpipe. It contains silex 85, oxide of iron 8, water 7. (LAUGIER.) It is found at Cantal, in Auvergne.

SUBSPECIES. 5. FETID QUARTZ.

This quartz is easily recognised by the peculiar odor, which it exhales, when struck with a hammer on its edges or angles. This odor strongly resembles that of sulphuretted hidrogen gas.—The external characters of this mineral are those of common quartz. Its color is usually gray, often marked with spots or stripes of a darker color. It is probably never white, nor perfectly transparent—sometimes faintly translucent. Its lustre is usually a little resinous. It is sometimes crystallized; and in some instances, at least, phosphoresces in the dark by friction.

This fetid property appears to be unequally diffused, even in the same small specimen, and is entirely driven off by exposure to a strong heat.

(Localities.) In France, near Nantz, it constitutes an ingredient of a coarse grained granite, or is found in loose masses, and is associated with crystallized feldspar and mica, which are not in the least degree fetid.

In the United States. In Maine, at Topsham, it exists in loose masses, which often contain very large crystals of feldspar and garnet; it has probably been detached from the coarse granite, which abounds in the vicinity.

DIVISION 2. The minerals, described under this division, have never been seen crystallized, nor perfectly transparent. They appear to be essentially composed of silex, which, in most cases, is equally pure as in the minerals of the first division. With the exception of the Hyalite and Cat's eye, they form the species, which

* Quartz hyalin granulaire. HAUY.

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Brongniart has called Silex. Some of the following varieties scarcely differ except in color, and do in fact pass into each other by imperceptible shades.

SUBSPECIES 6. CAT'S EYE.* KIRWAN. JAMESON.

This very beautiful mineral is highly chatoyant. It reflects, when polished, an effulgent, pearly light, sometimes yellowish or greenish, varying with the position of the eye, and much resembling the reflections, observable in the eye of a cat.† Its usual colors are greenish or yellowish gray, yellowish brown, reddish brown, or grayish white, with intermediate shades. It has been seldom seen in its native state. When brought from India, it is usually cut and polished in specimens not larger, than a hazel nut. Its fracture is imperfectly conohoidal or uneven, and shining. It is more or less translucent, or even semitransparent; and has the hardness of quartz.

The Cat's eye appears to be quartz, penetrated by fibres of asbestus; and from these white and opaque fibres, sometimes distinctly visible, its peculiar reflections arise.

It is composed of silex 95, alumine 1.75, lime 1.50, oxide of iron 0.25;=98.50. (KLAPROTH.)

Its geological situation is unknown; but it comes principally from Ceylon, and the coast of Malabar.

It is employed in jewelry, and is sometimes cut in the form of a plano-convex lens.

SUBSPECIES 7. CHALCEDONY.

Under this subspecies, we include several varieties, which have received distinct names in the arts. They have more or less resemblance in their general characters, and sometimes differ in color only; indeed two or more of them are often intimately united in the same mass.—Chalcedony occurs in small veins, or in cavities of other minerals, and appears to have been formed by the filtration of siliceous matter. It never appears in large, homogeneous masses.

Var. 1. COMMON CHALCEDONY.‡ KIRWAN. JAMESON. This variety is usually characterized by a cloudy or milky appearance, when held between the eye and the light, resembling milk, diluted with water. It is semitransparent, or only translucent in various degrees.

* Katzenauge. WERNER. Quartz agathe chatoyant. HAUY. Quartz hyalin chatoyant. BRONGNIART. L'Oeil de chat. BROCHANT.

† Hence its name; and hence the origin of the French term, chatoyant.

‡ Gemeiner Kalzedon. WERNER. Quartz agathe calcédoine. HAUY. Silex calcédoine. BRONGNIART. La Calcédoine commune. BROCHANT. It is said to have been first observed in Chalcedon, in Asia.

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Though sometimes nearly white, its more common color is gray, more or less shaded with blue, yellow, green, brown, red, &c. Sometimes its colors appear in stripes, veins, circles, clouds, spots, &c. and those, which are very dark, often become blood red, when viewed by transmitted light.

It occurs in amorphous masses, sometimes rolled, but more frequently under some imitative form, as globular, reniform, botryoidal, stalactical, &c. The surface is often rough or uneven.—Its fracture is usually even, though seldom smooth, sometimes a little conchoidal, splintery, or uneven, and nearly or quite dull. Its hardness is, at least, equal to that of flint, and its spec. gravity about 2.65.

The pseudomorphous crystals in prisms, cubes, &c. which it sometimes presents, appear to have been moulded in cavities, once occupied by crystals, or to arise from a thin deposite of Chalcedony about some real crystal.

In a specimen of greenish Chalcedony Klaproth found silex 96.75, water 2.50, alumine 0.25, oxide of iron 0.50. It is sometimes nearly allied to hornstone.

(Geological situation.) Chalcedony, whether amorphous, globular, stalactical, &c. is usually contained in amygdaloid, or porphyry, or in the cavities of these rocks; it sometimes traverses them in veins. The globular masses are often hollow, and have their interior lined with stalactites of Chalcedony, or crystals of amethyst, common quartz, mesotype, &c. and sometimes the central cavity is filled with water. In some instances the globules are not larger, than a pea.

Chalcedony is sometimes invested with crystals of quartz; and, on the contrary, quartz is sometimes covered by a deposite of Chalcedony. In some cases it is accompanied by bitumen, which either rests on its surface, or is even contained in its cavities. It sometimes forms the substance of petrifactions, at least in part.

Chalcedony has also been observed in granite and gneiss, as at Vienne, in France. (SAUSSURE.)

(Localities.) Oberstein, in the Palatinate of the Rhine, is one of the best localities of this mineral. It there occurs in an amygdaloidal rock, containing numerous cavities, and liable to decomposition.— Fine specimens are found in the islands of Faroe; Mr. Allan, in his late visit to these islands, observed the remains of a mass of Chalcedony, that had been 4 ft. in length by 2 ft. in its widest part.—It is found also in Vicentino and Iceland. In the latter place Mackenzie observed it in fossil wood.

In the United States. In Maryland, it is found 4 miles from Baltimore. (HAYDEN.)—In Pennsylvania, at Little Britain, in Lancaster Co. under various forms and very beautiful; (CONRAD.)

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also in Chester Co.—In New Jersey, near Trenton.—In Connecticut, 4 miles from Newhaven, near Saltonstall's pond, in secondary trap or amygdaloid; it is botryoidal or mammillary, and on one side of the specimen very often appear impressions of crystallized quartz, &c. it is often beautifully invested with crystals of quartz, sometimes forming geodes. Its color is usually yellowish gray, sometimes blue. (SILLIMAN.)—It has also been found on the banks of the Missouri.

Chalcedony receives a good polish, acquiring a high lustre, and is much esteemed in jewelry.

2. CACHOLONG.* This is a milk white variety of chalcedony. It is opaque or slightly translucent at the edges. Its texture is seldom sufficiently firm to enable it to give fire with steel, although its particles have the hardness of quartz. Its fracture is even, or conchoidal with large cavities, sometimes dull and sometimes glossy. It often adheres to the tongue.

The Cacholong accompanies common chalcedony, which it often envelopes, the two minerals being united by insensible shades. It also associates with flint and semiopal, with which it is sometimes nearly allied.

It is found loose in the fields on the borders of the river Cach,† in Bucharia, in masses, composed of alternate layers of Cacholong and common chalcedony.

It is sometimes set in rings, &c.

3. CARNELIAN.‡ KIRWAN. JAMESON. Its prevailing color is red, passing from a deep blood red to flesh red, or reddish white, which has sometimes a feeble tinge of yellow, or is nearly white. Its colors, or their different shades, sometimes appear in spots, or stripes, or gradually pass into each other. It most commonly is semitransparent, sometimes only translucent. Its fracture is perfectly conchoidal, nearly smooth, and has very little lustre. Its spec. gravity is about 2.61. It occurs in rounded or globular masses, or in stalactites; the surface is often rough, or invested with a brownish crust.

Before the blowpipe it loses its color, and becomes less transparent. It contains 99 parts of silex. (TROMSDORF.)

Its geological situation is similar to that of common chalcedony, which it often accompanies.—The finest specimens, sometimes called oriental Carnelian, come from Arabia and Hindostan.

* Quartz agathe cacholong. HAUY. Silex cacholong. BRONGNIART. Var. of common chalcedony. JAMESON.

Cholon in the language of the Calmuchs is said to signify a stone.

‡ Karniol. WERNER. Quartz agathe cornaline. HAUY, Silex cornaline. BRONGNIART. La Cornaline. BROCHANT.

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It receives a good polish, and is much employed for seals, bracelets, &c.

4. SARDONYX.* This variety differs from the carnelian in its color only, which is reddish yellow, or nearly orange, sometimes with a tinge of brown. It is scarcely possible to determine, in regard to some specimens, to which of the two varieties they belong.—Werner has applied the name of Sardonyx to those carnelians, whose colors are in alternate bands of red and white, and which, when the stone is cut in certain directions, resemble the flesh seen through the finger nail.—It often occurs in larger masses, than the preceding varieties of chalcedony.

5. PLASMA.† WERNER. JAMESON. Its color usually varies between grass and leek green, presenting different shades, which are often blended in the same specimen in spots, stripes, &c. Sometimes it presents whitish or brownish spots. Its fracture is conchoidal, and has a feeble, resinous lustre. It has the hardness and transparency of common chalcedony.

Before the blowpipe it becomes whitish.—Its color is never apple green, like that of chrysoprase.

This mineral, which was worn by the Romans in ornamental dresses, comes from Italy and the Levant. The green mineral, found at Bojanowitz in Moravia, in rounded masses in serpentine, and accompanied with hornstone and flint, has been referred to Plasma; but Mr. Jameson considers it a common chalcedony.

SUBSPECIES 8. HYALITE.‡ KIRWAN. JAMESON.

This mineral exhibits the usual appearance of a concretion, and differs little from chalcedony, except by possessing a vitreous lustre, and sometimes a very loose texture. Its surface is often shining and polished, like that of gum. It occurs in mammillary or botryoidal masses, in stalactites, in branches with an undulated surface, in grains, crusts, &c. Its fracture is conchoidal, or even, and sometimes foliated, and has a shining, vitreous lustre. Its texture is sometimes loose or porous; and, although the mass is very brittle, its particles have the hardness of quartz. Its color is white, either pure, or tinged with yellow, gray, or blue. It is sometimes opaque, and has a pearly or milky aspect; at other times it is nearly semitransparent. Its spec. gravity, sometimes 2.11, varies with its structure.

(Localities.) These concretions frequently occur in volcanic countries, abounding with hot springs, as in Iceland, the isle of Ischia,

* Quartz agathe sardoine. HAUY. Silex sardoine. BRONGNIART.

† Silex plasme. BRONGNIART. Le Plasma. BROCHANT.

‡ Hyalit. WERNER. Quartz hyalin concrétionné. HAUY. BRONGNIART.

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&c. The siliceous deposite, forming a basin around the celebrated Geyser, in Iceland, belongs to this variety; in the vicinity of this hot spring, even the grass, rushes, and the leaves of the trees become invested with a siliceous crust.—In Tuscany near Sancta Fiora, it occurs in stalactites; the Fiorite of Thompson.—In Mexico, on veins of opal, traversing porphyry. (HUMBOLDT.)—At Francfort, on the Main, in wacke or amygdaloid.—It is sometimes imbedded in basalt or serpentine. (KIRWAN.)

In the United States, it appears to exist in the Buhrstone of Georgia.

SUBSPECIES 9. HELIOTROPE.* JAMESON.

Its color is a deep green, peculiarly pleasant to the eye, and commonly not much differing from a leek green. It is usually variegated by small dots of a bright red; and is more or less translucent. Its fracture is imperfectly conchoidal, or even splintery, and glistening. Its spec. grav. is about 2.63.

Before the blowpipe it loses its color. It is by some supposed to be chalcedony, colored by chlorite or green earth. It differs from jasper by its translucency.

The finest specimens come from Asia. It has been found in Iceland, Bohemia, and Siberia, but of inferior beauty.

Like agates, it is employed by jewellers.

SUBSPECIES 10. CHRYSOPRASE.* JAMESON.

Its color is commonly apple green, often extremely beautiful; it sometimes passes to a lighter green, and sometimes to leek green. It is translucent, or sometimes semitransparent. Its fracture is dull and even, sometimes a little splintery, and sometimes smooth, especially in the leek green varieties. It occurs in amorphous or tabular masses. Its spec. gravity, according to Klaproth is 3.25, but Kirwan found it about 2.48. Its hardness differs little from that of flint.

Before the blowpipe it loses its color and translucency. It is composed of silex 96.5, alumine 1.5, oxide of nickel 1.00, and a little iron and lime. (KLAPROTH.) Its fine green color arises from the nickel.

(locality.) This mineral has been found only at Kosemütz, in Silesia. It occurs in veins or interrupted beds in serpentine, ac-

* Heliotrop. WERNER. Heliotropium. KIRWAN. Silex héliotrope. BRONGNIART. Quartz agathe vert obscur et ponctué. HAUY. L'Heliotrope. BROCHANT.

† Krisoprase. WERNER. Chrysoprasium. KIRWAN, Silex Chrysoprase. BRONGNIART. Quartz agathe prase. HAUY. La Chrysoprase. BROCHANT.

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companied by chalcedony, opal, quartz, and a peculiar green earth, which contains nickel, and has received the name of Pimelite.

It is highly esteemed in jewelry for ring stones, &c.

SUBSPECIES 11. OPAL.*

Those siliceous deposites, which have received the name of Opal, present some diversity in their external characters, and are usually divided into several varieties.

Var. 1. PRECIOUS OPAL.† JAMESON. This very beautiful mineral is best characterized by its relations to light. Its proper color is milk white, often slightly tinged with blue, like milk much diluted with water, or yellowish white; but, when viewed by transmitted light, it usually appears reddish or yellowish, sometimes presenting the appearance of flame. It also presents a very lively and irised play of colors, consisting of green, red, blue, yellow, and purple of various shades, and differently assorted, according to the varying position of the mineral. Sometimes only one color is reflected.

This Opal is traversed in all directions by numerous, minute fissures, and on this imperfection in its structure its peculiar beauties depend; for its playful changeability of color is produced by the refraction and reflection of light at these fissures, and is to be explained in the same manner, as the colored rings, between two plates of glass in the experiments of Newton.—It is more or less translucent and sometimes semitransparent, even in a high degree.

It is very easily broken; and its fracture is conchoidal, with a strong lustre, sometimes vitreous, but more often like that of resin recently broken.

It loses its color and transparency before the blowpipe, and by a sudden heat decrepitates. A specimen from Hungary, analyzed by Gerhard, yielded silex 95, alumine 5. Another by Klaproth gave silex 90, water 10.—It is liable to spontaneous decomposition, becoming dull, opaque, adherent to the tongue, and hydrophanous.

(Localities.) The precious Opal occurs in masses of inconsiderable size, sometimes spheroidal, &c. or in veins; and is found in a rock, which is partially decomposed, and appears to be an argillaceous porphyry. It thus occurs at Czerwenitza, in Hungary, which is one of its most remarkable localities.—It has also been found in Saxony, Iceland, France, Mexico, &c.

(Remarks.) The opal is cut and polished for ornamental work in rings, necklaces, &c. It was much esteemed by the ancients, and

* Quartz résinite. HAUY.

† Edler opal. WERNER. L'Opale noble. BROCHANT. Quartz resinite opalin. HAUY. Silex opale. BRONGNIART.

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Nonius, a Senator, is said to have suffered banishment, rather than part with a valuable Opal to Mark Anthony. (PLINY.) Large specimens are rare. Jameson mentions one in the imperial cabinet at Vienna 5 inches by 2½ inches. It is sometimes imperfectly imitated by artificial glasses; and substances, which resemble the opal in its play of colors, are said to opalesce.

2. COMMON OPAL.* JAMESON. This, in many of its characters, differs but little from the preceding variety. It does not, however, present that effulgence or play of colors, by which the precious opal is distinguished. Its color is white, shaded with gray, green, or yellow; sometimes milk white; it also presents other shades of green and yellow, and is sometimes brown or reddish. When viewed by transmitted light, the milk white and greenish varieties often change their colors. In its fracture, lustre, and transparency, it differs very little from the precious opal. Its spec. grav. varies from 1.96 to 2.14 in consequence of the fissures, by which it is traversed. It occurs in small masses, amorphous, rounded, reniform, &c.

In a specimen from Kosemütz Klaproth found silex 98.75, alumine 0.10, oxide of iron 0.10;=98.95.

(Localities.) It is sometimes in veins or masses, contained in porphyry and amygdaloid.—At Kosemütz in Siberia, it occurs in serpentine with chrysoprase, and appears to be colored green by nickel.—In Iceland, it alternates with chalcedony. (JAMESON.)—In Saxony, it exists in granite with hornstone and jasper. (WERNER.)

In the United States, on the banks of the Delaware, near Easton in Pennsylvania, Opal is found strongly characterized. (WISTER.)

Appendix.

HYDROPHANE.† This name denotes merely a peculiar property, which some minerals possess, of becoming more transparent in water,‡ and of again returning to their natural state, when removed into a dry air. This property, which depends on a certain structure in the mineral, is most frequently observed in certain varieties of the Opal; sometimes also in the cacholong. The Hydrophane has a porous structure, either originally, or in consequence of partial decomposition. When immersed in water, bubbles of air escape from its pores, while the water enters, and its weight is sensibly increased. But, when the pores are thus filled with water, a less portion of the light is reflected during its passage through the mineral, than if the

* Gemeiner opal. WERNER. L'Opale commune. BROCHANT.

† Silex hydrophane. BRONGNIART. Quartz résinite hydrophane. HAUY. Hydrophanes. KIRWAN.

‡ Hence the name, from the Greek Υδωζ, water, and ϕαινω, to show light.

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same pores were filled with air; consequently more light is transmitted, and the transparency increased. This explanation may be illustrated by the experiment, in which air and water are successively placed behind a denser medium of glass.

Before immersion it is slightly translucent, or nearly opaque, and often adheres strongly to the tongue. Some varieties become even opalescent by immersion. Hydrophanous opals possess a much stronger lustre, than the cacholong.

A specimen, analyzed by Klaproth, gave silex 93.16, alumine 1.62, water 5.25.

Good specimens are found at Hubertsberg in Saxony, and at Telkobania in Hungary, &c.

GIRASOLE.* This name also designates a particular property, observable in certain varieties of opal. The Girasole is milk white, or bluish white, but, when turned toward the sun,† or any bright light, it constantly reflects a reddish color. It is sometimes strongly translucent; and the finest specimens resemble a translucid jelly.

3. SEMI-OPAL.‡ JAMESON. This variety, which is a little harder, than the precious opal, is easily broken; and its fracture is imperfectly conchoidal with large cavities, or nearly even, usually more or less glistening and a little resinous, but sometimes nearly dull. The edges of the conchoidal fracture and those of the fragments are usually very sharp. It is more or less translucent, sometimes only in a slight degree at the edges, and some specimens are semitransparent. Its colors are numerous; white and gray, often shaded with yellow, green, red, or blue, sometimes milk white, and sometimes grayish black; it also presents distinct shades of yellow, green, red, and brown. Its colors are never lively; and, though generally uniform, are sometimes in spots, veins, &c. Its spec. grav. is variable, but does not exceed 2.54.

It is sometimes amorphous, and sometimes tuberose, reniform, stalactical, &c.

Though infusible by the blowpipe, it is often contaminated by foreign ingredients. It is liable to decomposition, and sometimes passes into a substance, resembling porcelain clay.

(Distinctive characters.) Its infusibility distinguishes it from pitchstone, which it often much resembles.—It rarely exhibits the peculiar, opaque, milky whiteness of the cacholong.—Its lustre, or its translucency, or both, will in most cases distinguish it from jasper;

* Silex girasol. BRONGNIART. Quartz résinite girasol. HAUY.

† Hence its name from the Latin, gyro, to turn, and sol, the sun.

‡ Halb-opal. WERNER. La Demi-opale. BROCHANT. Silex résinite. BRONGNIART. Quartz résinite commune. HAUY.

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into which, however, as well as hornstone and cacholong, it gradually passes.—From the common opal it usually differs in lustre, fracture, hardness, and often by the dullness of its colors and inferior transluency.

(Geolog. sit. and Localities.) It occurs in masses, veins, or this layers in amygdaloid, basalt, porphyry, &c.; also in granite and gneiss, and in veins, which traverse these rocks, especially those veins, which are metalliferous and contain silver. It sometimes constitutes the substance of organic remains of wood, &c.—Near Orleans, in France, it is found in carbonate of lime;—in Auvergne, it is sometimes filled with cavities, and decomposed at the surface.

In the United States. In Maryland, at the Bare Hills, near Baltimore, it occurs in thin veins in serpentine; its surface is yellowish brown, and carious; its recent fracture, however, is whitish, like chalcedony, but by exposure becomes brown. (GILMOR.)—In Pennsylvania, at the Falls of the Delaware, near Trenton Bridge, of a bluish gray color in granite; its transparency is much increased by immersion in water;—also in Upper Merian, in Montgomery Co. leek green and opaque, in serpentine. (SEYBERT.)

MENILITE.* JAMESON. This mineral occurs in small, irregular or roundish masses, often tuberose, or marked with little ridges on the surface. When broken, it appears brown or dark gray, though its exterior is often bluish or striped. It is translucent, often at the edges only. Its structure is a little slaty; its fracture more or less conchoidal or splintery, usually somewhat glistening and resinous. It scratches glass; and its spec. grav. is about 2.18. It is infusible by the blowpipe; and contains silex 85.5, alumine 1, lime 0.5, oxide of iron 0.5. water and carbonaceous matter 11;=98.5 (KLAPROTH.)

The Menilite has hitherto been found only in France; more particularly at Ménil-Montant, near Paris; it is imbedded in a slaty clay, which separates beds of Plaster stone.

SUBSPECIES 12. FLINT.† KIRWAN. JAMESON.

Flint is easily broken into fragments with very sharp edges; and its fracture is almost always perfectly conchoidal. A few splinters, however, sometimes appear; and the curvature is often so gradual, that a small portion of the surface, viewed by itself, appears plane. The surface of the fracture has usually a feeble lustre, being smooth and glossy, but is sometimes almost dull. It is translucent, but, in

* Menilit. WERNER. Silex Menilite BRONGNIART. Quartz résinite subluisant HAUY.

† Feurstein. WERNER. La Pierre à feu. BROCHANT. Silex pyromaque. BRONGNIART. Quartz agathe pyromaque. HAUY.

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general, only when in thin fragments, or at the edges. Its color is most commonly some shade of gray, either light or dark, sometimes bluish or yellowish gray, or grayish black, wax yellow, yellowish brown, brownish red, &c. The colors are sometimes intermixed in spots, stripes, &c. It is usually a little harder, than common quartz or jasper; but it has been remarked, that the yellowish and lighter colored varieties do not scintillate so plentifully, as those of a dark color, nor do they wear away the hammer of a gun lock so quickly. It, however, always gives lively sparks with steel more or less copiously. Its spec. grav. varies from 2.58 to 2.63.

It occurs most commonly in nodules of a moderate size, often irregular, sometimes globular, elliptical, tuberose, or perforated, and sometimes it is in plates, or in pebbles, or in grains, or is amorphous. It also occurs in pseudomorphous crystals.

When exposed to a strong heat, it loses its color, becomes opake, more brittle, and often decrepitates; but does not melt. It contains silex 08, lime 0.5, alumine 0.25, oxide of iron 0.25, water 1. (KLAPROTH.)

(Geological situation.) Flint is almost entirely confined to secondary rocks, or earths, where it occurs imbedded in chalk, calcareous marl, or even in compact limestone. The nodules of Flint, various both in size and form, are usually arranged in parallel beds, most commonly horizontal, sometimes oblique; still, however, the nodules of the same bed do not lie perfectly in contact with each other.—It also occurs in thin layers or beds between strata of compact limestone, or in sand.

The nodules of Flint, which occur in chalk, or even in compact limestone, are intimately united with the surrounding mass in such manner, that the calcareous substance often appears to have penetrated the Flint. Hence these flinty nodules, when taken from the quarry, are usually invested with an opaque, white, friable crust, which effervesces with nitric acid, and has been found to contain 10 per cent. of carbonate of lime. If this natural crust be removed, or the Flint be broken, a second, white, opaque, friable, and porous crust will be produced by exposure to the changes of the atmosphere; but it contains no carbonate of lime.—The whitish spots, which sometimes occur in the interior of Flint, contain from 2 to 7 per cent. of carbonate of lime.

In alluvial earths, Flint in the form of pebbles is not uncommon.—It has also been found in rolled pieces in veins, which traverse primitive rocks.

This mineral sometimes contains cavities, lined with crystallized quartz, sulphuret of iron, &c. The crystals of quartz are sometimes

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united with the Flint by imperceptible shades. Near Poligni in France, the cavities in the interior of Flint contain sulphur.

Masses of Flint, when taken from the earth, contain a great degree of moisture, which often appears on the surface of the fracture.

Flint also forms the substance of various petrifactions, as echinites, madrepores, &c. and sometimes exhibits impressions of leaves and other organic bodies.

It passes into hornstone, chalcedony, and common quartz.

It is difficult to explain the circumstances, under which the nodules of Flint, found in beds of chalk or marl, have been formed. These nodules cannot have received their rounded form from attrition; indeed their peculiar arrangement in beds, &c. forbids the belief, that they have been rolled and transported by water. It has been generally believed, that they were produced by the filtration of water into pre-existing cavities; and these cavities may have been produced by the escape of air, during the deposition of the calcareous strata, or may have once been occupied by animal substances, as mollusci, &c.

(Localities.) This mineral has been found in Denmark, Saxony, Poland, Spain, &c. but more particularly in the north of France, and on the opposite coast of England.

In the United States. In Pennsylvania, near Easton, Northampton Co. and near Reading, Berks Co. (SEYBERT.)—In New York, at Black Rock and in the Seneka prairies, imbedded in limestone; (MITCHILL.)—also near Saratoga Springs, in globular masses, dark gray, imbedded in limestone. (Lit. and Philos. Reper. v. 2.)—In Vermont, on Mount Independence, in Orwell. (HALL.)—In Connecticut, in detached rolled pieces near Newhaven;—also at Woodbridge in masses, penetrated by white veins and spots of calcareous spar. (SILLIMAN.)*

(Uses.) Flint is sometimes employed in the manufacture of glass, porcelain, and smalt; but its principal use is for gun flints, of which the manufacture is chiefly confined to France and England. The operation is simple, but requires judgment and dexterity. A small mass of Flint, being held in the hand, or supported on the knee, is divided by a hammer into fragments or splinters, and these splinters are afterward reduced to a proper form and size on the edge of a steel chisel by repeated small blows. A good workman can scale off and finish 1000 flints in three days.—Sometimes only a small number of the nodules, found in any one bed, is suitable for the manufacture of gun flints. The best Flint has a fracture not only

* May not some of the localities above mentioned belong to hornstone, rather than true Flint? The two minerals are often very nearly allied.

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conchoidal but smooth, and, in very thin fragments, presents a uniform semitransparence of a greasy aspect. (DOLOMIEU.)*

SWIMMING FLINT.† This mineral occurs in masses, whose texture is spongy, porous, or even cellular. Hence it often swims on the surface of water, till it has imbibed a certain quantity. Its powder is rough to the touch, and scratches glass and steel. It is easily broken, and presents a dull, earthy, or uneven fracture. Its color is whitish or gray, often with a tinge of yellow.

It contains silex 98, carbonate of lime 2. (VAUQUELIN.)

It has been found chiefly at St. Ouen, near Paris, in beds of chalk. It frequently contains a nucleus of common flint, with which it is intimately united.

SUBSPECIES 13. HORNSTONE.‡

Its fracture is usually dull, and splintery, often like that of wax;

* Brongniart, from the observations of Dolomieu, has described a mineral under the name of Silex Prasien, which he supposes to be a variety of flint. It is greenish or leek green; and has a dull or glimmering conchoidal fracture.—From the same authority he mentions another substance, to which he gives the name of silex jadien. Its color is pale green, and its texture fibrous. But it has neither the hardness, nor fusibility of jade.

† Schwimmstein. WERNER. Floatstone. JAMESON. Quartz nectique. HAUY. Silex nectique. BRONGNIART.

‡ Silex cornè BRONGNIART. Quartz agathe grossier HAUY.
Infusible varieties of the Hornstein of Werner, Hornstone of Kirwan and Jameson, and of the Pierre de Corne of Brochant.
So much ambiguity of meaning is attached to the word Hornstone, that it would be favorable to the interests of mineralogy, if this term could be banished from its nomenclature. It has by some been confounded with hornblende, and also with the roche cornéenne of Haüy. By others it has been applied to two minerals entirely distinct.
This confusion and obscurity in the use of the word, hornstone, appear to have arisen in part from accidental circumstances. It is asserted by Kirwan, on the authority of Henckel, that this word was originally employed by miners to designate a certain stone, which they found difficult to be cut through, in consequence of its tenacity, somewhat resembling that of horn. But a certain degree of translucency is also a character of horn. Hence, as mineralogists did not observe both these properties to unite in the same mineral, they subsequently applied the term, hornstone, to two distinct minerals, one of which possessed tenacity only, while the other was translucent, but not remarkably tenacious. Hence the application of the term, hornstone, to the mineral, now called hornblende, which is remarkably tenacious.
On the other hand, the writers of the Wernerian school have not indeed applied the name in question to hornblende, but they include under it two minerals totally distinct in their chemical characters and composition. One of them is the mineral here described, composed essentially of silex, and absolutely infusible; the other is always fusible, and frequently forms the base of porphyry. This latter mineral appears to be included in the petrosilex of many French writers, and the chert of the English. But the name, petrosilex, almost equally unfortunate with hornstone, has been variously employed; for remarks on which, see that species.
The Roche cornéenne of the French embraces hornblende slate, several varieties of argillite, &c.

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but sometimes it is more or less conchoidal with a very feeble or glimmering lustre. It is more or less translucent, sometimes at the edges only, and sometimes the whole mass, if thin, has the strong translucency of certain horns. It is less hard, than common quartz, and gives sparks rather feebly with steel, unless when it is passing into flint.

Its colors are numerous and usually dull. It is often gray, sometimes nearly white, but more frequently shaded with blue, yellow, black, or green, or it presents distinct shades of red, brown, or green. The colors are sometimes in spots, stripes, clouds, &c. It is usually amorphous, sometimes globular.

(Distinctive characters.) Its infusibility by the blowpipe distinguishes it from petrosilex, and jade.—Its translucency or splintery fracture will, in most cases, serve to separate it from jasper.—It is usually duller than flint, and does not, in general, so freely give fire with steel.—It never possesses the lustre of common quartz.—Some specimens, however, approach very near to flint, chalcedony, jasper, or common quartz, the latter of which is sometimes crystallized in its cavities or interstices.

(Geolog. sit. and Localities.) Hornstone often occurs in veins, especially metallic, in primitive mountains; and sometimes incrusts other minerals. It is also imbedded in rounded or irregular masses in secondary limestone. Sometimes it accompanies amethyst and agates.

In the United States. In Maryland, Washington Co. west side of the Blue Ridge, in large masses, with a splintery fracture, and constantly containing carbonate of copper;—also near Baltimore with a conchoidal fracture. (HATDEN.)—In Massachusetts, near Boston.—In Maine, near Belfast.

SUBSPECIES 14. SILICICALCE.*

This substance occurs in amorphous masses, which present a smooth, dull fracture, either conchoidal or even. It but seldom gives sparks with steel. Its color is gray, or brown, sometimes nearly black. With nitric acid it slightly effervesces; and before the blowpipe melts into a white scoria. It appears to be a mixture of flint, and

* Quartz agathe calcifère. HAUY. Silex silicicalce. BRONGNIART.

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carbonate of lime, and hence its fusibility. Indeed it sometimes embraces fragments of flint.

It exists in thin beds under strata of compact limestone in Provence; and alternates with similar limestone in the Pyrennees.

CONITE. This is supposed by Haüy to be a variety of Silicicalce. Its fracture is uneven or splintery; its color gray; and it is sufficiently hard to scratch glass. Its spec. gravity is 2.83; and it effervesces with nitric acid.

SUBSPECIES 15. BUHRSTONE.* (Millstone.)

The exterior aspect of this mineral is somewhat peculiar. It occurs in amorphous masses, partly compact, but always containing a greater or less number of irregular cavities. Sometimes the mass is comparatively compact, and the cavities small and less frequent, but they always exist even in specimens of a moderate size. These cavities are sometimes crossed by siliceous threads or membranes, much resembling the interior structure of certain bones; and are sometimes lined by siliceous incrustations, or crystals of quartz.

Its fracture is nearly even, sometimes dull, and sometimes smooth, like that of flint. Its color is gray or whitish, sometimes with a tinge of blue, and sometimes yellowish, or reddish.

(Geolog. sit. and Localities.) Near Paris, the Buhrstone occurs in beds, usually horizontal, and seldom more than 9 or 10 feet thick. It contains no organic remains. Its cavities are often crossed by threads, and filled with argillaceous marl or sand; but are very seldom lined by crystals of quartz. It usually rests on clay, and, when near the surface, is covered by ferruginous sand or pebbles. In the order of superposition, it constitutes the ninth of the horizontal beds or formations in the vicinity of Paris, counting upwards from the lowest, which is chalk. It lies over sandstone, containing marine fossils; and is covered by a fresh-water formation, of which part is calcareous, and part is siliceous, being itself a variety of the Buhrstone. This fresh-water formation contains shells, belonging to lakes and rivers.

In the United States. In Georgia, the Buhrstone is found near the Carolina line, about 40 miles from the sea. It is said to cover shell limestone. Some of its cavities are those of shells in a siliceous state, and lined by siliceous incrustations, or crystals of quartz. Others are traversed by minute threads, or contain a friable substance somewhat argillaceous.—In Pennsylvania, Northampton Co. a Buhrstone or cellular quartz is found; but the writer knows not its characters nor geological situation.

* Quartz agathe molaire. HAUY. Silex meulière. BRONGNIART. Var. of Flint of Jameson; and of Pierre à feu of Brochant.

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(Uses.) Its hardness, and cavities, when not too numerous, render it peculiarly useful for making millstones. Hence also it is sometimes known by the name of Millstone.

SUBSPECIES 16. JASPER.

Jasper is usually a little less hard than flint, or even common quartz; but it still gives fire with steel. Its fracture is generally more or less conchoidal, sometimes nearly even, and in some instances fine splintery or earthy. In most varieties the surface of the fracture is nearly or quite dull. It is entirely opaque, or sometimes feebly translucent at the edges; and presents almost every variety of color. Its spec. gravity varies from 2.30 to 2.70. It is often a conductor of electricity.

Before the blowpipe it loses its colors, but is infusible, even when the flame is urged by oxigen gas. With the compound blowpipe red Jasper melts into a grayish black slag with white spots. (SILLIMAN.) The silex, of which it appears to be essentially composed, is contaminated with alumine and oxide of iron in various proportions.

Several varieties deserve particular notice.

1. COMMON JASPER.* KIRWAN. JAMESON. Its most common colors are brown, red, and yellow, of different shades, and variously intermixed. It also occurs green, bluish, violet, or nearly black, and sometimes gray or white. The colors are in some cases arranged in spots or clouds. Green Jasper with red spots differs from heliotrope by its want of translucency.

Common Jasper is found in large amorphous masses, or in detached fragments.

Certain minerals, which are sometimes described, as varieties of red Jasper, although possessing a shining and nearly vitreous fracture, we have already referred to red ferruginous quartz.

2. STRIPED JASPER.† KIRWAN. JAMESON. This differs from the preceding variety chiefly in the arrangement of its colors, which are usually some variety of gray, yellow, red, and green; but these colors appear in stripes, veins, rays, in oval spots, or in curved, concentric zones.

This variety occurs in large beds. It is found very beautiful in the Uralian Mountains; sometimes exhibiting red and green stripes, equal and parallel;—and sometimes round or oval whitish spots on a brown or flesh colored ground, and hence denominated eyed Jasper.

* Gemeiner jaspis. WERNER. Jaspe commun. BRONGNIART. Quartz jaspe rouge, &c. HAUY. Le Jaspe commun. BROCHANT.

† Band Jaspis. WERNER. Jaspe rubanné. BRONGNIART. Quartz jaspe onyx. HAUY. Le Jaspe rubanné. BROCHANT.

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3. EGYPTIAN JASPER.* JAMESON. It is well characterized by its globular or spheroidal form, sometimes flattened, and by the arrangement of its colors. These colors are brown, yellowish brown, pale yellow, or yellowish gray, always arranged in zones more or less regular, nearly concentric, and sometimes with dots or dendrites of a different color interspersed. In fact, the brown or yellowish brown may generally be considered as forming colored designs upon a paler ground. Its fracture has a feeble lustre.

This variety is found in sand near Suez in Egypt, and the contiguous deserts. It there forms a constituent part of extensive beds of a siliceous breccia, which, by their decomposition, furnish these pebbles in a loose state.—A similar variety, whose colors are red, yellow, or gray, has been found in the Electorate of Baden, in argillaceous oxide of iron.

(Geological situation.) Jasper, including the common and striped varieties, is sometimes found in thick beds in the transition, or older secondary rocks; or even forms whole hills. It also occurs in certain veins, especially metallic, which traverse primitive rocks. In the Hartz, beds of Jasper rest on graywacke. Sometimes it accompanies basalt or greenstone. It is also found in masses of a moderate size in amygdaloid, and there accompanies chalcedony, or is disseminated in it, and forms a constituent part of agates; hence sometimes called agate Jasper.

It is not uncommon in detached or rolled masses in alluvial earths.

Jasper is often traversed by metallic veins, or by veins of quartz. It sometimes embraces, more especially when in veins, lithomarge, semi-opal, brown spar, garnets, the sulphurets of iron and silver, native bismuth, &c. It is not uncommon in veins, containing certain ores of iron.

According to Bertrand, beds of Jasper sometimes contain fossil shells and marine plants.

Jasper is never porphyritic. The base of that, which has been called jasper porphyry, is fusible, and is either petrosilex or compact feldspar.

In the opinion of many, Jasper has been formed by the filtration of silex into beds of ferruginous clay. It sometimes indeed contains small portions of indurated clay or lithomarge, and, at other times, borders on hornstone, flint, chalcedony, or opal. Jameson has described a mineral under the name of opal jasper, which he supposes intermediate between opal and Jasper. Its fracture is conchoidal,

* Egyptischer Jaspe. WERNER. Jaspe Egyptien. BRONGNIART. Egyptian pebble. KIRWAN. Quartz agathe onyx. HAUY. Le Jaspe Egyptien. BROCHANT.

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shining, and nearly vitreous. Its colors are some shade of red, brown, or yellow, either uniform, or in spots, veins, &c. It is less hard, than common Jasper. It has been found in porphyry near Tokay in Hungary, &c.

(Localities.) Its foreign localities are numerous. Among these are the Uralian and Altain mountains; in the latter of which its color is sometimes a beautiful white, with black dendritic figures.

In the United States. In Maryland, the common variety occurs near Baltimore, in detached masses, red, brown, and yellow.—In New Jersey, near Trenton and Woodbury of various colors.—In Connecticut, near Newhaven in rolled pieces—In Vermont, a very beautiful red Jasper has been found.

(Uses.) The high polish, of which Jasper is susceptible, the variety and richness of its colors render it of considerable value and use in the ornamental arts for vases, snuff-boxes, seals, sword handles, &c. The ceraunite, or thunder stone, often belongs to Jasper.

Appendix to the species Quartz.

AGATE. This name is usually applied to an aggregate of certain quartzy or siliceous substances, intimately combined, possessing a great degree of hardness, a compact and fine texture, agreeable colors, variously arranged and intermixed, and susceptible of a good polish. The minerals, which most frequently enter into the composition of Agates, are common chalcedony, carnelian, and jasper, to which are sometimes added flint, hornstone, common quartz, amethyst, heliotrope, and opal. The chalcedony is however the most common and abundant ingredient, and may frequently be considered the base of the Agate; in fact, some agates are composed entirely of chalcedony differently colored. In most cases, only two or three of the aforementioned ingredients occur in the same Agate; but, though variously intermixed, each ingredient usually remains perfectly distinct.

Agates exhibit the colors already mentioned, while describing the simple minerals, which compose them. But these colors are often so arranged, as to present the resemblance of some well known objects. Hence arises much of the beauty of Agates; and hence also most of the distinctive names they have received in the arts. Of these a few will be mentioned.

1. ONYX AGATE;* when the different colors are arranged in distinct parallel stripes or zones. If these zones are straight, it is sometimes called ribband Agate; if sinuous, or in a zigzag line, fortification Agate.

* Quartz agathe onyx. HAUY.

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2. EYED AGATE; when the colored zones are arranged in concentric curves. This Agate is, in fact, composed of a number of tubercles, each of which consists of concentric layers, enveloping a globular nucleus; this nucleus or pupil is sometimes radiated from the centre to the circumference, and may even be detached from its envelope. The lapidary, by cutting and rounding these Agates in a particular manner, produces a striking resemblance to the eyes of certain animals.

3. DOTTED AGATE;* when many of the colors appear in points or dots. Sometimes these dots are obviously jasper of various colors in a base of chalcedony.

4. MOSS AGATE; in the interior of this appear small filaments, sometimes green, brown, or yellowish, irregularly interwoven, like certain varieties of moss, or the fibres of certain roots. It has indeed been suggested by Daubenton, that these filaments may be really mosses, or some vegetable fibres, enveloped in the Agate at the time of its formation.

