Remember the Rainforest 1
The opinion of some geologists that diamonds and gold belong genetically to this formation of stratified layers is ever more widely expressed.
To the north of the Amazon River, this same stratified grain orogeny forms the group of the Parime Mountains,
made up in particular of granite and gneiss. Among the rolled pebbles, which we picked up from the Rio Branco riverbed, are many jaspers and shales,
which are reddish-brown in color; the first may well belong to the grain formation of the Amazon Basin. On the lower Rio Negro, it lies here and looms above a leptinite-like quartzite,
above gneiss and granite, whose pristine ridges are often uncovered.
In the upper region of this river, the same formation probably continues until the isthmus of Javita, which forms the watershed between the Upper Orinoco and the Negro River,
and could also be found again in the Apure and Lower Orinoco Basins, where, according to Mr. von Humboldt's remarks ("Voyage", V, 549), there is a layer of compact limestone,
similar to Jurassic limestone, as well as alternating layers of marl and lamelliform plaster.
In the upper region of Japura there is a grain of granite which, here and there, as in the Rio dos Deceos, contains a beautiful red labrador
Labrador, or basalt ?
and instead of mica, contains amphibole in twin crystals,
thereby transitioning to Syenite (but also contains quartz).
Araraquara's raw granite is particularly beautiful and excellent; It consists of silver-gray mica (margarita), in large rhomboid crystals,
white quartz and red-fleshed orthoclasium. As far as the distance observed in the formation of grains along the Solimoes, in the western direction, by Dr. Spix, I found no indication in his papers. The dark gray, chipped, very hard gres from the mouth of Javari on the western border of Brazil could be important; It probably belongs, as I mentioned above, to the stonework itself rather than to the Keupric.
The determination of the southern boundary of grain formation in the Amazon Basin remains to be investigated by future travelers. At best, I can tell from the news of travelers that, besides the waterfalls that hinder the Tocantins, Xingu and Tapajos rivers in their courses,
there is another orogenic formation in general, probably of primitive rock containing gold, which is the main feature of the geology of Minas Gerais, Goias and Mato Grosso.
Minas Gerais, Goias and Mato Grosso provinces
A comparative glance at these southern regions, from which the Amazon River receives so many of its tributaries, presents us with some facts, which are then in sharpest opposition to the geognostic conditions of the deepest part of the Amazon Basin: - in Minas Gerais and Sao Paulo, huge deposits, even whole mountains of compact limonite
in these provinces, in Goias and Mato Grosso, large extensions covered by an iron-containing formation (rich in oligyst and oligyst mycaceous iron)
Oligyst mycaceous iron
and, in this orogeny, gneiss and sand from its decomposition, a considerable amount of gold, and, moreover, also diamonds;
in contrast, in the deepest Amazon Valley, no trace of older orogenic formations, nor any metal appearing in considerable quantity; - formation of coals only to a small extent in that region; in this of the Amazon, almost nothing; but there is an organic coal, as it were, in the immense quantities of the woods; whereas in most of the other, particularly in the diamond territories, only grasses thrive in the meadows; - finally, in the Paraguay Basin ("parrot river") not far from the point where the watershed between it and the Amazon rises, an immeasurable richness of table salt springs from the ground,
which, in every flood of the river, renews itself (as happens along the Sao Francisco River in its northern region, and in some of the perennial rivers of Ceara and Paraiba do Norte); on the other hand, in the Amazon, no trace of cooking salt; Only grains identical to those of Sao Goncalo do Amarante in Piaui and other regions of this province that undermine alum and other salts: - give these contrasts the opportunity for many geological hypotheses.
Prehistoric archeology, that is, the history of our planet and its developments and transformations, is up to the naturalist who, from the great documents, presented by the earth itself, can at least give rise to several conjectures, such as these faults often suggest. It is a generally widespread opinion that the new world arose,