163

Humboldt. New Spain. Vol III. p. 130

Metals in Mexico rarely in secondary always in primitive & transition; the latter rarely appear in central Cordillera. particularly between 18° & 22° N. = formations of amph: porphyry greenstone amygdaloid basalt & other trap cover it to great thickness. = Coast of Acapulco granitic rock. — in parts of table granites & gneiss with gold veins visible: — "Porphyries of Mexico may be considered for most parts as rock eminently rich in mines of gold & silver."

 

165

Study Hoffmans account of steam acting on trachytes also Azores. We here have case of such vapours washing a rock

Veins concretionary; concretions determined by fissures as in septaria (& Chiloe case, at least corelation)

- Galapagos vein. vein of secretion. — metallic veins follow mountain chain there after NW.

same chemical laws as in concretions perhaps makes intersections richest –

Humboldt has urged phenomena in veins, chemical affinities like in composed rock granites syenite strangling &c of veins can only be accounted for by concretionary action, conjoined with other

state simplest case. concretions of clay iron stone; iron pyrite in a fossil

Insist strongly on the grand fact of Volcanic & non Volcanic. Then Solfataras.

(Mem: Micaceous iron ore.)

 

N.B. To show how metals may be transported by complicated chemical law & steam of salts, quite curious case of oxide of Iron by Mitterschlich Vol. II Journal of Nat. & Geograph Sciences?

 

167

St Helena has been slightly broken up, & has there not been vein of iron discovered?

Klaproth analysed silver ores from Peru consisted of native silver & brown oxide of Iron in Mexico sulphuretted silver arsenical grey copper, and antimony, horn silver, black silver & red silver, do not name native silver because not very abundant. #

muriated silver which is so rare in Europe common there accompanied by molybdated lead & argentiferous lead; sulfated Barytes very uncommon in Mexico. Fluor spar only in certain mines.

 

164

The above porphyries characterized by no quartz & amphibole frequently only vitreous felspar: = gold veins in a phonolitic porphyry. = several parts of N. Spain great analogy to Hungary. = Veins of Zimapan offer zeolite. stilbite. grammalite. pyenite. native sulphur. fluor spar. baryte. asbestos garnets. — carb & chron. of lead. orpiment. chrysoprase. opal:

Veins in Limestone & Grauwacke: Silver appears far more abundant in the upper limestone, which H. calls by several secondary names

 

[51] 166

H. says in Potosi the silver is contained in a primitive slate, covered by a clayey porphyry, containing grenats. In Peru on other hand, mine of Gualgayoc or Chota & Pasco in "alpine limestone" = "The wealth of the veins in most part totally independent of the nature of the beds they intersect". = In the Guatemala part. (& Chiloe do) no veins discovered. Humboldt suggests covered up by volcanic rocks

 

168

Vol III

"In general it is observed both in Mexico & Peru, that those oxidated masses of iron which contain silver are peculiar to that part of the veins, nearest to the surface of the earth." – p. 156

Mines of Batopilas in New Biscay, "Nature exhibits the same minerals there, that are found in the veins of Kongsberg in Norway. - namely dendritic silver intersecting carbonate of lime - native silver in Mexico

 171

above ancient freestone, limestone & other secondary rocks.

Vein traverses both Clay slate, Porphyry North 52 W, & is nearly the same with that of the veta grande of Zacatecas, & veins of Tasco & Moran — of Guanaxuato to SW. with respect to latter doubts whether bed or vein (very like that of Spital of Schemnitz in Hungary.) Humboldt says fragments from roof & penetrating overlying beds tells the secret. p. 189. "The small ravins into which the valley of Marfil is divided, appear to have a decided influence on the richness of the veta madre of

 

169

is always accompanied by Sulp. silver sometimes by selenite. - in New Spain, contrary to Europe argentiferous lead not abundant. = considerable quantity of silver procured from martial pyrites; great blocks of pure silver not common in America: In all climates distribution of silver in veins very unequal, sometimes disseminated sometimes concentrated: wonderful quantity of pure silver in S. America.

 

174

Under name of Sagitta Triptera D'Orbigny has figured animal with seta like my undescribed

p. 140. Flèche of Quoy et Gaimard.

D'Orbigny has described it with care to 3 species. I think I have much additional information #