5. DENDRITIC AGATE, OR MOCHA STONE;† in the interior of tihs appear brown, reddish brown, or blackish delineations of shrubs, deprived of their leaves. These dendritic appearances are probably produced by the filtration of the oxides of iron and manganese into the fissures of the Agate.

6. SPOTTED OR FIGURED AGATE;‡ when the colors appear in irregular spots, or in figures, bearing more or less of resemblance to clouds, stars, landscapes, &c.

7. BRECCIA AGATE; when the mass is composed of fragments of different Agates, united by a siliceous cement.

(Mode of formation.) Agates, though sometimes amorphous, usually occur in nodules, or rounded masses, and rarely in stalactites. They appear to have been formed by the filtration of siliceous particles into pre-existing cavities. It is, however, very remarkable, that the different stripes or zones in Agates should be so perfectly parallel, as we generally observe them; the parallelism extending to every angle, or irregular winding, which exists in the exterior zone, and which undoubtedly received its form from the interior walls of the cavity, in which the Agate was formed. This circumstance also strongly indicates, that such Agates have been formed by successive deposites of thin layers or coats of siliceous earth upon the sides of the cavities, which they now fill entirely or in part. These layers, whether chalcedony, carnelian, &c. are essentially composed of siliceous earth; and their various external characters may arise from the presence of col-

* Quartz agathe ponctué. HAUY

† Quartz agathe arborisé. HAUY.

‡ Quartz agathe panaché HAUY.

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oring matter, or some other foreign ingredient, or from the various circumstances, under which the deposites were made. The texture of Agates is said to be, in general, soarser near the surface, than toward the centre.

But, if the exterior coat was first formed, in what manner could this be penetrated by the siliceous earth to form the interior layers? To this it may be replied, that in many Agates, when cut in a certain manner, there appear distinct traces of the canal, by which the solution of silex had entered.

When the cavities have not been filled by the deposite, the Agate remains hollow, forming a geode; and its interior is lined with crystals of common quartz, amethyst, ferruginous quartz, chabasie, &c. The exterior of Agates is frequently invested with a brownish or yellowish crust.

(Localities.) The localities of Agates are, in general, the same as those of chalcedony, which enters so largely into their composition. They are found abundantly at Oberstein in Germany, disseminated in amygdaloid, or porphyry, and usually surrounded by a greenish earth. They are also found in other parts of Europe, in the East Indies, and South America.

In the United States, it has been found in Virginia, in Greenbriar Co.;—and in Maryland, near Baltimore.

(Uses.) Agates are employed both in the useful and ornamental arts; for wheel pivots in watches, for inlayed work, for mortars, boxes, seals, &c. &c. Much of their beauty depends on the art of the lapidary in cutting them in certain directions, in reference to their different structures, and zones of color. Thus, if the Agate be composed of mammillary concretions, a transverse section will exhibit numerous undulations.

Agates were much esteemed by the ancients, and many fine specimens of their art of engraving in cameo on these hard substances may be found in mineralogical cabinets and public museums. The term oriental is often applied to Agates, chalcedony, carnelian, &c. when very translucent and perfect, but without indicating their locality.

AGATIZED WOOD.* This substance appears to have been produced by the process, commonly called the petrifaction of wood. It is essentially composed of siliceous earth, which, it is highly probable, has been gradually deposited, as the vegetable matter was decomposed and removed.

Both its form and texture indicate its origin. Thus it presents,

* Holzstein. WERNER. Woodstone. KIRWAN. JAMESON. Quartz agathe xyloïde. HAUY. Le Bois petrifié. BROCHANT.

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more or less distinctly, the form of the trunk, branches, roots, or knots, which once belonged to the vegetable. The surface is rough or longitudinally striated.—Its texture is fibrous, and the fibres often intertwined, like those of wood. Its longitudinal fracture is usually fibrous or splintery, and its cross fracture imperfectly conchoidal with little or no lustre.

Its color is usually gray, either light or dark, or shaded with blue, yellow, &c. sometimes red or brownish. The colors are often in spots, stripes, clouds, &c. It is a little translucent, sometimes at the edges only. Its hardness is nearly that of common quartz; and its spec. gravity sometimes as high as 2.67.

(Localities.) In Europe it occurs in sandy loam or sandstone. Kirwan says "a stump of a tree 6 feet in length, and as many in diameter, with roots and branches thus petrified," has been found near Chemnitz in Saxony.

In the United States. On the banks of the Missouri.—In Maryland, in Ann Arundel Co.;—in Delaware, near Cape Henlopen;— in New Jersey, in the pine barrens. (SEYBERT.)

It is susceptible of a good polish.

OPALIZED WOOD.* This, like the preceding, has the form and texture of wood; the vegetable matter having gradually given place to a siliceous deposite possessing the characters of Semi-opal. Its texture is fibrous; its cross fracture conchoidal with a moderate lustre, which is often waxy or resinous. It does not give fire with steel, although it is difficultly scraped by a knife. Its spec. grav. lies between 2.0 and 2.6. Its colors are white or gray, often shaded with yellow or red, and pass into yellow or brown; they are sometimes arranged in spots, circles, &c. It is translucent, at least at the edges, and sometimes opaque.

This substance has been found near Schemnitz, &c. in Hungary.

SPECIES 14. TRIPOLI.† KIRWAN. BRONGNIART.

This useful mineral exhibits no one character remarkably striking. Its general aspect is usually dull and argillaceous, often resembling that of certain clays. Most commonly it occurs in friable or earthy masses, but is sometimes very considerably indurated.

Its powder is very fine, but, at the same time, dry and rough to the touch, and sufficiently hard to scratch metals, glass &c. It does not, like clay, form a paste with water, though it often easily crum-

* Holz-opal. WERNER. Wood-opal. JAMESON. Quartz résinite xyloïde. HAUY. Ligniform opal. KIRWAN. Opal ligniforme. BROCHANT.

† Trippel. WERNER. Tripoli. JAMESON. Le Tripoli. BROCHANT. Tripoli, et Thermantide tripoléenne. HAUY.

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bles in that liquid.—It is sometimes slaty, and sometimes granular, but its texture is seldom compact. Its fracture is dull and earthy, or, in the harder varieties, a little conchoidal. It s opaque, and its color is gray, sometimes very light, often tinged with yellow or red, and even passes into yellow, brown, or red.

Some specimens are very light, and adhere strongly to the tongue.

Before the blowpipe it does not melt, unless contaminated by foreign ingredients. In a strong heat, however, it hardens a little, and often becomes reddish. It sometimes contains a little carbonate of lime, and effervesces with nitric acid.

Although silex must constitute its most essential ingredient, being sometimes in the proportion of 90 per cent. its composition is probably somewhat variable. Indeed Tripoli can hardly be said to constitute a distinct species, as it results from the alteration of other minerals.

Tripoli differs from clay by the roughness and hardness of its powder, and by not forming a paste with water.

ROTTEN STONE. This name, though sometimes extended to the whole species, is usually confined to those varieties, which are most light and friable, and have a very fine grain.

(Geological situation.) Tripoli, so called from a place of that name in Barbary, whence it was formerly brought, appears to be the result of an alteration, produced in certain minerals, by the agency of either water or fire. In the former case, it appears to be a fine, siliceous sediment, deposited from water, and to have proceeded from the decomposition of certain siliceous minerals; the alumine and iron serving to unite the other particles.—In the latter case, it seems to have resulted from an alteration in sandy clay, or argillaceous slate by the action of fire, either volcanic or proceeding from inflamed coal mines.

It is found among secondary rocks, or in alluvial earths. Thus at Montelimart in France, it is mixed with fragments of basalt, &c.— Near Prague in Bohemia, it is situated between beds of sandstone. (DE BORN.)—Near Rennes, in Brittany, it is covered by sandstone, and contains trunks of trees, converted into Tripoli.—At Postchappel, in Saxony, its beds are in a mountain, containing coal.—In Auvergne are strata of argillaceous slate, black at one extremity, and, at the other, converted into a reddish Tripoli, with intermediate shades in the interval. (SAUSSURE.)—It is sometimes in mountains evidently volcanic.

The variety, called Rotten stone, occurs near Bakewell, in Derbyshire, and rests on compact limestone. It usually contains a little carbonate of lime. It is sometimes in nodules, which contain a nucleus of solid limestone, or of very indurated rotten stone.

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The Polishing slate, Polierschiefer of Werner, appears to be a variety of Tripoli. Its color is white or gray, more or less shaded with yellow. Its structure is slaty; its cross fracture dull and earthy. It is easily reduced to a fine, dry powder. It is very light, and strongly adheres to the tongue. Before the blowpipe it hardens a little,. but does not melt.—It is found near Bilin, in Bohemia, where it forms the upper part of a bed, which, at a greater depth, becomes more compact.

(Uses.) It is employed in polishing metals, stones, and glass. The Venetian Tripoli comes from the isle of Corfu, is slaty, yellowish red, and of a very good quality.—That of Derbyshire is highly esteemed.—It may be artificially prepared by calcining some argillites.

SPECIES 15. PORCELLANITE.* KIRWAN.

It presents various shades of gray, red, yellow, and blue, as pearl or bluish gray, brick red, &c. and is sometimes brown, greenish, or nearly black. These colors, or their different shades, are sometimes in spots, clouds, &c. and the mineral often resembles a brick, which has undergone a slight vitrification. Its fracture is imperfectly conchoidal or uneven, more or less glistening, and often has the aspect of certain porcelains. It is opaque, very brittle, and somewhat less hard, than quartz. It occurs in amorphous masses or fragments, which are often rifted.

Before the blowpipe it melts into a black scoria. A specimen, analyzed by Rose, yielded silex 60.75, alumine 27.25, potash 3.66, magnesia 3.00, oxide of iron 2.50;=97.16. It is most probably an alteration of some variety of argillaceous slate by pseudo-volcanic fires; and of course does not constitute a distinct species.

(Geological situation.) This mineral is not abundant, but appears to have been always found in the vicinity of coal mines, or in places, where such mines have probably once existed. It is sometimes marked with vegetable impressions of a brick red color.—It is found in large masses near the Pitch Lake in Trinidad, slate blue in the interior, but reddish externally. (NUGENT.)

SPECIES 16. SILICEOUS SLATE.*

This mineral occurs in masses, which are usually amorphous, sometimes rounded, but almost always traversed by numerous small

* Porzellan Jaspis. WERNER. Porcelaine Jasper. JAMESON. Jaspe Porcellanite. BRONGNIART. Thermantide porcellanite. HAUY. Le Jaspe porcelaine. BROCHANT.

† Kiesel schiefer. WERNER. Flinty slate. JAMESON. Siliceous schistus. KIRWAN. Le Schiste siliceux. BROCHANT. Jaspe schisteux. BRONGNIART.

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veins of quartz, usually white, sometimes gray or reddish. Its slaty structure is more or less distinct in masses of considerable size, which are also usually fissile; but the fracture of any single layer, or of small specimens, is a little spliutery, imperfectly conchoidal, or nearly even, and almost dull. In hardness it differs little from common quartz. Its colors are usually gray, bluish gray, or black, sometimes dark red, and sometimes striped or spotted. It is opaque, or somewhat translucent at the edges. Its spec. gravity lies between 2.59 and 2.64.

Before the blowpipe it is infusible, though some varieties become lighter colored. A specimen, analyzed by Cabal and Chevreuil, yielded silex 55.0, alumine 15.0, potash 8.0, lime 0.5, oxide of iron 10.0, water, carbon, and loss 11.5.

Var. 1. BASANITE.* KIRWAN. It differs but little from the common variety of siliceous slate. Its color is grayish or bluish black, or even perfectly black; its powder also is black. It is entirely opaque. In small specimens its fracture is usually even, sometimes a little conchoidal, and nearly dull. It occurs not only in amorphous masses, but in rolled pieces, which often incline to a trapezoidal form.

(Uses.) This variety is employed as a test or touchstone to determine the purity of gold; and hence its name, from the Greek ʙασανος, the trier. If a bar of gold be rubbed against the smooth surface of the touchstone, a metallic trace is left, by the color of which an experienced eye can form some estimate of the purity of the gold; but the judgment is still farther determined by the changes, produced in this trace by the application of nitric acid, which immediately dissolves those substances, with which the gold may be alloyed. Basalt and some varieties of argillite answer the same purpose. The touchstones, employed by the jewellers of Paris, are composed chiefly of hornblende. Brongniart calls it Cornéenne Lydienne. The ancients obtained touchstones from Lydia in Asia.

(Geological situation.) Siliceous slate exists in large masses or in beds, both in primitive and transition mountains. Its beds often occur in argillite, with which it sometimes alternates. It is also found in graywacke slate, or in nodules in mountains of transition limestone. It is sometimes in veins, the strata being parallel to the sides of the veins, and alternating with aluminous slate.

This mineral is perhaps most frequently observed in large insulated rocks, which have probably been detached from mountains or beds of the same substance. It is traversed not only by numerous veins

* Lydischer stein. WERNER. Lydian stone. JAMESON. La Pierre de Lydie. BROCHANT.

31

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of quartz, but by seams or rifts, usually lined with the oxide of iron. Hence the fragments of this substance, which are observable out of place. Thus it occurs in rolled pieces, scattered on plains, or in the beds of rivers.—It sometimes embraces anthracite between its layers; indeed it is probable, that carbon usually enters into its composition.

(Localities.) In the United States. In Massachusetts, at Topsfield, Essex Co.—In New Hampshire, at Northampton, in scattered fragments.—The variety called Basanite occurs in Pennsylvania, near Reading and Bethlehem.—In Maine, at Topsham, in rolled pieces on the banks of the Androscoggin.

SPECIES 17. PETROSILEX.*

This mineral has in general a fine, close texture. When most translucent, it often resembles hornstone or flint. Other varieties, slightly translucent at the edges, more resemble jasper.

Its fracture is usually more or less splintery, sometimes like that of wax, and, at the same time, is often somewhat conchoidal; but in some varieties it is nearly or quite smooth and largely conchoidal, while in others the splinters are so fine, that it appears almost earthy. The surface of the fracture is usually dull, but has sometimes a feeble lustre.

It usually gives sparks with steel, though sometimes with great

* Fusible varieties of the Hornstein of Werner, the Hornstone of Jameson, and the Pierre de corne of Brochant. Pétrosilex agatoïde et jaspoïde. BRONGNIART. Feldspath compacte céroïde. HAUY
The term Petrosilex has been almost equally unfortunate with that of Hornstone. Kirwan mentions Petrosilex as a synonyme of hornstone. The Abbé Haüy in his Mineralogy appears to include under the name Petrosilex the fusible varieties of the hornstone of Werner, the pitchstone of Werner, and some varieties of the compact feldspar of Werner. But in his Tableau Comparatif, since published, he has united Petrosilex to the species feldspar, under the variety feldspath compacte; and this union is sanctioned by the opinions of Dolomieu, Saussure, Lelievre, &c. Brongniart, who has published the latest systematic work on mineralogy, among the French, has a species, bearing the name of Petrosilex; and, according to his own remarks, some of its varieties belong to the compact feldspar, others to the fusible hornstone, and others to the clinkstone of Werner.
It is indeed true, that these three last mentioned minerals do often closely resemble each other. But it is also true, that they differ in several of their characters, especially when extremes are compared, and that their analysis has hitherto received but little attention. We are therefore induced to adopt, for the present, the distinctions of Werner in regard to compact feldspar and clinkstone, and to appropriate the name Petrosilex to the fusible varieties of his hornstone. (See note on hornstone, the 13 subspecies of quartz.)

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difficulty. When in thin fragments, it is often strongly translucent, but varies from this to a very slight translucency at the edges. It exhibits several shades of white, gray, yellow, red, and green, variously intermixed, as reddish white, greenish gray, &c. and is sometimes reddish brown, brown, or nearly black. Its colors are occasionally arranged in spots, veins, &c. Its spec. gravity extends from 2.62 to 2.74.

(Chemical characters.) One essential character of Petrosilex is that of being fusible into an enamel, which is usually white, and, when viewed with a glass, often contains numerous bubbles. Some varieties can be melted only in very small fragments, while others fuse without difficulty. It does not effervesce with acids. A specimen of rose colored petrosilex yielded Godon de St. Memin silex 68.0, alumine 19.0, potash 5.5, lime 1.0, oxide of iron 4.0, water with a little loss 2.5.

The distinctive characters of Petrosilex are not always easily perceptible in small specimens, more especially, when it is passing into other minerals. Its fusibility sufficiently distinguishes it from that variety of quartz, called hornstone.—From compact feldspar it very often differs by its strong tendency to a conchoidal fracture.—Sometimes it approaches very near to some varieties of argillite or clinkstone.

(Geological situation.) This mineral appears to be confined to primitive or transition rocks, where it occurs in large masses, or veins, or in extensive beds, or even forms whole mountains. Hence it is found associated with argillite, syenite, greenstone, &c.

It often contains crystalline particles of feldspar, quartz, epidote, &c. and, when these crystals of feldspar become sufficiently abundant, it constitutes the base of the hornstein (hornstone) porphyry of Werner. Such porphyries are reddish, greenish, &c. but seldom black.

Petrosilex, whether simple or porphyritic, is liable to decomposition; and hence its surface is frequently invested with an earthy crust, which sometimes adheres to the tongue.

(Localities.) In the United States, this mineral is abundant in Massachusetts, near Boston, in the towns of Malden, Dorchester, Milton, &c. where it forms beds, or even hills. Sometimes its colors are red and white, arranged in parallel veins or stripes, either straight or curved. At Malden, a dark red variety is diversified by other shades of red in veins. At Milton, it occurs greenish white, and strongly translucent; and some varieties are there marked with fleshcolored spots. Petrosilex, in the vicinity of Boston, is sometimes contiguous to argillite and syenite, and also to another rock, which

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is composed of nodules of quartz, argillite, petrosilex, feldspar, &c. and which probably belongs to the grauwacke of Werner. Even when not porphyritic, it very often contains minute particles of quartz, epidote, feldspar, sulphuret of iron, &c. and sometimes, as on Brush hill turnpike, it exhibits dendritic figures of the oxide of manganese. (GODON.)

(Uses and Remarks.) Some varieties of Petrosilex are susceptible of a high polish. When homogeneous, the softer kinds may be employed as honestones; indeed, according to B. de Saussure, the Turkey stone often belongs to this species.

According to M. Godon, the vicinity of Boston furnishes Petrosilex perfectly analogous to the Turkey stone; and also a veined Petrosilex, which strongly resembles certain antique engraved stones, wrought by the Greeks and Romans in Basso relievo.

SPECIES 18. CLINKSTONE.* JAMESON.

This mineral has a structure more or less slaty, and is generally divisible into tabular masses, which are sometimes very thin, like those of argillite. The cross fracture is most commonly splintery, sometimes conchoidal or even. It has only a glimmering lustre.

This mineral is easily broken; and, when struck by a hammer, is sonorous, like a metal, especially if in thin tables. Hence its name. Its hardness, which is never less than that of basalt, and often greater, usually enables it to give sparks with steel.

Its color is usually gray, often shaded with dark green, or with yellow, or blue; and, according to Emmerling, it is sometimes green, or grayish black. It is frequently translucent at the edges, sometimes opaque. Its spec. grav. is about 2.57.

It occurs in extensive masses, which are often composed of columnar or tabular distinct concretions, more or less regular.

Before the blowpipe it easily melts into a glass nearly colorless. (JAMESON.) It contains silex 57.25, alumine 23.50, soda 8.10, lime 2.75, water 3.00, oxides of iron and manganese 3.50;=98.10. (KLAPROTH.) By exposure to the atmosphere its surface is a little decomposed.

Clinkstone sometimes approaches very near to petrosilex, or compact feldspar, and, according to Jameson, it sometimes passes into pitchstone, and basalt.—It is, in general, sensibly harder, than some varieties of argillite, which it may resemble.

(Geological situation.) This mineral is usually found among secondary rocks; sometimes in beds resting on basalt. It is some-

* Klingstein. WERNER. La Pierre sonnante. BROCHANT. Pétrosilex feuilleté. BRONGNIART.

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times vesicular, its cavities being lined by very minute crystals. It is frequently rendered porphyritic by crystals of feldspar, and then constitutes Clinkstone porphyry, or the porphir scheifer (porphyry slate) of Werner.

It is also found in transition, and perhaps even in primitive rocks.

Clinkstone is not uncommon in Bohemia and other parts of Germany;—and at Lamlash, in the island of Arran, it occurs in very beautiful, columnar concretions. (JAMESON.)

SPECIES 19. PUMICE.* KIRWAN. JAMESON.

Pumice is rough to the touch, and has a texture more or less spongy or porous; its pores or vesicles are sometimes roundish, and often elongated. It is very light, and often swims on water, having a specific gravity of only 914. In most cases it is too brittle to give sparks with steel, but its powder scratches both glass and steel.

It has usually a fibrous structure, the fibres being sometimes curved and parallel, and sometimes interlaced, or arranged in all directions. When the fibres are large, their lustre is glistening and vitreous, but, when very fine, it is somewhat silken. The cross fracture is uneven or imperfectly conchoidal, and vitreous.

But a fibrous structure is not essential to Pumice. Some varieties appear to be an accumulation of oblong, vitreous bubbles or vesicles; while others are composed of minute flakes or scales, but still sufficiently light to swim on water. Kirwan mentions a variety, in which no fibres are discernible, whose fracture is dull, uneven, and splintery, and whose specif. gravity is the same, as that of water. Indeed Spallanzani asserts, that visible pores are not essential to Pumice.

The colors of Pumice are grayish white, or gray, sometimes with a shade of yellow or blue, also brown, reddish brown, or red, greenish, and sometimes grayish black, or black. Spallanzani supposes Pumice to be always black, when ejected from a volcano. In the mass it is opaque, or translucent at the edges, but in minute fragments is often strongly translucent.

(Chemical characters.) Pumice is fusible by the blowpipe into a whitish enamel or glass. Its composition is probably a little variable. In a specimen from Lipari Klaproth found silex 77.5, alumine 17.5, potash and soda 3.0, iron 1.75;=99.75.

(Geological sit. and Localities.) On the origin of Pumice different and even opposite opinions exist. Some contend, that it is always a volcanic product; others assert, that it is frequently, if not

* Bimstein. WERNER. Ponce. BRONGNIART. La Pierre ponce. BROCHANT. Lave vitreuse pumicée. HAUY.

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always an aqueous deposite; while others, who admit, that it has been ejected from volcanoes, deny that it has undergone the action of volcanic fires.

That the origin of Pumice is, in many cases, volcanic appears to be supported by evidence perfectly satisfactory. It has a semi-vitrified aspect, approaching more or less to that of glass. It is most frequently found in countries at present volcanic, or which give indications of having formerly been so. It does not, however, occur in all volcanic countries. The fires of Etna and some other volcanoes seem to have seldom or never produced it.

In 1783, flames continued for several months to rise out of the sea about 30 miles from Cape Reikianes, a promontory at the southwest corner of Iceland; during which time vast quantities of Pumice washed on shore. (MACKENZIE.)—At Campo Bianco, in the island of Lipari, Pumice occurs in extensive, distinct beds, nearly horizontal. These beds are not continuous, but are composed of globular masses, feebly united, or entirely distinct, and varying in size from that of a hazel nut to a foot in diameter. If these masses of Pumice were ejected from a volcano, they would assume a globose form, while passing through the air. In some instances the vesicles are elongated, and the fibres extended in the direction of the strata, or supposed current. (SPALLANZANI.) In the same island, Pumice and obsidian are intimately united, or even pass into each other; and both exhibit very strong evidence of having flowed in a current from the crater of a volcano.—Pumice is abundant in the isles of Milo and Santorini, in the Archipelago.—In Teneriffe and Iceland it is found united to obsidian, between which a gradual transition may sometimes be observed. (CORDIER, and MACKENZIE.)

It sometimes contains crystals of feldspar, mica, ceylanite, &c.

In Hungary, however, Pumice accompanies pearly obsidian, which alternates with a porphyry, containing crystals of feldspar, quartz, and mica. (ESMARK.) Sometimes also Pumice alternates with basalt. (JAMESON.) In the Euganean mountains it is intimately united with pitchstone. (SPALLANZANI.)

But, if Pumice be, in many cases, an imperfect vitrification, it has undoubtedly originated from different substances, in different places. Among these are supposed to be granite, pitchstone, petrosilex, and obsidian; indeed the vitreous obsidian of Hungary, according to Brongniart, may be changed by heat into a substance resembling white Pumice.*

* The vitreous, capillary filaments, sometimes fine as those of wool, and moveable by the breath, which have been found in the isles of Bourbon and Lipari, appear to be a volcanic glass, rather than Pumice.

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(Uses.) It is employed in a state of powder for polishing glass, metals, stones, &c. and in the preparation of parchment. It is also employed, as a building stone, in constructing arches. The Pumice of commerce is obtained chiefly from Lipari.

SPECIES 20. OBSIDIAN.*

This mineral, in its general aspect, resembles certain kinds of glass, or of enamel. Its fracture is vitreous or pearly; thus constituting two varieties, under which it is more convenient to describe this species, than to collect its characters into one view.

Var. 1. VITREOUS OBSIDIAN.† This variety has a strong resemblance to glass. Its fracture is distinctly conchoidal, with large cavities, and strongly shining with a lustre more or less vitreous. The surface of the fracture often exhibits a waved or striated appearance, and its aspect is sometimes a little unctuous.—It strikes fire with steel, but is brittle, and falls into sharp edged fragments. Most commonly it is translucent at the edges, or opaque; but some varieties are translucent, and, in thin scales, transparent. Its color is black, either deep and pure, or tinged with green, brown, blue, or gray, and sometimes passes to green, brown, or gray, or is even yellow, or red. The darkest colors often discover a tinge of green by transmitted light.—A chatoyement with a silken lustre is sometimes perceived in certain greenish obsidians, when viewed perpendicularly to the direction of their beds, and is probably produced by a great number of little bubbles, very much elongated in the direction of the beds.—Its spec. grav. extends from 2.34 to 2.43, or even to 2.90. It occurs in amorphous masses, or in fragments or grains, often rounded.

(Chemical characters.) Before the blowpipe it intumesces more or less, and melts into an opaque, porous, or spongy enamel, sometimes much larger than the original fragment. This enamel is usually grayish or white; some varieties not only preserve their color during fusion, but even acquire some transparency. It contains silex 78.0, alumine 10.0, potash 6.0, lime 1.0, oxides of iron and manganese 3.6;=98.6. (KLAPROTH.)

It often much resembles pitchstone, but usually differs more or less in lustre and fracture.

2. PEARLSTONE.‡ JAMESON. This variety appears to have a structure more or less granular, and is traversed by fissures in va-

* Obsidienne. BRONGNIART. Lave vitreuse obsidienne. HAUY.

† Obsidienne vitreuse. BRONGNIART. Obsidian. WERNER. KIRWAN. JAMESON. L'Obsidienne. BROCHANT.

‡ Perlstein. WERNER. Le Perlstein. BROCHANT. Obsidienne perlée. BRONGNIART. Lave vitreuse perlée. HAUY.

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rious directions. It is hence very brittle, sometimes almost friable. Its fracture is uneven or granular, or sometimes imperfectly conchoidal, shining and pearly. It is opaque, or translucent at the edges. Its color is usually some shade of gray, sometimes tinged with blue, green, red, or yellow, or is red, reddish brown, &c.

It scratches glass, even when too brittle to give fire with steel. Its spec. grav. varies from 2.25 to 2.54. When moistened by the breath, it frequently exhales an argillaceous odor.—It is always amorphous, and usually vesicular.

(Chemical characters.) Before the blowpipe it intumesces very considerably, but does not melt into a globule. A specimen from Hungary yielded Klaproth silex 75.25, alumine 12.00, potash 4.50, lime 0.50, oxide of iron 1.60, water 4.50;=98.35.

(Geological sit. and Localities.) Obsidian is found in grains, or in scattered and insulated fragments, or in beds, or in large masses, which resemble a cooled current of lava.

Beds of Obsidian are variously inclined, and composed of layers, usually parallel, and often separated by a very thin, earthy stratum, whose nature is unknown. They are sometimes traversed by veins of other minerals. Such beds occur in Peru, Iceland, Lipari, &c.—In this last island, Monte Castagna is composed entirely of Obsidian, arranged in beds of variable thickness; this Obsidian often contains cavities, which are sometimes crossed by transparent, delicate threads, resembling glass; its colors are black, greenish, &c. (SPALLANZANI.)—Beds of Obsidian are sometimes nearly vertical.—Some Obsidians are rendered porphyritic by containing crystals of feldspar and quartz.

Obsidian is also found in large masses, which exhibit more or less distinctly the appearance of having once been so fluid, as to flow in currents. Such currents exist in Lipari, where they are intimately connected with pumice; (DOLOMIEU.)—also in Teneriffe, Peru, and Mexico.

Sometimes Obsidian occurs in insulated fragments, often globular, and scattered on the soil; sometimes also it is imbedded in pumice. (BRONGNIART.) In the isle of Ponce these globular masses sometimes embrace plates of yellow mica, and white, vitreous grains, which appear to be semi-vitrified feldspar. In Iceland, Obsidian occurs not only at the foot of Hecla, but in fragments, scattered over a great part of the island.—Near Okhotsk, on the gulph of Kamschatka, it occurs in little pearly white globules in sand, and is the Marekanite of Karsten.

In Peru, Obsidian is found on certain volcanic summits in the Andes, at an elevation of nearly 15,000 feet. In Mexico, it is some-

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times contiguous to porphyry; and in Teneriffe to basalt and clinkstone.

The preceding remarks refer chiefly to localities of vitreous Obsidian.

Near Tokay, in Hungary, the pearly Obsidian is mingled with fragments of granite, gneiss, &c. It also occurs in beds, which alternate with those of a porphyry, containing crystals of feldspar, quartz, and mica. In fact, the pearlstone or pearly Obsidian is itself porphyritic or amygdaloidal, and often contains nodules or grains of black, vitreous Obsidian. According to Gerhard, Obsidian is sometimes contained in granitic rocks.—Pearly Obsidian is found also in the island of Egg, one of the Hebrides, and near Sandy Brae in Ireland.

(Origin of Obsidian.) The origin of Obsidian, like that of pumice, is by some attributed to volcanic fire, by others to water. It must be obvious, however, that the vitreous Obsidian is most frequently found in volcanic countries. The apparently semi-vitrified feldspar, which it sometimes contains, its own vitreous texture, and its association with pumice, afford also plausible arguments in favor of an igneous origin. Indeed both varieties undoubtedly pass into pumice.

On the other hand, the association of Obsidian with granite and porphyry, and its arrangement in parallel beds, seem to support the hypothesis of an aqueous origin. It also passes into pitchstone. Its intumescence during fusion, in consequence of the liberation of a great quantity of gas, is also urged as an objection to a previous fusion. But it may be replied, that its first fusion was effected under a pressure, sufficient to prevent the escape of the gas.

Hence some mineralogists have suggested a compromise, by granting a volcanic origin to the Obsidian of Iceland, Italy, &c. and retaining the pearly Obsidian of Hungary, as an aqueous production. But the occurrence of vitreous Obsidian in that, which is pearly, and the extensive masses of pearly Obsidian in Mexico, apparently in currents, suggest new difficulties.

(Uses.) In Mexico and Peru the black, vitreous Obsidian is employed for constructing mirrors, and for various ornamental purposes. It is there manufactured even into knives and razors. It is sometimes called the gallinaceous stone of Peru, and the black agate of Iceland.

SPECIES 21. PITCHSTONE.* KIRWAN. JAMESON.

This mineral, especially when recently broken, has often a strong

* Pechstein. WERNER. La Pierre de poix. BROCHANT. Rétinite. BRONGNIART.

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resemblance to pitch or resin in its lustre and texture; and hence its name. Most commonly its fracture is imperfectly conchoidal with cavities either large or small, but sometimes it passes to splintery or uneven. Its lustre, though usually more or less shining and resinous or greasy, sometimes inclines to vitreous.

It is very brittle, and does not readily give fire with steel, though it is not easily scraped by a knife. It is more or less translucid, frequently at the edges only, and is sometimes opaque. Its colors are very numerous, but generally dull and uniform. They are several shades of green; black, mingled with green, brown, or gray; brown, tinged with red, green, or yellow; a few shades of gray and red, and sometimes it is yellowish or bluish. Its spec. grav. varies from 2.29 to 2.64.

It occurs in amorphous masses, which sometimes exhibit granular, prismatic, or lamellar distinct concretions. Hence its structure is sometimes fissile or slaty.

(Chemical characters.) Before the blowpipe it whitens, swells, and melts into a porous, whitish enamel. A specimen from Meissen in Saxony yielded Klaproth silex 73.0, alumine 14.5, soda 1.75, lime 1.0, oxides of iron and manganese 1.1, water 8.50;=99.85. A greater proportion of soda has been found by Klaproth and Bergman in other specimens. Pitchstone is liable to decomposition, by which it is sometimes converted into an argillaceous mass.

(Distinctive characters.) This mineral often much resembles obsidian; but its fracture is less perfectly conchoidal, and it seldom, if ever, possesses that vitreous or pearly lustre, which characterizes obsidian.—From jasper or semi-opal its fusibility easily distinguishes it.

(Geological sit. and Localities.) Pitchstone occurs in very large beds, sometimes forming whole mountains; also in veins, and insulated masses of various sizes. Sometimes it contains crystals of feldspar and quartz, and thus becomes the base of a porphyry.

Near Meissen, in Saxony, Pitchstone alternates with a porphyry, whose base is petrosilex; and this porphyry alternates with gneiss, is connected with syenite, and traversed by metallic veins.—Near Planitz, in Saxony, it forms the mass of the mountain, and embraces a black substance with a feeble silken lustre, which melts into a black glass, and contains 33 per cent. of carbon. (BRONGNIART.) It is found abundantly in Arran and other Scottish isles connected with secondary rocks. (JAMESON.)—In Teneriffe it is associated with basalt and clinkstone.

Near Dublin, in Ireland, it is in veins, which traverse granite It has a slaty structure, and exhibits lamellar concretions. In the vein, the layers, sometimes 1/4 of an inch thick, are perpendicular to

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the horizon; they divide into rhomboidal fragments. Its spec. grav. is 2.29. (Fitton in Geolog. Trans. v. i.)

In the United States. In Maryland, it is found at the Bare Hills, 7 miles from Baltimore, in serpentine. (HAYDEN.)—In Connecticut, near Newhaven.

(Remarks.) The resemblance of Pitchstone to obsidian, into which it sometimes passes, and certain geological circumstances have induced some to suppose its origin volcanic. But, in many cases, its natural associations render its aqueous origin unquestionable. Spallanzani is inclined to suppose it sometimes volcanic, and sometimes aqueous. At Monte Sieva, in the Euganean mountains, he observed Pitchstone, containing a light, fibrous, cellular pumice intimately united with it.

SPECIES 22. SPODUMEN.* WERNER.

This mineral has hitherto been observed only in laminated masses, easily divisible into prisms with rhomboidal bases, of about 100° and 80°. These prisms are further divisible in the direction of the shorter diagonals of their bases, and are thus resolved into triangular prisms. All the lateral faces both of the quadrangular and triangular prisms are smooth, shining, and pearly; but the cross fracture is uneven or splintery with very little lustre.

The Spodumen strikes fire with steel, and its spec. grav. is about 3.20. It is very brittle; more or less translucent; and usually greenish white, sometimes apple green.

(Chemical characters.) Before the blowpipe it exfoliates into little yellowish or grayish scales, which however are not always equally distinct. These scales then unite and melt into a grayish, transparent globule of glass. When heated in a crucible it also splits into scales, having the two colors already mentioned, but in a few days they all become dark gray. It contains silex 64.4, alumine 24.4, potash 5.0, lime 3.0, oxide of iron 2.2;=99. (VAUQUELIN.)

From adularia, which it somewhat resembles, it differs by its greater spec. gravity, and the results of mechanical division.—It differs from the ichthyophthalmite also in its primitive form, chemical characters, &c.

(Localities.) This rare mineral has been found in the iron mine of Uton, in Sweden, associated with reddish feldspar, greasy quartz, and black mica;—also in Norway.

* Spodumenc. JAMESON. Triphane. HAUY. BROCHANT. BRONGNIART.

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SPECIES 23. LEPIDOLITE.* KIRWAN. JAMESON.

This mineral, at first view, appears to be composed of small grains, sometimes extremely minute, and has an uneven or splintery fracture, with a moderate lustre. But these grains, among which little pearly scales are often interspersed, are themselves composed of a great number of minute foliæ or spangles, like those of mica. These foliæ also, when separated from the mass, have a glistening, pearly lustre, and are variable in size.

It is moderately hard, and may easily be cut by a knife. It is pulverized with difficulty, and its powder is soft to the touch. The color of the mass often resembles that of the lilac, the violet or purple being sometimes strongly tinged with red; it is also rose red, sometimes nearly white. The single laminæ are usually pearly or silver white. The edges of the mass are translucent. Its spec. grav. varies from 2.81 to 2.85.

(Chemical characters.) Before the blowpipe it intumesces a little, and easily melts into a colorless, translucent globule. With the addition of nitre the globule becomes violet. (HAUY.) According to Klaproth, it contains silex 54.5, alumine 38.25, potash 4.0, oxides of iron and manganese 0.75, water with a little loss 2.5. In another specimen Vauquelin found silex 64, alumine 20, potash 14, lime 2.

(Geological sit. and Localities.) Near Rosena, in Moravia, where it was first found, it occurs in large, rose colored foliæ, and in masses of considerable size, disseminated in gneiss, and accompanied by feldspar, quartz, mica, schorl, &c.—In Sweden in a quartzy rock.—In France, near Limoge, in a vein of quartz, traversing a granite, which contains large beryls.—In the isle of Elba, in an aggregate of quartz and feldspar.

SPECIES 24. MICA.† HAUY. KIRWAN.

Mica appears to be always the result of crystallization, but is rarely found in regular, well defined crystals. Most commonly it appears in thin, flexible, elastic laminæ, which exhibit a high polish and strong lustre. These laminæ have sometimes an extent of many square inches, and, from this, gradually diminish, till they become mere spangles, discoverable indeed by their lustre, but whose area is scarcely perceptible by the naked eye. They are usually found united into small masses, extremely variable in thickness, or into crystals more or less regular; their union, however, is so very feeble,

* Lepidolith. WERNER. Lepidolithe. HAUY. BRONGNIART. BROCHANT. its name is from the Greek Λιπις, a scale, and Λιθος, a stone.

† Mica. BRONGNIART. JAMESON. BROCHANT. Glimmer. WERNER. It is often improperly called isinglass.

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that they are easily separable, and may be reduced to a surprising degree of tenuity. In this state their surface becomes irised, and their thickness does not much exceed a millionth part of an inch.

The crystals of Mica are sometimes right prisms with rhombic bases, whose angles are 120° and 60°. This is also the primitive form, in which one side of the base is to the height of the prism nearly as 3 to 8. Its integrant particles have probably the same form.— It also occurs in six-sided tables, or six-sided prisms, usually short, and sometimes truncated on their terminal edges.—Also in rectangular laminæ.

The structure of mica is always foliated, but the foliæ may be straight, curved, or undulated; sometimes they appear like broad fibres, parallel or diverging, or are marked with plumous striæ. The surface, whether of the crystals, masses, or separate laminæ, has a shining or splendent lustre, which is usually metallic, sometimes like that of silver or gold; and sometimes like that of polished glass, or a little pearly. The lateral divisions of the laminæ are almost always dull.

It is easily scratched by a knife, and in most cases even by the finger nail. Its surface is smooth to the touch, and very seldom slightly unctuous; its powder is dull, usually grayish, and feels soft. In thin laminæ, it is very often more or less transparent; but in other cases it is translucent, sometimes at the edges only. When black and opaque in the mass, the separate laminæ are often semitransparent.—Its colors are silver white, gray, often tinged with yellow, green, or black, or nearly black; also brown, yellow, reddish, green, &c.

Its spec. grav. extends from 2.53 to 2.93; and, when rubbed on sealing wax, it communicates to the wax negative electricity.

(Chemical characters.) It is fusible by the blowpipe, though sometimes with difficulty, into an enamel, which is usually gray or black. The colored varieties are most easily fusible; and black mica gives a black enamel, which often moves the needle. It contains, according to Klaproth, silex 48.0, alumine 34.25, potash 8.75, oxide of iron 4.5, oxide of manganese 0.5;=96. Sometimes the potash is in greater proportion, and in black mica the oxide of iron is sometimes as high as 22 per cent.—Mica is subject to decomposition by exposure to the atmosphere, and is sometimes converted into a kind of steatitic matter.

(Distinctive characters.) Mica differs from talc by its elasticity, its want of unctuosity, and by communicating negative electricity to sealing wax.—It is less hard than diallage, which is not elastic.— It sometimes resembles cyanite, but the latter is harder, not elastic,

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and infusible.—It may also resemble the greet oxide of uranium, but the latter is brittle, and melts into a black scoria.—It is easily distinguished from micaceous oxide of iron.

The following are its most important varieties.

Var. 1. LAMINATED MICA.* It occurs in large plates, which often contain many square inches. It has been called Muscovy glass or talc, being found abundantly in that country.

2. LAMELLAR MICA.† This is the more common variety. It exists in small foliæ, either collected into masses, or disseminated in other minerals. It is sometimes in extremely minute scales, which, when detached from the mass, appear like sand.

Sometimes the lamellæ are convex, and placed one upon another with an increasing extent, so that they form an inverted pyramid.

3. PRISMATIC MICA.‡ This variety is not common. The laminæ are easily divisible, parallel to their edges, into minute prisms, or even into delicate filaments. The edges of the laminæ have usually more lustre, than those of the other varieties.

It occurs in Connecticut, at Litchfield;—and in Maine, at Topsham.

