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1835 Coquimbo — to Guasco 109

Upon this again we had the ordinary granite containing three thin parallel layers of the other kind. — Although in appearance this is very regular stratification: yet we find on close inspection in the common granite, veins of compact euritic granite, others of a black. hornblendic variety, angular imbedded fragments of same. —

Also same kind form of fragments of the white close grained kind, which alternated. — And in this latter again there are angular fragments of the common granite (themselves including the black pieces). — So that in place of simplicity, there is most intricate confusion. —

Proceeding in a NE direction: we come on a grand formation of mica slate, which appears to form a band parallel to the granite mountains. — Mica slate either with large contorted plates of quartz; or with thinner & more even ones, in the latter case the micaceous mineral passes very much into the character of clay slate. — The cleavage is all high about 70° the dip

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1835 Coquimbo — Guasco 110

not quite uniform, either about ENR or NE by E. — Near Sauce we again have granite in which are some copper mines. And on road from Sauce to Freirina (in valley of Guasco) we again come to a great band of micaceous schists. — The district of these slates, a short distance to the South abounds with copper mines. — The matrix of many of the veins is talcaceous: some pure soapstone, which I have seen curiously interlaced by thin plate of metallic copper. — The soapstone is thought a favourable sign. — Much of the ore are carbonates. — I saw in one specimen some fine sulphate of copper. — In these mountains, as well as the syenitic & greenstone ones to the North of Coquimbo, the few springs are all partially saline. — It may be suspected that these waters do not owe their origin to the very scanty rains of this country. — In these second mountains of micaceous slate; the proper rock is associated with some black glossy kinds. like

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1835 Guasco 111

ampelite, other brown glossy ones & some blue clay slate. — The cleavage irregular, perhaps N & S. the ordinary mean direction. —

V. before. The constitution of the rock is identical with the formations of Concepcion, Chiloe & Chonos. Archipelago. When in the morning, a horizontal stratum of white mist winding amongst the mountains represented an ocean. — I might have believed that there were islands in that latter Archipelago of Chonos. —

Near Freyrina an extensive trappean formation. At the Port of Guasco there is a great variety of curious slaty rocks; some very ferruginous, others jaspery (a). or feldspathic (ate pounded & used to make bricks for the furnaces). the latter often porph. with feldspar. — These lie to westward & I believe conformably to some perfect mica slate as before. — to which formation I feel no doubt they belong. — The dip is various in one part SW by S. & then ESE! — There are very many dykes & injected masses of brownish trappean rocks, probably belonging to hills above alluded to. —

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(a) Near Freyrina, there are some hills of what appears an altered hard slate. The laminae have an irregular N & S direction. —

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1835 Guasco 112

[the page is numbered 596 and 112, and immediately follows 594 and 111. There is no sign of 595.]

V. All this maritime district of granitic rocks & various slates is highly auriferous & contains many good minerals of copper. —

In the Cordilleras. I hear of extensive gypseous. formation. — Fossil shell, chiefly Terebratulae are very abundant, near Guasco Alto. V. specimens; judging from a fragment they occur in a pale coloured calcareous certy rock. (a) — I saw specimen of the R. Claro Pecten (unequal) Bivalve & heard of Ammonites. —

From Guasco to the Hacienda of Potrero Seco, which is in the valley of Copiapò half way between the Villa & the Cordilleras. — From the country being a desert it is necessary to travel fast & hence the geology was nearly unintelligible.

About 2 leagues to the East of Ballenas saw the Escarpement of Porph. Breccia the road enters on this formation very obliquely. — The rocks being the red fine grained sandstone with cryst particles of carb of lime & the white calcareo siliceous stones, abo already mentioned, containing fragments of shells. (B) — The structure of the first low ranges, appeared of this nature

[sketch] W E

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(a) In the vicinity of Guasco Alto very many silver mines

(B) Part of this structure, namely the strata dipping internally is common on the face of the outer ranges & central Cordilleras. — We must suppose either, that a fault commonly takes place, or the ridge or crest of an anticlinal band — or that one side only is elevated

(1) [sketch] (2) [sketch]