Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 2 - By Alexander Von Humboldt And Aime Bonpland.
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They Are Not Long And Narrow Streams As In
Auvergne, But Large Sheets, Streams That Appear Like Real Strata.
The
lithoid masses here cover, if we may use the expression, the shore of
the ancient interior sea; everything subject to destruction, such as
the liquid dejections, and the scoriae filled with bubbles, has been
carried away.
These phenomena are particularly worthy of attention on
account of the close affinities observed between the phonolites and
the amygdaloids, which, containing pyroxenes and
hornblende-grunsteins, form strata in a transition-slate. The better
to convey an idea of the whole situation and superposition of these
rocks, we will name the formations as they occur in a profile drawn
from north to south.
We find at first, in the Sierra de Mariara, which belongs to the
northern branch of the Cordillera of the coast, a coarse-grained
granite; then, in the valleys of Aragua, on the borders of the lake,
and in the islands, it contains, as in the southern branch of the
chain of the coast, gneiss and mica-slate. These last-named rocks are
auriferous in the Quebrada del Oro, near Guigue; and between Villa de
Cura and the Morros de San Juan, in the mountain of Chacao. The gold
is contained in pyrites, which are found sometimes disseminated almost
imperceptibly in the whole mass of the gneiss,* and sometimes united
in small veins of quartz. (* The four metals, which are found
disseminated in the granite rocks, as if they were of contemporaneous
formation, are gold, tin, titanium, and cobalt.) Most of the torrents
that traverse the mountains bear along with them grains of gold.
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