(Geological situation.) Although mica never occurs in beds, or large insulated masses, there is no substance more universally diffused through the mineral kingdom. It is an essential ingredient in granite, gneiss, and mica slate; and occurs also in syenite, porphyry, and other primitive rocks. Its crystals sometimes appear in the fissures of these rocks, or in the cavities of veins, which traverse them; in these veins also often occur the large plates of laminated mica. Even when disseminated in granite, &c. it is sometimes in perfectly regular crystals. In some cases it constitutes small veins. To limestone, quartz, &c. it often communicates a slaty texture.

Mica occurs also in greenstone, basalt, sandstone, and other secondary rocks; especially in the sandstone and shale, which accompany coal.—It is abundant in the sand of primitive countries, and exists even in that, which is far distant from primitive rocks.—It is often connected with volcanic rocks.

But, notwithstanding this universal diffusion of Mica, it has most probably, in all cases, been formed among primitive rocks. Hence, when found in secondary rocks or alluvial earths, it has undoubtedly arisen from the disintegration of primitive rocks, and been subsequently transported by water.

* Mica foliacé. HAUY. BRONGNIART.

† Mica lamelliforme—ecailleux—hémisphérique. HAUY.

‡ Mica filamenteux. HAUY. BRONGNIART.

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(Localities.) Very fine specimens have been found in Russia, Siberia, &c.

In the United States, Mica is very abundant. In Pennsylvania, at Germantown, it is crystallized in six-sided tables and prisms. (WISTER.)—In Connecticut, at Woodbury, it is violet.—In Massachusetts, at Chesterfield and Goshen, in the granite, which contains the indicolite and green tourmaline; its colors, which are very delicate, are violet, reddish, and yellow.—In New Hampshire, in Grafton, 20 m. E. from Dartmouth College, in large laminæ, adhering to quartz;—also near Bellows Falls, in Walpole.—In Maine, almost every variety of Mica is found at Topsham, near Bowd. College; it is often in six-sided tables, sometimes equilateral, and sometimes elongated; also in rhomboidal prisms.—In Brunswick, its color is sometimes a very beautiful green.

(Uses.) It has been employed, instead of glass, in the windows of dwelling houses; also in ships of war, because it is not liable to be broken by the concussion, produced by the discharge of cannon. In lanterns it is superior to horn, being more transparent, and not so easily injured by heat.—When in thin, transparent laminæ, sufficiently large, it is useful to defend the eyes of those, who travel, against high winds, and severe storms of snow.—When of suitable color and in minute scales, it is employed to ornament paper, which is then said to be frosted; the scales of Mica are made to adhere by a solution of gum or glue.

SPECIES 25. LEUCITE.* JAMESON.

The Leucite usually appears in regular, well defined crystals, contained under twenty four faces, which are equal and similar trapeziums; or it may be viewed as a double eight-sided pyramid, each of whose vertices is formed by four planes, standing on the alternate edges of the pyramids. They are sometimes elongated. Their primitive form is probably a cube, and their integrant particles irregular tetraedrons.

The surface of perfect and unaltered crystals is smooth, and not striated like that of garnets of a similar form, although they sometimes exhibit seams parallel to the shorter diagonals of the faces. The size may vary from that of a pin's head to an inch in diameter; and the angles and edges are sometimes rounded.—The Leucite occurs also in grains, or fragments of crystals.

Its colors are usually gray, or white, often impure, and sometimes

* Leuzit. WERNER. La Leucite. BROCHANT. Amphigene. HAUY. BRONGNIART. Vesuvian. KIRWAN. The term Leucite is derived from the Greek Λινхος, white.

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shaded with yellow, or even with red. Some crystals are nearly or quite transparent, others only translucent, and some are opaque.

Its fracture, in certain directions foliated, is in others imperfectly conchoidal or uneven, somewhat shining and vitreous, when the crystal is unaltered.—The Leucite scratches glass with difficulty, and is sometimes almost friable. Its spec. grav. is about 2.47.

(Chemical characters.) Before the blowpipe it is infusible. Its powder converts the vegetable blue to green. It contains silex 53.75, alumine 24.62, potash 21.35;=99.72. (KLAPROTH.)

Its infusibility alone is sufficient to distinguish it from the garnet and analcime, which have similar forms; it also differs from them in other characters.

(Geological sit. and Localities.) It is often imbedded in lava and in basalt. In porous or scorious lavas, the crystals are more friable and opaque, than those in more compact lavas, or in basalt. Sometimes, however, it is opaque and earthy, even when perfectly enveloped in lava. Its altered state must, in this case, be attributed to the action of volcanic fire, rather than to that of moisture or sulphurous acid. Its crystals are sometimes united into very considerable masses.

All lavas do not contain crystals of Leucite. They are abundant in the lava of Vesuvius, but seldom or never in that of Etna. They occur in large quantities near Naples and Rome. Leucite is sometimes associated with masses, composed of mica, hornblende, feldspar, &c. which appear to have been ejected from volcanoes, without having undergone the action of fire.

In Bohemia the Leucite is found in basalt.—In the Pyrennees in granite (LELIEVRE);—and in Mexico in a gangue, which contains gold. (DOLOMIEU.)

In regard to those Leucites, found in lava, Werner, Dolomieu and others suppose these crystals to have pre-existed in the mineral, which, by its fusion, has produced the lava; and in consequence of their infusibility to have remained more or less unaltered by volcanic fire.

De Buch and others think, that the Leucite has crystallized within the fluid lava. This idea is in part suggested by the fragments of lava, and even of augite, which are often found enveloped in crystals of Leucite. But to this it may be replied, that fragments of basalt, or of whatever produced the lava, might have been originally inclosed in the crystal, and afterwards converted into the state of lava by a degree of heat, insufficient to fuse the surrounding Leucite.

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SPECIES 26. FETTSTEIN.* WERNER.

This mineral has a crystalline structure and foliated fracture in certain directions. It is divisible parallel to all the sides of a rhomboidal prism, and also in the direction of the shorter diagonals of the bases; in other directions its fracture is uneven. Its lustre is shining and greasy; and hence probably its name. It is slightly chatoyant.

It scratches glass, and gives fire with steel. It is brittle; and its specific grav. is from 2.56 to 2.61. It is translucid at the edges; and its colors are greenish gray, or sea green, or bluish.

It is fusible by the blowpipe into a white enamel. It contains silex 46.5, alumine 30.25, potash 18.0, lime 0.75, oxide of iron 1.0, water 2.0;=98.50. (KLAPROTH.) The analysis of Vauquelin is nearly the same.

It has been found near Arendal, in Norway, with feldspar and hornblende.

When cut, it sometimes exhibits a play of colors, like the cat's eye.

SPECIES 27. LAPIS LAZULI.† KIRWAN.

This interesting and indeed valuable mineral may generally be recognised by its color, especially with the assistance of a few chemical experiments. When pure, its color is a fine azure blue, a little darker or lighter; sometimes also it approaches sky or smalt blue. It is usually in amorphous or rounded masses of a moderate size, but has recently been observed in dodecaedrons with rhombic faces. Its structure is finely granular, almost compact; and its fracture uneven, sometimes a little foliated; it is dull, or has only a feeble lustre. It is opaque, or a little translucent at the edges.

It scratches glass, but does not easily give sparks with steel, and that only in certain parts. Its spec. grav. in pure specimens is about 2.36, but it is sometimes 2.94.

(Chemical characters.) If previously calcined, it loses its color in the mineral acids, and forms with them, when concentrated, a thick jelly. It retains its color at a temperature of 100° W. but may be melted by the blowpipe into a white or gray enamel. In the analysis of this mineral, chemists have obtained very different results; and it is impossible, at present, to say what is its true composition. A part of the difficulty undoubtedly arises from foreign ingredients,

* Pierre grasse. HAUY. The writer has never seen this mineral; but the above description rests on the authority of Haüy and Count D. Borkowski.

† Lazurstein. WERNER. Azure Stone. JAMESON. Lazulite. HAUY. BRONGNIART. La Pierre d'Azur. BROCHANT. The Arabians call it Axul.

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which are visibly mingled with it. Clement and Desormes, from Lapis Lazuli of the greatest beauty and much purer than usual, obtained silex 35.8, alumine 34.8, soda 23.2, sulphur 3.1, carbonate of lime 3.1, and in some experiments a little iron; but the two last they do not consider essential. If this analysis be correct, this mineral cannot receive its color from a blue sulphuret, or blue oxide of iron.

(Distinctive characters.) The intensity of its blue, and some other characters will generally distinguish it from the Lazulith of Werner, which we annex as a subspecies.—It also resembles the azure colored ores of copper; but the latter become black in a moderate heat, and communicate to ammonia a blue color.

(Geological sit. and Localities.) When found in place, it appears to have occurred in primitive rocks, especially in granite. It is accompanied with garnets, carbonate of lime, quartz, feldspar, and sulphuret of iron, with some of which it is often intermixed. But it more frequently occurs in scattered, rolled fragments.

It has been found chiefly in China, Persia, and Bucharia. It also exists in Russia, and in Siberia near lake Baikal.

(Uses.) It receives a high polish; and its fine color, often marked by yellow spots or veins of sulphuret of iron, renders it extremely beautiful, and much esteemed for many ornamental works. But its chief use is to furnish the ultramarine blue, a pigment remarkable for the durability of its color.—To extract the coloring matter, the mineral, having been repeatedly heated and immersed in vinegar, is reduced to a very fine powder. This powder is formed into a paste with melted resin, wax, and linseed oil; and this paste is ground with warm water, which extracts the coloring matter, and deposites it as a sediment. In this process, the oil is supposed to form a kind of soap with the soda; and the particles of the ultramarine, being thus rendered smooth and slippery, escape, by the assistance of the hot water, from the particles of the gangue, which are retained by the wax.—This pigment is employed with oil.

SUBSPECIES 1. LAZULITE.*

We subjoin this mineral not without a strong suspicion, that it belongs to another species. Its color is a light indigo blue, but darker than smalt blue. It is opaque, or translucent at the edges. It is sometimes massive, and sometimes in prisms, either hexaedral or tetraedral. Bernhardi says it is often in regular octaedrons with truncated edges, passing to a dodecaedron with rhombic faces. Its fracture is uneven, but in one direction imperfectly foliated, and its lus-

* Lazulith. WERNER. Azurite. JAMESON. Le Lazulithe. BROCHANT. Lazulite de Klaproth. BRONGNIART. Lasulit de Verner. HAUY.

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tre is moderate. It scratches glass. Its streak is nearly bluish white. (BROCHANT.)

Before the blowpipe it is infusible, but becomes light gray and earthy. With borax it forms a yellowish glass. Its color is not attacked by pure alkalis; and acids have but a feeble action on this mineral. It contains alumine 71.0, silex 14.0, magnesia 5,0, carbonate of lime 3.0, potash 0.25, iron 0.75, water 5.0;=99. (KLAPROTH.) Its composition differs much from that of the common Lapis Lazuli.

This mineral occurs massive at Vorau in Stiria with quartz and mica, in a thin vein, traversing mica slate.—In Salzburg it is found crystallized.

SPECIES 28. SCHORL. WERNER. JAMESON.

This mineral is, in general, easily recognised. It most frequently occurs in long, prismatic crystals, more or less regular, whose lateral faces are almost always longitudinally striated. These prisms usually present six, nine, or twelve sides, and are terminated at both extremities by three principal faces. But the edges and solid angles on and around one, and sometimes both, of these triedral summits are variously truncated. Hence, in most cases, the two summits differ from each other in the number of their faces, although, in consequence of the smallness of some of these faces, this difference would often escape the eye, without careful observation. Thus the prism has often nine sides with one triedral summit, while the other summit may have five, six, seven, or nine faces. Sometimes the prism has twelve sides with one triedral summit, while the other summit presents five or even nineteen faces.—The prism may have twenty four sides.

Their primitive form, not easily obtained by mechanical division, is an obtuse rhomb (Pl. IV, fig. 1.), of which the plane angle at the summit is 113° 34′. The integrant particles are tetraedrons. Haüy has described seventeen secondary forms, of which we select a few.

A nine-sided prism (Pl. IV, fig. 2.), terminated at one extremity by three faces, and at the other by six, of which three are larger than the others, and stand on those three lateral edges of the prism, each of which contains an angle of 120°. It is sometimes described as a three-sided prism, bevelled on its lateral edges. Indeed this prism frequently appears to have only three sides, which however are more or less sensibly convex. Sometimes the edges of the triedral summit are truncated.†

* Tourmaline. HAUY. BRONGNIART. Le Schorl. BROCHANT.

† The Aphrizite, a variety of Schorl, is sometimes in nine-sided prisms, which exhibit the last mentioned modification of the triedral summit; and sometimes in six-sided prisms.

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A nine-sided prism (Pl. IV, fig. 3.), of which one summit has three and the other seven faces.

The prism is sometimes so short, that the two summits almost meet, and the crystal then resembles an obtuse rhomb, truncated on some of its edges.

A six-sided prism, terminated by three faces, which stand on the lateral edges, and are often modified by truncation, on one summit at least.

Sometimes the crystals are cylindrical, and marked with projecting edges or channels; sometimes they are acicular, or even capillary; and sometimes short and very thick.—Schorl also occurs in amorphous masses or fragments.

The electric powers of Schorl constitute one of its most striking characters. By friction it becomes positively electric; but, by exposure to a certain degree of heat, it acquires positive electricity at one extremity, and negative at the other. But in all cases, where the two summits have a different configuration, that summit, which has the greater number of faces, becomes positive. According to Bournon, however, some crystals from Ceylon, perfectly similar at both summits, acquire opposite electricities.

Schorl is very brittle; it scratches glass, and is harder than hornblende, but seldom so hard as quartz. Its fracture is more or less conchoidal, or uneven, and sometimes the cross fracture is slightly foliated. Its lustre is vitreous, and varies from glistening to splendent. Some prisms are articulated. Its spec. grav. extends from 3.05 to 3.36.

It is sometimes opaque, and often translucent, or even transparent. Its most common color is black, but it also occurs green, brown, blue, yellowish, and red of different shades, and sometimes white.

(Chemical characters.) Before the blowpipe it easily melts, and is converted, with ebullition, into a grayish white or brownish enamel, sometimes nearly compact and sometimes vesicular. The red Schorl or rubellite is infusible. A specimen from Eibenstock yielded Klaproth silex 36.75, alumine 34.50, potash 6.0, magnesia 0.25, oxide of iron 21.0;=98.50. Another specimen from Spessart yielded him almost precisely the same results. Sometimes a little lime appears to be accidentally present.

(Distinctive characters.) An attention to the electric powers of Schorl, its vitreous, conchoidal fracture, and fusibility into an enamel, will generally prevent it from being confounded with actynolite, augite, tremolite, chrysolite, emerald, epidote, melanite, and hornblende, the last of which it most resembles. (See hornblende.)

Several varieties deserve further notice.

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Var. 1. COMMON SCHORL.* JAMESON. This variety is very common and abundant. It is opaque, or slightly translucent at the edges of thin fragments. Its color is usually a shining, velvet black, but sometimes a little brownish or smoky. Its crystals are often cylindrical or acicular, and very frequently aggregated. Hence this variety often appears in irregular masses, composed of imperfect, prismatic crystals, sometimes parallel and sometimes diverging. When the prisms are very minute, the broken mass exhibits a fibrous or radiated fracture. These aggregated prisms are in general easily separable.—Sometimes masses of Schorl are composed of granular concretions, or of fragments, forming a kind of breccia.

This variety in some cases so abounds with particles of iron, which serve as conductors, that its electric powers are very weak, or even imperceptible.

2. TOURMALINE.† KIRWAN. JAMESON. This variety includes those Schorls, whose colors are green, brown, yellow, greenish blue, and those, which are white or limpid. The preceding colors present various shades, some of which are so deep, that the crystal, when nearly opaque, appears to be black. It is more or less translucent, and sometimes transparent. It is, however, often the case, that, when a Tourmaline is viewed perpendicularly to the sides of the prism, it is more or less transparent, but, if observed in the direction of the axis, it is opaque, even when the length of the prism is less, than its thickness.—The transparent Schorls generally, but not always, exhibit stronger electrical powers, than those, which are opaque.—The Tourmaline is usually in distinct crystals.

GREEN TOURMALINE.‡ It presents several shades, varying from leek green to olive green. Some from Brazil are emerald green, and have been called Brazilian emeralds.

In the United States. In Massachusetts, at Chesterfield, in Hampshire Co. it occurs in granite, associated with the indicolite and rubellite; indeed prisms of rubellite are sometimes perfectly inclosed within those of the green Tourmaline. Its color varies from a deep to a pale green. The crystals are of various sizes, sometimes four or five inches in length. They are sometimes imbedded in a very beautiful laminated feldspar. (WATERHOUSE.)

YELLOW TOURMALINE. It is sometimes honey yellow, or nearly orange.—In the U. States. In Pennsylvania, at London Grove,

* Gemeiner Schö;rl. WERNER. Le Schorl noir. BROCHANT. Tourmaline noir. HAUY. Tourmaline Schorl. BRONGNIART. Schorl. KIRWAN.

† Tourmalin. WERNER. Tourmaline verte, &c. HAUY. Le Schorl électrique. BROCHANT.

‡ Tourmaline emeraudine. BRONGNIART.

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Chester Co. it exists in transparent crystals with the silico-calcareous oxide of titanium. (CONRAD.)

WHITE TOURMALINE. According to Dolomieu, this rare variety, which is found at St. Gothard, &c. exists in granite in the isle of Elba, and is there partly white and partly black.

3. INDICOLITE.* This variety, as its name indicates, has an indigo blue color, sometimes so dark, that it appears almost black, like common Schorl, unless viewed at the edges, and sometimes a light azure or nearly sky blue, or even with a tinge of green. Its crystals have the forms of the species, and are sometimes acicular. It is less easily fusible, than common Schorl; and some specimens scratch quartz.

(Localities.) This variety is rare in Europe, but has been found in Sweden.

In the United States. It has been found in New York, at Haarlem Heights.—In Massachusetts, it occurs abundantly at Goshen, in Hampshire Co. in a coarse grained granite, of which the feldspar is white and laminated, or sometimes granular, and the mica yellowish, violet, or rose colored. The crystals are sometimes light azure blue and small, particularly in the granular feldspar; but the blue of the larger crystals is so very deep, that it appears black, except at the edges, which are translucent, and transmit a fine deep blue and sometimes sea green light. Its more common form may be referred to Pl. IV, fig. 2. It is generally opaque, but sometimes translucent, or even transparent. (Bruce's Min. Jour. v. i.)—It occurs also in Chesterfield, an adjoining town, in the same granite, which contains green tourmaline and rubellite.

SUBSPECIES 1. RUBELLITE.† KIRWAN.

This mineral resembles Schorl in the form of its crystals, and its power of acquiring opposite electricities by heat; but it sensibly differs in its chemical characters.

Its color is red of various shades, as crimson, pink, or peach blossom red, or violet red, like the lilac, or even darker, and sometimes with a tinge of green. It is transparent, or only translucent. It sometimes slightly scratches quartz; and its spec. gravity is about 3.07.—Its crystals are sometimes cylindrical or acicular, and aggregated in groups.

The Rubellite loses its color and transparency before the blowpipe, but remains infusible. A violet red specimen from Siberia yielded Vauquelin silex 42, alumine 40, soda 10, oxide of manganese and

* Tourmaline indicolite. BRONGNIART. Tourmaline indigo. HAUY.

† Tourmaline Rubellite. BRONGNIART. Tourmaline apyre. HAUY. Daourite—Siberite—red schorl of others.

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iron 7;=99. It is very remarkable, that a mineral of this composition should be infusible.

(Localities.) In the Uralian mountains the Rubellite is found in granite, accompanied with common Schorl.

In the U. States. In Massachusetts, at Chesterfield, Hampshire Co. it exists in granite, which also contains green Tourmaline, indicolite, and emerald. The crystals are usually translucent, and pink red, often long and slender; and are sometimes embraced in those of the green Tourmaline.

In the cabinet of the late Mr. Greville, which has been purchased by the British Government at 13,727 pounds sterling, and deposited in the National Museum, there is a specimen of Rubellite from the kingdom of Ava, valued at 10001. (JAMESON.)

(Geolog. sit. of the species.) Schorl has hitherto been found only in primitive rocks, particularly in granite and gneiss, or in veins, which traverse these rocks. It also occurs in mica slate and argillite. Sometimes it even enters into the composition of rocks. At St. Gothard it occurs in a micaceous Dolomite. It is sometimes found in metallic veins.

(Localities.) Schorl exists in almost every primitive mountain. Madagascar, Spain, and the Tyrol furnish fine specimens. In the United States, the localities of several rare varieties have already been noticed. In Maryland, at Jones' Falls, near Baltimore, in a vein of granite, the crystals of black Schorl are sometimes more than three inches in circumference. (GILMOR.)—In Maine, common Schorl is very abundant, particularly in the towns of Hallowell, Gardiner, Litchfield, Bowdoin, and Bowdoinham. At the last mentioned place, the crystals are sometimes uncommonly large, being from one and a half inch even to three inches in their mean diameter, and in some instances nearly one foot in length. The edges, angles, and one termination even of these large crystals are often extremely perfect. They are sometimes imbedded in a very white quartz.—At Brunswick, masses of black Schorl, composed of imperfect, aggregated prisms, sometimes contain fragments of quartz, and also numerous smooth, dull, roundish fragments of feldspar, about the size of shot, or a pea.— At Parker's island in the Kennebec, it is sometimes translucent at the edges, and transmits a brownish light.

(Remarks.) The electrical powers of Schorl are rendered sensible by exposing it to any degree of heat between 100° and 212° Fahr. The crystal may conveniently be held, near the centre of the prism, by a pair of forceps with a wooden or glass handle, and in this state uniformly exposed to hot coals, or the flame of a candle, or plunged in hot water. For the mode of using the electrometer, see Introd. art. 140. Or the crystal, when excited, may be suspended

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by a thread of silk; and, on presenting another excited crystal or a stick of excited sealing wax, attraction or repulsion will be observed. Ashes and similar light bodies will be attracted by both poles.

If a crystal of Schorl be heated somewhat above the limit just mentioned, it loses its electricity. By increasing the heat, however, to a certain degree, it again becomes excited, but its electric poles are inverted.

The word Schorl is by some derived from Schorlaw, a village in Saxony, and by others from the Swedish word skorl, brittle. But, whatever may be its origin, it has, till recently, been employed in a very loose manner, and applied to a great number of minerals, totally different from each other, and from the mineral, to which it is now limited. Thus the term Schorl, with some modifying epithet, has been applied to epidote, augite, axinite, staurotide, cyanite, actynolite, pycnite, tremolite, and several of the oxides of titanium, &c. &c. &c.

SPECIES 29. ANDALUSITE.* JAMESON.

The hardness of this mineral is nearly equal to that of corundum; for it scratches quartz, and sometimes spinelle. Its spec. gravity is 3.16. Its structure is more or less distinctly crystalline. Indeed it sometimes appears in imperfect four-sided prisms, nearly or quite rectangular, and divisible in the direction of one of the diagonals of the bases. Its longitudinal fracture is foliated, and its cross fracture a little splintery. It has usually very little lustre. Its colors are flesh red, reddish white, reddish brown, violet, or grayish black. It is a little translucent, but chiefly at the edges. It sometimes occurs in masses about the size of an egg.

It is perfectly infusible by the blowpipe. It contains alumine 52, silex 88, potash 8, iron 2. (VAUQUELIN.)

It differs from feldspar by its greater hardness and its infusibility; and from corundum by its structure and less spec. gravity. Some mineralogists, however, are inclined to believe this mineral to be feldspar, intimately mixed with corundum—and hence its hardness.

(Geological sit. and Localities.) The Andalusite has been found only in primitive rocks. In Forez in France, it occurs in a vein of feldspar, traversing granite.—In Spain, in granite and often embraces plates of mica.—In Ireland, in the County of Wicklow, in mica slate. It is usually in grayish black, slender, imperfect prisms, variously aggregated. It is accompanied by an uncommon mineral, resembling indurated talc, in rhomboidal prisms, yellowish gray, faintly translucent, easily cut by a knife, and fusible into a white

* Andalusit. WERNER. Andalousite. BRONGNIART. Feldspath apyre. HAUY. BROCHANT.

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enamel. Of these prisms the Andalusite often forms the axis, from which the talky substance seems to radiate in foliæ. (Fitton in Geolog. Trans. v. i.)

In U. States, in Maine at Readfield, from which place I have seen only one small specimen; it appears to have been taken from granite.

SPECIES 30. FELDSPAR.* JAMESON.

This important and widely distributed mineral has, in most of its varieties, a structure very distinctly foliated. It scratches glass, and gives sparks with steel, but its hardness is a little inferior to that of quartz. When in crystals or crystalline masses, it is very susceptible of mechanical division at natural joints, which, in two directions perpendicular to each other, are extremely perfect; but in the third direction they are usually indistinct.

The primitive form thus obtained is an oblique-angled parallelopiped (Pl. IV, fig. 4.), whose sides are inclined to each other in angles of 90°, 120°, and 111° 28′. The four sides, produced by the two divisions perpendicular to each other, have a brilliant polish, while the other two are dull; this is a distinctive character of great importance. Its integrant particles have the same form, as the nucleus. Its spec. gravity usually lies between 2.43 and 2.70.—It possesses double refraction, which however is not easily observed. It is usually phosphorescent by friction in the dark.

(Chemical characters.) Before the blowpipe it melts into a white enamel or glass, more or less translucent. The results of analysis have not yet been perfectly satisfactory in regard to the true composition of Feldspar. It appears probable, however, that not only silex and alumine, but also lime and potash are essential ingredients.

In a specimen of green Feldspar Vauquelin found silex 62.83, alumine 17.02, potash 13.0, lime 3.0, oxide of iron 1.0;=96.85. In another specimen of common Feldspar Chenevix found silex 64.0, alumine 24.0, lime 6.25, oxide of iron 2.0;=96.25. According to Vauquelin, the variety called Adularia contains silex 64, alumine 20, potash 14, lime 2. But in the same variety Chenevix found silex 68.5, alumine 20.5, lime 7.0, oxide of iron 1.5;=97.50. The variety called Petuntze yielded Vauquelin silex 74.0, alumine 14.5, lime 5.5;=94.

From corundum and chrysoberyl Feldspar may be distinguished by its inferior hardness, less spec. gravity, and fusibility.

Feldspar presents several varieties deserving particular notice.

* Feldspath. WERNER. HAUY. BROCHANT. Felspath. BRONGNIART.

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Var. 1. COMMON FELDSPAR.* KIRWAN. JAMESON. This variety occurs in fragments often rolled, also in grains in sand, but more commonly in masses of a moderate size, forming an ingredient of compound minerals. It is not unfrequently in regular crystals. Of the primitive form already mentioned, Haüy has described twenty modifications.

The crystals of Feldspar, seldom very small, are sometimes several inches both in diameter and length; their faces are shining, and their edges sometimes very perfect. Their prevailing form is an oblique prism, whose sides are unequal, and vary in number from four to ten. The terminating faces, of which two are commonly larger than the others, are subject to great variation in number and extent; indeed they often seem to have no symmetry in their arrangement, a circumstance, which arises from the obliquity and irregularity of the primitive form. It is very common to find certain faces unduly extended at the expense of others. The crystals are often grouped, and frequently exhibit hemitropes. We select a few forms for description.

It sometimes presents the primitive form, slightly altered by truncation on two opposite edges.

Also an oblique four-sided prism (Pl. IV, fig. 5.), of which the two bases and two opposite sides are rectangular parallelograms, and the other two sides oblique-angled.

Also an oblique four-sided prism with diedral summits; the terminating faces stand on the obtuse lateral edges, and form with each other an angle of 128° 56′. The lateral edges of this prism, as well as those of the summits, are sometimes truncated. This prism is sometimes so short, and one face of each summit so unduly extended, that the crystal appears to be a rhomb, or a rhombic table.

Also a six-sided prism, terminated by diedral summits; the two edges, on which the terminating faces stand, are usually formed by the four narrower faces of the prism. The crystal is sometimes tabular.

Also a ten-sided prism (PI. IV, fig. 6.), or rather the preceding six-sided prism, truncated on four of its lateral edges by planes, which form with the contiguous sides an angle of 150°. These prisms are sometimes compressed or have a tabular form; and are very often grouped, two and two, touching by their hexagonal faces.

Another form is a six-sided prism (Pl. IV, fig. 7.), terminated at each extremity by five faces, arranged without symmetry.

In fine, all its forms may be referred to a four or six-sided prism,

* Gemeiner Feldspath. WERNER. Le Feldspath commun. BROCHANT. Felspath commun. BRONGNIART.

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variously truncated and terminated. One of its hemitrope crystals is represented Pl. IV, fig. 8;—they often appear to be rectangular four-sided prisms.

The longitudinal fracture is foliated, and its lustre more or less shining and vitreous, sometimes pearly, especially in certain spots; the cross fracture is uneven or splintery, and nearly dull. It is easily broken, and falls into rhomboidal fragments, which have four polished faces.—The foliæ are sometimes curved, or arranged like the petals of a flower.

It is more or less translucent, sometimes nearly or quite opaque, and presents a great variety of colors. Among these are white, tinged with gray, yellow, green, or red; gray, often with a shade of blue, several shades of red, as flesh or blood red; to which must be added green, yellow, brown, or even black.

This variety is very abundant, and constitutes an essential ingredient of granite, gneiss, syenite, and greenstone. Of granite and syenite it sometimes forms two thirds of the whole mass. It exists also in argillite, porphyry, &c. Its crystals, though sometimes imbedded, are more often found in the fissures or cavities of these rocks, and are sometimes associated with epidote, axinite, chlorite, amianthus, carbonate of lime, quartz, magnetic oxide of iron, &c.

GREEN FELDSPAR. This rare subvariety has an apple green color, varying somewhat in intensity, and sometimes marked with whitish stripes. It scratches green diallage, which it a little resembles.

(Localities.) It was first found in the Uralian mountains.—In the U. States. It is found in Maryland, near Baltimore, in granite.—In Maine, at Topsham, near Bowd. Coll. it appears in imperfect crystals, imbedded in an aggregate of mica and quartz.

2. ADULARIA.* JAMESON. This is the most perfect variety of Feldspar, and bears to common Feldspar, in many respects, the relation of rock crystal to common quartz.

Adularia is more or less translucent, and sometimes transparent and limpid. Its color is white, either a little milky, or with a tinge of green, yellow, or red. But it is chiefly distinguished by presenting, when in certain positions, whitish reflections, which are often slightly tinged with blue or green, and exhibit a pearly or silver lustre. These reflections, which are often confined to certain spots, proceed in most cases from the interior of the crystal.

This variety occurs massive, in rolled pieces, and in regular crystals, which are sometimes very large and perfect, exhibiting the

* Adular. WERNER. Felspath adulaire. BRONGNIART. L'Adulaire. BROCHANT. Moonstone. KIRWAN. Feldspath uacré. HAUY.

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forms already described. It often presents hemitrope crystals, whose structure, when the crystal is cut in a certain direction and polished, is rendered obvious by the laminæ, which are arranged in different directions without crossing each other, in consequence of the inversion of one half of the crystal.—Sometimes even four crystals are grouped.

It passes by imperceptible shades into common Feldspar. From cat's eye it is sufficiently distinguished by its structure.—It does not, like spodumen, exfoliate or split into small lamellæ before it melts; their primitive forms are also different.

(Localities.) It occurs in the fissures and cavities of granite, gneiss, mica slate, &c. associated with quartz, mica, common feldspar, schorl, &c. The finest specimens come from Adula, one of the summits of St. Gothard, whence its name is derived.

In the United States. In Maryland, near Baltimore, it occurs in granite; it is of a pure white, reflecting a light blue. (GILMOR.)— In Pennsylvania, in the granite of Germantown; it is amorphous and transparent; (WISTER.)—also on Conestoga creek, 9 miles from Lancaster; it is transparent and associated with brown spar. (CONRAD.)—In New York, in the vicinity of the city, veins of quartz, which traverse limestone, contain small crystals of Adularia. (BRUCE.)—In Massachusetts, at West Springfield.—Also at Southampton in the same granite, which contains galena; it is white, with a slight tinge of yellow, green, or blue. (WATERHOUSE.)

(Remarks.) Adularia is sometimes cut into plates and polished. The fish's eye, moonstone, and argentine of lapidaries come chiefly from Persia, Arabia, and Ceylon, and belong to Adularia, as do also the water opal and girasole of the Italians.

3. OPALESCENT FELDSPAR.* This very beautiful variety is distinguished by its property of reflecting light of different colors, which appear to proceed from its interior. Its proper color is gray, often dark or blackish gray, or yellowish gray, and some specimens are marked with whitish spots or veins. But, when held in certain positions, in regard both to the eye and the incident light, it reflects a very lively and beautiful play of colors, embracing almost every shade of green and blue, and several shades of yellow, red, gray, and brown. These colors, or their intermediate shades, are usually confined to certain spots, and even the same spot changes its colors in different positions, as from blue to green.

These reflections appear to arise from some alteration in the lam-

* Feldspath opalin. HAUY. BRONGNIART. Labradorstein. WERNER. Labrador stone. KIRWAN. JAMESON. La Pierre de Labrador. BROCHANT.

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inæ by decomposition, by which fissures are produced in the direction of the natural joints; hence they suddenly appear or disappear, as the specimen moves.

Its other characters resemble those of common Feldspar.—Its foliated structure distinguishes it from the cat's eye.

(Localities.) It was first found on the island of St. Paul, on the coast of Labrador, in rounded fragments.—Near Petersburg, in Russia, it exists in granite;—and, according to Jameson, it occurs also in greenstone and syenite.

It is much esteemed in jewelry.

4. AVENTURINE FELDSPAR.* Its colors are various; but it contains little spangles or points, which reflect a brilliant light, sometimes yellowish from a flesh colored ground, or whitish from a yellowish brown or greenish ground.

It has been found in Siberia with the green Feldspar; and on the border of the White sea, near Archangel.—Also in the U. States, in Maryland, near Baltimore. (GILMOR.)

5. PETUNTZE.† This would probably be arranged under the common variety of Feldspar, had it not received some additional importance from its use in the manufacture of porcelain. It appears in fact to be that variety of Feldspar, which the Chinese call Petuntze.

It is nearly or quite opaque, and its color is usually whitish or gray. It has in most cases less lustre, than common Feldspar. Its fracture is lamellar, although its masses often have a coarse granular structure.

It most frequently occurs in beds, and usually contains a little quartz. Its powder is said to have a slightly saline taste.

(Uses.) It is employed in the enamel of porcelain ware; and enters, in certain proportions, into the composition of the porcelain itself. Any variety of Feldspar, which contains very little or no metallic oxide, would undoubtedly answer the same purpose.

6. GRANULAR FELDSPAR. This is sometimes merely an alteration of the common variety by partial decomposition;‡ and then it forms an intermediate step in the passage of common Feldspar to porcelain earth or kaolin. Its fracture is dull or has a feeble lustre, and may be uneven, earthy, or imperfectly foliated. It is nearly or quite opaque. It varies much in hardness, and is sometimes friable even between the fingers.

It is said also to be less fusible, than the common variety, proba-

* Feldspath aventuriné. HAUY. BRONGNIART.

† Felspath Pétuntzé. BRONGNIART. Var. of feldspath laminaire. HAUY.

‡ Aufgelö;ster feldspath. WERNER. Disintegrated feldspar. JAMESON. Feldspath granulaire? HAUY.

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bly in consequence of having lost some of its potash. Crystals of Feldspar, although still retaining their form, are sometimes found in this disintegrated state. Its color is usually white, though sometimes tinged with other colors.

In other cases, the granular structure of Feldspar appears to be the result of a confused crystallization, as in the case of granular limestone. It has sometimes even a saccharoidal aspect, strongly resembling masses of white sugar.

The Feldspar, which occurs in thin layers in gneiss, mica slate, and greenstone, has often a granular structure.

7. COMPACT FELDSPAR.* The mineral, which we place under this variety, occurs in grains or fragments, disseminated in other minerals, or in large amorphous masses. Its texture is compact; its fracture is splintery, but, at the same time, when examined with a glass, it usually exhibits minute grains or foliæ; its lustre is never more than glistening, and often less. It is more or less translucent, but often at the edges only. Its colors are white or gray, often shaded with green or blue; it also occurs green or red.

Before the blowpipe it melts into a whitish enamel.

This compact variety of Feldspar constitutes large masses or beds; and is sometimes the base of certain porphyries. It also enters into the composition of some greenstones, and constitutes the imbedded Feldspar in some porphyries. It is often associated with quartz and mica, and evidently passes into common Feldspar. It occurs in the Alps remarkably well characterized.

Appendix to compact Feldspar.

BLUE FELDSPAR OF STIRIA.† It is very doubtful whether this mineral belongs to Feldspar, from which it differs in specific gravity, fusibility, and composition. Its texture is usually compact with an uneven or splintery fracture, but sometimes a little foliated. Its lustre is feeble. It scratches glass, but is less hard than quartz; and is commonly translucent at the edges only. Its color is sky blue, often pale, or even bluish white. Its specific gravity is 3.06.

Before the blowpipe it whitens and forms a kind of frit, but does not melt into an enamel. It contains alumine 71.0, silex 14.0, magnesia 5.0, lime 3.0, potash 0.25, water 5.0, oxide of iron 0.75;=99. (KLAPROTH.)

This mineral has been found only near Krieglach, in Stiria, where

* Var. of dichter feldspath of Werner; of compact feldspar of Jameson; of feldspath compacte of Haüy; and of petrosilex of Brongniart.

† Feldspath bleu. HAUY. BRONGNIART. Var. of dichter feldspath. WERNER. Var. of compact feldspar. JAMESON. Var. of Felsite. KIRWAN.

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it forms part of an aggregate with quartz and talc. Karsten has united it with the Lazulite of Stiria and Saltzburg.

(Geological sit. of Feldspar.) In addition to what has already been said under the several varieties, we remark, that Feldspar is found chiefly in primitive rocks. It very seldom constitutes large, homogeneous beds. On the contrary, it forms, as we have seen, an ingredient of granite, gneiss, syenite, greenstone, and porphyry. It sometimes constitutes thin beds, or layers, or veins, which traverse gneiss, mica slate, &c. and is often mingled with other minerals in the same vein.

Feldspar is, however, sometimes found in transition or secondary rocks. It is sometimes disseminated in grains or crystals in graywacke, amygdaloid, and basalt. Compact stratified limestone sometimes contains crystals of Feldspar. (BROCHANT.)

It is very common in certain volcanic productions, to which it gives a porphyritic aspect.

Feldspar is almost always accompanied by quartz or mica, or both; and is sometimes colored green by chlorite. It often contains magnetic oxide of iron, which is sometimes so intimately united, that, although imperceptible by the eye, the Feldspar itself is magnetic, and even possesses polarity; for a minute fragment, being made to float on water, will be attracted and repelled by different poles of a magnet.

Feldspar, especially in some of its varieties, is very subject to decomposition by the action of air and moisture. This process, indicated by change of color, diminished lustre and cohesion, may be observed in all stages from sound Feldspar to Kaolin or porcelain earth. It is also attended by the loss of the potash, or some other ingredient, which rendered the Feldspar fusible; for the resulting earth is infusible. (See Kaolin.) This tendency to decomposition is perceptible in the Feldspar, contained in porphyry, as well as in that of granite.

It is unnecessary to enumerate the localities of a mineral so abundant, as is Feldspar in the United States. The common variety frequently occurs in extremely beautiful laminated masses in the granite of Maryland, Pennsylvania, Massachusetts, and Maine.

SPECIES 31. JADE.* BRONGNIART.

The most striking, general characters of Jade are a great degree of hardness, a remarkable tenacity, which renders it difficult to break, a color more or less green, a resinous or oily aspect when polished. and fusibility into a glass or enamel.

Much obscurity, however, pervades many descriptions of this min-

* Nephrit. WERNER. Nephrite. JAMESON. Le Nephrite. BROCHANT.

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eral, which have been published. And in fact the several minerals, usually included in this species, differ so much in composition, or in certain chemical characters, that we shall at once subdivide the species for the purpose of description.

SUBSPECIES 1. NEPHRITE.*

The hardness of Nephrite is, in general, at least equal to that of quartz, and sometimes greater. It possesses a peculiar tenacity, which renders it difficult to break, to cut, and to polish. Its surface is a little unctuous to the touch, and, when polished, has an oily aspect. Its fracture is splintery and dull, unless rendered glimmering by foreign intermixture. It is sometimes very strongly translucent, and sometimes only at the edges. Its color varies from leek green to greenish white, or almost white, and has sometimes a slight tinge of blue, or yellow. Brochant says its fresh fracture presents a paler green, than that of the surface. Its spec. grav. varies from 2.95 to 3.04. It occurs amorphous, or in rolled masses with a smooth, oily surface.

By the blowpipe it is easily fusible, with some ebullition, into a globule of white semi-transparent glass. According to T. Saussure, it contains silex 53.75, lime 12.75, soda 10.75, potash 8.50, alumine 1.50, oxide of iron 5.0, oxide of manganese 2.0, water 2.25;=96.50.

(Localities.) Nothing is known of the geological situation of the Nephrite in India and China, whence it is frequently brought, and has hence been called oriental Jade.

In the U. States. In Pennsylvania, in Montgomery Co. 10 miles from Philadelphia, it occurs in serpentine. (WISTER.)—In Rhode Island, at Smithfield; it is sometimes in veins, but usually in large nodules, in granular limestone; it is very translucent, of a delicate greenish white, and constitutes a very beautiful mineral. (MEADE.)

