Granite Predominates There Over The Other Rocks; And Though, In Both Continents, The Granite Of Ancient Formation Is Pretty Generally Destitute Of Gold-Ore, We Cannot Thence Conclude That The Granite Of Parima Contains No Vein, No Stratum Of Auriferous Quartz.

On the east of the Cassiquiare towards the sources of the Orinoco, we observed that the number of these strata and these veins increased.

The granite of these countries, by its structure, its mixture of hornblende, and other geological features alike important, appears to me to belong to a more recent formation, perhaps posterior to the gneiss, and analogous to the stanniferous granites, the hyalomictes, and the pegmatites. Now the least ancient granites are also the least destitute of metals; and several auriferous rivers and torrents in the Andes, in the Salzburg, Fichtelgebirge, and the table-land of the two Castiles, lead us to believe that these granites sometimes contain native gold, and portions of auriferous pyrites and galena disseminated throughout the whole rock, as is the case with tin and magnetic and micaceous iron. The group of the mountains of Parima, several summits of which attain the height of one thousand three hundred toises, was almost entirely unknown before our visit to the Orinoco. This group, however, is a hundred leagues long and eighty broad; and though wherever M. Bonpland and I traversed this vast group of mountains, its structure seemed to us extremely uniform, it would be wrong to affirm that it may not contain very metalliferous transition rocks and mica-slates superimposed on the granite.

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