(Uses.) Nephrite does not receive a brilliant polish. But, in consequence of its great tenacity and hardness, it is, in India, cut and polished for certain kinds of jewelry. In Turkey and Poland, it is employed for the handles of sabres, knives, &c. Some very delicate works have been executed with Nephrite, in consequence of its tenacity; it has been formed even into small chains.—It was formerly worn in little plates, &c. as an amulet, attached to the neck, &c. for the purpose of removing nephritic complaints; hence its name.

* Gemeiner Nephrit. WERNER. Common Nephrite. JAMESON. Le Nephrite common. BROCHANT. Jade nephretique. HAUY. Var. of Jade. KIRWAN.

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SUBSPECIES 2. SAUSSURITE.*

This differs a little from nephrite in its external characters, and very considerably in its composition. Its specif. grav. is greater, being at a mean about 3.35. It is said to be a little harder, than the nephrite, and it is, at least, equally tenacious; but it receives a higher and less oily polish. Its colors also are green, sometimes deep, and sometimes greenish gray, or white with a slight tinge of green or even of blue. It is usually translucent at the edges. It occurs in rolled pieces, or amorphous masses, and its structure is sometimes a little foliated.

It melts before the blowpipe, like nephrite. It contains silex 44.0, alumine 30.0, soda 6.0, lime 4.0, potash 0.25, oxide of iron 12.5, oxide of manganese 0.05;=96.80. (T. SAUSSURE.) An analysis by Klaproth gives silex 49.0, alumine 24.0, lime 10.5, soda 5.5, magnesia 3.75, oxide of iron 6.5;=99.25.

(Localities.) This subspecies belongs to primitive mountains, and sometimes occurs in considerable masses. It was first found by Saussure in rolled pieces near the lake of Geneva. It exists also near Turin, on mount Musinet, which is composed chiefly of serpentine; also in Corsica; and in all these localities it is mingled with diallage. At Corsica it contains magnetic oxide of iron.

SUBSPECIES 3. AXESTONE.† JAMESON.

The fracture of this mineral is more or less splintery and glimmering. The structure of large specimens is a little slaty. Its hardness is less, than that of nephrite; it is more easily broken, and often falls into tabular fragments. It is usually translucent; sometimes at the edges only. Its color varies from a dark or leek green to grass and olive green, or even greenish gray.—It occurs amorphous, sometimes in rolled fragments.

It is less easily fusible, than nephrite or Saussurite, and melts, without effervescence, into a black enamel. (BRONGNIART.) It often appears to be nearly allied to serpentine.

This miner has been found chiefly in S. America, New Zealand, and the islands of the South Sea.

It receives a tolerable polish; and is employed by the natives of the aforesaid islands for making hatchets and other instruments; hence its name.

* Jade de Saussure. BRONGNIART. Feldspath compacte tenace. HAUY.
It is included under the preceding subspecies by Werner, Jameson, Brochant, and Kirwan.

† Jade axinien. BRONGNIART. Jade ascien. HAUY. Beilstein. Pierre de trache. BROCHANT.

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SPECIES 32. EMERALD.*

The Emerald is always crystallized; and almost invariably appears in regular, hexaedral prisms, more or less perfect, and sometimes slightly modified by truncations on the lateral or terminal edges, or on the solid angles. Sometimes the terminal edges are bevelled, and sometimes the truncations on these edges are so deep, that the prism seems to have pyramidal terminations, whose vertices are truncated. Two of the aforementioned modifications are sometimes combined in the same crystal.—The primitive form, of which Haüy has described six modifications, is a regular hexaedral prism, whose sides are squares. The integrant particles are triangular prisms.

The Emerald is a little harder than quartz, which it of course scratches, though not very easily. Its spec. grav. lies between 2.60 and 2.77. It becomes electric by friction, and possesses double refraction in a feeble degree. It is often transparent, sometimes only translucent in various degrees. Its prevailing color is green, sometimes very lively and beautiful, and sometimes pale, or yellowish, or bluish.

(Chemical characters.) Before the blowpipe it is fusible, though not very easily, into an enamel or glass, often a little frothy. It appears to be essentially composed of silex, alumine, and glucine; but is sometimes colored by the oxide of chrome, and sometimes by that of iron. On this difference of coloring matter, usually accompanied by certain differences of external characters, we establish two subspecies, the precious Emerald, and Beryl. Both have the same essential characters; and it is extremely probable, that they gradually pass in to each other by containing both oxides.

SUBSPECIES 1. PRECIOUS EMERALD.†

The precious Emerald is, in general, well characterized by that pure and lively green color, which has hence received the name of emerald green. Its color, however, varies a little, sometimes inclining to verdigris or grass green, and sometimes becoming rather pale.

Its crystals are usually small, and short; their lateral faces are shining and smooth, or sometimes longitudinally and feebly striated. Its fracture, sometimes a little foliated, is in most cases imperfectly conchoidal or uneven; its lustre is vitreous and more or less shining.

The precious Emerald contains silex 64.50, alumine 16.0, glucine 13.0, lime 1.60, oxide of chrome 3.25;=98.35. (VAUQUELIN.) The fine color of this Emerald is derived from the oxide of chrome. A specimen from Peru melted before the compound blowpipe into a

* Emeraude. HAUY. Béril. BRONGNIART.

† Schmaragd. WERNER. Emerald. KIRWAN. JAMESON. Emeraude verte. HAUY. L'Emeraude. BROCHANT. Béril Emeraude. BRONGNIART.

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transparent, green globule. (SILLIMAN.) In one specimen Klaproth found the oxides of both chrome and iron, thus showing, that the two subspecies may pass into each other in regard both to composition and color.

This Emerald may resemble the green tourmaline; but the latter is electric by heat, the former by friction only.

(Geological sit. and Localities.) The geological situation of the precious Emerald has not been much observed. It sometimes occurs in the sand of rivers, and other alluvial earths. It has been seen in a gangue of the sulphate and carbonate of lime; but this may not have been the original situation.

The finest Emeralds have been found near Manta in Peru; and in the valley of Tunca, in the province of Santa-Fe, near the mountains of Popayan. Some Emeralds from Peru have been seen six inches in length by two in diameter; but this size is very uncommon. They are found in veins, which traverse argillite, or in cavities of granite; and are accompanied by quartz, feldspar, sulphuret of iron, &c. It exists also in Ceylon, Egypt, and Ethiopia, from the last two of which the ancients are supposed to have obtained Emeralds.

The greater part of the Emeralds, hitherto found in the United States, belong to the following subspecies. But it is highly probable, that the precious Emerald has also been observed in the same gangue, which contains the beryl, although analysis has not yet confirmed the indications, which the external characters afford. Thus at Haddam, in Connecticut, has been found an Emerald of a deep green, an inch in diameter and several in length, which bears a strong resemblance to the Peruvian Emerald. It is in the cabinet of Col. Gibbs. (Bruce's Min. Jour. v. i.)—So also at Topsham, in Maine, have been found several Emeralds, which exhibit a lively and beautiful green, scarcely, if in any degree, inferior to that of the finest Peruvian Emeralds; their surfaces also were nearly or quite free from striæ. Both these localities will be mentioned under the following subspecies.

(Uses and Remarks.) When transparent, and of a lively uniform green, the Emerald is extremely pleasant to the eye, and is employed in the most expensive kinds of jewelry.—This name has sometimes been applied to other minerals; thus the green tourmaline has been called Brazilian emerald; the green sapphire, oriental emerald; and the green fluate of lime, false emerald.

SUBSPECIES 2. BERYL.*

Its prevailing color is green of various shades, as mountain or

* Edler Beril. WERNER. Precious Beryll. JAMESON. Le Beril noble. BROCHANT. Béril Aiguemarine. BRONGNIART. Berryll. KIRWAN. Emeraude limpide, vert-bleuâtre, jaune-verdâtre, &c. HAUY. Aigue marine—Aqua marina of some.

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grayish green, &c. but always pale; it also passes through bluish green to sky blue, and through yellowish green to a pale or honey yellow; it is sometimes greenish white, grayish, whitish, or even limpid. It has also been found rose red. Different colors sometimes appear on the same crystal.

Its crystals are usually longer and larger, than those of the precious Emerald. Their size, however, is extremely variable; sometimes they are very long and even acicular, while at other times they are one foot in length by several inches in diameter—and have been observed even one foot in diameter. They exhibit all the intermediate sizes. The lateral faces are longitudinally striated, sometimes so deeply, that the edges of the prism are rendered indistinct, or entirely effaced, and the crystal becomes cylindrical.—Two or more of the lateral planes are sometimes so unduly extended, that the prisms appear nearly tetraedral or triedral.—Some prisms are curved, or even geniculated; others are perforated in the place of the axis, and sometimes contain other minerals in the cavity; in fine, they often intersect each other, or are collected into groups of considerable size.— The Beryl also occurs in amorphous, crystalline masses of a moderate size.

Its fracture is imperfectly conchoidal or uneven, and often a little foliated, even more so than that of the precious emerald; its lustre is vitreous, and more or less shining. Its prisms are often traversed by seams, perpendicular to the axis, and in that direction are extremely brittle; sometimes they are articulated, like the prisms of basalt, one surface of the cross fracture being convex and the other concave.

The Beryl contains silex 68, alumine 15, glucine 14, lime 2, oxide of iron 1. (VAUQUELIN.) With the compound blowpipe it melts with ebullition into a globule of bluish, milky white glass. (SILLIMAN.)

(Distinctive characters.) The Beryl is harder than the apatite, with which it has often been confounded; and the powder of the apatite is phosphorescent on hot coals.—It is harder and less heavy, than the pycnite, which it may also resemble.—From the tourmaline it may be distinguished by its inability of becoming electric by heat.

(Geological sit. and Localities.) The Beryl belongs to primitive rocks, more especially to granite. It is often found in graphic granite, or in veins, which traverse this rock.—It is associated with quartz, feldspar, mica, garnets, schorl, topaz, fluate of lime, oxide of tin, and magnetic oxide of iron.

Some of the finest Beryls are found in Dauria, on the frontiers of

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China, in veins, which traverse granite; their gangue is argillaceous. The Beryl occurs also in the Uralian mountains, and other parts of Siberia; and is most frequently in graphic granite.—It is found limpid in the granite of Elba.—Good specimens are brought from Brazil.

In France, near Limoge, it is found in a vein of quartz in granite; it is in whitish green crystals sometimes a foot in length by sit inches in diameter, commonly translucid, sometimes yellowish white at the surface.

In the United States. In Maryland, near Baltimore, in granite; but in most cases the crystals are imperfect. (GILMOR.)—In Pennsylvania, on the banks of the Schuylkill, 3 m. above the permanent Bridge; on Chesnut Hill 10 m. from Philadelphia; and in Germantown finely crystallized; in all instances imbedded in granite (WISTER);—also near Chester.—In New York, at Sing Sing 35 m. from the city, in granite (MACLURE);—also near the city in veins of granite, which traverse gneiss.—In Connecticut, at Brookfield, Huntington, Chatham, &c. in granite. Also at Haddam, on Connecticut river, in granite, which forms a vein in gneiss; the crystals are variable in size, generally light yellowish green, sometimes amber yellow; sometimes also a deep green (see precious Emerald); a crystal in the cabinet of Prof. Silliman measures seven inches in length by nine inches in the diagonal diameter (SILLIMAN and Bruce's Journ. v. i.)—In Massachusetts, at Chesterfield, in Hampshire Co. in granite; the crystals vary from a small size to that of a foot in diameter; their color is usually a light green, and they much resemble the French Beryl at Limoge. (Bruce's Min. Jour. v. i.) A rose colored Emerald or Beryl one inch in diameter, has recently been found in Chesterfield with the Rubellite, and is now in the cabinet of Col. Gibbs.—The Beryl is also found in the vicinity of Northampton, Goshen, and Boston.—In Maine, it is found, more or less constantly, in a coarse grained granite from 5 m. east of Bath in Lincoln Co. to 5 as west of North Yarmouth in Cumberland Co. an extent of about 65 miles. At Topsham, near Bowd. Coll. it is sometimes imbedded in graphic granite, and often in a brittle, smoky quartz in a large grained granite. This granite constitutes veins in gneiss, and the Beryl sometimes appears in the contiguous gneiss. The crystals are often in well defined hexaedral prisms, transparent, and perfectly resembling the Siberian Beryl; sometimes also nearly opaque. Their colors are pale green, yellowish, bluish, or even whitish. In the same granite are also a few crystals, which present a pure, uniform, and rich green, and obviously belong to the precious Emerald.—Sometimes the Beryls have a corroded aspect, or are per-

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forated longitudinally in the place of the axis, and the cavity in some instances contains plates of mica, &c.—At Bowdoinham in large crystals in graphic granite.

(Uses and Remarks.) The Beryl is but little employed in jewelry, as its pale colors, numerous cracks, &c. much diminish its value. The name of Beryl has been sometimes erroneously applied to the apatite, greenish quartz, cyanite, pycnite, epidote, and even to certain topazes.

SPECIES 33. EUCLASE.* HAUY.

This very rare mineral has hitherto been seen only in crystals, which, if complete, would present seventy eight faces. Of these, fourteen belong to the prism, which may be viewed as an oblique four-sided prism, bevelled on all its lateral edges, and truncated on two of the edges, produced by the bevelments. Each termination has thirty two faces.

The Euclase yields with uncommon facility to a mechanical division in one direction, parallel to the axis of the prism; and the laminæ, thus separated, have a very strong vitreous lustre. Another division is less easily effected at right angles to the preceding, but still parallel to the axis; thus giving a rectangular four-sided prism for the primitive form. The cross fracture is conchoidal and vitreous.

The Euclase is remarkably brittle,† but sufficiently hard to scratch quartz. It is transparent, and possesses a strong double refraction. Its color is a light sea green. Its spec. grav. is about 3.06.

Before the blowpipe it becomes opaque, and melts into a white enamel. It contains, on a mean of two analyses by Vauquelin, silex. 35.5, alumine 18.5, glucine 14.5, oxide of iron 2.5;=71. The loss of 29 parts is probably water and an alkali.

Nothing is known of its associations with other minerals. It has been found in Peru only.

SPECIES 34. BASALT.‡ WERNER. JAMESON.

This mineral, so interesting in the study of geology, is never crystallized. It occurs, however, not only in large amorphous masses, but also under a columnar, tabular, or globular form. Its most common color is grayish black, sometimes inclining to brownish gray, and sometimes to brownish or bluish black. Some varieties have a tinge of green. The exterior is often brown or reddish brown in consequence of decomposition. The color of its streak is a light gray. It is opaque, or sometimes feebly translucent at the edges.

* Euklas. WERNER. Euclase. BRONGNIART. BROCHANT. JAMESON.

† Hence its name, from the Greek , and κλαζω, to break.

‡ Basalte. BRONGNIART. BROCHANT. Trap. KIRWAN. Lave lithoïde basaltique. HAUY.

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Its fracture is usually uneven or fine splintery, sometimes a little conchoidal, earthy, or nearly even. It has no lustre, unless from the presence of foreign substances. It is difficult to break, and frequently sonorous, when struck.

Even when not decomposed, it is always less hard than quartz, but very often gives a few sparks with steel. Its spec. gravity, though somewhat variable, probably lies between 2.87 and 3.00. It usually moves the magnetic needle, and sometimes discovers polarity.

Basalt is by no means always perfectly homogeneous; for it often contains hornblende, olivine, and augite, and sometimes leucite, melanite, feldspar, quartz, mica, magnetic oxide of iron, &c. It sometimes exhibits vesicles or cavities, which, in most cases at least, seem to have been produced by the loss or decomposition of imbedded minerals. These cavities, sometimes empty or filled with water, are often lined or even filled with steatite, calcareous spar, zeolite, chalcedony, clay, &c. and thus give to the mass an amygdaloidal aspect.

(Chemical characters.) Before the blowpipe it melts into an opaque, black or grayish black glass, which is often attracted by the magnet. Its melting point is not far from 100° W. and, when very slowly cooled, melted Basalt resumes its former stony aspect.—From the Basalt of Staffa, Kennedy obtained silex 48, alumine 16, lime 9, soda 4, oxide of iron 16, muriatic acid 1, water 5;=99. In the Basalt of Hassenberg, Klaproth found silex 44.5, alumine 16.75, lime 9.5, magnesia 2.25, soda 2.6, oxide of iron 20.0, oxide of manganese 0.12, muriatic acid 0.05, water 2.0;=97.77. Without great caution, its analysis must be affected by the imbedded minerals.

It passes by insensible shades into greenstone, wacke, and perhaps clinkstone.

Basalt is more or less subject to decomposition, partly, at least, in consequence of the action of the atmosphere upon its iron, which exists in a low state of oxidation, as is evident by its action on the needle. Hence the brownish, friable, or even earthy crust, which often invests its exterior. Those Basalts, which seem to approach very near to greenstone, decompose most rapidly. Indeed the whole mass is sometimes converted into an earthy, argillaceous substance; in which the once imbedded crystals of hornblende remain unchanged.

Var. 1. COLUMNAR BASALT.* This is the more common form of Basalt, when not amorphous. But the supposition, that these prisms are real crystals, is rendered altogether inadmissible by the uneven-

* Figurate Trap or Basalt of Kirwan, which also includes the two following varieties. Basalt prismatique. BRONGNIART.

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ness of their sides, the irregularity of their angles, and other circumstances obvious on inspection.

These columns vary in the number of their sides from three to nine; but most frequently have only five or six. Their diameter reaches from three inches to three feet or more; their length also is extremely variable, sometimes only a few inches, and sometimes 40 or 60 feet, or even 100 feet, according to Jameson. They are sometimes jointed or articulated; that is, one transverse surface of the prism, at the place of the joint, is concave, while the other is convex, and accurately corresponds to the concavity, in which it is confined in part by a prolongation of the lateral edges of that portion of the prism, which contains the concavity. Sometimes the distance between the joints is less, than the diameter of the prism.

These basaltic columns, whether straight or curved, are variously grouped. Sometimes they are closely united; in other instances a space intervenes, either empty, or filled by some foreign substance. Sometimes the columns are perpendicular; sometimes inclined, or nearly horizontal, and not unfrequently collected into immense groups with diverging prisms. Those columns, which may be said to belong to the same series, often have nearly the same height, while a contiguous series has also a common level, either above or below the former.—It has also been remarked, that, when columns of Basalt touch each other, the contiguous sides have an equal extent, and that a protuberance on one prism has a corresponding depression on the other.—Sometimes the columns are irregular;—and have in a few instances been seen cylindrical. (FAUJAS.)

2. TABULAR BASALT. It occurs in masses of a moderate size, and composed of thin layers, which are usually of unequal thickness.

3. GLOBULAR BASALT.* These globular masses are sometimes composed of concentric layers, and contain a nucleus of compact Basalt, or some other substance, as a fragment of shell limestone. Sometimes they consist of prisms radiating from a centre. They vary in diameter from six to thirty inches; and are sometimes compressed or lenticular.

Globular Basalt is usually scattered on the surface of basaltic mountains. Faujas, however, mentions a hill in Scotland, composed entirely of these balls.

4. AMORPHOUS BASALT.† This presents all the essential charac-

* Basalte sphéroïdal. BRONGNIART.

† Common Trap. KIRWAN. The Ferrilite, and perhaps the Mullen Stone of Kirwan, may be referred to this variety of Basalt. The term, Whin Stone, in Scotland and other parts of Great Britain, is sometimes applied to Basalt but is also extended to Greenstone, Syenite, &c.

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ters of Basalt. It is more frequently porous or cellular, than the other varieties. Its fragments often tend to a quadrangular form.

(Geological situation.) Basalt is a secondary rock, which usually presents itself in beds, or in columns. It sometimes constitutes insulated mountains of a conical form, and considerable altitude, but never by itself forms an extensive chain of mountains.

It is usually incumbent on other rocks, as granite, gneiss, mica slate, argillite, porphyry, greenstone, wacke, compact limestone, sandstone, or on gravel, clay, or beds of coal. It very often appears in large insulated masses, of a conical or tabular form, constituting the summits of mountains, which are composed of materials totally different from Basalt.—It sometimes occurs at a very considerable elevation; thus on the Riesengebirge, in Silesia, it is 4,000 feet above the level of the sea, and near the peak of Teneriffe it is 11,000 ft. above the same level.

The Basalt, which constitutes either entire hills, or only the summits of mountains, almost always occurs in columns, or in beds. It is frequently traversed by rents in various directions; and hence the numerous fragments, which so often cover the sides and bottoms of basaltic mountains.

Beds of Basalt are variable both in thickness and inclination. But, in general, they are not parallel to the strata, on which they rest. Sometimes, however, Basalt is incumbent on wacke, greenstone, and clinkstone-porphyry, into all which it passes by insensible shades. When columnar Basalt rests on wacke, the prismatic divisions sometimes extend into the wacke.

In some instances, beds of Basalt alternate with those of other minerals, or are covered by them. Thus greenstone and clinkstone-porphyry often rest on Basalt.—In Scotland, Basalt sometimes alternates with argillaceous slate, sandstone, limestone, &c.—In the Vicentine, in Italy, twenty beds of Basalt alternate with as many beds of compact limestone. (DOLOMIEU.)—In Graciosa, one of the Canary islands, strata of Basalt repeatedly alternate with those of a yellowish marl, which is itself often divided into irregular prisms, analogous to those of Basalt. (HUMBOLDT.)—In Auvergne, it alternates with shell limestone. (DOLOMIEU.)—1n Bohemia, the isle of Mull, and other places beds of coal lie between those of Basalt. (REUSS. JAMESON.)—In Teneriffe, it alternates with clinkstone-porphyry, obsidian, and perhaps pitchstone.—In fine, Basalt sometimes contains fragments of sandstone or limestone, or rolled pieces of quartz, &c.

Masses of Basalt are sometimes traversed by walls or perpendicular veins of the same substance; and these walls always possess a different structure from that of the beds, which they traverse. In

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Scotland they are called dikes, and in Ireland gaws. Even these dikes are sometimes intersected by other small veins of Basalt.

The same countries, which contain Basalt in beds or in prisms, sometimes present it also in veins, which may traverse primitive, transition, or secondary rocks. The Basalt of these veins is often divided into little prisms, placed perpendicular to the walls of the vein. In Ireland, near Carrickfergus, is a vein of Basalt, composed of several distinct beds, each of which is differently divided into prisms;—near Ballycastle, a vein of Basalt intersects alternate beds of sandstone and coal. (RICHARDSON.)

It is extremely rare to find metallic substances, even in small quantities, connected with Basalt.

The recent formation of Basalt is clearly indicated by the minerals, which it accompanies, and especially by its alternation with beds of shell limestone and coal, and by the organic remains of shells, which the Basalt of Bohemia, the Vicentine, Ireland, &c. sometimes contains.

Basalt is sometimes found in countries decidedly volcanic. But it very seldom occurs near the crater of volcanoes still active; on the contrary, it usually appears near the foot of volcanic mountains, and sometimes almost surrounds them. Hence it is covered by lavas, but probably never rests upon them. Hence it may be often difficult to distinguish amorphous Basalt from the contiguous lava. It is abundant at the foot of Etna, and is found in Iceland, Bourbon, and Teneriffe; while it is rare in the vicinity of Vesuvius.

But, according to Gioeni, basaltic columns exist at the summit of Mount Etna, nearly on a level with the base of its crater. And Spallanzani, the intrepid observer of volcanoes, saw, in the crater of Vulcano, one of the Lipari islands, pentagonal, articulated prisms, sometimes intimately united to the sides of the crater, and sometimes in a great measure detached.—May not, however, the substance observed in both these cases be called basaltiform lava, rather than Basalt?

(Localities.) Of these the most remarkable is in the county of Antrim, in the north of Ireland. The Giant's Causeway, near Cape Fairhead, is composed of basaltic columns, usually perpendicular, and closely applied to each other. These columns are mostly hexagonal, sometimes pentagonal, &c. and have distinct and numerous articulations. This causeway projects into the sea, presenting a visible area of about 600 feet in length by 25 feet in breadth, taken on an average, and exclusive of detached columns; but its extent under water is unknown. The height of the columns above the strand is about 40 feet; and they are terminated so nearly on the same level, that one may

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walk on them, as on a pavement. The diameter of the prisms is sometimes two feet; and their edges, though so long washed by the sea, appear to be as perfect, as ever.

The small island of Staffa, one of the Hebrides, is composed entirely of Basalt, both amorphous and columnar, and appears to rest on red sandstone. In this island is the celebrated cave of Fingal. The walls of this grotto are composed of columnar Basalt, and support its roof, which also is formed of basaltic prisms, variously inclined, and united by the filtration of various substances into the interstices. This cavern sends forth a remarkable sound, produced by the dashing of the waves against its sides.—The surface of this island is alluvial, consisting of rounded fragments of granite, gneiss, mica slate, quartz, and sandstone, &c. Whence came these fragments of primitive rocks? (M'CULLOCK.)

There appears to be a vast deposite of Basalt, extending northeasterly from the northern parts of Ireland through the Hebrides, and the northwestern parts of Scotland.

Basalt occurs also on the summits of the chain of metalliferous mountains, which separates Bohemia from Saxony. These basaltic summits, either tabular or conical, are almost always insulated. The central parts of the mountains, which compose this chain, are granite, covered by gneiss and argillite. The argillite is covered by wacke, from which it is often separated by gravel, sand, clay, and sometimes coal; and on the wacke the Basalt usually rests. Sometimes also the Basalt is covered by greenstone. It is often columnar, but never contains any metallic veins, although placed on mountains abounding with them.

The mountain Weissenstein, in Hessia, rests on compact limestone, on which are found beds of sand, clay, wacke, and Basalt; this series is three times repeated in the same order, and the lowest series contains lignite or brown coal. (JAMESON.)—At Scheibeuberg, in Saxony, a bed of gravel rests on gneiss; and the gravel is covered by clay, which passes into wacke, and the wacke into Basalt, which rests upon it. (BROCHANT.)—The summit of mount Meisner, in Hessia, exhibits a tabular mass of Basalt more than 300 feet thick, and covered by greenstone. The body of the mountain is composed of inclined strata of compact limestone and red sandstone; on the sandstone is a bed of brown coal with bituminous clay; and on this a thin stratum of wacke, succeeded by beds of Basalt nearly horizontal.

Columnar Basalt is also found near Andernach on the Rhme; and in very fine prisms in Auvergne, &c. &c.

It is extremely doubtful, whether any Basalt, strictly speaking, has yet been observed in the United States; although it is said to exist

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on the Stony Mountains. The columnar and prismatic masses, which exist in various parts of the U. S. are undoubtedly a secondary, basaltiform greenstone, which, in some cases, may perhaps be passing into Basalt. In all specimens, which the writer has seen, the eye, especially when assisted by a glass, could discover feldspar, constituting one ingredient.

(Origin of Basalt.) The opinions of mineralogists on the origin of Basalt may be reduced to three general classes; although the supporters of the same theory may sometimes differ from each other in minor circumstances.

1. All Basalt has been deposited from water, like granite, &c. This, which has been called the Neptunian theory, has been supported by Bergman, Werner, Kirwan, Jameson, by most of the German mineralogists, and a few among the French.

2. All Basalt is a product of volcanic fire. The supporters of this opinion are found chiefly among the French and Italians.

3. Basalt is sometimes of aqueous origin, and sometimes an igneous product. Its locality, &c. must determine the fact in any given instance. This opinion has been supported by Spallanzani, Dolomieu, Fortis, &c.

The limits, assigned to this volume, will permit us barely to recite in a very brief manner the most important arguments in favor of the Neptunian and Volcanic theories, with the replies, which have been made to some of them.

In support of the aqueous origin of Basalt it is contended;

1. If there be a series of different minerals, intimately united and gradually passing into each other, the same origin must be attributed to the whole series; and hence, if one member be an aqueous deposite, the whole series must have been produced in the same manner. Now Basalt often forms one member of a series, beginning with gravel, sand, and clay; this clay gradually becomes less sandy and harder, till it passes into wacke, and the wacke is by insensible degrees lost in Basalt. The sand and clay are undoubtedly aqueous deposites; and the conclusion in such cases is obvious.

2. Basalt is frequently found in parallel, horizontal, and sometimes thin beds; and these beds sometimes alternate with sandstone and limestone, which are undoubtedly of aqueous origin.—Further, currents of lava are narrow at their sources, but broad and thick toward their extremities; they never occur in thin, parallel, horizontal beds of uniform density, like Basalt.

3. Basalt sometimes stands on coal, or bituminous wood, unaltered by fire, or it even contains beds of coal.

4. Basalt is sometimes intimately united to limestone, or even

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contains it in its interior. But this limestone is not calcined; it still retains its carbonic acid, whereas the limestone found in lavas is calcined and friable.

5. Basalt embraces many substances, which are easily fusible, as zeolite, feldspar, hornblende, &c. but these are unaltered and retain their water of crystallization.

To this it has been replied, that these substances may have been formed in Basalt by filtration, since its fusion.

6. Basalt sometimes contains organic remains of both animals and vegetables.

7. Basalt does not exhibit in its texture and internal appearance any marks of previous fusion. The cavities, which it sometimes contains, do not resemble those, which are produced by the ebullition of a melted mass.

But it is replied, that the stony aspect and compact texture of Basalt is no proof, that it has not been fused. For it appears, from the experiments of Sir James Hall and others, that, when melted Basalt is very slowly cooled, it reassumes its former texture and appearance; whereas, when rapidly cooled, it remains a vitreous mass.

8. The analysis of Basalt shows, that it contains water in its composition, whereas undoubted lavas contain no water.

9. The Basalt, which is insulated on the summits of certain mountains, cannot have a volcanic origin. For, if each basaltic summit once issued from the mountain, on which it now rests, the interior of that mountain could not exhibit a series of regular beds, traversed in various directions by metallic and other veins, as is found to be the fact. But, if the Basalt, for example, which forms the summits of a chain of primitive mountains in Saxony, already described, has proceeded from one grand current of lava, it may be asked, how could this lava be lodged on these summits, without filling the intervening vallies?

Some of the more direct arguments in favor of the volcanic origin of Basalt are the following.

1. Basalt is abundant in the vicinity of many volcanoes; and Sir Will. Hamilton observed some basaltic columns, ejected from Vesuvius in 1779. But Basalt, as well as granite, may be ejected from a volcano without previous fusion. Further, Basalt may accompany volcanic mountains, be melted by their fires, and converted into lava; but it is no longer Basalt. The Neptunians do in fact believe, that Basalt is very often the mother stone of lava.

2. The black color, porosity, and magnetic polarity of Basalt are circumstances in favor of its volcanic origin.

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3. The minerals, which often accompany Basalt, strongly resemble those, found in the vicinity of active volcanoes.

4. The prismatic form, which some Basalts assume, has probably arisen from the sadden cooling and consequent contraction of melted masses of lava in the air or in the sea.

But, in the first place, the prismatic form is common to Basalt and several other minerals, whose origin is undoubtedly aqueous, such as greenstone, granite, porphyry, and marl. And this form may be produced by desiccation as well, as by cooling.

Secondly, it does not appear, that lavas necessarily assume a prismatic form by plunging into water. Spallanzani carefully examined the island of Ischia, whose lavas have entered the sea, but did not find one prismatic column. The lava of Vesuvius, which in 1794 reached the sea, did not divide into columns.

It may be further replied, that melted Basalt, when suddenly cooled, ought to produce a vitreous mass. But in answer it is suggested, that the heat of volcanoes is probably insufficient to vitrify Basalt; that it merely produces a dilatation of the mass, and, by separating the particles from each other, enables them to move freely among themselves; and that the flowing of lava is in part effected by the presence of melted sulphur or bitumen, as earth or mud is made to flow, when suspended in water.

Patrin has suggested, that Basalt may have been produced during the muddy eruptions of submarine volcanoes. Hence the sandstone, the unburnt coal, the uncalcined limestone, &c. Hence volcanoes on the surface of the earth cannot produce Basalt.

On the supposition of a double origin, the Basalt of Saxony, Ireland, and Scotland would probably be ascribed to an aqueous deposite, and that of Auvergne, Italy, and Sicily to volcanic fires.

The arguments in favor of the aqueous origin of Basalt seem decidedly to preponderate, although difficulties still remain. But it is undoubtedly true, that Basalt often closely resembles real lava; they are sometimes found in contact, or the Basalt is actually enveloped by the lava. Even in this case the Basalt may often be distinguished by the uncalcined carbonate of lime, which it contains.

(Uses.) When calcined and pulverized, it may be employed as an ingredient in water-proof mortar. It is sometimes used as a touchstone for metals; or is employed in the manufacture of green glass bottles.—The ancients, and particularly the Egyptians, executed some of their monuments and statues in Basalt. Among these are said to be the statue of Minerva at Thebes, and that of Memnon at the temple of Serapis.

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SPECIES 35. WACKE.* JAMESON.

Its colors are greenish gray, often deep and even passing into blackish green; also gray, brown, or grayish black, sometimes with a shade of yellow or red. It is always opaque.

Its fracture is usually even, sometimes a little conchoidal, or uneven, or nearly earthy; it is dull, or glimmering from foreign intermixture. Its streak has a little lustre.

Its hardness is moderate. It is easily broken, and may be cut by a knife; it is rather soft to the touch. It frequently moves the magnetic needle; and its spec. grav. varies from 2.53 to 2.89.—Wacke is never crystallized; it occurs in amorphous masses, sometimes compact, and sometimes vesicular.

By the blowpipe it melts into an opaque, porous mass. It passes into basalt, between which and clay it appears to be intermediate. It is more easily decomposed than basalt.

(Distinctive characters.) It does not, like common clay, adhere to the tongue, nor form a paste with water.—Its softness to the touch and easy fusibility distinguish it from indurated clay.—It does not, like marl, effervesce with acids.—Careful attention is sometimes necessary to distinguish it from secondary greenstone, partially decomposed.

(Geological situation.) Wacke belongs to secondary rocks. It is sometimes in beds, which are associated with basalt. Very frequently it occurs in veins, which almost always traverse metallic veins, but seldom contain any metallic substances; hence the Wacke is of more recent formation than the veins, which it traverses. Its veins are sometimes found in mica slate and argillite.

Wacke embraces several minerals, which seem to have been enveloped by it at the time of its formation. Among these are basaltic hornblende, native bismuth, magnetic iron, and mica. The mica is disseminated in black, shining laminæ, and is somewhat characteristic of wacke in certain doubtful cases. Sometimes it contains veins of calcareous spar and fragments of primitive rocks; but neither augite nor olivine have been observed.

When the cavities in Wacke are in part or entirely filled with calcareous spar, green earth, zeolite, chalcedony, agates, &c. it constitutes one variety of amygdaloid.

It sometimes contains fossil bones and petrified wood; indeed whole trees have been found in a vein of Wacke at Joachimsthal in Bohemia.

* Wakke. WERNER. La Wakke. BROCHANT. Wacken. KIRWAN. Vake. BRONGNIART.

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This mineral is probably found more abundantly in Germany, than in any other country.

SPECIES 36. DIPYRE.* HAUY.

This mineral appears in minute prisms, either single, or feebly adhering to each other in fascicular groups. The insulated crystals appear to be eight-sided prisms, having natural joints parallel to the sides of a rectangular, quadrilateral prism, and to the diagonals of its bases.

The Dipyre is translucid, grayish or reddish white, and sufficiently hard to scratch glass. Its longitudinal fracture is foliated; its cross fracture conchoidal; its lustre vitreous and shining; and its spec. grav. about 2.63.

Before the blowpipe it melts with ebullition, and its powder on hot coals phosphoresces with a feeble light. It contains silex 60, alumine 24, lime 10, water 2;=96. (VAUQUELIN.)

Its fusibility distinguishes it from the pycnite; and its phosphorescence from the sommite.

It is found near the river Mauleon, in the Pyrennees, in steatite, sometimes mixed with sulphuret of iron.

SPECIES 37. SCAPOLITE.† JAMESON.

This rare mineral, sometimes massive, usually appears in long prismatic crystals, having four or eight sides. The latter form, which may be called a four-sided prism, truncated on its lateral edges, is sometimes terminated by four-sided summits, whose faces are inclined to the alternate lateral planes, on which they stand, at angles of 120°. The primitive form is a four-sided prism, which is very easily divisible, parallel to the diagonals of its bases, which are squares.—The crystals, usually long, sometimes cylindrical or acicular, are often in groups, composed of parallel, diverging, or intermingled prisms.

The longitudinal fracture is foliated; indeed some crystals might be mistaken for a collection of little plates of mica, arranged in the direction of the axis. The cross fracture is often uneven.

The Scapolite presents a considerable diversity of color, lustre, and hardness, which appears to arise in part from a partial decomposition, perhaps the loss of the water of crystallization. Sometimes

* Dipyre. BROCHANT. BRONGNIART. Schmelzstein. WERNER. JAMESON. Its name is derived from the Greek Δνο, two, and πνζ, fire, indicating the double effect of fire to produce fusion and phosphorescence in this mineral.

† Skapolith. WERNER. Scapolithe. BROCHANT. Paranthine. HAUY. BRONGNIART.

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its color is gray, grayish, yellowish, or greenish white, or silver white; and it is then either simply translucent, or has a pearly or almost metallic lustre, like that of mica. Sometimes it is slightly pearly, or has a dull white aspect, as if it had effloresced; and sometimes it is opaque, and of a dull brick red.

When unchanged, it scratches glass; in other cases it scratches carbonate of lime, or is friable. Its spec. grav. varies from 3.68 to 3.71.

Before the blowpipe it intumesces, and melts into a shining, white enamel. It contains, according to Laugier, silex 45.0, alumine 33.0, lime 17.6, soda and potash 2.0, iron and manganese 1.0;=98.6.

An attention to its crystalline form and structure, its specific gravity, and its inability to become electric by heat, or to form a jelly with acids, will, in general, be sufficient to distinguish it from certain varieties of zeolite, stilbite, prehnite, or analcime, which it more or less resembles.

It strongly resembles the Wernerite both in the form of its crystals, and the measure of their angles. Indeed these two species are so similar in composition, that they ought probably to be united.

(Locality.) The Scapolite has been found only iu an iron mine, at Arendal in Norway, accompanied with mica, quartz, epidote, feldspar, carbonate of lime, Wernerite, &c.

SPECIES 38. WERNERITE.* HAUY.

The Wernerite, a rare mineral, occurs in eight-sided prisms (Pl. IV. fig. 9.), terminated by four-sided summits, whose faces form with the alternate lateral planes, on which they stand, an angle of about 121°. Or it may be called a four-sided prism, truncated on its lateral edges. The primitive form appears to be a quadrangular prism with square bases.—It also occurs in irregular grains.

The Wernerite strikes fire with steel, but is scratched by feldspar. Its fracture is both imperfectly foliated and uneven, with a moderate lustre, a little pearly or resinous. Its spec. grav. is 3.60.

It is usually more or less translucent; and its color is greenish gray, or olive green, and sometimes white. The surface of the crystals sometimes has the lustre and aspect of an enamel.

Before the blowpipe it froths, and melts into an opaque, white enamel. A mean of two analyses by John gives silex 45.5, alumine 33.5, lime 13.22, oxide of iron 5.75, oxide of manganese 1.47;=99.44.

Its mode of fusion by the blowpipe, and its imperfectly foliated

* Wernerite. JAMESON. BROCHANT BRONGNIART. Arktizit. WERNER.

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structure may serve to distinguish it from most minerals, which it resembles.

(Localities.) At Arendal, Norway, it exists in an aggregate of red or grayish feldspar and quartz. Sometimes its crystals are contained in laminated masses of scapolite.—It has also been found in Sweden and Switzerland.

SPECIES 39. AXINITE.* HAUY. BRONG.

This mineral is sometimes in tabular masses, but most commonly in crystals, which are easily recognised. The general form of these crystals, certain small faces being neglected, is a very oblique rhomb, or rather four-sided prism, so flattened, that some of its edges become thin and sharp, like the edge of an axe.† The primitive form is a four-sided prism (Pl. IV, fig. 10.), whose bases are parallelograms with angles of 101° 30′ and 78° 30′. The integrant particles are oblique triangular prisms. M. Haüy has described five secondary forms, of which we mention two; viz.

The very oblique four-sided prism above mentioned, truncated on two opposite lateral edges;—also the preceding form with two additional faces (Pl. IV, fig 11.), being truncations on two opposite terminal edges of the prism, and forming with its bases an angle of 153° 26′. Other small faces are sometimes found on the prism.—The crystals have a strong, vitreous external lustre, and the faces not produced by truncation are usually striated.

The crystals are sometimes tabular, and are often so arranged, as to form little cells.

Its hardness is intermediate between that of feldspar and quartz, by the latter of which it may be scratched. It gives fire with steel, yielding an odor like that produced by flint. Its fracture is imperfectly conchoidal, uneven, or splintery, somewhat shining and vitreous. Its spec. grav. varies from 3.21 to 3.30.

Its colors are brown, violet, or brownish violet, gray or whitish, and sometimes green. It is transparent, or translucent, sometimes at the edges only, or is quite opaque.—The green crystals appear to be colored by chlorite, which sometimes renders them opaque. They are generally free from striæ, and better defined, than the violet crystals. Sometimes one part of a crystal is violet and nearly transparent, while the other is green and nearly opaque. Some crystals are merely coated by chlorite.—Most of the violet crystals are electric by heat.

* Axinit. WERNER. Thumerstone. KIRWAN. JAMESON. La Pierre de Thum. BROCHANT.

† Hence its name.

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(Chemical characters.) Before the blowpipe it easily melts, with ebullition, into a dark gray enamel, which with borax becomes olive green. It contains, according to Vauquelin, silex 44, alumine 18, lime 19, iron 14, manganese 4;=99.

(Geological sit. and Localities.) Axinite is a rare mineral. It is found in primitive rocks, more particularly in fissures or veins, which traverse them. In Dauphiny, it is associated with quartz, feldspar, epidote, and asbestus.—In the Pyrennees, with quartz and limestone.—In Norway, near Arendal, with feldspar and epidote; and near Konsberg it exists in limestone with mica, quartz, &c.—It occurs in lamellar masses near Thum, in Saxony, whence the name Thumerstone.

SPECIES 40. GARNET.*

This very common mineral usually occurs in crystals more or less regular. The general aspect of its crystals, even when perfect, is somewhat spherical, in consequence of the great number of their sides, which is never less than twelve, frequently twenty four, sometimes thirty six, sixty, or even eighty four. It presents five or six varieties of form, including the primitive dodecaedron. This dodecaedron is composed of twenty four triangular pyramids, whose vertices unite at the centre, and whose bases are one half of each rhombic face, when divided by the shorter diagonal. These pyramids, whose faces are all equal and isosceles triangles, show the form of the integrant particles.—Its principal forms are the following.

A dodecaedron, its primitive form, with rhombic faces (Pl. IV, fig. 12.), whose plane angles are 109° 28′ and 70° 32′; the mutual inclination of any two contiguous faces is 120°.—Or it may be viewed as a six-sided prism, terminated by three faces, which stand, at each extremity, on alternate, but different lateral edges.—The crystal is sometimes so elongated, that six of its sides become oblique-angled parallelograms.

The preceding dodecaedron is sometimes truncated on all its edges by long, hexaedral faces (Pl. IV, fig. 13.), making with the contiguous faces, which remain rhombs, angles of 150°. This crystal has thirty six faces, of which twelve are rhombs, and twenty four are elongated hexaedrons.—When all the edges between the rhombs and hexaedrons of the preceding form are truncated, the crystal has eighty four faces.

Another form presents twenty four equal and similar, trapezoidal faces (Pl. IV, fig. 14.), which are usually striated in the direction of the longer diagonals. Or it may be described as a double eight-sided

* Grenat. HAUY. BRONGNIART.

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pyramid, whose summits are formed by four planes, which, at each extremity, stand on alternate, but different lateral edges.—Sometimes twelve of its solid angles are truncated.*

Certain faces of these crystals are sometimes extended, at the expense of others, but still preserve their proper angles of incidence; sometimes also the faces are a little convex. Their average size is that of a pea, but they are sometimes smaller than a pin's head, and sometimes five or six inches in diameter.

Garnet sometimes occurs in fragments or grains, and in amorphous masses, either lamellar or granular.

Its several varieties are not equally hard; they however strike fire with steel and scratch quartz. Its fracture is uneven, more or less conchoidal, and sometimes foliated; its lustre, though variable in degree, is usually vitreous, sometimes resinous. Its spec. grav. extends from 3.55 to 4.23. It is sometimes magnetic.—Its prevailing color is red of various shades; but it is often brown, and sometimes green, yellow, or black. It is usually translucent, sometimes transparent, and often opaque.

(Chemical characters.) It is easily melted by the blowpipe into a dull, black enamel, which is often magnetic. The essential ingredients of the Garnet are probably silex, alumine, and lime, although it can hardly be said, that its true composition is known, notwithstanding the numerous analyses, which have been made. Klaproth and Vauquelin have found from 52 to 35 of silex, from 28 to 6 of alumine, from 33 to 2 of lime, and from 41 to 7 of oxide of iron. In one analysis no lime was found, and in a few instances 8 or 10 per cent. of magnesia appeared.

Some of these results, at least in their proportions, have very probably been modified by the gangue, whence the Garnet was taken. Thus the proportion of lime or alumine may be increased by a calcareous or argillaceous gangue; and the magnesia, at least in garnets taken from serpentine, &c. may be accidental.—After all, it is very possible, that the garnet now includes some minerals, which do not belong to the species.

(Distinctive characters.) The Garnet sometimes resembles the hyacinth, the leucite, and the idocrase; but the two first are infusible, and the last melts into a shining glass. The uniform incidence of 120° of all the contiguous faces of the dodecaedral variety will also distinguish it from the hyacinth, and several minerals, which approach it in form.—The aplome in rhombic dodecaedrons is striated parallel to the shorter diagonal.

* The prismatic crystals, described by some writers, are probably some of its other forms elongated.

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Var. 1. PRECIOUS GARNET.* JAMESON. This variety is most commonly in crystals, sometimes in rounded grains. Its color is crimson red, often with a tinge of blue or violet, or sometimes nearly cherry red. Its fracture is sometimes perfectly conchoidal with a strong lustre. Its spec. gravity is almost always above 4.00. Though sometimes translucent, it is often transparent; but frequently impure at the centre.

In one specimen Klaproth found silex 35.75, alumine 27.25, oxide of iron 36.0, oxide of manganese 0.25;=99.25. Another from Bohemia yielded Vauquelin silex 36, alumine 22, lime 3, oxide of iron 41;=102. In one specimen Klaproth found magnesia.

This variety occurs in primitive or even secondary rocks, and sometimes in alluvial earths. Fine specimens are found in India and Bohemia; but it occurs in most countries.

The term oriental, as applied to this variety, indicates not the locality, but merely a great degree of perfection. It is brought from Syrian in Pegu, and hence called Syrian Garnet.

2. PYROPE.† JAMESON. BROCHANT. It occurs in small masses or grains, often rounded, but never in crystals. Its color is a poppy or blood red, frequently with a tinge of orange, even in the dark blood red, when presented to the light. It is usually transparent with a splendent, vitreous, conchoidal fracture.

It contains, according to Klaproth, silex 40.0, alumine 28.5, magnesia 10.0, lime 3.5, oxide of iron 16.5, oxide of manganese 0.25;=98.75.

In Bohemia, it occurs in alluvial earths, and at Ely in Scotland in the sand on the sea shore. In Saxony, it is imbedded in serpentine and wacke.

3. COMMON GARNET.‡ KIRWAN. JAMESON. It is sometimes massive, having a lamellar or granular structure, and very frequently crystallized. Considerable masses are sometimes formed by the aggregation of imperfect crystals.—Its fracture is often uneven, sometimes foliated, but never perhaps perfectly conchoidal; its lustre is usually glistening, and less vitreous, than that of the precious Garnet. It is also less hard; and is sometimes extremely brittle.

It is usually more or less translucent, sometimes at the edges only, or is even opaque. Its colors or their shades are numerous;

* Edler Granat. WERNER. Grenat noble. BRONGNIART. BROCHANT. Grenat vermeil, &c. HAUY. Oriental Garnet. KIRWAN.

† Pyrop. WERNER. Grenat Pyrope. BRONGNIART. Grenat granuliforme. HAUY. Bohemian Garnet of many.

‡ Gemeiner Granat. WERNER. Grenat common. BROCHANT. BRONGNIART. Grenat brun, rougeâtre, &c. HAUY.

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among which are brownish, blackish, or yellowish red, &c. leek green, olive green, &c. brown, reddish or yellowish brown, orange yellow, topaz or pale yellow, whitish, greenish or brownish black, &c. Its spec. grav. is usually below 4.00.

It melts a little easier than the preceding varieties. From a greenish yellow specimen Klaproth obtained silex 44.0, alumine 8.5, lime 33.5, oxide of iron 12.0, and a little oxide of manganese. From a red garnet Vauquelin obtained silex 52.0, alumine 20.0, lime 7.7, oxide of iron 17.0;=96.7.

This variety occurs abundantly and extensively. It is found in all classes of rocks, but more particularly in the primitive.

COLOPHONITE.* KARSTEN. It is distinguished by the glossy, resinous aspect of its fracture. It occurs in small amorphous, granular masses, or in grains, or even in crystals. Its colors are usually orange yellow, reddish, yellowish brown, or deep brown.

A specimen, analyzed by Simon, yielded silex 35.0, alumine 15.0, lime 29.0, magnesia 6.5, oxide of iron 7.5, oxide of manganese 4.75, oxide of titanium 0.5, water 1.0;=99.25.

It has been found in Norway, the Siennese territory, &c.

TOPAZOLITE. BONVOISON. We mention this subvariety of Garnet, which has been found in Piedmont, in pale topaz yellow, or nearly olive green dodecaedrons, on account of its analysis, which offers a new earth in the Garnet. It contains silex 37, alumine 2, lime 29, glucine 4, iron 25, manganese 2;=99. (Journal de Physique, Janv. 1807.)†

4. MELANITE.‡ JAMESON. This Garnet is opaque, and velvet black, sometimes nearly grayish black. It is always in crystals, which are dodecaedrons, sometimes with truncated edges, or belong to the trapezoidal form. Its fracture is somewhat conchoidal or even foliated; its lustre, especially the external, is often strong.

It contains silex 35.5, alumine 6.0, lime 32.5, oxide of iron 25.25, oxide of manganese 0.4;=99.65. (KLAPROTH.)

(Localities.) At Frascati, near Vesuvius, it occurs in a rock, by some supposed to be volcanic, and is accompanied by feldspar, hornblende, and idocrase.—Near Mount Somma, and perhaps in the Py-

* Grenat resinite. HAUY.

† The Succinite of Bonvoisin, found also in Piedmont, in serpentine, occurs in globular masses about the size of a pea, of an amber yellow, almost transparent, not sufficiently hard to scratch glass, and fusible into a black glass. It is by some referred to the Garnet, by others to the idocrase.

‡ Melanit. WERNER. Le Melanite. BROCHANT. Grenat noir. HAUY. Grenat Melanite. BRONGNIART. Black garnet of some. Its name is derived from the Greek, Мελας, black.

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rennees, it exists in calcareous rocks; and in Bohemia in basalt.—In the U. States, in Pennsylcania, at Germantown, 6 miles from Philadelphia, in gneiss; its crystals are polyedrons with twenty four trapezoidal faces, varying from the size of a pin's head to one inch in diameter; they are opaque, and their color is a shining velvet black; spec. grav. 3.616. (WISTER.)

SUBSPECIES 1. MANGANESIAN GARNET.*

This mineral is sometimes massive, and sometimes in crystals with twenty four trapezoidal faces, a little translucent at the edges. Its color is a deep hyacinth or brownish red.

It is fusible by the blowpipe; and, when melted with borax and a little nitre, the globule is violet. It contains silex 35, alumine 14, oxide of manganese 35, oxide of iron 14. (KLAPROTH.)

Near Aschaffenberg, in Franconia, it occurs in granite.

In the U. States. In Maine, at Jones' Eddy, near Bath, it is found massive. Its color is brownish red, its fracture uneven, sometimes conchoidal, and its lustre a little resinous. Its general structure is slaty, or rather the mass seems to be composed of smaller, tabular masses, which, by exposure to the air, become disposed to separate.—It has been analyzed by Vauquelin, and found to contain a large quantity of manganese.—It sometimes embraces magnetic iron, &c.

(Geological Remarks.) The Garnet occurs almost always in crystals, grains, or fragments; and indeed it never forms extensive, continuous masses. It is however so abundant in certain compound rocks, that it may almost be said to form their base.

The Garnet, especially the common variety, is abundantly disseminated in primitive rocks, more particularly in mica-slate, granite, gneiss, and greenstone; and often occurs in veins or fissures, which traverse these rocks. It is sometimes imbedded in certain simple minerals, as serpentine, talc, hornblende, lithomarge, &c. It is also associated with ores of iron, lead, &c. in metallic veins or beds. The amorphous variety, mixed with quartz, &c. sometimes constitutes large beds.

The Garnet occurs also in transition or secondary rocks, as in greenstone, compact limestone, sandstone, &c. On the peak of Eredlitz, in the Pyrennees, is a brownish limestone, traversed by white veins, and containing black, white, and red garnets; the black garnets are in the brownish part of the stone, and the white garnets in the white veins. (RAMOND in Brongniart.)—It has been remarked, that garnets in secondary rocks generally separate from their gangue with more ease, than those imbedded in primitive rocks; a circum-

* Grenat manganésié. BRONGNIART.

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stance, which indicates, that these garnets existed before they were enveloped by the substance of the secondary rocks.

The garnet is found also in alluvial earths. In Bohemia, near Meronitz, &c. the precious Garnet and Pyrope are found in an alluvial earth, composed chiefly of fragments of serpentine and basalt, united by an argillaceous or marly cement; the same earth contains hyacinth, sapphire, emerald, &c. and even fossil shells. The garnets are brought to view by repeatedly washing this earth.

(Localities.) It is unnecessary to add any further remarks in regard to foreign localities.—This mineral is very common in the United States, in the granite of which it seems to be more abundant, than in that of many other countries. In the interior of North Carolina, Garnets have been found as large, as a child's head. (MACLURE.)— In New York, near Fishkill, they are rose colored.—In Connecticut, at Haddam they are sometimes four inches in diameter, have a laminated texture, and are extremely brittle. (SILLIMAN.)—In Vermont, the precious Garnet is found in Bethel and Royalton, in small but remarkably perfect crystals, imbedded in a steatitic rock. (HALL.)— In New Hampshire, near Dartmouth College, the precious Garnet exists in dodecaedrons in greenstone. (HALL.)—In Massachusetts, in Newbury, amorphous garnet is associated with tremolite, epidote, &c. —In Maine, at Brunswick, they are sometimes orange red;—at Topsham are found both the precious and common garnet; the crystals are sometimes less than the head of a pin, and sometimes several inches in diameter; they vary in color from an opaque reddish brown to a transparent lively red. The writer has a Garnet, at the centre of which was found a crystal of beryl.

(Uses.) The precious Garnet and the Pyrope are sometimes employed in jewelry; but their color is so intense, that it is sometimes necessary to excavate them on one side. It is very remarkable, that transparent Garnets should be capable of containing 30 or 40 per cent. of iron, and even of moving the needle.—The common variety may be advantageously employed as a flux for iron ores. The powder of the Garnet may also be used in polishing hard bodies.

The carbuncle of the ancients was probably a Garnet; according to Pliny, it was sometimes formed into vessels, capable of containing nearly a pint.

SPECIES 41. APLOME.* HAUY.

This very rare mineral has been observed only in dodecaedrons with rhombic faces, marked by striæ, parallel to the shorter diagonals. This dodecaedron is supposed to be derived from a cube, by

* Aplome. BROCHANT. BRONGNIART.

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one of the most simple* laws of decrement, viz. that of a single range of particles, parallel to all the edges of a cube.

The Aplome gives fire with steel, and feebly scratches quartz. Its spec. grav. is 3.44. Its fracture in some parts is uneven and nearly dull, while in others it is shining and slightly conchoidal. Its color is usually a deep brown, sometimes yellowish green. It is usually opaque, but the small crystals often transmit an orange colored light.

It is fusible by the blowpipe into a blackish glass. It is composed of silex 40.0, alumine 20.0, lime 14.5, oxide of iron 14.5, oxide of manganese 2.0, ferruginous silex 2.0;=93. (LAUGIER.)

It differs from the garnet in the direction of its striæ, and its inferior spec. gravity.

It has been found in Siberia and Saxony.

SPECIES 42. EPIDOTE.† HAUY. BRONGNIART.

This substance, though recently permitted to form a distinct species, is by no means rare, and exhibits a considerable diversity of external aspect. When in crystals, it is sufficiently well characterized; but some of its amorphous varieties are not easily recognised, especially when they enter into the composition of aggregates.

It is frequently in crystals, of which the primitive form is a right prism, whose bases are parallelograms with angles of 114° 37′ and 65° 23′; the sides of the base and the height of the prism, are nearly as 9, 8, and 5. Its integrant particles have the same form.

The crystals of Epidote occur in prisms, which have usually six or eight sides, and sometimes ten or twelve; but, in almost all cases, the four sides, which belong to the primitive form, are larger, than the others. These prisms are often well defined and variously terminated; they frequently have longitudinal striæ, and are sometimes long and slender.

Of the ten secondary forms, described by Haüy, we select a few.

A six-sided prism (Pl. IV, fig. 15.), terminated at each extremity by two faces, which stand on the two narrowest sides, and form with each other an angle of 110° 06′, and with the sides, on which they stand, an angle of 124° 57′.

Also a six-sided prism (Pl. IV, fig. 16.), each summit having seven faces, of which one is perpendicular to the axis.

Also another six-sided prism (Pl. IV, fig. 17.); each summit presents eleven faces, of which one is at right angles to the axis.

Two of the lateral planes are often so narrow, that the prism ap-

* Hence its name from the Greek, Απλοος, simple.

† Pistazit. WERNER. Pistazite. JAMESON. (See Introd. art. 203.)

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pears to have only four sides. Indeed these crystals are sometimes described as oblique four-sided prisms, truncated on their lateral edges, and bevelled at their extremities, or otherwise terminated.—Sometimes the crystals are compressed, cylindrical, or acicular, being often collected into groups, in which they diverge, radiate, &c. and the fracture of these groups is often fibrous.

Epidote, more imperfectly crystallized, appears in granular masses, to which, however, distinct crystals are often attached.—It also occurs in grains, forming a kind of sand;—and sometimes in amorphous, compact masses.

It scratches glass, and gives fire with steel; and has a spec. grav. of about 3.45. Its fracture, parallel to the sides of the primitive form, is foliated; its cross fracture uneven; and its lustre usually vitreous and shining.

Its color is commonly some shade of green, varying from yellowish green to blackish or bottle green; also gray, yellowish gray, yellow, greenish yellow, and brown, or even brownish black. It is sometimes opaque, usually translucent, and many crystals are transparent.

(Chemical characters.) Before the blowpipe it melts into a dark brown or blackish scoria; and this property, according to Saussure, is very characteristic. Of the common variety a specimen from near Oisans yielded Descotils silex 37.0, alumine 27.0, lime 14.0, oxide of iron 17.0 oxide of manganese 1.5;=96.5. In another from Arendal Vauquelin found silex 37.0, alumine 21.0, lime 15.0, oxide of iron 24.0, oxide of manganese 1.5, water 1.5.

(Distinctive characters.) The Epidote often much resembles the actynolite; but the latter melts into a grayish enamel, and is divisible into rhomboidal prisms, whose angles are 124½° and 55½°.— Its fusibility into a scoria distinguishes it from certain varieties of greenish asbestus, which melts into an enamel, and yields a soft powder, whereas that of Epidote feels dry.—It often strongly resembles hornblende; but the latter is less hard, its fracture is usually less vitreous, and it melts into a black glass.—Epidote is easily distinguished from the beryl and schorl.

We subjoin a notice of two varieties, which have received distinct names.

Var. 1. ZOISITE.* JAMESON. It usually occurs in striated, rhomboidal prisms, much compressed, and sometimes rounded. These crystals are commonly incomplete at their extremities, and often aggregated. Its colors are gray, brown, or grayish yellow; and its

* Zoisit. WERNER. From Baron Von Zois, its discoverer.

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fracture has somewhat of a pearly lustre. It passes into the common variety.

A specimen from the Alps yielded Klaproth silex 45, alumine 29, lime 21, oxide of iron 3;=98.

It is found in primitive rocks, accompanied by quartz, mica, cyanite, &c. in Carinthia, Tyrol, &c.

2. SKORZA.* BROCHANT. It occurs in grains of various sizes, sometimes very fine, of a yellowish green color, somewhat vitreous in their appearance, and sufficiently hard to scratch glass. Its fusibility into a blackish scoria and its composition show, that it belongs to Epidote; indeed it appears to be nothing more, than a granular Epidote disintegrated.

Klaproth obtained from it silex 43.0, alumine 21.0, lime 14.0, oxide of iron 16.5, oxide of manganese 0.25;=94.75.

(Localities.) This variety has received its name from the inhabitants of Transylvania, where it is found near Muska, on the banks of the river Arangos.—In the U. States, in Maine, at Brunswick, it occurs on the banks of the Androscoggin between strata of gneiss or of an aggregate of quartz, feldspar, and hornblende.

SUBSPECIES 1. MANGANESIAN EPIDOTE.†

It occurs in acicular, prismatic crystals, foliated in the direction of the axis, and closely applied to each other in groups. It is opaque, and has a violet color.

It contains at least 12 per cent. of the oxide of manganese.—It has been found in Piedmont, in gneiss, accompanied with the oxide of manganese, quartz, asbestus, &c.

(Geolog. sit. of the species.) Epidote is most frequently found in primitive rocks, into the composition of which it sometimes enters, even in very considerable proportions. Its crystals are usually found in the fissures or other cavities of these rocks, or of the veins, which traverse them; and are sometimes disseminated in the minerals, which fill these veins, such as quartz and carbonate of lime. Indeed granular or compact Epidote often constitutes the whole vein, which varies from many inches to less than one tenth of an inch in width.—Epidote is often associated with quartz, garnets, feldspar, hornblende, actynolite, axinite, schorl, asbestus, chlorite, magnetic oxide of iron, &c.

(Localities.) In France, near Oisans, it occurs with amianthus, axinite, crystallized feldspar, &c.—In Norway, near Arendal, with magnetic iron, quartz, garnets, phosphate of lime, &c. Its crystals

* Epidote Skorza. BRONGNIART. Epidote arenacé. HAUY.

† Epidote manganesifère. HAUY. Epidote violet. BRONGNIART.

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are sometimes very large and perfect, being several inches in length with a proportional thickness.—In England, at the Malvern Hills, in Worcestershire, is a rock, composed of nearly equal parts of Epidote and hornblende, with a little mica, and traversed by slender veins of compact Epidote in various directions. (HORNER.)

In the United States. In Maryland, at Jones' Falls, near Baltimore, in fine crystals, imbedded in a vein of crystallized feldspar and chlorite. (GILMOR.)—In Pennsylvania, near Frankford, 5 miles from Philadelphia;—also in Montgomery, Chester, York, and Delaware Counties.—In New Jersey, at Trenton, in green six-sided prisms.—In New York, near Hudson.—In Connectieut, at the Milford Hills, near Newhaven, in primitive greenstone; the Epidote is usually in veins or amorphous masses; but sometimes in radiated crystals in a vein of calcareous spar, traversing greenstone slate. (SILLIMAN.)—In Massachusetts, near Boston, at Brighton, Dedham, Lynn, &c. in veins, traversing syenite and greenstone, and often entering into their composition; it is usually compact, but sometimes crystallized in cavities; the veins vary in width from that of a sheet of paper to three inches or more (GODON.);—also at Newbury in large crystals in the fissures of a rock, whose base is an amorphous garnet.—In New Hampshire, at Franconia, in the iron mine, in light yellow, acicular crystals, interwoven confusedly (GIBBS.);—also at Portsmouth in acicular crystals, radiated in groups in a porphyritic hornblende. (MACLURE.)—In Maine, at Topsham, Brunswick, &c. It is sometimes in crystals, but usually granular or compact, in veins traversing granite, gneiss, greenstone, and other primitive aggregates. Veins of granular Epidote, more than a foot in width, and containing quartz and schorl intermingled, sometimes traverse granite.

SPECIES 43. CINNAMON STONE.* JAMESON.

This very rare mineral has been subjected to but few observations. In some respects it resembles the garnet, and in composition approaches the idocrase.

It is found in grains or fragments, usually of a yellowish brown, or brownish orange color, with a rough surface. It scratches quartz with some difficulty. Its fracture is imperfectly conchoidal with small cavities, and shining. It is transparent, or only translucent. Its spec. grav. is 3.60.

Before the blowpipe it melts into a brownish black enamel. It contains silex 38.8, lime 31.25, alumine 21.2, oxide of iron 6.5;=97.75. (KLAPROTH.)

It has been brought from Ceylon, where it is found in sand.

* Kannelstein. WERNER. HAUY.

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SPECIES 44. ALLOCHROITE.* HAUY.

This mineral resembles certain varieties of the garnet in some of its physical characters, but more particularly in composition.

It occurs in amorphous masses with a slaty structure. Its fracture is uneven or imperfectly conchoidal, and glistening or dull. It is difficultly broken, gives sparks with steel, and is not easily scratched by quartz. It is opaque, or translucent at the edges; and its colors are yellowish or brownish gray, pale yellow, or reddish yellow. Its spec. grav. varies from 3.50 to 3.73.

It is fusible by the blowpipe, according to Vauquelin, into an opaque, smooth, black enamel. With phosphate of soda and ammonia an enamel is formed, which, by cooling, exhibits several changes of color, passing through reddish yellow and green to yellowish white. It contains silex 37.0, lime 30.0, alumine 5.0, oxide of iron 18.5, oxide of manganese 6.25;=96.75. (ROSE.) The analysis of Vauquelin closely resembles this.

It was found by Dandrada in Norway, near Drammen, accompanied by carbonate of lime, magnetic iron, and brown garnets; the garnets are sometimes intimately united with the Allochroite.

SPECIES 45. IDOCRASE.† HAUY. BRONGNIART.

This mineral is sometimes massive, and very often in prismatic crystals, which are usually short, with highly polished and strongly shining surfaces. The primitive form, of which Haüy has described eight modifications, is a four-sided prism with square bases, and one side of the base is to the height nearly as 13 to 14; hence it differs but little from a cube, and is divisible into triangular prisms for the integrant particles.

It has recently been observed under its primitive form.—Sometimes this form is terminated by four-sided pyramids, whose faces correspond to the sides of the prism.—Sometimes the primitive form is converted into an eight-sided prism (Pl. IV, fig. 18.), by truncations on its lateral edges, and is terminated by four-sided summits, whose vertices are truncated by planes, parallel to the bases of the prism; the oblique faces of the summits are inclined to the sides of the prism, on which they stand, in an angle of 127° 06′, and the truncations on the lateral edges form with the contiguous sides an angle of 135°.—Sometimes its crystals appear to be short, rectangular

* Allochroïte. BROCHANT. BRONGNIART.

† Vesuvian. WERNER. Vesuviane. JAMESON. La Vesuvienne. BROCHANT. The term Idocrase is derived from the Greek Ιδεα, form, and Κρασις, mixture, indicating that its forms are, in some degree, a mixture of the forms of certain other minerals.

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prisms, or nearly cubes, truncated on all the edges, both terminal and lateral.—By farther truncations the prism acquires sixteen sides; and one secondary form, if complete, would present ninety faces. The lateral faces are often feebly striated in the direction of their length; and the crystals are sometimes tabular.

Idocrase is somewhat harder than quartz. Its fracture is uneven or a little conchoidal, and more or less shining and resinous.—The massive varieties have sometimes a structure both granular and foliated.

Its colors are green, varying from a pale yellowish or light olive green to blackish green; also brown, yellowish or reddish brown, reddish yellow, or hyacinth red. It is often translucent, sometimes transparent, and sometimes nearly or quite opaque. It possesses double refraction, and varies in spec. grav. from 3.08 to 3.42.

(Chemical characters.) By the blowpipe it very easily melts into a yellowish translucent glass, which afterwards becomes black. (BRONGNIART.) From the Idocrase of Vesuvius Klaproth obtained silex 35.5, lime 33.0, alumine 22.25, oxide of iron 7.5, oxide of manganese 0.25;=98.5—and in that of Siberia he found silex 42.0, lime 34.0, alumine 16.25, oxide of iron 5.5, with a trace of manganese;= 97.75.

(Distinctive characters.) It sometimes resembles the garnet; but the latter is heavier, its faces are in general less highly polished, it is less easily fusible, and does not yield a translucent glass.—The Idocrase and meionite are sometimes in octaedral prisms, whose lateral faces have the same incidence; but the faces of the tetraedral summits of the Idocrase are inclined to each other at 129° 30′, and those of the meionite at about 136°; and further, the meionite melts with effervescence into a spongy glass.—The chrysolite, olivine, and zircon are infusible.

(Geological sit. and Localities.) It is found abundantly in the vicinity of Vesuvius in the cavities of a rock, composed chiefly of quartz, feldspar, mica, talc, and carbonate of lime; and is accompanied by garnet, hornblende, meionite, sommite, zeolite, &c.—At Kamschatka, it exists in a greenish white serpentine.—In Piedmont, on the plane of Mussa, in serpentine, which is also traversed by veins of massive Idocrase. (BONVOISIN.) The crystals from Piedmont sometimes present the primitive form.

The Idocrase is sometimes cut and polished for jewelry.

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SPECIES 46. MEIONITE.* HAUY.

The Meionite occurs in grains, or small crystals, whose more common form is an eight-sided prism, or a four-sided prism, truncated on its lateral edges, and terminated by low four-sided pyramids, whose faces make with the lateral planes, on which they stand, angles of 121° 45′, and are inclined to each other at about 136°.—Sometimes the prism has sixteen sides, and some of the edges between the prism and pyramid admit truncations.—-The primitive form is a right prism with square bases, of which one side is to the height of the prism nearly as 9 to 4.

It scratches glass. Its longitudinal fracture is foliated; its cross fracture a little conchoidal; and its lustre shining and vitreous. It is translucent, and sometimes transparent, but traversed by small fissures. It is limpid or grayish white, and sometimes white.

Before the blowpipe it easily melts with a lively ebullition and some noise into a white, spongy glass.

(Distinctive characters.) An attention to the chemical characters, and the measures of the angles or edges about the terminating pyramids will, in general, be sufficient to discover lines of distinction between this species, and the zeolite, idocrase, harmotome, and sommite; especially as the terminating pyramids of the Meionite are lower than those of similar forms in the other minerals.—The Meionite much resembles the Wernerite in the measures of its angles; but the terminating faces of the Wernerite stand on the lateral faces of the primitive form, whereas in the Meionite they correspond to the truncated lateral edges of the primitive form.

The Meionite has been found only at Mount Somma, near Vesuvius; and usually adheres to fragments of carbonate of lime, which are unaltered by fire.

SPECIES 47. BYSSOLITE.† SAUSSURE.

Little is yet known concerning this rare mineral. It occurs in very delicate filaments, which are usually short; and, though somewhat stiff, are still flexible and elastic. They are attached perpendicularly to the surface of other minerals, sometimes resembling a kind of moss. Their color is olive green, or brownish yellow, and their lustre a little silky.

* Meionit. WERNER. Meionite. BROCHANT. JAMESON. BRONGNIART. Its name is derived from the Greek Μειων, less, indicating the lowness of the terminating pyramids, and the consequent shortness of the axis of the primitive form.

† Amianthoïde Byssolite. BRONGNIART. Var. of Amianthoide. HAUY. The name Byssolite appears to be derived from the Greek, Вνσσος, a kind of flax.

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It contains, according to Saussure, silex 34, alumine 43, lime 9, oxide of iron 19.

It has been found in the Alps; and near Oisans, in France, where it is attached to gneiss.

SPECIES 48. PREHNITE.* HAUY.

This substance appears to be always the result of crystallization. It is sometimes massive, and sometimes in crystals, whose forms are often indeterminable in consequence of their aggregation. The primitive form, which it sometimes presents, is a right prism, whose bases are rhombs with angles of about 103° and 77°. This prism, however, as well as all the distinct crystals of Prehnite, have a tabular form, with four, six, or eight sides.

Its fracture is foliated, parallel to the base of the primitive form, and uneven in other directions; its lustre is moderate and somewhat pearly. It scratches glass, though sometimes feebly, and often gives sparks with steel. Its spec. grav. extends from 2.60 to 2.94. It is electric by heat, but both electric poles seem to have the same configuration, contrary to the usual fact.

A peculiar light green color is somewhat characteristic of this mineral. Its color however varies from apple green to greenish white or nearly white; and sometimes it has a tinge of yellow or is yellowish gray. When partially decomposed, it often assumes a dull white. It is more or less translucent, or even transparent.

(Chemical characters.) It intumesces considerably before the blowpipe, and then melts into a porous slag or enamel, sometimes greenish; but the color, at least in some specimens, appears to depend on the degree of heat. A specimen from the Cape of Good Hope yielded Klaproth silex 43.8, alumine 30.33, lime 18.33, oxide of iron 5.66, water 1.16;=99.28.

(Distinctive characters.) It resembles the stilbite; but the latter is less hard, and its lustre is more pearly.—It does not, like zeolite, form a jelly with acids.—Its mode of fusion distinguishes it from feldspar.

Var. 1. CRYSTALLIZED PREHNITE. The crystals of Prehnite are sometimes in rhomboidal or hexagonal tables, insulated and distinct, with smooth shining surfaces. The hexagons may be viewed as rhomboidal tables, truncated on their two acute edges; and the eight-sided table is sometimes described as a four-sided prism, whose extremities are bevelled, and the edges of the bevelments truncated. These tabular crystals are often grouped. Sometimes the groups are composed of rhomboidal or hexagonal plates a little curved, touching each other

* Prehnit. WERNER. Prehnite. JAMESON. BRONGNIART. BROCHANT.

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in the middle only, and diverging somewhat toward their extremities; hence these groups resemble a fan or a sheaf.

2. KOUPHOLITE.* BROCHANT. It occurs in minute, rhomboidal plates, of a greenish or yellowish white, translucid, glistening, and a little pearly.

It has been found in the Pyrennees, adhering to carbonate of lime; or grouped, or scattered upon the sides of cavities in a hornblende rock, and mixed with chlorite and epidote.

3. FIBROUS OR MASSIVE PREHNITE.† This variety embraces those crystalline masses of Prehnite, whose texture is usually fibrous or radiated, and sometimes nearly or quite compact. It is often in small globular and tuberose masses, radiated from the centre; many of these masses are sometimes united.—In other cases the fibres are parallel, or but slightly divergent.

Sometimes the mass is composed of small laminæ promiscuously intermingled. In fine, these masses are sometimes so compact, that a fibrous structure is scarcely discernible, or appears only in certain parts.—Fine crystals are found in the cavities of massive Prehnite.

(Geological sit. and Localities.)This mineral was first brought from the Cape of Good Hope by Colonel Prehn; and hence its name. It is generally of a purer green than that found in Europe, and sometimes forms considerable masses.—In France, crystallized Prehnite occurs at Oisans, in gneiss and primitive greenstone, and is sometimes impregnated with chlorite, which seems to render its crystals more regular.—In Germany, the fibrous Prehnite is found near Oberstein in globular masses in a porphyry or amygdaloid; it accompanies or even contains carbonate of copper and native copper.—Near Edinburgh and Glasgow, it exists in secondary greenstone, and is sometimes in veins with parallel fibres.—It is often associated with zeolite in greenstone.

In the United States. In Connecticut, near Newhaven, it exists in secondary greenstone, which also contains zeolite. The Prehnite occurs in veins or in nodules, with a radiated structure, sometimes with crystals on the surface; at the Pine Rock it forms perpendicular veins, rarely more than one fourth of an inch in thickness;—also near Berlin, &c. (SILLIMAN.)—In Massachusetts, in Brookfield, Watertown, and Charlestown. At the last mentioned place, it occurs in greenstone, and presents rhomboidal or hexagonal tables, or radiated masses, and has the usual colors of Prehnite. (WATERHOUSE.)

* Prehnite Koupholite. BRONGNIART. Prehnite lamelliforme, rhombordale. HAUY. From the Greek Κονφος, light, and Αιθος, a stone.

† Prehnite fibreuse—globuliforme radiée—compacte. HAUY. Prehnite compacte. BRONGNIART.

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SPECIES 49. ÆDELITE. KIRWAN. BRONG.

The only description of this mineral, hitherto published, is that of Mr. Kirwan, who did not himself possess a specimen.

It occurs in tuberose masses, whose fracture is generally fibrous, sometimes splintery, and nearly dull. It gives fire with steel; and its spec. grav. is 2.51. Its color is light gray, sometimes tinged with red; also brown or green with shades of yellow.

Before the blowpipe it intumesces, and melts into a frothy mass. It contains silex 62 to 69, alumine 18 to 20, lime 8 to 16, water 3 to 4. (BERGMAN.)

It has been found only at Adelfors and Messeberg, in Sweden, in the fissures of greenstone or rocks of hornblende.

SPECIES 50. STILBITE.* HAUY. BRONG.

This mineral was once associated with zeolite, from which, however, it differs in several important characters.

Its structure and fracture in one direction, which is parallel to two opposite sides of the primitive form, are perfectly foliated, the foliæ being often slightly curved; in other directions its fracture is uneven. Its lustre, except on the cross fracture, is shining, and almost invariably pearly.

The Stilbite scratches carbonate of lime, but scarcely glass. It is translucent, and sometimes transparent. Its color is usually white, either pure, or shaded with gray, yellow, or red; also brown or orange red. It is not electric by heat; and its spec. grav. is 2.50.

The primitive form of its crystals is a four-sided prism, whose bases are rectangular parallelograms, of which the sides and the height of the prism are as the numbers 3, 5, 2; its integrant particles have the same form.

Of the primitive form, which it sometimes presents, Haüy has described five modifications. One of these is a four-sided prism (Pl. IV, fig. 19.), terminated by four faces. The sides are hexagonal, and the summits are sometimes truncated, as in the figure; when the truncation is near the base, the faces of the summits appear like truncations on the solid angles. Sometimes this prism is so compressed, that it becomes a six-sided table, bevelled on four of its edges.—Another form is an oblique four-sided prism (Pl. IV, fig. 20.), truncated on two opposite, lateral edges. Two edges of this prism contain an angle of 130° 24′, and the solid angles, formed by the same edges with

* Blættriger Zeolith and some varieties of Strahliger Zeolith. WERNER. Foliated Zeolite and some varieties of Radiated Zeolite. JAMESON.
Its name is from the Greek Στιλζο, to shine, alluding to its lustre.

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the base, are truncated. This crystal may be called a six-sided prism, and sometimes all its solid angles are truncated.

These crystals have smooth surfaces with a strong lustre; they are often grouped, sometimes in bundles, resembling a fan, and sometimes in globular masses, radiating from the centre.

The Stilbite also occurs in foliated masses, and sometimes its texture becomes nearly or even quite compact, with a diminished lustre.

(Chemical characters.) On hot coals it whitens and exfoliates. Before the blowpipe it intumesces, and melts into a spongy mass. It contains silex 52.0, alumine 17.5, lime 9.0, water 18.5;=97. (VAUQUELIN.) It does not form a jelly with acids.

(Distinctive characters.) It differs from zeolite in not becoming electric by heat, or forming a jelly with acids, and also in its structure.—It is less hard than Prehnite, and undergoes changes on hot coals, which that mineral does not.

(Geological sit. and Localities.) The Stilbite sometimes occurs in the fissures of primitive rocks. It is also associated with zeolite in amygdaloid, greenstone, and other trap rocks; and sometimes with chabasie.—At Strontian in Scotland, it exists in veins of sulphuret of lead, &c.—At Arendal, in Norway, it is brown and still pearly.— In the Tyrol, it appears in little pearly plates of an orange red, or in globular masses with a dull fracture. In the Faroe islands, in trap rocks, finely crystallized in rectangular prisms, which are sometimes one inch in length and three fourths of an inch thick. (ALLAN.) Mr. A. supposes, that he has also found the Stilbite in large cubes, sometimes with truncated angles, in the same islands.

SPECIES 51. ZEOLITE.*

The Zeolite is sufficiently hard to scratch carbonate of lime, and sometimes the softer kinds of glass in a slight degree. It is electric by heat, one summit of its prisms becoming positive and the other negative; the latter is usually that summit, which was connected with the gangue. Its spec. grav. is about 2.08.

It is usually translucent, sometimes transparent, and exhibits double refraction. Its prevailing color is white, either pure, or with shades of gray, yellow, green, or red; it is also yellow or brownish yellow.

The Zeolite is sometimes in distinct crystals, whose surfaces have a strong lustre, slightly pearly. Their natural joints are parallel to the sides of a quadrangular prism, with square bases, which is the

* Mésotype. HAUY. BRONGNIART. Fasriger Zeolith and some varieties of Strabliger Zeolith, WERNER. Fibrous Zeolite and some varieties of Radiated Zeolite. JAMESON.

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primitive form. This form differs but little from a cube; for any one side of the base is to the height of the prism nearly as 9 to 8. Its integrant particles are triangular prisms.

It sometimes presents the primitive form, of which Haüy has described five modifications. Its more common forms are the following.

A four-sided prism, terminated by four-sided pyramids, whose faces make with the lateral planes, on which they stand, angles of 114° 06′. This prism is sometimes truncated on its lateral edges; and sometimes so compressed, that it becomes a six-sided table, bevelled on its four smaller sides.—Sometimes the faces of the summits correspond to the lateral edges of the prism, and the vertices of the summits are also truncated. Certain faces also are sometimes much elougated at the expense of others.—These crystals, sometimes acicular, are variously grouped, and often so closely applied to each other, that the terminations only appear.

Zeolite is very often in small masses, produced by the aggregation of acicular or even capillary crystals.

These masses are often composed of several fascicular groups of minute crystals; and in each group the crystals or fibres diverge or even radiate from one point, and at the surface frequently appear distinct from each other, or exhibit pyramidal terminations.—Sometimes the mass is reniform or globular, with fibres radiating from the centre.—In fine, the fibres are sometimes so minute and intimately united, that the mass appears compact, and its fracture splintery.

The longitudinal fracture of these masses is almost always fibrous. The fibres, usually divergent, are sometimes extremely minute and delicate, and sometimes so broad, that the fracture appears foliated. Its lustre is glistening and more or less pearly or silky. The cross fracture is uneven or imperfectly conchoidal.

Some Zeolites phosphoresce by friction.

(Chemical characters.) Before the blowpipe it melts with very considerable intumescence or ebullition* into a whitish, spongy enamel, attended by a little phosphorescence. When reduced to powder, and thrown into nitric acid, it is converted into a jelly in the course of a few hours, unless the quantity of acid be too great. According to Vauquelin, it contains silex 50.24, alumine 29.3, lime 9.46, water 10.0;=99. Pelletier obtained silex 50, alumine 20, lime 8, water 22. But the analysis of Smithson Tennant gives a very different composition. In a crystal of Zeolite, furnished him by Haüy, he found silex 49.0, alumine 27.0 soda 17.0, water 9.5;=102.50.† The Zeolite is susceptible of spontaneous decomposition, probably by losing its water.

* Hence its name from the Greek Ζεω, to boil, and Αιθος, a stone.

† If this be correct, the Natrolite is a variety of Zeolite.

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(Distinctive characters.) Its power of forming a jelly with acids, and of becoming electric by heat, will, in general, easily distinguish it from the stilbite, analcime, chabasie, and harmotome.— The Prehnite is harder than the Zeolite, and does not form a jelly with acids.

We subjoin a notice of three varieties.

Var. 1. MEALY ZEOLITE.* JAMESON. It occurs in opaque, dull, friable masses, with an earthy fracture, and a yellowish or reddish white color. It is very light, and not electric by heat.—It appears to be an alteration of the common Zeolite; and sometimes occurs as a crust on crystallized Zeolite.

2. CROCALITE.† This variety is but little known. Its color is brick red, or orange. It is sometimes in reniform or globular masses, with a radiated texture. It is found in amygdaloid, &c.

At Adelfors, in Sweden, has been found a mineral, which Brongniart refers to the Crocalite. Like the mealy Zeolite, it appears in tender, earthy masses of a brick red color. With nitric acid it forms a jelly, which disappears in a few hours. The same amygdaloid at Adelfors seems to contain both Zeolite and stilbite of a reddish color.

3. NEEDLE STONE. JAMESON. This appears scarcely to differ from the common variety, unless in being a little harder. Its crystals are acicular four-sided prisms, terminated by low pyramids. They are often collected into masses, of which the longitudinal fracture is fibrous, and the cross fracture uneven and vitreous. Its color is yellowish white.

This variety has been found in Brittany, and Iceland.

(Geological situation.) Zeolite, which never occurs in large masses, is most frequently found in amygdaloid, basalt, greenstone, and clinkstone porphyry. It sometimes incrusts these rocks, or is disseminated in them, or exists in veins. Its crystals adhere to the sides of fissures or cavities in these rocks, or its globular masses entirely fill these cavities. It is sometimes associated with Prehnite, stilbite, calcareous spar, chalcedony, native copper, &c.

Zeolite also occurs in primitive rocks, as granite, gneiss, and greenstone.

The ease, with which Zeolite is altered by fire, is a strong objection to the volcanic origin of those rocks, in which this mineral is found. Some, indeed, have suggested, that Zeolite may have been formed in volcanic rocks by filtration, during their immersion in water. To this, however, there are strong objections. Others avoid these difficulties by denying the existence of Zeolite in rocks really

* Mehl Zeolith. WERNER. Mesotype alterèe. HAUY.

† Mesotype Crocalite. BRONGNIART.

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volcanic.—It is asserted by Brongniart, that the Zeolites of volcanic countries are never found in recent lavas. Thus, at Etna, Zeolite occurs only in the basalt, which forms the base of the mountain, and has not been observed in the actual products of this volcano.

(Localities.) The Zeolite is found in France, Iceland, the Faroe islands, &c. In the last named islands it occurs in groups of transparent diverging needles from one to two inches long, perfectly well terminated; it sometimes embraces native copper. (ALLAN.)— Near Edinburgh, the Zeolite is sometimes phosphorescent in the dark, even when gently rubbed by the finger.

In the United States. In Maryland, near Baltimore, at Jones' Falls, in a vein, traversing gneiss; this Zeolite is yellowish with a pearly lustre, in small quadrangular prisms, with pyramidal terminations, and is accompanied by chlorite, feldspar, epidote, &c. (GILMOR.) Some of the crystals from this locality appear to exhibit the primitive form of the Zeolite, which by the eye cannot be distinguished from a cube.—In Pennsylvania, on the Schuylkill, 4 miles from Philadelphia, in the fissures of a hornblende rock; it is white with a pearly lustre, in laminæ about one eighth of an inch thick. (WISTER.)—In New Jersey, at Hoboken.—In Connecticut, near Newhaven, in horizontal veins in secondary greenstone, or incrusting the surface of the stone; it is in crystals, or radiated masses, or presents the mealy variety. (SILLIMAN.)

The name Zeolite has been extended to several different species of minerals. Thus the stilbite has been called foliated or pearly Zeolite; the analcime, hard Zeolite; and both analcime and chabasie, cubic Zeolite.

SPECIES 52. LAUMONITE.* HAUY.

This very singular mineral has received its name from that of its discoverer, Gillet Laumont.

In its natural and unchanged state, it exists in laminated masses, composed of prismatic distinct concretions, or in irregular groups of more perfect prismatic crystals. It is, according to Bournon, sufficiently hard to scratch glass. Its fracture is distinctly foliated in two directions, which appear to be parallel to the sides of a rhomboidal prism. Its colors are usually grayish white, or white, which is often tinged with red. It is more or less translucent, or even transparent. Its spec. grav. is 2.23.

Its crystals appear to be four-sided prisms, slightly oblique, sometimes terminated by diedral summits, and sometimes truncated on their lateral edges. Bournon supposes the primitive form to be a

* Lomonit. WERNER. Lomonite. JAMESON. Mesotype Laumonite. BRONGNIART. Zeolithe efflorescente. BROCHANT.

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four-sided prism with rhombic bases. The lateral planes are longitudinally striated.

But, by exposure to air, especially if dry and warm, most of the foregoing characters disappear. The Laumonite, thus exposed, more or less rapidly disintegrates; its laminæ separate, and it falls into irregular, prismatic fragments, whose surfaces are often striated. Indeed, according to Brochant, it is sometimes eventually reduced to a white powder, a little fibrous and glimmering.—With this disintegration other properties change. The mineral becomes opaque, extremely friable, and usually milk white, more or less pearly.

If unchanged specimens are immersed for one or two hours in a strong solution of gum Arabic, they will be defended from the action of the air.

The Laumonite is fusible by the blowpipe with a slight ebullition into a white enamel. It forms a jelly with acids.

(Localities.) This mineral was first observed near the lead mine of Huelgoet in Brittany, attached to the sides of the veins. It has since been observed in the islands of Faroe, and at Paisley in Scotland, &c.—That from Brittany effloresces most rapidly.

In the U. States. In Connecticut, the Laumonite has been discovered by Prof. Silliman in veins in the greenstone around Newhaven. He remarks, that one specimen effloresced in his hands, and completely crumbled down. The specimen, which Prof. S. has been kind enough to send me, has fallen into small, irregular, prismatic fragments, extremely friable; some of them are whitish and pearly, and in others the white is very slightly tinged with red. Most of the fragments, when thin, retain a small degree of translucency.

SPECIES 53. MELILITE.* HAUY.

This rare mineral has been seen only in very minute crystals, perfectly regular and well defined, although not larger, than a grain of millet. Their form is cubic or prismatic; and the cube is sometimes truncated on its edges, or passes into a cuneiform octaedron. Their color is usually honey† yellow, sometimes hyacinth red; but their surface is often coated with a yellow or reddish brown oxide of iron. They are glistening, semitransparent, and sufficiently hard to scratch steel. They are not electric by heat.

Before the blowpipe the Melilite melts without ebullition into a compact, greenish, transparent glass. Its powder in nitric acid forms a transparent jelly; but, if small fragments be thrown in, they merely lose their color, and become less fusible.

* Melilite. BROCHANT. BRONGNIART.

† Hence its name from the Greek, Мελι, honey, and Λιθος, a stone.

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The preceding characters sufficiently distinguish it from the zeolite, analcime, chabasie, and stilbite.

It has been found in the fissures and cavities of lava near Rome; and is accompanied by the substance called Pseudo-sommite.

SPECIES 54. SODALITE. THOMPSON.

This mineral, recently known, occurs massive, or in dodecaedrons with rhombic faces, sometimes so elongated, as to assume the aspect of six-sided prisms, terminated by three-sided summits. It is with difficulty scratched by iron. Its structure is foliated, and its cross fracture conchoidal; its lustre is shining and resinous, except on the cross fracture, where it is vitreous. It is translucent and its color is a light or bluish green. Its spec. grav. is 2.37.

When heated to redness, it becomes dark gray, but is infusible by the blowpipe. It contains, according to Thompson, silex 38.52, alumine 27.48, soda 23.50, muriatic acid 3.0, lime 2.7, volatile matter 2.1, iron 1.0;=98.3. Ekeberg found silex 36.0, alumine 32.0, soda 25.0, mur. acid 6.75, iron 0.25.

It occurs in primitive rocks with garnets, hornblende, augite and sahlite.

SPECIES 55. NATROLITE.* JAMESON. BRONGNIART.

This substance has usually occurred in small, reniform, rounded, or irregular masses, composed of very minute fibres. The fibres are divergent, or even radiate from a centre; and are sometimes so very minute and close, that the fracture appears almost or quite compact. It has little or no lustre.—Sometimes also it presents minute crystals, especially on the surface of its masses, whose forms appear to be similar to those of the Zeolite.

Its colors are yellowish white, yellowish brown, pale yellow sometimes tinged with red, and whitish. Different colors or shades of color are usually arranged in undulated and parallel stripes. It is translucent at the edges. Its angles feebly scratch glass; and its spec. grav. is 2.16 or 2.20.

Before the blowpipe it easily melts into a white glass, which often contains small bubbles. In nitric acid it is reduced in the course of a few hours, without effervescence, into a jelly somewhat thick. It contains silex 48.0, alumine 24.25, soda† 16.5, water 9.0, oxide of iron 1.75;=99.5. (KLAPROTH.) This result is very similar to that obtained by Smithson Tennant from the Zeolite.

It has been found chiefly at Roegau, in Suabia, near the lake of

* Natrolith. WERNER. Natrolithe. HAUY.

† Hence the name Natrolite, derived from Natron.

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Constance; and is imbedded in an amygdaloid, whose base is wacke or clinkstone.

SPECIES 56. ANALCIME.* HAUY. BRONG.

This mineral is rare, and exhibits but few varieties, which, however, differ considerably in some of their characters. It is generally crystallized; and has hitherto presented only two secondary forms.—One of these is a cube (Pl. IV, fig. 21.), having each solid angle formed by three triangular faces, inclined to the sides of the cube at about 145°.—The other is a solid, contained under twenty four trapezoidal faces, perfectly similar to one of the forms of the garnet, and that of the leucite. Their primitive form, and that of their integrant particles is a cube. The surface has often a strong lustre.

Analcime is also found amorphous, and sometimes in reniform or radiated masses.

It is limpid, or grayish white, also white, or flesh red more or less deep, and sometimes has a tinge of yellow. It is translucent, or even nearly transparent, and sometimes opaque. When the crystal is not opaque, its fracture is undulated or imperfectly foliated; but, if opaque, its fracture becomes uneven; its lustre is shining.

The Analcime slightly scratches glass, and by friction acquires a weak† electricity. Its spec. grav. is between 2 and 3.

Before the blowpipe it melts without intumescence‡ into a white semi-transparent glass. It does not form a jelly with acids. It yielded Vauquelin silex 58.0, alumine 18.0, soda 10.0, water 8.5, lime 2.0;=96.5.

(Distinctive characters.) It is distinguished from the leucite by its fusibility; and from the garnet by its inferior hardness and specific gravity.—It is not electric by heat, like the zeolite.—It wants the pearly lustre of the stilbite, and its crystals do not, like those of the stilbite, exfoliate, when exposed to a moderate heat.

(Geological sit. and Localities.) This mineral is sometimes found in wacke and basalt, attached to the sides of cavities, or even occupying the whole cavity. But it seems to have entered by filtration; for its crystals do not, like those of leucite, impress their forms on the substance, which contains them.

It has been found near Catania and Etna, in Sicily.—The trapezoidal variety is found chiefly near Dunbarton, in Scotland; and the crystals are sometimes more than one inch in diameter.

* Kubizit. WERNER. Var. of Cubic zeolite. JAMESON. Var. of zeolithe cubique. BROCHANT.

† Hence its name from the Greek Αναλχις, weak.

† Some mineralogists have observed an intumescence during fusion.

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SAROOLITE. THOMPSON. This subvariety is found at Mt. Somma in flesh-colored cubo-octaedral crystals, nearly transparent.—A similar substance is found also at Castel in the Vicentin, in small flesh-colored masses, or trapezoidal crystals in wacke; it is accompanied by whitish Analcime, into which it seems to pass.

SPECIES 57. BILDSTEIN.* WERNER.

The Bildstein strongly resembles common steatite in its physical characters, but differs essentially in its composition.

Its texture is very compact. Its fracture is splintery in one direction, and more or less slaty in the other; it is nearly or quite dull.—This mineral is soft, easily cut by a knife, and reducible into a fine unctuous powder. Its surface also is usually very unctuous to the touch.—It is sometimes strongly translucid, and sometimes nearly or quite opaque. Its color is greenish gray more or less deep, sometimes inclining to yellowish gray, or brownish yellow; also reddish white or flesh red. Some specimens are veined or spotted. Its spec. grav. varies from 2.78 to 2.81; and, when rubbed on sealing wax, it communicates positive electricity.

Before the blowpipe it whitens, becomes harder, and is reduced into a kind of enamel. It contains, according to Vauquelin, silex 56, alumine 29, potash 7, water 5, lime 2, oxide of iron I. In a translucid specimen Klaproth found silex 54.0, alumine 36.0, water 5.5, oxide of iron 0.75;=96.25. It hence appears, that alumine, which sometimes forms the hardest earthy minerals, can also take the place of magnesia in the production of unctuosity.

(Remarks.) Nothing is known of the natural situation or associations of this mineral. It is brought from China, and always under some artificial form; and hence the names Figure or Sculpture stone, or Bildstein, of similar signification. These figures are supposed often to represent the idols or pagods of the Chinese.—The Bildstein is susceptible of a polish.

SPECIES 58. NACRITE.† BRONGNIART.

This mineral occurs in coats or reniform masses, composed of very minute shining scales, or spangles. Their color is pearly gray, or silver white, often with a tinge of green and sometimes of red. It is friable, and, when rubbed between the fingers, feels very unctuous, and leaves on the skin a pearly gloss, especially if the mineral be

* Figure stone. JAMESON. Talc glaphique. HAUY. Steatite Pagodite. BRONGNIART. La Pierre a sculpture. BROCHANT.

† Erdiger Talk. WERNER. Earthy talc. JAMESON. Le Talc terreux. BROCHANT. Talc granuleux. HAUY. Talcite. KIRWAN. The term Nacrite, from the French, alludes to its pearly lustre.

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previously plunged in water for a few minutes. It is very light, and swells a little in water.

The Nacrite is easily fusible by the blowpipe. Water, in which this mineral has been digested for some time, changes the vegetable blue to green; and even precipitates metallic solutions. (LUCAS.) A specimen, analyzed by Vauquelin, yielded silex 56, alumine 18, potash 8, water 6, lime 3, iron 4;=95.

Its chemical characters sufficiently distinguish it from talc.—It seldom, if ever, presents the green color of chlorite.—It is much more unctuous to the touch, than lepidolite.

It is found in scales, coats, or reniform masses, in the cavities or interstices of primitive rocks, particularly of crystallized quartz.—Piedmont, Freyberg in Saxony, &c. furnish this mineral.

SPECIES. 59. CHABASIE.* HAUY. BRONG.

This substance, always crystallized, sometimes presents its primitive form, which is an obtuse rhomb, scarcely distinguishable by the eye from a cube, its plane angles being 93° 36′ and 86° 24′.—This rhomb is sometimes truncated (Pl. IV, fig. 22.) on six edges by planes, which unite, three and three, at two opposite angles, while the remaining six angles are also truncated, thus giving a solid with eighteen faces. Even this solid is subject to farther truncations.

The Chabasie scarcely scratches glass. Its fracture is imperfectly foliated; and its spec. gravity 2.71. It is translucent, or sometimes transparent. Its color is white, or grayish white, sometimes with a rosy tinge, which is often only superficial. It is not electric by heat.

Before the blowpipe it intumesces a little, and easily melts into a white, spongy mass. It does not effervesce, nor form a jelly with acids. The analysis of Vauquelin gives silex 43.33, alumine 22.66, soda and potash 9.34, water 21.0, lime 3.34;=99.67.

The preceding characters will easily distinguish the Chabasie from zeolite and carbonate of lime.—Its crystalline forms, though sometimes similar, are still different from those of the Analcime; and the latter does not intumesce before the blowpipe, but melts into a semi-transparent glass.—It cannot be easily confounded with the stilbite.

(Localities.) The Chabasie exists in the fissures and cavities of basalt, and wacke. It is thus found in the north of Ireland.—Near Oberstein in Germany, its crystals are sometimes attached to the interior of geodes of agate.—In the Faroe islands, the stilbite accompanies the Chabasie, whose crystals it sometimes penetrates.

* Schabasit. WERNER. Var. of cubic zeolite of JAMESON; and of Zeolithe cubique of BROCHANT.

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SPECIES 60. ALLANITE. THOMPSON.

This mineral, first noticed as a distinct species by Mr. T. Allan of Edinburgh, occurs massive, and in oblique four-sided prisms with angles of 117° and 63°; also in six-sided prisms, terminated by foursided summits. It scratches hornblende, but not feldspar. Its fracture is conchoidal with small cavities; its lustre shining and resinous, a little metallic. It is opaque, and dark brown, or brownish black. Its powder is greenish gray. Its spec. grav. is between 3 and 4.

Before the blowpipe it froths, and is converted into a scoria. In nitric acid it forms a jelly. It contains silex 35.4, lime 9.2, oxide of cerium 33.9, alumine 4.1, oxide of iron 25.4, volatile matter 4.0. (THOMPSON.)

It is found in Greenland, and associated with mica and feldspar.

SPECIES 61. YENITE. HAUY. BRONG.

This mineral has recently been made known by M. Lelièvre, who has named it Yenite in commemoration of the battle of Jena, changing the initial letter for a particular reason.

It is usually in prismatic crystals, which are sometimes oblique four-sided prisms, with angles of 112° 37′ and 67° 23′, terminated by four-sided pyramids, whose faces are inclined to the lateral planes at about 128° 29′.—Sometimes the prism is nearly rectangular, and terminated by diedral summits, whose faces stand on the obtuse lateral edges, and are inclined to each other at about 113°.—It also occurs in eight-sided prisms, terminated at each extremity by eight faces, four of which are placed on the lateral edges, and four on the lateral planes. Their primitive form is probably an octaedron, of which five or six modifications have been observed.

The Yenite is opaque, and has a black or brownish black color, even when reduced to powder. The lateral faces are longitudinally striated; and, when the color is black, the surface is shining.

It also occurs in masses, composed of diverging fibres or crystals; sometimes the fibres are nearly parallel and very closely united. Its imperfect prisms are sometimes of the size of the finger.

This mineral scratches glass, and gives a few sparks with steel, but is scratched by adularia. Its spec. grav. extends from 3.82 to 4.06. Its longitudinal fracture is a little foliated; its cross fracture conchoidal or uneven; and its lustre resinous.

Before the blowpipe the Yenite is easily fusible into a dull, opaque, black globule, strongly attracted by the magnet. It contains silex 30.0, lime 12.5, oxide of iron 57.5. (VAUQUELIN.) By exposure to the atmosphere, its exterior is converted into an earthy, ochreous crust.

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The crystals of Yenite resemble those of dark colored epidote; but they differ in the measure of their angles, spec. gravity, &c.

(Localities.) The Yenite has been found almost exclusively at two places in the island of Elba;—at Rio-la-Marine it occurs in insulated or grouped crystals, disseminated in a green substance, whose nature is not well determined. This green mineral forms a thick bed, resting on granular limestone, and contains also epidote, quartz, arsenical and magnetic iron.

SPECIES 62. SCHAALSTEIN.* WERNER.

This substance usually appears in masses, composed of thin laminæ, collected into large prismatic concretions; and sometimes in hexaedral prisms or tables. Its natural joints are parallel to the sides of a prism, slightly rhomboidal. Its fracture is a little imperfectly foliated, shining and pearly. It is easily broken, and, when scraped in the dark with an iron point, is phosphorescent. (HAUY.) Its spec. gravity is 2.86.—It is translucent; and its color is grayish or pearly white, sometimes with a tinge of green, yellow, or red.

When immersed in nitric acid, a few bubbles of air escape, and the fragment then separates into grains. (HAUY.) It contains silex 50, pure lime 45, water 5. (KLAPROTH.)

This substance is very rare, and has been found chiefly at Dognatska, in the Bannat, accompanied by garnets and carbonate of lime.

SPECIES 63. ICHTHYOPHTHALMITE.† JAMESON.

This mineral occurs in laminated masses; or in regular crystals, having a strong, and peculiar external lustre, which is intermediate between vitreous and pearly.

The primitive form of its crystals, under which it has probably been observed, is a four-sided prism with rectangular bases, whose sides and the height of the prism are as the numbers 14, 18, and 15. Three or four secondary forms have been observed, in which this prism is more or less modified. Sometimes the eight solid angles are truncated by triangular faces. The crystals are sometimes tabular and intersect each other.

It is easily divisible by percussion into laminæ, whose broader surfaces are splendent and somewhat pearly; in other directions it presents a glistening, uneven fracture. Indeed if a fragment of this

* Schaalstone. JAMESON. Spath en table. HAUY. BRONGNIART. Pierre calcaire testacée. BROCHANT.

† Fischaugenstein. WERNER. Apophyllite. HAUY. BRONGNIART. Ichtyophtalme. BROCHANT. The word Ichtbyophthalmite is derived from the Greek, Іχθνς a fish, and Оφθαλμος, an eye.

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mineral be applied by one of its sides to a hard body, and strongly rubbed, it separates into thin laminæ, like those of selenite. It is very easily broken.

It scarcely scratches glass, and does not give sparks with steel. Its spec. grav. is 2.46. It is often semi-transparent, sometimes only translucent, even at the edges. Its color is yellowish white, or grayish, sometimes with a tinge of red or green.

(Chemical characters.) When exposed to the flame of a lamp, it exfoliates. Before the blowpipe it melts with some difficulty into a white enamel. Its fragments, placed in cold nitric acid, are gradually converted into a whitish, flaky substance; its powder forms a jelly in nitric or muriatic acid. It contains silex 51, lime 28, potash 4, water 17. (FOURCROY and VAUQUELIN.)

It is lighter and harder than sulphate of barytes, but much less hard, than adularia, both of which it may resemble.

(Locality.) It has been found in Sweden in the iron mine of Utoe. Its gangue is a reddish, lamellar carbonate of lime, and it is accompanied by hornblende, and a granular oxide of iron.

SPECIES 64. HARMOTOME.* HAUY. BRONG.

This singular mineral is always in crystals, which are, in general, easily recognised. Its single crystals are rectangular four-sided prisms, broad or compressed, and terminated by four-sided pyramids, whose faces stand on the lateral edges, and are inclined to each other at about 121° 58′.—But this mineral is usually found in double crystals (Pl. IV, fig. 23.), composed of two of the preceding crystals, so intersecting each other, that the two broader planes of one prism are perpendicular to the broader planes of the other, throughout their whole length. Hence these intersecting prisms have a common axis, and their terminating faces, taken two and two, coincide in the same plane. In fact, this double crystal may be viewed as a four-sided prism with four-sided summits, and rectangular grooves in the place of its lateral edges.

These crystals are often grouped. Their primitive form is an octaedron, divisible in planes, which pass by the edges†, contiguous to the summits, and through the centre; thus giving tetraedrons for the integrant particles. Only three secondary forms have been observed.

Its color is grayish or milk white, sometimes with a tinge of yellow. It is translucent or opaque, and sometimes nearly transparent.

* Kreutzstein. WERNER. Cross Stone. JAMESON. Staurolite. KIRWAN. Pierre cruciforme. BROCHANT.

† Hence its name, from the Greek, Αςμος, a joint, and Тεμуω, to divide.

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It scarcely scratches glaas; and its spec. gray. varies from 2.33 to 2.36. Its longitudinal fracture is foliated, and more or less shining, and its cross fracture uneven.

Before the blowpipe it melts with some intumescence into a white, transparent glass. Its powder on hot coals phosphoresces with a greenish yellow light. It contains silex 49, barytes 18, alumine 16, water 15;=98. (KLAPROTH.)

This mineral does not exfoliate, like the stilbite, on hot coals; nor is it electric by heat, like the zeolite—The prisms of the staurotide cross each other in such directions, that their axes never coincide, like those of the Harmotome.

(Localities.) It has been found at Andreasberg, in the Hartz, in metallic veins, with laminated carbonate of lime, the sulphurets of lead, iron, &c.—Also at Strontian, in Scotland, in veins.—At Oberstein, its single crystals are attached to the interior of geodes of agate.

SPECIES 65. CHRYSOLITE.*

The Chrysolite, though harder than glass, is less hard than quartz, by which it may be scratched. Its prevailing color is some shade of green, more or less intermixed with yellow or brown. It is often transparent, sometimes only translucent. It possesses double refraction in a high degree, which may be observed by viewing an object through one of the larger faces of the summits of its crystals, and the opposite side of the prism. Its spec. grav. varies from 3.22 to 3.42. Its fracture is more or less conchoidal, and sometimes a little foliated, parallel to the axis of the crystals.

It occurs sometimes in crystals, sometimes in small amorphous masses or in grains, and sometimes in rolled pieces.

Its crystals have presented six secondary forms, which, originate from a four-sided prism with rectangular bases, whose sides are to each other nearly as 11 to 25. All its secondary forms are eight, ten, or twelve-sided prisms, terminated by cuneiform or pyramidal summits, having six, eight, or ten oblique faces, and one face perpendicular to the axis, or this face may be called a truncation of the summit. One of these forms is an eight-sided prism (Pl. IV, fig. 24.), or a fouraided prism, truncated on its lateral edges, and terminated by nine faces, of which eight are oblique and stand on the lateral planes.— Sometimes this prism is terminated by seven faces; of which six are oblique, two of them standing on opposite sides of the prism, and the other four on the faces, produced by the truncation of the lateral edges.

The edges and angles of these crystals are frequently blunted;

* Peridot. HAUY. BRONGNIART.

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certain faces are often a little convex; and the broader lateral planes are usually striated longitudinally.

Before the blowpipe it becomes brownish, but does not melt. It is essentially composed of silex and magnesia, either of which may be predominant, as appears by the analysis under each variety.

The Chrysolite is harder and heavier than phosphate of lime, which it sometimes resembles.—It is not electric by heat, like the tourmaline of a similar color, from which, as well as from the idocrase, it differs by its infusibility.—This species presents two varieties.

Var. 1. COMMON CHRYSOLITE.* This variety embraces most of the crystals, already described.—It also occurs in small, angular or rounded masses, which almost always have a rough, scaly, or fine splintery surface. The crystals, when uninjured, have a strong lustre.

Its fracture is conchoidal, splendent, and vitreous. It is usually transparent. Its prevailing color is a pistachio or olive green, in which the green is more or less blended with yellow and brown; sometimes also it is grass green or nearly reddish brown.

With borax it melts into a greenish, transparent glass. It contains magnesia 50.5, silex S8.0, oxide of iron 9.5;=98. (VAUQUELIN.)

Its geological situation is but little known. The rolled pieces are undoubtedly found in alluvial earths. The Chrysolite, employed in the arts, comes chiefly from the Levant.—It has been found in Bohemia; and in Hungary it is said to be imbedded in serpentine.—It has also occurred in the vicinity of some volcanoes, as in the isle of Bourbon, &c.

(Uses.) It is sometimes employed in jewelry, but is not highly esteemed. Werner has suggested, that the yellow chrysolite of the ancients is the modern topaz.—Certain beryls and topazes have been erroneously referred to this variety.

2. OLIVINE.† JAMESON. This variety very rarely, if ever, occurs in crystals; but presents itself in grains, or in roundish masses of various sizes, sometimes indeed, according to Faujas, weighing nearly one hundred pounds.

Its structure is sometimes more or less foliated. Its fracture is imperfectly conchoidal or uneven, and its lustre shining and often resinous. Its masses are often composed of granular distinct concretions.—It is generally translucent, sometimes nearly transparent. Its prevailing color differs but little from an olive green; and hence its

* Krysolith. WERNER. Chrysolite. KIRWAN. JAMESON. La Chrysolithe. BROCHANT. Peridot Chrysolithe. BRONGNIART.

† Olivin. WERNER. L'Olivine. BROCHANT. Peridot Olivine. BRONGNIART. Peridot granuliforme et lamelliforme. HAUY.

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name. It also occurs asparagus green, yellowish green, or greenish yellow. It is less heavy than the common Chrysolite.

In nitric acid it loses its color; and with borax melts into a dark green bead. In a specimen from Unkel Klaproth found silex 50.0, magnesia 38.5, lime 0.25, oxide of iron 12.0;=100.75.

The Olivine is subject to decomposition. It gradually becomes friable, yellowish or reddish brown; and is eventually converted into a yellowish brown, ochrey substance.*

(Geolog. sit. and Localities.) This mineral is most frequently found in Basalt, and is usually accompanied by Augite. It is abundant in the basalt of Bohemia, France, &c. but all basalt does not contain it.—It is somewhat remarkable, that Olivine has seldom or never been found in wacke and other minerals, which so frequently accompany basalt.

It also occurs in substances ejected from volcanoes; as in the lava of Vesuvius and Hecla, where it is also associated with augite.—In Siberia it has probably been found in a mass of native iron.

SPECIES. 66. LABRADOR STONE.†

This mineral has hitherto been found only in laminated masses. When viewed in the direction of the laminæ, which are usually a little curved, it has a lustre nearly metallic, and its color is a dark copper red, or reddish brown slightly tinged with yellow, and sometimes steel gray; but in other directions it appears brownish, or greenish black. It is opaque, and scratches glass, but scarcely gives fire with steel. Its spec. grav. varies from 3.35 to 3.43.

The result of its mechanical division is a prism with rhombic bases, whose angles are about 100° and 80°; and this prism is further divisible in the direction of the two diagonals of its bases.

It contains silex 54.25, magnesia 14.0, alumine 2.25, lime 1.5, oxide of iron 24.5, water 1.0;= 97.5. (KLAPROTH.)

It has hitherto been found only on the coast of Labrador, particularly on the island of St. Paul, where it is accompanied by opalescent feldspar.

This mineral has usually been described as a variety of hornblende.

* The Limbilite of Saussure, found in a porphyry, near Brisgaw, has been supposed to be a decomposed Olivine, which it sufficiently resembles in its external characters. But it is fusible into a compact, shining, black enamel; a circumstance, however, which may result from its state of partial decomposition.

† Labradorische Hornblende. WERNER. Labrador Hornblende. JAMESON. KIRWAN. La Hornblende du Labrador. BROCHANT. Hypersthene. HAUY. BRONGNIART.

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But, as it obviously belongs to a different species, its name ought not to retain the word hornblende.

SPECIES 67. TREMOLITE.* JAMESON.

The Tremolite sometimes occurs in distinct crystals, but more frequently in fibrous or radiated masses, composed of minute, imperfect prisms or fibres. One of its secondary forms is a very oblique four-sided prism, with diedral summits, whose faces are placed on the acute lateral edges; the terminal edge of each summit is oblique to the axis, and contains an angle of 149° 38′; and each obtuse edge of the prism contains an angle of 124.34 —Sometimes this crystal has its acute lateral edges truncated. (Pl. IV, fig. 25.)—Sometimes also the obtuse lateral edges, and even the edges of the summits are truncated.

The rhombic surface, brought to view by the transverse fracture of these prisms, is sometimes marked by a line, passing diagonally from one acute edge to the other; and hence the name Grammatite, given this mineral by Haüy. The primitive form is an oblique rhombic prism, whose sides are inclined at 124 ½° and 55 ½°. It appears to be the same as that of hornblende.

These crystals are seldom regular and well defined. They are often very much compressed or flattened, and sometimes cylindrical. Their sides are longitudinally, and often deeply, striated, and sometimes curved.

The Tremolite sometimes appears in thin, broad bundles, more or less long, and composed of parallel fibres, or minute prisms with rounded edges.—Sometimes its crystals are acicular, delicately fibrous, and collected into groups or masses, in which the fibres may be parallel, diverging, or radiated.—It also occurs in laminated masses. The longitudinal fracture of these masses of Tremolite is fibrous; but the breadth of these fibres is sometimes imperceptible by the eye, and sometimes so great, that the fracture becomes foliated; its lustre is usually shining or glistening, and often pearly, but sometimes more or less vitreous. Its cross fracture is uneven or undulated with a moderate lustre.

The hardness of Tremolite, examined in mass, often appears variable, in consequence of the brittleness of its fibres. It however always scratches glass; its fibres are stiff, hard, and rough, and, when rubbed on glass with a little water, destroy its polish and wear its surface. Its powder is a little rough to the touch.

The Tremolite is white, often tinged with gray, yellow, green, or

* Tremolith. WERNER. La Tremolithe. BROCHANT. Grammatite. BRONGNIART. Var. of Amphibole. HAUY.

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red; also gray, sometimes smoky, or even blackish gray. It is some. times nearly or quite opaque, and often translucent; some crystals are transparent, and, with an increase of transparency, its lustre becomes more vitreous. Its spec. grav. usually lies between 2.92 and 3.20.

The phosphorescence, which most Tremolites exhibit both by heat and friction, sometimes even with a feather, is an accidental property, arising from particles of dolomite, attached to the Tremolite, or contained in its interior. For, when the dolomite is removed by an acid, no phosphorescence appears; and Tremolite, taken from an argillaceous gangue, is never phosphorescent. (BOURNON.)

(Chemical characters.) Before the blowpipe it melts into a white glass, full of pores or blebs. Three specimens of white Tremolite from St. Gothard yielded Laugier silex 41 to 28.4, lime 30.6 to 15.0, magnesia 18.0 to 15.25, water and carbonic acid 23. In a common Tremolite Lowitz found silex 52, lime 20, magnesia 12, carbonate of lime 12;=96. In a fibrous Tremolite Klaproth found silex 65.0, lime 18.0, magnesia 10.33, water and carbonic acid 6.5, oxide of iron 0.16;=99.99. The results of the analyses of this mineral seem to depend in an unusual degree on the nature of its gangue. Thus Tremolites taken from dolomite, a compound carbonate of lime and magnesia, generally yield a large proportion of carbonate of lime, and little or no alumine; while others, taken from an argillaceous gangue, have yielded 14 per cent. of alumine. It is probable, however, that only silex, lime, and magnesia are essential to the composition of the Tremolite, and that the carbonic acid is derived from the gangue. Indeed the Tremolite almost always embraces numerous particles of its gangue.

(Distinctive characters.) The electric powers of zeolite and the chemical characters of both zeolite and stilbite form lines of distinction between those minerals and the Tremolite.—The fibrous Tremolite often much resembles some varieties of asbestus; but this latter mineral is less hard, and very seldom scratches glass even slightly, unless it contains some harder foreign substance; its powder is soft to the touch, and frequently agglutinates a little under the pestle.—The results of fusion may serve to distinguish it from actynolite.

The Tremolite is often described under several subspecies or varieties; but the distinctive characters between these varieties are of but little consequence, depending in part on the different breadths of the fibres. These varieties gradually pass into each other, and sometimes two or more of them appear in the same specimen.

Var. 1. COMMON TREMOLITE.* JAMESON. The larger and more

* Gemeiner Tremolith. WERNER.

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distinct crystals belong to this variety; also those masses, whose structure is more or less foliated, or whose fracture presents broad fibres, whether parallel, diverging, or interlaced.

GLASSY TREMOLITE.* JAMESON. It is sometimes in acicular crystals, or in masses, whose fibres are narrow, and moderately diverging. It is intersected by transverse seams, and is very easily frangible. Its lustre has often more or less of a vitreous aspect.

2. FIBROUS TREMOLITE.† It occurs in masses, composed of fascicular groups of minute, diverging fibres; its fracture is often very delicately fibrous, glistening with a silky lustre. Sometimes the fibres radiate from a centre; and sometimes they proceed in cones from different centres, and intercept each other. It is often very tender. In a few instances it has been seen violet blue.

3. BAIKALITE,‡ KIRWAN. It occurs in groups of acicular prisms, sometimes very long, and sometimes radiating from a centre. Its color is greenish, often with a shade of yellow; and its lustre sometimes silky. According to Kirwan, its spec. grav. is only 2.20, and it melts into a dark green glass. It contains silex 44, lime 20, magnesia 3O, oxide of iron 6. (LOWITZ.)

It has been found near lake Baikal, in Siberia, in foliated limestone.—In Chinese Tartary it occurs in dolomite. (PATRIN.)

(Geolog. sit. and Localities.) Tremolite occurs most frequently in carbonate of lime, more particularly in dolomite. It is abundant and very beautiful in the vicinity of St. Gothard, usually in dolomite, and associated with mica, talc, &c. Indeed it is said to have been first observed in the valley of Tremola, on St. Gothard; and hence its name.—Near Nantz, its fibres are seen radiating on granite. (DAUBUISSON.)—At Cornwall, in a dark green serpentine with asbestus. (GREC.)—According to Jameson, it is found near Edinburgh in secondary trap rocks with prehnite.

In the United States. In Maryland, at several places not far from Baltimore in carbonate of lime. (DE BUTTS.)—In Pennsylvania, in Chester Co. sometimes with carbonate of lime, asbestus, and serpentine; at London grove it is very beautiful, (CONRAD.)—In New York, at Kingsbridge;—and also near the city in granular limestone; sometimes it seems altogether distinct from the limestone. (BRUCE.)— Also near Lake Champlain.—In Connecticut, at Washington, in Litchfield Co. both in dolomite and granular limestone; it is in flat prismatic crystals, or in very beautiful fibrous and radiated

* Glasartiger Tremolith. WERNER.

† Asbestartiger Tremolith. WERNER. Asbestous Tremolite. JAMESON. Var. of Amphibole fibreux. HAUY.

† Var. of Amphibole aciculaire. HAUY.

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masses, with the aspect of white silk; also on Milford Hills, near Newhaven, where all its varieties occur with dolomite and quartz. (SILLIMAN.)—In Massachusetts, in Newbury, not two miles from Newburyport and near the turnpike, in fibrous, radiated masses; the accompanying minerals are granular limestone, serpentine, asbestos, garnet, &c.

SPECIES 68. ASBESTUS.*

Asbestus exhibits a considerable diversity of aspect; and sometimes more resembles a product of the vegetable, than of the mineral kingdom,

Its structure is always fibrous; and, although it has never presented distinct crystals, its fibres sometimes appear to be rhomboidal prisms. Its masses are sometimes composed of filaments easily separable, extremely delicate, flexible, and more or less elastic. In other cases, the fibres are stiff, closely adhering, and discover very little flexibility or elasticity. Its lustre is often silky or pearly.

When pure, it is seldom sufficiently hard to scratch glass even in a slight degree; and its fibres have sometimes the softness of cotton. Its powder is soft to the touch, and frequently agglutinates a little under a pestle.

When Asbestus is nged in water, an absorption takes place, affecting the spec. grav. of the mass, which is also a little softened. It is usually translucent, at least at the edges, but sometimes opaque. Its colors are some variety of white, gray, or green, and sometimes of brown, yellow, red, or even of black.

(Chemical characters.) Asbestus, in fragments of a moderate size, is infusible in a common fire. The heat of the blowpipe, however, is sufficient to melt a very minute fragment into a glass or enamel, somewhat variable in color, but in most cases presenting a tinge of green. Its essential ingredients appear to be silex, magnesia, and lime.—This species presents several varieties.

Var. 1. AMIANTHUS.† KIRWAN. Its masses are composed of delicate filaments, very flexible, and somewhat elastic, often long and resembling threads of silk. The fibres are easily separable by friction, and may often be made to assume the appearance of a silken tuft. Sometimes indeed they occur loose.

The fibres of Amianthus are usually straight, and perhaps always parallel. They have, in most cases, a glistening silky lustre; and are soft to the touch, sometimes like the finest silk. They are nearly

* Asbest. WERNER. JAMESON. Asbeste. HAUY. BRONGNIART. BROCHANT.

† Amianth. WERNER. JAMESON. L'Amianthe. BROCHANT. Asbeste Amianthe, BRONGNIART. Asbeste flexible. HAUY.

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or quite opaque; and their color is white, usually tinged with green or gray; sometimes also silver white, greenish, or reddish. Its spec. grav. varies from 90 to 2.57.

If the extremity of a single filament be presented to the flame of a lamp, it recoils upon itself, and a small, friable globule is formed. But, if a tuft of many fibres be thrown into a fire, it suffers no change. It contains, according to Chenevix, silex 59.0, magnesia 25.0, lime 9.5, alumine 3.0, oxide of iron 2.25;=98.75.

(Localities.) Fine specimens are found in Savoy, where its filaments are sometimes a foot in length.—In Corsica it is so abundant, that Dolomieu employed it for packing his specimen.—It is very abundant in the Pyrennees.

(Uses.) When the filaments are long and very flexible, they may be spun, and woven into cloth, by mixing them with flax, and employing much oil. When this cloth is thrown into the fire, the flaxen fibres are consumed, and a kind of canvas remains. If this cloth be soiled, it may be cast into the fire with safety, and thus restored to its original purity and whiteness. Hence the name of this variety, from the Greek Αμιαντος, unpolluted. The ancients preserved the ashes of their dead by wrapping the body in this cloth before combustion.

Madame Perpenti has succeeded in manufacturing the fibres of Amianthus into cloth without any additional ingredient. Her process consists in softening the Amianthus in water, beating it, rubbing it, and dividing it with a comb, having fine steel points. The fibres, thus obtained, are extremely delicate, but sufficiently strong.

Amianthus has also been manufactured with success into paper; and, could an incombustible ink be prepared, manuscripts might be rendered safe from destruction by fire.

It has also been employed as an incombustible wick for lamps. And it has been suggested, that the perpetual lamps of the ancients contained wicks of this kind, constantly supplied with oil. Hence perhaps the name of this species, which is from the Greek Ασζισος, inextinguishable.

2. COMMON ASBESTUS.* The structure of this variety, which passes into the preceding, is always fibrous; but the fibres are stiff and hard, scarcely flexible and elastic even in a slight degree, and strongly adhere together; indeed the adhesion is sometimes so great, that the fracture becomes a little splintery. Its fibres, whether fine or coarse, straight or curved, are usually parallel, but sometimes diverge in fascicular groups, or radiate from a centre. Its lustre is glisten-

* Gemeiner Asbest. WERNER. Common Asbest. JAMESON. Asbestos. KIRWAN. Asbeste dur. HAUY. BRONGNIART. L'Asbeste commune BROCHANT.

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ing, and often somewhat pearly or resinous. It is translucent, at least at the edges; and its color varies from leek green to greenish gray, and is sometimes olive green, or yellowish gray. It breaks into splintery fragments; and its spec. grav. extends from 2.54 to 3.03.

It is more easily fusible than the other varieties. A specimen, analyzed by Bergman, gave silex 68.9, magnesia 16.0, lime 12.8, alumine 1.1, oxide of iron 6.0;=99.8.

This variety sometimes resembles actynolite or tremolite; but its powder is soft, while that of the other two is dry and harsh.

3. MOOUNTAIN CORK.* This variety is so light, that it ordinarily swims on water, its spec. grav. usually varying between 0.68 and 0.99. Its structure is fibrous; but the fibres, very seldom parallel, are mingled and promiscuously interwoven, thus leaving numerous pores; hence its low spec. gravity, and its power of absorbing a large quantity of water.

Although its hardness is sometimes considerable, it may usually be impressed by the finger nail; and, when rubbed, it presents a shining streak. It has little or no lustre; and its fibres are so fine, that its fracture, at first view, appears compact and uneven. Its more common colors are gray, grayish or yellowish white, and sometimes yellowish brown, or pale yellow. It is usually opaque.

Its structure often closely resembles that of cork. When in thick, spongy masses, it has been called rock or fossil flesh. Sometimes it appears in plates or membranes; when these are hard, they have been called rock or fossil leather; when thin and flexible, rock or fossil paper.

It is less easily fusible, than the other varieties. It contains, according to Bergman, silex 56.2, magnesia 26.1, lime 12.7, alumine 2.0, iron 3.0.

This variety is found in Saxony, France, &c. and sometimes in metallic veins.—Near Alais, in France, it occurs on the surface of the soil, in long whitish masses, resembling human bones.

4. LIGNIFORM ASBESTUS.† KIRWAN. The texture of this mineral, under certain points of view, somewhat resembles that of wood. Its structure is irregularly fibrous, the fibres being straight or curved, parallel, interlaced, or a little diverging. They adhere strongly, but are less stiff, than those of the common variety, and usually a little

* Berg Kork. WERNER. Rock Cork. JAMESON. Suber montanum. KIRWAN. Asbeste tressé. HAUY. Asbeste suberiforme. BRONGNIART. La Liege de montagne. BROCHANT.

† Berg Hotz. WERNER. Rock Wood. JAMESON. Asbeste ligniforme. HAUY. BRONGNIART. Le Bois de montagne. BROCHANT.

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flexible. It breaks into fragments, which somewhat resemble splinters of wood. Its color is usually brown, sometimes a little reddish or yellowish.

It is with difficulty melted by the blowpipe.—In Europe, this variety is found chiefly in the Tyrol.

5. COMPACT ASBESTUS.* This variety is compact in a comparative sense only. It has a very close texture; but its masses are divisible into filaments more or less delicate, especially after being exposed to moisture. Its color is usually a deep green. It much resembles a fibrous serpentine; and has been found in the Uralian mountains, and in the Pyrennees.

(Geological situation.) Asbestus, which never occurs in large masses, is usually found among the more recent of the primitive rocks. It is sometimes in veins, which traverse granite and gneiss, and often mingled with the various crystallized substances, which fill these veins. It sometimes penetrates quartz or calcareous spar, giving them a silky or fibrous appearance. It is also found in metallic veins.

In the Uralian mountains it exists in small masses, composed of fascicular groups of diverging fibres, in mica (PATRIN.) Argillaceous slate is sometimes traversed by of Asbestus.

But it more frequently occurs in serpentine steatitic rocks, constituting whole veins, which vary from a few lines to several inches in breadth.

Asbestos is sometimes associated with talc, magnetic iron, &c. and in some instances its fibres are spread over the surface of crystallized feldspar, like hair.

(Localities.) This mineral is by no means rare. Some of the more remarkable foreign localities have been mentioned under the first variety.

In the United States. In Maryland, at the Bare Hills, &c. not far from Baltimore, amianthus, common, radiated, and ligniform Asbestus occur in serpentine. (GILMOR.)—In Delaware, the common variety is very abundant in serpentine, in Christiana Hundred, Newcastle Co. (CONRAD.)—In Pennsylvania, in Chester and Montgomery Cos. &c. Near Philadelphia soft fibres of amianthus traverse masses of crystallized quartz.—In New Jersey, near Hoboken, in serpentine.—In New York, 4 miles from the city, is found a rare mineral in radiated masses, which is by some referred to Asbestus; but in the opinion of Prof. Bruce it strongly inclines to Tremolite.—In Connecticut, near Newhaven, chiefly in serpentine, and very abundant; the amianthus is sometimes nearly as fine as that of Corsica; the common variety is whitish green, with dolomite and granular

* Asbeste compacte. BRONGNIART.

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limestone adhering, and bitter spar and magnetic iron disseminated; also at New Milford. (SILLIMAN.)—In Massachusetts, at Brookline, &c. in the vicinity of Boston;—also at Newbury, not 2 miles from Newburyport, near the turnpike, the amianthus and common variety appear in veins, intersecting a very beautiful, precious serpentine.

SPECIES 69. DIOPSIDE.* BRONGNIART.

This mineral, yet rare, appears in prismatic crystals, more or less regular. It sometimes presents their primitive form, which, according to Haüy, is an oblique quadrangular prism, with rhombic bases, and in all respects similar to the primitive form of the augite. These quadrangular prisms are often small and elongated, and frequently bent and imperfect. The bases of the primitive form sometimes present pyramidal terminations, and the lateral edges are truncated or bevelled, in some cases producing a twelve-sided prism (Pl. IV, fig. 26.), of which eight sides are usually narrower than the other four; this prism has summits with six faces.

The prisms are sometimes compressed or tabular, sometimes cylindrical and longitudinally striated; they are often aggregated into fibrous or radiated masses. Sometimes also crystals of Diopside are united to massive, granular, or almost compact varieties of the same substance.

Its fracture, parallel to the bases of the primitive form, is more distinctly foliated, than in the direction of the sides. The smaller crystals are often opaque, while the larger are frequently more or less translucent. The colors of the Diopside are green, usually pale or only greenish white, and sometimes yellowish or grayish white. The small four-sided prisms sometimes exhibit a pure, lively green; and the larger crystals are sometimes nearly white. Its spec. grav. is 3.23. It scarcely scratches glass.

It melts by the blowpipe, though with difficulty, into a limpid or grayish glass. It contains silex 57.0, magnesia 18.25, lime 16.5, oxides of iron and manganese 6.0;=97.75. (LAUGIER.)

(Localities.) The Diopside in four-sided prisms, associated with granular carbonate of lime, specular oxide of iron, &c. is found in fissures or veins, traversing a black serpentine, on the plain of Mussa, in Piedmont; and was hence named Mussite by its discoverer, Bonvoisin.—The twelve-sided prisms, usually accompanied by garnets, were discovered by the same mineralogist near the village of Ala, in Piedmont; and by him called Alalite.

* Var. of Pyroxene. HAUY.

42

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The variety, first called Mussite, resembles the sahlite; and in fact Haüy considers both Diopside and sahlite as varieties of augite.

SPECIES 70. SAHLITE.* JAMESON.

The Sahlite has been observed in four or eight-sided prisms, whose laminæ are sometimes marked by parallel lines. But it more frequently occurs in small laminated masses, or in granular concretions: and the same mass sometimes exhibits both a granular and laminated structure. It easily yields to mechanical division, and the result is a four-sided prism, nearly rectangular, with natural joints parallel to the diagonals of its bases. Its fracture, parallel to the sides of the prism and one of the aforementioned diagonals, is more or less foliated; and the lustre is, in general, moderately shining. Its cross fracture is usually uneven and nearly dull, but sometimes presents foliæ oblique to the axis. Its primitive form, therefore, cannot differ much from that of the augite; and indeed Haüy believes it to be the same.

The Sahlite is soft to the touch, scarcely scratches glass, and may be scraped by a knife. In thin plates it is translucent, but, in thicker masses, at the edges only. Its colors are greenish gray or grayish green, and sometimes pale green. Its spec. grav. is 3.23.

It melts with ebullition by the blowpipe, though not easily, into a porous glass. It contains silex 53, lime 20, magnesia 19, alumine 3, iron and manganese 4;=99. (VAUQUELIN.)

This mineral is softer to the touch than Augite; and its internal lustre is usually less lively.

(Localities.) It was first found in a silver mine near Sahla, in Sweden, by Dandrada; and hence its name. It has also been found in Norway, and in the mountain Odon-Tchelon, in Siberia. At the latter place it is accompanied by mica and beryl, and its crystals present oblique transverse divisions, more shining than usual.—In the U. States, it exists near Lake Champlain. (GIBBS.)

SPECIES 71. AMIANTHOIDE.† HAUY. BROCHANT.

It occurs in tufts, composed of long capillary filaments, flexible and very elastic; more flexible than the fibres of common asbestus, but stiffer and more elastic than those of amianthus. Its color is olive green, sometimes inclining to yellow or brown; and its lustre is somewhat shining and silky.

It melts with difficulty before the blowpipe into a blackish en-

* Sahlit WERNER. Malacolithe. BROCHANT. BRONGNIART. Var. of Pyroxene. HAUY.

† Amianthoïde capillaire. BRONGNIART.

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amel. It contains silex 47.0, lime 11.3, magnesia 7.3, oxide of iron 20.0, oxide of manganese 10.0;=95.6. (VAUQUELIN.)

At Oisons in France, it is accompanied with epidote, feldspar, quartz, and oxide of manganese.

SPECIES 72. AUGITE.*

This mineral is not always easily recognised, unless it be in distinct crystals, which is often the case. Its secondary forms, of which nine or ten have been observed, are all six or eight-sided prisms, usually short, and terminated at each extremity by two principal faces. They originate from an oblique prism (Pl. IV, fig. 27.) with rhombic bases, whose sides are inclined to each other at angles of 92º 18′ and 87° 42′; its integrant particles are triangular prisms.

One of its forms is a six-sided prism, of which two lateral edges contain angles of 92° 18′, and the other four, angles of 133° 51′.— This prism is sometimes terminated by diedral summits, whose terminal edges are oblique to the axis, and whose faces, standing on the two least obtuse edges of the prism, are inclined to each other in an angle of 120°. Most commonly two of the lateral planes are broader, than the other four; sometimes the reverse.—Sometimes the preceding crystal is converted into an eight-sided prism (Pl. IV, fig, 28.) by truncations on those lateral edges, on which the terminating faces were placed.—Sometimes the terminal edge of the summit, or only one of its solid angles, is truncated.

Sometimes it appears in hemitrope crystals, in which one extremity has a four-sided summit, and the other presents a re-entering angle. Sometimes its prisms cross each other, but not, like the staurotide, at constant angles.

It also occurs amorphous, or in rounded fragments, or in grains.

The Augite has a foliated structure in two directions, parallel to the sides of the primitive form. It is harder than hornblende or olivine, scratches glass, and gives sparks with steel, Its spec. grav. varies from 3.10 to 3.47.

It is fused with difficulty by the blowpipe; but in small fragments melts into an enamel, which, in the colored varieties, is black. Its essential ingredients appear to be silex, lime, magnesia, and alumine,

Its greater hardness, the results of mechanical division, and its difficult fusibility will, in general, be sufficient to distinguish it from hornblende, which it often resembles.—It cannot easily be confounded with schorl.

It has two varieties.

* Pyroxene HAUY. BRONGNIART.

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Var. 1. COMMON AUGITE.* This embraces the distinct crystals of Augite, already described. Their surface is often smooth and shining; and the smaller prisms are frequently very perfect.—It not unfrequently occurs in grains, or small masses, either amorphous or rounded. Its longitudinal fracture is more or less foliated, and its cross fracture uneven; when not in crystals its fracture is often somewhat conchoidal. Its lustre is shining, often strongly, and a little resinous.

Though in general nearly or quite opaque, it is sometimes translucent, and some green crystals are feebly transparent. Very thin fragments of opaque crystals often transmit a greenish light. Its colors are black, greenish black, deep or blackish green, leek or yellowish green, and sometimes brown, gray, or even white. The green shade is often advantageously brought to view by moistening the surface. The color of its powder, except in the whitish varieties, is greenish gray.

In a specimen from Franconia Klaproth found silex 52.0, lime 14.0, magnesia 12.75, alumine 5.75, oxide of iron 12.75, of manganese 0.25, water 0.25;=97.75. In another from Frascati he found silex 48.0, lime 24.0, magnesia 8.75, alumine 5.0, oxide of iron 12.0, of manganese 1.0;=98.75.

The Augite is subject to decomposition, though less so than olivine, and is eventually reduced into a yellowish green, argillaceous mass. (BROCHANT.)

(Geological sit. and Localities.) This variety of Augite often exists in volcanic productions, even in recent lava and scoria; indeed some volcanic ejections, as at Stromboli, &c. are in a great degree composed of crystals of Augite. These crystals are very abundant in the scoria of Monte Rosso, near Etna; they also occur loose at the same mountain in a kind of sand, which, according to Spallanzani, consists of triturated scoria.

Many believe, that the Augite, thus found, pre-existed in the stone, from which the lava has originated, having suffered little or no alteration by the fire, which produced the lava. Sometimes, however, the fire has rendered it more brittle, and acid vapours have destroyed its color; indeed white augite sometimes retains its original color in the interior.

Others suppose, that Augite has actually crystallized in the interior of the melted lava. This opinion receives some support from the remark of Mr. Thompson, who asserts, that he saw acicular crys-

* Augit WERNER. Augite. JAMESON. L'Augite. BROCHANT. Pyroxene Augite. BRONGNIART.

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tals of Augite, sublimed and attached to the walls of a church, which was enveloped by the lava of Vesuvius in 1794.

This Augite is also common in basalt, accompanied by olivine and basaltic hornblende; its crystals or amorphous masses have usually more lustre, than when found in lava.

Augite sometimes occurs in primitive rocks. Very large crystals are found in the iron mines near Arendal in Norway; and sometimes pass by insensible shades into the coccolite.

In the U. States, at the northern extremity of the island of New York, white Augite is imbedded in primitive limestone. Its crystals, either small or several inches in length, are eight-sided prisms, of which two sides are often so much larger than the others, that the crystal becomes tabular. The terminations of these prisms, sometimes like those already known, have also presented a new and more complex variety of form. Spec. grav. 3.1. (BRUCE.)

2. COCCOLITE.* JAMESON. This variety is composed of granular, distinct concretions,† easily separable, often by the finger only, and varying in size from that of a pin's head to that of a pea, or still larger. These concretions are bounded by smooth, but irregular faces, often a little convex; they sometimes present a few well defined edges, and often resemble crystals with rounded angles and edges. Sometimes they pass into laminated masses, which divide very easily into prisms slightly rhomboidal.

Its structure is foliated in two directions, though not always very distinctly; its fracture is sometimes a little conchoidal; its lustre is vitreous and shining. Its spec. grav. lies between 3.31 and 3.37.—Its grains are often translucent, sometimes opaque. Its colors are green of several shades, as grass, olive, or light leek green, also blackish green or black, red, brown, or reddish brown.

It contains, according to Vauquelin, silex 50.0, lime 24.0, magnesia 10.0, alumine 1.5, oxide of iron 7.0, of manganese 3.0;=95.5. It melts before the blowpipe, but not easily.

(Localities.) It was first found in the north of Europe, where it exists in primitive rocks. Near Arendal, in Norway, it is associated with magnetic iron, mica, carbonate of lime, &c. The black concretions are sometimes mingled with others of a bright red.

In the United States. In New York, at West Chester.—In Vermont, the Coccolite has been found in several places near Lake Champlain, and probably offers some new varieties of color. It is

* Kokkolith. WERNER. Coccolithe. BROCHANT. Pyroxene Coccolithe. BRONGNIART. Pyroxene granuliforme. HAUY.

† Hence its name, from the Greek, Кοϰϰος, a grain.

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sometimes in masses of a dull black color. But at Charlotte, its masses are composed of easily separable concretions, whose prevailing colors are brownish red, or brown, deep blood red, orange, or pale red; with these, other concretions of a lively green are intermingled. Although some of these concretions from Charlotte seem to be almost prismatic, their structure is, in general, less distinctly foliated, than that of the Coccolite from Norway, and their lustre more vitreous.—At Rodgers Rock, eight miles from Ticonderoga, it forms a mass, weighing a number of tons; its colors are numerous, and its grains very small. (HALL. See Lit. & Philos. Repert. v. i. p. 379.)

SPECIES 73. HORNBLENDE.*

This very common mineral may, in general, be easily recognised. Though sometimes in regular and distinct crystals, it is more commonly the result of a confused crystallization; and appears in masses, composed of laminæ, acicular crystals, or fibres, variously aggregated.

When its structure is sufficiently regular, mechanical division is easily effected in a longitudinal direction; and its crystals are found to be composed of laminæ, situated parallel to the sides of an oblique four-sided prism (Pl. IV, fig. 29.) with rhombic bases; the sides of this prism are inclined to each other at angles of 124° 34′ and 55° 26′. The longitudinal fracture, which of course is foliated, usually presents the broken edges of many laminæ extending one beyond another.—Of the five or six modifications of the primitive form, which have been observed, the three following are the most common.

A six-sided prism, of which two opposite lateral edges contain angles of 124° 34′. Each summit is formed by three rhombic faces, standing on alternate, lateral edges, but not on the same edges at both extremities.—The same six-sided prism is sometimes terminated, at one extremity, by four trapezoidal faces (Pl. IV, fig. 30.), corresponding to four of the lateral planes, and, at the other extremity, by two pentagonal faces, standing on two opposite lateral edges.—Sometimes also this prism has, at one extremity, the three-sided summit of the first variety, and, at the other, the diedral summit of the second variety.—Although the two summits of these crystals are often unlike each other, both in the number and arrangement of their faces, it cannot be inferred, that they ought to become electric by heat; for the summits of the tourmaline differ only by the addition of certain faces, at one extremity, to those faces, which are common to both extremities.

Hornblende, though less hard than schorl, usually scratches glass,

* Amphibole. HAUY. BRONGNIART.

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and sometimes with difficulty gives a few sparks with steel. Its powder is dry and not soft to the touch. It is often opaque, sometimes translucent. Its prevailing colors are black and green, often intermixed. Its spec. grav. usually lies between 3.15 and 3.38.

(Chemical characters.) Before the blowpipe it melts with considerable ease; the common hornblende into a black or grayish black glass, and actynolite into a gray or yellowish gray enamel. It yields by analysis silex, alumine, magnesia, and lime, but in variable proportions, arising in part, without doubt, from the nature of its gangue. Its colors are produced by the oxides of iron and of chrome.

(Distinctive characters.) Its laminated structure, its inferior hardness, its inability of becoming electric by heat, and sometimes the results of fusion may be employed to distinguish it from schorl.—It is less hard and more easily fusible than Augite.—It differs from epidote in hardness, and the results of fusion.—Its powder is not soft to the touch, like that of asbestus.

This species admits a twofold division, founded chiefly on a difference of color, produced by the oxides of iron and of chrome.

SUBSPECIES 1. COMMON HORNBLENDE.

This subspecies is much more common and abundant, than actynolite, the following subspecies. It embraces all those minerals, to which Werner has given the name of Hornblende, with the exception of the substance, which he has called Labrador Hornblende.

It is sometimes crystallized under the forms already described; and very often occurs in lamellar or fibrous masses. Its prevailing color is black, sometimes brownish or grayish black, and very frequently more or less tinged with green, or even passes into a deep or blackish green, or dark greenish gray; but the tinge of green is never lively. The color of its streak or fine powder is greenish gray. The black varieties are usually opaque, and the greenish, translucent at the edges.

Its crystals are sometimes perfect and distinct; but very often so aggregated, that it is difficult to perceive their form, although the prisms are sometimes large, and their edges well defined. Sometimes these groups are composed of channelled, cylindrical, or very minute prisms, either parallel or diverging, and sometimes intersecting each other.

Its longitudinal fracture is more or less distinctly foliated with a lustre somewhat shining, or even splendent. Its cross fracture is uneven or a little conchoidal, and has a moderate lustre.

Masses of hornblende, whether fibrous, lamellar, or nearly compact, possess a remarkable tenacity, which renders them tough and

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difficult to break; indeed a considerable cavity may often be produced by a hammer, before the mass breaks. They exhale, when moistened by the breath, a peculiar, argillaceous odor; and often appear less hard, than the distinct crystals.

A specimen, analyzed by Klaproth, yielded silex 42.0, alumine 12.0, lime 11.0, magnesia 2.25, oxide of iron 30.0, of manganese 0.25, water 0.75;=98.25. In a crystal of basaltic Hornblende from Cape de Gate, Laugier found silex 42.02, alumine 7.69, lime 9.8, magnesia 10.9, oxide of iron 22.69, of manganese 1.15, water 1.92;=96.17. In another crystal from Fulda, Klaproth found silex 47.0, alumine 26.0, lime 8.0, magnesia 2.0, oxide of iron 15.0, water 0.5;=98.5 Hornblende is liable to decomposition at its surface, becomes more friable, and assumes a ferruginous brown color.

We notice several varieties, distinguished by geological considerations, or diversity of texture.

Var. 1. BASALTIC HORNBLENDE.* JAMESON. This variety, though found in lava and volcanic scoriæ, is very often in Basalt; and hence the term basaltic. It is almost always in distinct crystals, whose color is a pure black, sometimes very slightly tinged with green, or rendered brownish by decomposition. Their surface is sometimes strongly shining, and sometimes dull and invested with a ferruginous crust.

Its structure is more foliated, than that of the other varieties, and its crystals more brittle.—It is also less easily fusible.

This variety is found near Vesuvius, and near Cape de Gate in Spain. It is common in the basalt of Saxony, Bohemia, &c. Sometimes its crystals are found loose in those earths, which have resulted from the decomposition of basalt.

2. LAMELLAR HORNBLENDE.† Its masses are sometimes composed merely of lamellæ, and sometimes of granular concretions of various sizes, having a lamellated structure. Hence the fracture is foliated, but the foliæ are variously inclined or interlaced. Sometimes the lamellæ are continuous and extended; and sometimes the grains are so fine, that the mass appears compact.

3. FIBROUS HORNBLENDE.‡ It occurs in masses, composed of acicular crystals or fibres, either broad or narrow, parallel or interlaced, and sometimes diverging in fascicular groups, or promiscuous-

* Basaltische Hornblende. WERNER. La Hornblende basaltique. BROCHANT. Amphibole schorlique basaltique. BRONGNIART.

† Amphibole lamellaire. HAUY. BRONGNIART. Gemeiner Hornblende. WERNER. Common Hornblende. JAMESON.

‡ Amphibole fibreuse. HAUY.

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ly. Sometimes the fibres are so curved or even curled, that the texture resembles that of knotty wood.

4. SLATY HORNBLENDE, Or HORNBLENDE SLATE.* JAMESON. This variety scarcely differs from the preceding, except in the slaty structure of its masses. For each individual layer, either straight or curved, is composed of very minute fibres, diverging in bundles or promiscuously, and often interlaced. It presents the usual colors of Hornblende; but its lustre is often moderate.

(Geological situation.) Common Hornblende occurs in all classes of rocks, but chiefly in the primitive. It is an essential ingredient in syenite and greenstone. We have already noticed the existence of its crystals in basalt and lava. It often occurs, either crystallized or massive, in granite, gneiss, mica slate, syenite, limestone, &c. or in veins, which traverse these rocks. Sometimes it forms large masses or even beds in gneiss and argillite, and contains magnetic oxide of iron, sulphuret of iron, mica, &c.—Hornblende slate sometimes constitutes large beds in argillite and other primitive rocks. It often contains quartz, feldspar, mica, &c. and, by an increase of these foreign ingredients, it passes into gneiss, or greenstone, or even into chlorite slate. Hornblende is sometimes porphyritic.

(Localities.) Of a mineral so very common we mention but one locality; and that for the purpose of noticing an uncommon aggregate, into the composition of which hornblende enters in a large proportion. This aggregate is found at Brunswick in Maine, and is contiguous to a bed of primitive limestone. It is stratified, and even fissile, and consists of white granular limestone and fibrous Hornblende, with a little mica intermixed. It sometimes resembles gneiss.

SUBSPECIES 2. ACTYNOLITE.† JAMESON.

This mineral possesses all the essential characters of Hornblende. In fact, common Hornblende and Actynolite, separated only by slight differences, when viewed in the extremes, do, in other cases, insensibly pass into each other. The Actynolite has usually a greater translucency, a more lively green color, arising from the chrome, which it contains, and differs also in the result of fusion by the blowpipe.

The Actynolite occurs in prismatic crystals, which are commonly long and incomplete, sometimes extremely minute and even fibrous, and variously aggregated into masses more or less large. Its prevailing color is green, sometimes a pure emerald green, but varying

* Hornblende Schiefer. WERNER. Amphibole Hornblende schisteux. BRONGNIART. La Hornblende schisteuse. BROCHANT.

† Strahlstein. WERNER. La Rayonnante. BROCHANT. Var. of Amphibole. HAUY. Amphibole Actinote. BRONGNIART.

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from a dark or leek green to a pale green, which is sometimes shaded with gray, yellow, or brown. Its colors are liable to change in consequence of decomposition. It scratches glass, but its prisms are often very brittle in a transverse direction. Its cross fracture is often a little conchoidal, and more shining than that of common Hornblende. Its spec. grav. is about 3.30.

It melts by the blowpipe into a gray or yellowish gray enamel. It contains, according to Laugier, silex 50.0, magnesia 19.25, lime 9.75, alumine 0.75, oxide of iron 11.0, oxide of chrome 5.0;=95.75. Its green color is derived from the Chrome, but is often modified by the large quantity of iron, which is present.

It presents but few varieties, and these pass into each other.

Var. 1. COMMON ACTYNOLITE.* JAMESON. It is sometimes in long hexaedral prisms, or four-sided prisms, truncated on their acute lateral edges, with summits almost always incomplete. Their surface is often splendent, and sometimes longitudinally striated. They are translucent, and sometimes nearly transparent.

It is sometimes in masses, composed of flattened or compressed prisms, more or less broad, and commonly diverging. It has also been observed in fascicular groups of broad prisms, which are often curved; their color is greenish gray with a shining and somewhat pearly lustre.

It sometimes presents lamellated or granular masses, differing from common Hornblende merely in the liveliness of their green color.

CLASSY ACTYNOLITE.† JAMESON. It is often in masses, composed of slender, compressed, acicular crystals, or of minute fibres. Its prisms are very brittle, being crossed by transverse rents. Their lustre is often strong and vitreous.

2. ACICULAR ACTYNOLITE.‡ This variety occurs in delicate, capillary prisms or fibres, united in groups, in which the fibres, sometimes parallel, more frequently diverge; and, in some cases, intersect each other, or radiate from a centre. Its lustre is glistening, and somewhat silky or pearly. Its color is usually a paler green, and more mixed with gray, yellow, or brown, than that of the common variety; it is sometimes nearly black. Its masses are often very tender.

FIBROUS ACTYNOLITE.§ This subvariety may easily be mistaken

* Gemeiner Strahlstein. WERNER. Amphibole hexaèdre. HAUY. Amphibole Actinote hexaèdre. BRONGNIART.

† Glasartiger Strablstein. WERNER.

† Asbestartiger Strahlstein. WERNER. Asbestous Actynolite. JAMESON.

§ Amphibole fibreuse. HAUY. Amphibole Actinote fibreux. BRONGNIART.

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for asbestus. It is composed of delicate, parallel fibres, which easily separate by pressure between the fingers, and are converted into a kind of down; the lustre is a little silky. But these fibres are distinguished from those of amianthus by their stiffness and brittleness. Their color is greenish white or whitish.

(Geological situation.) The Actynolite is found in primitive rocks, or in veins, which traverse them; it is sometimes in metallic beds. It is, perhaps, most common in minerals, which contain magnesia. Its more distinct crystals occur in talc, quartz, and limestone.

(Localities.) It is abundant at Zillerthal in the Tyrol, and at St. Gothard.—In the United States, it is not uncommon. In Maryland, near Baltimore, all its varieties occur in granite or gneiss. (DEBUTTS.)—In Pennsylvania, at Concord, Chester Co. in large masses of an emerald green color. (CONRAD.)—In Connecticut, near Newhaven, in serpentine; its structure is generally radiated. (SILLIMAN.)—In Maine, at Brunswick, all its varieties occur, sometimes in granite and gneiss, but more frequently in limestone.

SPECIES 74. DIALLAGE. HAUY. BRONGNIART.

This species has seldom, if ever, been seen in distinct crystals. Its varieties also differ very considerably from each other in some of their external characters; indeed the difference of composition between certain minerals, referred to this species, is so great, that one is compelled to doubt the accuracy of the analysis, or the identity of the minerals.

The Diallage has a foliated structure, and, in one direction,* is easily divisible into laminæ with smooth, polished faces, sometimes traversed obliquely by cracks or seams. Indeed a rhomboidal prism, with bases nearly square, has been obtained by mechanical division. Its cross fracture is usually uneven with very little lustre. It always scratches carbonate of lime, and sometimes makes a slight impression on glass. Its spec. grav. is about 3.00.

Before the blowpipe it melts with some difficulty into a gray, or grayish green enamel. Its composition will be seen under its varieties.

The Diallage sometimes resembles feldspar; but the latter is harder, and its laminæ easily separate at natural joints in two directions.—The same characters will serve to distinguish Diallage from Hornblende.

* The name Diallage is derived from the Greek Διαλλαγη, difference, alluding to the difference of lustre, &c. between its natural joints.

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Var. 1. GRANULAR DIALLAGE.* Its color is a fine grass green, or emerald green. It is opaque, or slightly translucent. It has a shining, foliated fracture in one direction, with a lustre sometimes pearly, or like that of satin. In some specimens the texture is both lamellar and fibrous. Its masses are usually composed of granular distinct concretions, but sometimes appear very compact.

It contains silex 50, alumine 21, lime 13, magnesia 6, the remaining 10 parts being chiefly the oxides of chrome, iron, and copper. (VAUQUELIN.)

(Localities.) At Mount Musinet, near Turin, and also near the lake of Geneva, it is imbedded in a variety of jade (Saussurite).—In Corsica, it is sometimes connected with the same variety of jade; it also, according to Brongniart, enters into an aggregate of feldspar and petrosilex.—Near the Lizard Point, Cornwall, an aggregate of granular Diallage and feldspar is found between serpentine and gray-wacke. (BERGER.)

These aggregates, containing Diallage, are sometimes polished, and employed in ornamental work. Such is the verde di Corsica of the Italians.

2. RESPLENDENT DIALLAGE.† This variety occurs in masses of a moderate size, or in laminæ, which, according to Emmerling, are sometimes hexaedral. Its laminæ, sometimes a little curved, have usually a metallic lustre, often strong, and sometimes accompanied with the reflective power of polished metals. When the reflecting surfaces of the laminæ are parallel, or situated in the same plane, as is usually the case, their brilliancy suddenly appears or disappears, as the position of the specimen is changed.

Its color is usually a deep bottle green, or a metallic gray almost silver white; sometimes also olive green, brown, or blackish. Some specimens have a deep brown color, slightly tinged with violet, and a lustre less metallic than usual.—It is somewhat less hard, than the preceding variety; and its spec. gravity is a little below 3.00.

It sometimes passes into granular Diallage, the same natural joint extending itself from one variety to the other. (HAUY.)

It contains, according to Drappier, silex 41, magnesia 29, alumine 3, lime 1, water 10, oxide of iron 14;=98. But, according to Heyer, it contains silex 52.0, alumine 23.33, lime 7.0, magnesia 6.0, iron 17.5;=105.83.

This variety is usually imbedded in serpentine. Near Turin, it

* Kö;rniger Strahlstein. WERNER. Granular Actynolite. JAMESON. Diallage verte. HAUY. BRONGNIART. Smaragdite. SAUSSURE.

† Diallage métalloïde. HAUY. Diallage chatoyant. BRONGNIART. Schillerstein. WERNER. Shiller Stone. JAMESON. Spath chatoyant. BROCHANT.

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is sometimes associated with jade and granular Diallage. Mica, talc, quartz, garnets, magnetic iron, &c. are among its accompanying minerals.

3. BRONZITE.* Its structure is usually more distinctly foliated, than that of the preceding variety; and its laminæ, though somewhat less shining, still retain a lustre almost metallic. Its lustre does not so suddenly disappear by a slight change of position, as in the preceding variety. Its colors are brass or bronze yellow, or tombac brown. In thin plates it is translucid; and its spec. grav. is sometimes 3.20.

It contains silex 60.0, magnesia 27.5, oxide of iron 10.5, water 0.5;=98.5. (KLAPROTH.) It is almost infusible.

It is usually found in small masses, disseminated in serpentine.

SPECIES 75. MACLE.† HAUY. BRONGNIART.

The Macle has occurred only in crystals, whose different parts are arranged in a very peculiar manner. The form of these crystals is a four-sided prism, whose bases are rhombs, but differ very little from squares. But each crystal, when viewed at its extremities, or on a transverse section, is obviously composed of two very different substances; and its general aspect is that of a black prism, passing longitudinally through the axis of another prism, which is whitish.

The black and white parts of these crystals exhibit some diversity of arrangement, which we shall endeavor to illustrate by one figure (Pl. IV, fig. 31.), in which nearly all the varieties are combined.

Sometimes a black rhomb, whose sides are parallel to those of the crystal, occupies the place of the axis, while four small, black lines pass from each angle of this rhomb to the corresponding angles of the exterior white prism.—Sometimes four other black rhombs appear at the four angles of the white prism, and are joined to the central rhomb by the four black lines already mentioned; the sides of these rhombs are parallel to those of the central rhomb, but are not always well defined.—The preceding crystal sometimes exhibits a considerable number of black lines, parallel to the sides of the black rhombs, as in the figure.—Sometimes four white prisms are so arranged, as to present a cross, still retaining the central rhomb and the four black lines; and sometimes the re-entering angles of this cross contain the four additional black rhombs.—In another variety the whole prism is black, excepting its sides, which are invested with a pearly white coat of Macle.

These crystals, often long, are sometimes very minute; in some instances their edges are rounded.

The term Macle, as the name of a distinct species, applies to the

* Diallage metalloïde. HAUY. BRONGNIART.

† Hohl Spath. WERNER. Hollow Spar. JAMESON. Macle. BROCHANT.

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whitish prisms only. The black rhombs and lines are an argillaceous substance of the same nature, as their gangue, with a few whitish particles of Macle intermixed.

The crystals of Macle present a considerable number of natural joints, which lead to an octaedron for their primitive form. M. Haüy has remarked, that, if we consider the whole crystal as a prism of Macle, the continuity of whose parts is interrupted by the black substance, all these interruptions are in the direction of some of the natural joints. In some cases, at least, the black central prism is diminished in size, while proceeding from one extremity to the other, being somewhat pyramidal.

The structure of the Macle is sometimes foliated, but, in general, more or less imperfectly, or is even compact; its fracture, which varies accordingly, has a feeble lustre, sometimes a little resinous. It scratches glass, when its structure is distinctly foliated.—Its powder is soft, or a little unctuous to the touch. It is opaque, or sometimes translucent. Its color is white or gray, often shaded with yellow, green, or red.—Its spec. grav. is 2.94; and it communicates to sealing wax negative electricity by friction.

The Macle, or white part of the crystal, melts with difficulty by the blowpipe into a white enamel.

(Localities.) The Macle is almost always imbedded in a black argillaceous slate.—It has been found in France, Spain, Portugal, Germany, and England. The variety, in which the black prism is merely invested with a thin coat of Macle, is found in the Pyrennees.

In the United States. In Massachusetts, Worcester Co. at Sterling, two miles from Lancaster, it occurs abundantly in a dark bluish argillite. Its crystals are of various sizes, and sometimes very perfect. Many of them are often found in the space of a few square inches; and, when only their extremities are visible, as is usually the case, the argillite presents a striking and singular aspect.—In New Hampshire, 26 miles from Portsmouth, on the road to the White Hills. (MACLURE.)—In Maine, at Brunswick and Georgetown, in small quantities.

SPECIES 76. NATIVE MAGNESIA. BRUCE.

The structure of this new and interesting mineral is very distinctly foliated; and the foliæ frequently radiate from a centre. Their lustre is more or less shining and pearly; and they are somewhat elastic.

The laminæ when separate, are transparent; in the mass, only semitransparent; and, by exposure to the weather, their surface becomes dull and opaque.

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It is soft, and may be scratched by the finger nail, like talc. It slightly adheres to the tongue; and its spec. grav. is 2.13. Its color is white, often tinged with green; its powder is a pure white.

It becomes opaque and friable before the blowpipe, and its weight is diminished. In diluted sulphuric acid it entirely dissolves without effervescence, and yields a limpid solution extremely bitter to the taste. According to Professor Bruce, to whom we are indebted for a knowledge of this mineral, it is composed of pure magnesia 70, water 30.

It is sufficiently distinguished from talc by its solubility in acids.

(Locality.) It is found at Hoboken in New Jersey, in veins from a few lines to two inches in thickness; they traverse serpentine in various directions, and, near the sides of the vein, the serpentine is sometimes intermixed with the foliæ of the magnesia.

(Remarks.) We have been induced to form a distinct species of this mineral, because we have seen no satisfactory evidence, that any of the substances, heretofore called native magnesia, ought to be associated with it. The two varieties of the Magnesite of Brongniart, found at Baudissero and Castella Monte, in Piedmont, are the only foreign minerals, hitherto described, which approach in any considerable degree to native magnesia. They, however, differ materially from the mineral just described; this is pure, crystallized magnesia, having a foliated structure—those are compact, never pure, and, when analyzed, have always yielded more or less carbonic acid. Indeed their composition is so different, that, were they admitted into this species, they must be arranged as a subspecies.

According to M. Giobert, the magnesian substance, found at Castella Monte, contains no carbonic acid, when in the bosom of the earth, but imbibes it from the atmosphere during an exposure of a few weeks; he believes also, that the variety from Baudissero has derived from the atmosphere the carb. acid, which it contains, even when first removed from the quarry. He therefore is inclined to consider both as native magnesia, contaminated with about 15 per cent. of silex.

Giobert, in his two memoirs on these substances, observes, that the magnesian mineral from Castella Monte does not effervesce with acids, when first taken from the earth; while that from Baudissero always discovers more or less effervescence during solution. Brongniart in his mineralogy remarks, that these Piedmontese magnesites do not effervesce in concentrated acids. We might therefore suppose, that the total want of effervescence in the mineral from Castella Monte, as stated by Giobert, arose from the great concentration of his acid, had he not also asserted, that this mineral gave no indication of carb. acid, when exposed to the action of fire.—We conclude

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these observations with the remark of Haüy in his Tableau Comparatif, where he says, it would be singular, if this magnesian earth had absorbed, during its exposure to the air, so great a quantity of carbonic acid, as is sometimes indicated by analysis; for, in the mineral from Castella Monte, 46 per cent. of this acid was found by Morveau.

SPECIES 77. MAGNESITE. BRONGNIART.

This species, as its name indicates, embraces those minerals, which contain a greater or less quantity of magnesia, and, at the same time, cannot be referred to any other species. This magnesia is sometimes combined with carbonic acid, and always with silex, in variable proportions.

It is hardly possible to give any specific, external characters; for these vary with the composition.—In general, however, its spec. gravity is low, not rising much above 2.00, and sometimes falling below 1.00. It is usually more firm and tenacious than chalk, but varies considerably in hardness, and the cohesion of its parts. Most commonly it is a little unctuous to the touch, and receives a polish from the finger nail. Its colors are white, gray, pale yellow, and reddish white. It does not form a paste with water, unless beaten for a long time.

(Chemical characters.) By the action of fire it diminishes in bulk, but does not melt, unless much mixed with other earths. Though frequently containing carbonic acid, it seldom effervesces even with the stronger acids, unless they be diluted. If moistened with a small quantity of sulphuric acid, efflorescences or even minute crystals of sulphate of magnesia appear in the course of a few days. This is one of its most decided characters; and by this it may be distinguished from chalk and certain clays.

Some of its varieties have received distinct names.

Var. 1. KEFFEKIL.* KIRWAN. Its color is white or gray, usually tinged with yellow. It occurs in dull, opaque masses, which are a little unctuous to the touch, and have an earthy texture. It is often porous, like tufa; and is very light, sometimes swimming on water, and sometimes its spec. grav. reaches 1.60.

It is infusible by the blowpipe, but hardens by the action of heat. It is partially soluble in acids without effervescence. A specimen, analyzed by Klaproth, yielded silex 50.5, magnesia 17.25, lime 0.5, carbonic acid 5.0, water 25.0;=98.25.

It occurs in masses, and is sometimes disseminated in other minerals, or forms a superficial bed. In Natolia, it fills a vein more than

* Meerschaum. WERNER. JAMESON. L'Ecume de mer. BROCHANT. Magnesite plastique. BRONGNIART.

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six feet wide, traversing compact limestone. Though soft, when taken from the quarry, it hardens and becomes white by the action of the air.

(Uses.) This mineral, being soft and tenacious when recently obtained, is moulded into tobacco pipes and other vessels, and afterward slightly baked. Of this substance the Turkey tobacco pipes are formed.

2. ARGILLO-MURITE.* KIRWAN. This variety is exceedingly light, and swims on water, till absorption takes place. Its spec. grav. varies between 1.87 and 0.36. It feels or and its powder is both very fine and very hard. Its color is grayish white, clouded with yellow.

Its weight and bulk are diminished and its hardness increased by exposure to a porcelain heat, but it does not melt. It does not effervesce in acids; and, according to Fabroni, contains silex 55, magnesia 15, alumine 12, lime 3, water 14, iron 1.

This substance, found near Castel-del-Piano, has been manufactured by Fabroni into bricks, which float on water.

3. Magnesite of Piedmont. This is not easily diffusible in water, and is with difficulty formed into a paste. It does not effervesce in concentrated acids, and is infusible by the blowpipe. Both its hardness and spec. grav. are variable, and it is sometimes difficult to break.

That, which is found at Baudissero, is opaque and very white. It is compact, and has a dull, conchoidal fracture. Though sometimes soft, it is not easily reducible to a very fine powder. Its hardness is sometimes considerable, but is not affected by exposure to the air. It is sometimes mammillary or tuberose.

It contains magnesia 68.0, silex 15.6, carbonic acid 12.0, water 3.0, sulphate of lime 1.6;=100.20. (GIOBERT.)

It is found in veins, traversing serpentine.

Another of these Magnesites is found at Castella Monte. Its fracture is earthy or slightly conchoidal, and, when recently made, appears white; but, by exposure to the air, it becomes dull, or yellowish. Its thin fragments are translucent. It is unctuous to the touch, adheres to the tongue, and is easily cut by a knife.

It contains magnesia 26.8, silex 14.2, carbonic acid 46.0, water 12.0;=98.50. (MORVEAU.) (See remarks on these two Magnesites of Piedmont under the preceding species.)

Both these Piedmontese Magnesites are employed in the manufacture of porcelain at Vineuf.

* Argile legere. BRONGNIART.

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4. Magnesite of Vallecas, in Spain. It is opaque and grayish white; and has a dull, uneven fracture. When recently obtained, or when moistened, it may easily be cut by a knife. When dry, it swims on water for a short time. It does not diffuse itself in water; but, if beaten for a long time, it forms a paste, which is inferior to that of clay.

It does not effervesce with acids. It does not melt in a porcelain heat, but becomes harder, and diminishes in bulk.

It occurs near llecas in Spain, in extensive beds. Flint and cacholong, intimates, united with the Magnesite, are found in the fissures of these beds.

This mineral is employed in the manufacture of porcelain at Madrid.

5. Magnesite of Salinelle, in France. This has a slaty structure. When moist, its thin parts are a little translucent, and its color chocolate brown; but, when dry, it becomes more solid, and its color passes to gray or reddish. It is infusible; but, by exposure to a strong heat, it becomes very white. It contains silex 55, magnesia 22, water 23. (VAUQUELIN.)

6. Magnesite? of Baltimore, in the United States. We know not where else to notice this uncommon mineral, till its properties shall have been further investigated. From some experiments it appears to contain magnesia; it effervesces briskly in nitric acid, and is converted by the blowpipe into a light, white powder.

These circumstances have induced us to place this mineral among the Magnesites, from which, however, it differs in most of its physical characters.—Its effervescence in acids seems to exclude it from the preceding species.

It sometimes appears in small, flat prisms with diedral summits, and sometimes in mammillary masses, composed of crystals radiating from a centre, and invested with a yellowish substance. The insulated crystals are white and transparent.

This mineral is found in very narrow veins in serpentine, at the Bare Hills, near Baltimore. (HAYDEN and GILMOR.)

(Remarks.) It has been seen, that several of the preceding Magnesites are used in the manufacture of porcelain. They may also be advantageously employed in the preparation of sulphate of magnesia (Epsom salt) by the assistance of sulphuret of iron. (GIOBERT.)It should be remembered, that earths, which contain any considerable quantity of magnesia, not saturated with carbonic acid, are injurious to vegetation.

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SPECIES 78. SERPENTINE.* KIRWAN. JAMESON.

This substance, though sometimes strongly resembling other minerals, is, in general, easily recognised. Its grain is more or less fine, and its texture compact. It may always be cut or scraped with a knife, sometimes with difficulty, and often very easily; but it never yields to the finger nail.

Serpentine usually presents some shade of green, varying from a deep green to greenish gray, often intermixed with yellow, and sometimes with red, &c. The color is sometimes uniform, but more frequently different colors appear in spots, stripes, veins, &c. and in polished specimens sometimes resemble the colors of a serpent; hence the name. Its colors and their peculiar arrangement are somewhat characteristic.

Its fracture varies even in the same specimen; it is frequently splintery, even, or conchoidal, but sometimes uneven or earthy, or a little slaty. It is dull, or possesses only a feeble lustre. Its surface, which is sometimes glossy, like varnish, is soft to the touch; but its powder is decidedly unctuous. Its spec. grav. usually lies between 2.57 and 2.70. It sometimes moves the magnetic needle, and even possesses polarity.

(Chem. characters.) Before the blowpipe it hardens, yet does not melt; but, when impure, is reduced to a frit. A specimen, analyzed by Chenevix, yielded magnesia 34.5, silex 28.0, alumine 23.0, lime 0.5, water 10.5, oxide of iron 4.5;=101. The proportion of magnesia varies from 23 to 36 per cent. But, as Klaproth found no alumine in Serpentine from Saxony, perhaps magnesia and silex are the only essential ingredients. It usually contains the oxide of iron, and sometimes that of chrome. Its analysis, however, must, without great caution, be sensibly affected by the foreign substances, so common in Serpentine.

Serpentine is often nearly allied to the harder varieties of steatite and potstone, and may sometimes resemble even slaty chlorite or certain varieties of argillite.—Its degree of hardness, and its colors, or their peculiar arrangement, are its most distinctive characters in these cases.

It presents two varieties, which sometimes pass into each other.

Var. 1. PRECIOUS SERPENTINE.† JAMESON. Its colors are uniform; they are generally leek green or blackish green, often more or less shaded with yellow. It is always translucent, and the transmit-

* Serpentin. WERNER. Serpentine. BROCHANT. BRONGNIART. Roche serpentineuse. HAUY.

† Edler Serpentin. WERNER. Serpentine noble. BRONGNIART. BROCHANT.

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ted light has usually a tinge of yellow, even when the reflected light is a deep green; for the same reason the splinters or scales on its fracture are very often yellowish.

Some of the hardest Serpentines belong to this variety. Its fragments often have very sharp edges. Its fracture, though variable, is perhaps most frequently conchoidal or splintery. Its lustre is often more or less glistening and waxy.

2. COMMON SERPENTINE.* JAMESON. It presents numerous shades of green, varying from leek green, greenish black, or brownish black to greenish or bluish gray, with much yellow or brown intermixed; it is sometimes yellow or red. These colors, seldom uniform, are arranged in stripes, veins, clouds, spots, dots, &c. Hence a specimen of this Serpentine frequently resembles a compound rock. It is opaque, or translucent at the edges.

Its hardness is often less, than that of precious Serpentine. Its fracture is nearly dull, and presents most of the varieties already mentioned. When moistened, it frequently exhales an argillaceous odor.

(Geological situation.) Serpentine is associated both with primitive and transition rocks; and occurs in masses or beds, which are sometimes extensive, or constitute even whole mountains.

The oldest Serpentine exists in beds in gneiss, mica-slate, and argillite, and is usually accompanied or even mixed with granular limestone, with which indeed its beds sometimes alternate. This formation embraces most of the precious Serpentine, and is much more rare than the following.

A second or more recent formation, consisting chiefly of common Serpentine, occurs in large masses, or extensive beds, or forms even whole mountains. It rests on primitive rocks, or is associated with those of the transition period.

Serpentine, especially the common variety, embraces other minerals, in veins or in beds, or disseminated in masses more or less large. Among these are steatite, talc, asbestus, magnesite, lithomarge, &c. also quartz, garnets, magnetic iron, chromate of iron, &c. It seldom contains metallic substances insufficient quantity to be explored. At Cornwall, native copper, mixed with steatite, is found in veins, traversing Serpentine; and in Piedmont beds of magnetic iron sometimes alternate with those of Serpentine.

(Localities.) This mineral is not rare. At Zö;blitz, in Saxony, it is very abundant, and its quarries have been long explored.—It is very common in Corsica, and very beautiful at Portsoy in Scotland. Humboldt has observed a remarkable Serpentine in the Upper Palatinate.

* Gemeiner Serpentin. WERNER. Serpentine commune. BRONGNIART. BROCHANT.

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It acts on the magnetic needle at the distance of more than twenty feet, although it presents no indications of magnetic iron. The southern parts of this mass possess north polarity, and the northern parts the reverse.—At the Lizard Point in Cornwall, Serpentine is surrounded on all sides by gray-wacke, with which however it is not in contact; in one place a rock, composed of feldspar and diallage, intervenes. (BERGER)—On the summit of Mount Rose the older Serpentine occurs in horizontal beds. (SAUSSURE.)

In the United States. In Maryland, it occurs at the Bare Hills, near Baltimore, belonging chiefly to the common variety.—In Pennsylvania, Serpentine is found in the counties of Montgomery, Chester, &c.—In New Jersey, at Hoboken.—In Connecticut, near Newhaven, particularly on Milford Hills. The precious Serpentine is imbedded in nodules or irregular masses in primitive limestone, and receives a very high polish. The common variety occurs in extensive beds, connected with limestone, with which it is frequently so blended, as to produce a great variety of figures and colors in slabs, taken from these rocks; its colors are yellow and green. It contains magnetic oxide of iron and chromate of iron, both of which also exist in the limestone. (SILLIMAN.)—In Rhode Island, near Newport. (MEASE.)—In Massachusetts, near Newburyport, in granular limestone, with which it is often irregularly mingled. The precious Serpentine of this place is often extremely beautiful, and perfectly resembles that of St. Kevens, in Cornwall. Its color is sometimes a deep or even blackish green. It is often traversed by veins of amianthus.

(Uses.) Serpentine is easily cut, and the fineness and closeness of its grain render it susceptible of a high polish. It is wrought into little boxes, and various articles for ornamental or even for useful purposes. At Zö;blitz in Saxony, several hundred persons are employed in this manufacture.

The aggregate of serpentine and limestone, irregularly mingled, is called Vert antique, and constitutes a very beautiful marble.

SPECIES 79. STEATITE. (Soapstone.)

Although, in conformity to most mineralogists, Steatite is here separated from talc, it is undoubtedly a variety of that mineral, being the result of a confused crystallization, or of precipitation. (See chemical characters of common Steatite.)

All the varieties of Steatite are so soft, that they may be cut by a knife, and, in most cases, scratched by the finger nail. Its powder and surface are soft and more or less unctuous to the touch. It is seldom translucent, except at the edges. Its fracture is, in general, splintery, earthy, or slaty, with little or no lustre. By friction it communicates to sealing wax negative electricity.

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Exposed to heat it becomes harder, but is almost infusible by the blowpipe. It appears to be essentially composed of silex, magnesia, and perhaps alumine.

Var. 1. COMMON STEATITE.* This variety is usually solid, and its texture compact; sometimes it is almost friable, and its texture earthy. Its surface is very often like soap to the touch, and usually receives a polish from the finger nail. It is sometimes so soft, that it may be cut, like soap, and sometimes its hardness approaches that of the softer varieties of serpentine.

In most cases it is translucent at the edges only, and often very feebly. Its color is usually gray or white, seldom pure, but variously mixed with yellow, green, or red, and is sometimes a pale yellow, reddish, or green of different shades. The colors sometimes appear in spots, veins, &c.

Its spec. grav. usually lies between 2.58 and 2.79. When solid, it is somewhat difficult to break. Its fracture is nearly or quite dull, and in most cases splintery or earthy, but sometimes a little slaty, uneven, or conchoidal. When passing into talc, it possesses more or less lustre, sometimes waxy.

Steatite has also been observed in fibrous masses, or in minute threads, traversing more compact varieties, or even other minerals.

It sometimes presents pseudomorphous crystals, which appear to have been moulded in cavities, once occupied by true crystals. Sometimes these crystals have obviously derived their form from hexaedral prisms of quartz, and exhibit even the transverse striæ of these prisms. Sometimes the form is taken from crystals of carbonate of lime.

(Chemical characters.) Before the blowpipe it whitens and becomes hard, and is with difficulty reduced into a whitish paste or enamel, often however only at the extremity of the fragment. Vauquelin obtained from a compact, reddish Steatite silex 64, magnesia 22, alumine 3, water 5, iron and manganese 5;=99. A specimen from Bareuth yielded Klaproth silex 59.5, maguesia 30.5, water 5.5, iron 2.5;=98. In the Steatite of Cornwall, he found silex 48.0, magnesia 20.5, alumine 14.0, water 15.5, iron 1.0;=99.

The results of the first two analyses almost perfectly resemble those, which the same chemists obtained from laminated talc, and show beyond a doubt, that Steatite and talc belong to the same species. Further, when compact Steatite is bruised in a mortar or strongly heated, it is, in many cases, obviously composed of very minute foliæ or scales. In fine, Steatite agrees with talc in its composition; and in

* Speckstein. WERNER. Steatite. JAMESON. Steatite commune. BRONGNIART. BROCHANT. Talc steatite HAUY. Semi-indurated and indurated Steatite. KIRWAN. Soapstone of some.

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most of its physical characters, does not so widely differ from laminated talc, as do several varieties of carbonate of lime from calcareous spar. The different electricities, communicated to sealing wax by talc and Steatite, cannot be considered an objection to the identity of the two minerals; for it is well known, that the kind of electricity is sometimes determined by very trivial circumstances, as the degree of roughness, friction, &c. in the substances employed.

(Distinctive characters.) When Steatite is passing into talc, it is almost impossible to draw a line of distinction; but in most cases the characters already given will be sufficient.—It is sometimes nearly allied to serpentine, and in this case its unctuosity is scarcely perceptible, and it differs chiefly by an inferior degree of hardness.—When friable, like chlorite, it still differs from that mineral by its dullness, greater unctuosity, and infusibility.

(Geological situation.) Common Steatite occurs in masses, or veins, or small beds in primitive and transition rocks, more particularly in serpentine. It is sometimes mixed with talc, mica, quartz, and asbestus; or is found incrusting other minerals.—It is sometimes imbedded in wacke; and sometimes occurs in metallic veins.

(Localities.) This mineral is not uncommon. That, which is found in Arragon, in Spain, has been called Spanish chalk.—In the principality of Bareuth, it occurs in yellowish white pseudomorphous crystals, apparently of the same nature, as the mass of Steatite, in which they are imbedded. The crystals are six-sided prisms, transversely striated; and the same mass contains also crystals of quartz.— The Steatite of Cornwall is impure, and more earthy than usual; it exists in veins traversing serpentine.

In the United States. In Maryland, at the Bare Hills, near Baltimore, several varieties of Steatite occur in serpentine; it is sometimes fibrous. (HAYDEN.)—In Pennsylvania,in Montgomery Co. 10 miles from Philadelphia, and other parts of the State.—In New Jersey, on the Delaware, opposite Easton; it is white, and suitable for architecture. (WOODBRIDGE.)—In Connecticut, near Newhaven, &c.—In Vermont, the substance, commonly called soapstone, is found at Oxford, Grafton, Athens, &c. but the writer knows not, whether it belongs to this variety of Steatite.

2. POTSTONE.* KIRWAN. JAMESON. Its hardness is nearly the same, as that of common Steatite; but it is more tenacious, and though easily cut, it breaks with some difficulty. Its surface is Smooth and even unctuous to the touch. Its fracture is uneven, or

* Topfstein. WERNER. La Pierre ollaire. BROCHANT. Talc ollaire. HAUY. Serpentine ollaire. BRONGNIART.

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earthy, and sometimes slaty or almost foliated; the layers are often undulated. It has usually a moderate lustre, often a little waxy.

It is seldom transluceut, except at the edges, and sometimes opaque. Its color is usually greenish gray of various shades, sometimes reddish, or yellowish, or even green; often spotted. Its spec. gravity lies between 2.87 and 3.02; and it usually exhales an argillaceous odor, when moistened by the breath.

According to the analysis of Wiegleb it contains magnesia 38.54, silex 38.12, alumine 6.66, lime 0.41, iron 15.02.

It is often extremely difficult to distinguish this mineral from indurated talc; but, in general, it is less distinctly, foliated, and is less easily broken.

It is usually found in connexion with serpentine; and is sometimes mixed with chlorite, talc, mica, &c. At Como, in Italy, is a quarry, which was open in the days of Pliny; hence the name lapis Comensis.

(Uses and Remarks.) The substance, employed in the arts under the name of Soapstone, usually belongs to Steatite, but sometimes to lamellar or indurated talc. The soapstone of Springfield in Massachusetts, and Francestown in New Hampshire appears to be composed chiefly of talc.—Steatite is not susceptible of a good polish. But its softness and tenacity, in consequence of which it may be cut or turned into articles of various forms, and its property of becoming hard by exposure to heat, render it a useful mineral in the arts. Hence it may be employed for the hearths of furnaces, the sides of fireplaces and stoves, &c. The potstone has even received its name from having been manufactured into culinary vessels; and such vessels are in very general use in the country of the Grisons, &c. (BRONGNIART.) It resists for a long time the action of the fire.

The common Steatite has even been employed for the purpose of engraving. For, being easily cut, when soft, it may be made to assume any desired form, and afterwards rendered hard by heat; it then becomes susceptible of a polish, and may be variously colored by metallic solutions.

Brongniart supposes, that certain unctuous earths, which savages of the lowest order are known to eat, may be referred to the common Steatite. Thus the inhabitants of New Caledonia employ, as food, a soft, friable, greenish earth, containing magnesia 37, silex 36, iron 17. Humboldt relates a similar fact in regard to a tribe of savages on the banks of the Oronoke in S. America.

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SPECIES 80. TALC. BRONGNIART.

The structure of this mineral, sometimes fibrous, is most commonly foliated. The foliæ are more or less flexible, but never elastic. Both its surface and powder are unctuous to the touch. It is so soft, that it may be scratched by the finger nail. When rubbed on cloth, it leaves a whitish trace, often somewhat pearly.

It has always some lustre, which is often strong and pearly, or a little metallic. It is translucent, and in thin plates transparent. Its prevailing colors are green and white with intermediate shades. Its spec. grav. varies from 2.58 to 2.87. When rubbed on sealing wax, it communicates to the wax positive electricity.

Talc is sometimes crystallized in six-sided tables or laminæ, whose primitive form is a prism with rhombic bases.

Before the blowpipe it whitens, its laminæ separate, and their extremities melt into a white enamel. A specimen of common Talc yielded Vauquelin silex 62.0, magnesia 27.0, alumine 1.5, water 6.0, oxide of iron 3.5.

Var. 1. COMMON TALC.* KIRWAN. JAMESON. This variety sometimes presents the crystalline form before mentioned; but usually appears in delicate and very flexible laminæ, united, like those of mica, into small masses, and, like those also, easily separable. Its laminæ, sometimes curved or undulated, have usually a shining or even splendent lustre, pearly or metallic; and, when thin, are transparent. Their surface is soft, and, in most cases, very unctuous to the touch. Sometimes, however, the unctuosity of the surface is feeble. Its colors are apple green or greenish white, passing to silver white, and sometimes leek green, reddish or yellowish white.

FIBROUS TALC. The fibres are often large and obviously composed of very narrow, elongated laminæ. Sometimes the mass has the appearance of petrified wood (ligniform talc.) Sometimes it resembles coarse fibres of asbestus.

(Distinctive characters.) The inferior hardness, want of elasticity, difficult fusibility, and, in most cases, the unctuosity of Talc will distinguish it from mica.—Chlorite and nacrite are fusible; and cyanite, which Talc sometimes resembles, is much harder.

(Geological sit. and Localities.) This variety, though not uncommon, is never very abundant. It occurs in primitive or transition rocks; frequently in serpentine. It is often associated with actynolite, limestone, steatite, indurated Talc, &c.

That, which is brought from the mountains of Salzburg and Tyrol

* Gemeiner Talc. WERNER. Le Talc commune. BROCHANT. Talc laminaire. BRONGNIART. Talc hexagonal et laminaire. HAUY.

45

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to Venice, is known in commerce by the name of Venetian Talc.— In the United States. In Maryland, it occurs near Baltimore, where it is fibrous, ligniform, &c. and sometimes foliated. (HAYDEN.)— In Pennsylvania, Delaware Co. where it is sometimes crystallized. (WISTER.)—In Connecticut, at Haddam, it enters into the composition of granite.—In Massachusetts, at Southampton, with sulphate of barytes.—In Maine, at Brunswick, in granular limestone with actynolite, and sulphuret of iron; its colors are silver white and apple green.

2. INDURATED TALC.* JAMESON. It is somewhat harder, less unctuous, and less flexible, than common Talc; indeed its laminæ are sometimes almost destitute of flexibility. Its fracture is foliated, often imperfectly, or almost slaty with curved layers, and sometimes fibrous or radiated; its lustre is somewhat shining and often pearly. Unless in thin plates, it is translucent at the edges only. Its colors are greenish gray, or nearly white, yellowish green, or leek green, and sometimes bluish.

SCALY TALC. Its masses are composed of small scales, rather than continuous laminæ. Its color is pearly white or greenish. It is found in Piedmont; and sometimes called French Chalk.

Indurated Talc often strongly resembles steatite, especially the variety called potstone.—It differs from serpentine in its structure, and is also less hard.

(Geological sit. and Localities.) It occurs in beds, sometimes considerably extensive, in gneiss, mica slate, argillite, and serpentine, and is accompanied by chlorite, asbestus, &c. At Zillerthal in the Tyrol, it contains tourmaline, staurotide, cyanite, &c.—In the U. States; it has been observed near Baltimore in Maryland, and at Hoboken, in New Jersey, &c.

(Uses.) Talc is sometimes used instead of chalk for tracing lines. The common variety forms the basis of the rouge, employed by ladies, the Talc being colored by an extract from the Carthamus Tinctorius.

The name Talc is sometimes erroneously extended to mica; and there is indeed sometimes a strong resemblance between the two minerals.

SPECIES 81. CHLORITE.† BRONGNIART.

This substance may always be easily cut by a knife, and in most cases it receives an impression from the finger nail. It is sometimes considerably solid, and sometimes friable or earthy. Its masses ap-

* Verhærteter Talc. WERNER. Talc endurci. BRONGNIART. BROCHANT.

† Talc chlorite. HAUY.

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pear to be composed of minute scales, prisms, or grains, easily separable, sometimes even by friction between the fingers. It is easily reducible to a grayish green powder, which is soft or a little unctuous; its surface also is more or less sensibly unctuous. Its color is almost always some shade of green,* usually very dark. It exhales, when moistened by the breath, an argillaceous odor. By friction it communicates to sealing wax negative electricity. (HAUY.)

(Chemical characters.) Before the blowpipe it melts into a scoria or enamel of a gray or blackish color. The results of its analysis are so various, that it is hardly possible to determine what is essential to its composition. Vauquelin obtained silex 26.0, alumine 18.5, magnesia 8.0, oxide of iron 43.0, muriate of soda and potash 2.0, water 2.0;=99.50. In another specimen Klaproth found silex 53.0, alumine 12.0, magnesia 3.5, lime 2.5, oxide of iron 17.0, water 11.0; =99. But the results of Hoepfner's analysis are silex 41.15, magnesia 39.47, alumine 6.13, lime 1.50, oxide of iron 10.15, water 1.5;=99.90.

Var. 1. COMMON CHLORITE.† JAMESON. It is in masses more or less solid, having an earthy, or very minutely foliated fracture, and a glimmering lustre. These masses are sometimes composed of minute, hexaedral prisms or laminæ, sometimes a little curved. It is opaque; and its color is usually a dark leek green or blackish green, sometimes also mountain or grass green, also brownish, or grayish. Even the paler varieties, when moistened, often exhibit a shade of green.

EARTHY CHLORITE.‡ This subvariety is characterized by the feeble cohesion of its particles; and occurs in friable masses, composed of glimmering scales, or in a loose state.

(Geological situation.) Common Chlorite, whether solid or earthy, is frequently found in primitive rocks, but it never forms very large masses. It occurs in cavities, or in veins, or is disseminated. It is often mixed with quartz, feldspar, carbonate of lime, axinite, &c. sometimes investing or even penetrating and coloring these minerals. Sometimes it forms small beds, containing quartz, feldspar, mica, hornblende, sulphuret of iron, &c. and is often found in metallic veins.—It passes into the following variety.

(Localities.) In the U. States. In Maryland, near Baltimore, it is abundant.—In Pennsylvania, in Chester Co. near the Warwick

* Hence its name from the Greek, Хλωζος, green.

† Gemeiner Chlorit. WERNER. Chlorite commune. BRONGNIART. BROCHANT. Chlorite compacte. HAUY.

† Chlorit erde. WERNER. Chlorite earth. JAMESON. Chlorite terreuse. HAUY. BROCHANT.

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iron works, it contains sulphuret of iron. (SEYBERT.)—In Connecticut, at Brookfield, &c. it is abundant, and near Newhaven it penetrates quartz and calcareous spar. (SILLIMAN.)—In Maine, at Topsham, in granite, either disseminated, or filling cavities, whose sides are lined with projecting crystals of feldspar.

Common Chlorite is sometimes formed into inkstands, &c. Prof. Silliman has an ancient Indian pipe, made of this substance.

2. SLATY CHLORITE, or CHLORITE SLATE.* JAMESON. Its color is blackish green, more or less deep, sometimes mountain green, or greenish gray. It exists in opaque, solid masses, composed of minute scales, like common Chlorite. Its fracture is slaty with layers usually curved or undulated, and glistening. Sometimes its fracture is scaly, or presents small foliæ. Its surface is in some cases very considerably unctuous.

(Geological sit. and Localities.) This variety is found in veins, or thin layers, and sometimes in extensive beds in primitive rocks, especially in argillite. It very frequently contains octaedral crystals of magnetic iron with garnets and quartz.—It exists also in secondary rocks. Sometimes it passes into mica slate, argillite, or greenstone slate.

In the United States. In Pennsylvania, Montgomery Co. near the Schuylkill, it contains numerous crystals of octaedral iron. (SEYBERT.)—In Connecticut, near Newhaven, in thin veins in secondary greenstone; and these veins are divided by still thinner veins of quartz and calcareous spar in the direction of the layers. On the Milford Hills, it appears in layers about one fifth of an inch thick between primitive marble and primitive greenstone; it is soft and unctuous, and not unfrequently stained red by a coloring matter, whose nature is not well known. Near Westhaven, it forms extensive strata, sometimes almost passing into argillaceous slate; but at the beach, one mile below Westhaven, it is decidedly Chlorite slate, and abounds with magnetic oxide of iron. (SILLIMAN.) See magnetic iron sand.

3 FOLIATED CHLORITE.† JAMESON. This Chlorite, which I have never seen, is perhaps a variety of common Chlorite more distinctly crystallized than usual. According to Jameson and Estner, it occurs in six-sided tables a little elongated, and sometimes grouped into cylindrical or conical masses. Its foliæ are usually curved and flexible, shining, and almost opaque. It is nearly blackish green.

At St. Gothard, it is attached to the walls of a vein, traversing mica slate.

* Chlorit schiefer. WERNER. Chlorite Schisteuse. BRONGNIART. BROCHANT. Chlorite fissile. HAUY.

† Blättriger Chlorit WERNER.

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4. GREEN EARTH.* KIRWAN. JAMESON. Its color is a pleasant green more or less deep, sometimes bluish or grayish green, and passing to olive or blackish green. Its fracture is dull, and fine grained earthy, or a little conchoidal. It is somewhat unctuous to the touch, and often adheres to the tongue. It is easily reducible to powder. Its spec. grav. is 2.63. (KIRWAN.)

It contains, according to Vauquelin, silex 52.0, alumine 7.0, magnesia 6.0, potash 7.5, oxide of iron 23.0, water 4.0;=99.5. Klaproth found silex 53, magnesia 2, potash 10, oxide of iron 28, water 6;=99. Is it, in fact, a variety of Chlorite?

(Geological sit. and Localities.) It has usually been found in amygdaloid, porphyry, or basalt, sometimes filling cavities or only lining them, and sometimes investing other minerals. In Bohemia it sometimes forms beds. (REUSS.) At Monte Baldo, near Verona, it is explored, as an article of commerce.

In the United States. In New Jersey, it occurs near Imlaytown. (SEYBERT.)—In New York, on Hudson's river.—In Massachusetts, near Boston, in amygdaloid.

This earth is ground with oil, and employed as a paint.

SPECIES 82. SOMMITE.† JAMESON.

This mineral, sometimes in grains, is more commonly in small, regular, six-sided prisms, sometimes truncated on the terminal edges; this six-sided prism is also the primitive form. Its fracture, parallel to the axis, is foliated; its cross fracture conchoidal; and its lustre shining. Its angles are sufficiently hard to scratch glass; and its spec. grav. is 3.27. Its color is grayish white, or greenish gray. It is translucent, and sometimes almost transparent.

By the blowpipe it melts with difficulty into a transparent, homogeneous glass. In nitric acid its transparent fragments become cloudy or partially opaque. It contains silex 46, alumine 49, lime 2, oxide of iron 1;=98. (VAUQUELIN.)

It does not phosphoresce on hot coals, like certain crystals of phosphate of lime, which it resembles.—It is less hard, than the emerald.

This mineral has been found only in the cavities of lava near Vesuvius, at Mt. Somma; hence its name. It is there associated with mica, hornblende, and idocrase.

* Grün erde. WERNER. La Terre verte. BROCHANT. Talc zographique. HAUY. Chlorite Baldogée. BRONGNIART.

† Nepheline. HAUY. BRONG. BROCHANT. Nephelin. WERNER.

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SPECIES 83. ANTHOPHYLLITE.* HAUY. BRONGNIART.

This substance has been observed only in amorphous masses, whose longitudinal fracture is foliated or radiated, and whose cross fracture is uneven. The lustre of the most perfect laminæ is somewhat metallic. Its natural joints, of which two are much more perfect than the others, are parallel to the faces of a rectangular four-sided prism. —It is rather difficult to break, and strongly scratches fluate of lime, but produces little or no effect on glass. It is feebly translucent at the edges, and its color is brown, tinged with violet. Its powder is whitish, and rough to the touch. Its spec. grav. varies from 3.11 to 3.29.

Before the blowpipe it is infusible. It contains silex 62.66, alumine 13.33, magnesia 4.0, lime 3.33, oxide of iron 12.0, of manganese 3.25, water 1.43. (JOHN.)

It is softer, lighter, and has less lustre, than Labrador Stone.—It has been found only at Kongsberg in Norway.

SPECIES 84. PINITE.† HAUY. JAMESON.

The Pinite has hitherto been found only in crystals. Their primitive form, and that, which they usually present, is a regular six-sided prism. All its edges are liable to truncation; hence it sometimes appears as a nine or twelve-sided prism, and sometimes four sides are unduly extended at the expense of the others.

These crystals are brittle; their fracture is uneven or splintery, and sometimes more or less foliated, parallel to the sides of the primitive form. Some crystals separate into very distinct layers parallel to their bases. Their lustre, sometimes very feeble, is, on certain parts, glistening, and slightly metallic or resinous.

It is easily scraped by a knife, and sometimes adheres to the tongue. Its powder is unctuous to the touch, and, when moistened by the breath, exhales a strong, argillaceous odor. Its color is brown, tinged with black or red, and sometimes blackish gray. It is nearly or quite opaque, except in the brown varieties, which are a little translucid. Its spec. grav. is about 2.95.

Before the blowpipe it is infusible. A specimen from Saxony yielded Klaproth alumine 63.75, silex 29.5, oxide of iron 6.75. In another from France Drappier found alumine 42.0, silex 46.0, oxide of iron 2.5, loss by calcination 7.0;=97.5.

(Geological sit. and Localities.) It was discovered near Schneeberg, in Saxony, in a mine called Pini; hence its name. It is there imbedded in granite.—In Auvergne, France, it is also imbedded in granite; these crystals are sometimes a little translucent, and the

* Antophyllith. WERNER.

† Pinit WERNER. Pinite. BRONGNIART. BROCHANT. Micarelle. KIRWAN.

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transmitted light has a tinge of green or gray. In the U. States. In Connecticut, at Haddam, in a micaceous rock; the crystals are sometimes several inches long and considerably regular. (SILLIMAN.)

ARGILLACEOUS MINERALS.

These substances never exhibit crystals, nor even possess a crystalline structure. They appear to be mechanical deposites from water, or the result of decomposition. Although silex and alumine are the predominating ingredients, their proportions are variable, and other earths or even alkalis are occasionally present. By some mineralogists these argillaceous minerals have been unjustly degraded, and their names permitted to appear on the pages of an appendix only, while others, with equal injustice, have exalted them above their just rank, and considered mere varieties as distinct species. We have adopted those divisions, which appeared to be most convenient.

SPECIES 85. ARGILLACEOUS SLATE.

The minerals, included in this species, have almost always a slaty structure, more or less distinct, with layers either straight or curved. Their hardness is somewhat variable; but they may always be scratched by iron, and frequently by copper. Some varieties are dull, while others possess considerable lustre. Their color is gray, often with shades of blue, yellow, green, red, brown, purple, or black. These colors, always dull, are sometimes uniform, and sometimes in spots, stripes, &c.

They are composed chiefly of silex and alumine; but lime, magnesia, and iron are usually present, and sometimes alkali, carbon, bitumen, manganese, &c.

Var. 1. ARGILLITE, or COMMON ARGILLACEOUS SLATE.* KIRWAN. Its longitudinal fracture is slaty; but the layers, either straight or undulated, thick or thin, separate with very different degrees of ease. Sometimes its slaty structure is very indistinct, and the fracture, at least in small specimens, becomes earthy or splintery, and a little conchoidal. It is seldom perfectly dull; frequently its lustre is glistening, sometimes shining, and often a little silky.

Its fragments are usually tabular or splintery. Though a little variable in hardness, it is more or less easily cut or scraped by a knife.

Its streak is grayish white, sometimes with a tinge of red. Its spec. grav. lies between 2.67 and 2.88. It does not adhere to the

* Thon Schiefer. WERNER. Clay Slate. JAMESON. Le Schiste argileux. BROCHANT.

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tongue, nor does it always yield an argillaceous odor, when moistened. It is opaque, and its colors are gray, often more or less shaded with blue, green, yellow, red, or black; also grayish black, purplish, reddish, or bluish brown, &c.

It is fusible by the blowpipe into an enamel or scoria. In a variety from Anglesey, Kirwan found silex 38, alumine 26, magnesia 8, lime 4, iron 14. M. Godon, in an Argillite from Roxbury near Boston, which he says was hard and resembled petrosilex, found silex, alumine, lime, potash, soda, and the oxides of iron and manganese.

SHINING ARGILLITE.* Its layers, seldom perfectly straight, are often undulated, sometimes even plaited, and have a lustre more or less shining and silky in one direction. Its colors are gray, yellowish gray, deep bluish gray, &c.

This Argillite is always primitive; and hence never contains organic remains. It abounds with ores. It often much resembles mica slate, into which it passes.

ROOF-SLATE.† In its most perfect state is is characterized by easily splitting into large, thin, and straight layers or plates, which are sonorous, when struck by a hard body. It is dull, or has only a feeble lustre. Its colors are blackish gray, or bluish black, bluish or reddish brown, greenish, &c. It is often sufficiently hard to receive a trace from copper.

It belongs both to primitive and secondary rocks.

(Uses.) This slate, when it possesses the requisite properties, is employed to cover the roofs of buildings. But all roof-slate, mineralogically speaking, is not suitable for the purpose. Some are too solid and do not split easily, or the plates are too thick, or not sufficiently straight; some absorb too much water, and even fall to pieces by the action of moisture and frost; and others contain sulphuret of iron, which hastens their decomposition. Indeed different parts of the same bed seldom furnish slates of equal quality; the upper part is generally too friable, or too much cracked.—Blocks of slate split most easily, when recently taken from the quarry.

When of a dark bluish or grayish black color, and sufficiently soft, it is employed for writing slates.

It is also employed for monuments in grave yards. Indeed some varieties of Argillite are used for whetstones and grindstones.

(Geological situation.) Argillite is very abundant in primitive mountains; sometimes also it is associated with transition or secon-

* Schiste luisant. BRONGNIART.

† Schiste Ardoise. BRONGNIART. Argile schisteuse tabulaire—et tegulaire. HAUY.

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dary rocks. It generally appears in extensive strata or beds, seldom perfectly horizontal, often highly inclined, and sometimes even perpendicular. Its beds are sometimes interposed between those of other minerals; and sometimes constitute whole mountains or even chains of mountains.—It has also been observed in veins. (WERNER.)

Argillite always covers granite, when both occur together; and, when found with gneiss or mica slate, it usually covers them also.

Thus the oldest or shining Argillite usually rests on mica slate, and sometimes alternates with it; it alternates also with gneiss, syenite, and granular limestone. It is sometimes traversed by large veins of other minerals, and abounds with ores, either in beds or veins. The mountains near Potosi and Lima, rich in ores, are said to be composed of this Argillite.

Roof-slate, whether primitive or secondary, is often traversed by layers or thin veins of quartz or carbonate of lime, which divide the strata into rhomboidal masses.

Argillite sometimes contains beds of novaculite, aluminous and graphic slates, chlorite slate, indurated talc, hornblende, greenstone, &c. It often contains crystals of sulphuret of iron, and other simple minerals.

The organic remains found in secondary Argillite are chiefly those of the vegetable kingdom, sometimes also of fish and crustaceous animals.

Argillite usually occurs in the vicinity of granite, gneiss, or mica slate. Its mountains have rounded summits with gentle acclivities, and do not present rough and steep cliffs, like those of granite and gneiss; they are generally covered by a fertile soil.

Argillite passes by insensible shades into chlorite slate, petrosilex, gray-wacke slate, &c.

(Localities.) Argillite abounds in various parts of the United States, but we shall mention only some of the varieties, which have been, or may be, employed as roof-slates. In Pennsylvania, Wayne Co. it exists on the banks of the Delaware, about 75 m. from Philadelphia; this slate is of good quality. (MEASE.)—In New York, at New Paltz, Ulster Co.—and at Rhinebeck, Dutchess Co.—In Vermont, at Dummerstown, in strata nearly vertical; at Rockingham; and at Castleton, where it is of a pale red. (HALL.)—In Maine, at Waterville and Winslow on the banks of the Kennebec, about 20 miles above Hallowell; it separates into smooth and regular tables.

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2. SHALE.* KIRWAN. This variety often differs but little from secondary Argillite, and it is sometimes difficult to distinguish them. It is generally less solid and softer than the Argillite, and is often very easily cut by a knife; its spec. grav. is also usually less, being about 2.64. It adheres somewhat to the tongue, yields an argillaceous odor, absorbs water considerably, and often gradually falls to pieces in that liquid, but never forms a paste.

Its fracture is slaty, sometimes nearly earthy, and is dull, unless rendered glimmering by mica. Its layers are often thick, and its surface is frequently knobby. It is opaque, and its colors are gray, bluish or yellowish gray, grayish black, brown, reddish, or greenish.

It is fusible by the blowpipe.

BITUMINOUS SHALE.† KIRWAN. JAMESON. This subvariety is blackish brown, sometimes grayish. Its fracture is slaty. It is usually very soft, a little unctuous to the touch, and its streak has some lustre. Its spec. grav. is about 2.00. (KIRWAN.)

This Shale is impregnated with bitumen, and burns with a flame more or less bright. It sometimes very slowly effervesces with acids.

(Geological situation.) Shale is associated with various secondary rocks, with which it often alternates. It very frequently accompanies coal; and indeed the presence of Shale is considered a very strong indication of the existence of coal in its vicinity. It often contains mica, and the sulphuret of iron.

The Bituminous Shale is found connected with beds of coal and of the common Shale, into both of which it gradually passes. It sometimes contains impressions of fish.

Shale often exhibits very distinct and complete impressions of vegetables, especially of ferns and reeds. The smaller plants are situated in the direction of the strata; and when the two layers, between which a plant is contained, are separated, one of them presents the impression of the plant, depressed below the surface, and the other bears a corresponding relief. It has, however, been remarked in regard to these plants, that only the upper surface of the leaf is brought to view by the separation of the layers, while the under surface, which bears the parts of fructification, remains attached to the Shale, or, in other words, the relief and the cavity almost always present the same side of the leaf. To explain this, it has been suggested by Brugnières, that the relief or projecting part is composed of the substance of

* Schiefer Thon. WERNER. Slate Clay. JAMESON. L'Argile schisteuse. BROCHANT. Var. of Schiste argileux. BRONGNIART. Var. of Argile schisteuse. HAUY.

† Brandschiefer. WERNER. Le Schiste bitumineux. BROCHANT. Schiste argileux bitumineux. BRONGNIART.

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the leaf, penetrated by carbon, or by particles of Shale, and that the under surface of the leaf, in consequence of its roughness, has contracted with the Shale a stronger union, than the upper surface.

(Localities.) Shale is found in various parts of the United States, as in Virginia and Ohio, where it is connected with coal;—in Pennsylvania with coal and anthracite;—in Rhode Island with anthracite; and is more or less marked with vegetable impressions.—But one of its most interesting localities is at Westfield, near Middletown, in Connecticut. This Shale is highly bituminous, and burns with a bright flame. It abounds with very distinct and perfect impressions of fish, sometimes a foot or two in length, the head, fins, and scales being perfectly distinguishable. A single specimen sometimes presents parts of three or four fish, lying in different directions, and between different layers. The fish are sometimes contorted, and almost doubled. Their color, sometimes gray, is usually black; and the fins and scales appear to be converted into coal. The same Shale contains impressions of vegetables, sometimes conver