Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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This
Same Phenomenon Has Been Remarked By Von Buch In Sweden; But In The
Temperate Parts Of Europe Garnets Are In General Contained In
Serpentine And Mica-Slates, Not In Gneiss.
In the walls which
enclose the gardens of Caracas, constructed partly of fragments of
gneiss, we find garnets of a very fine red, a little transparent,
and very difficult to detach.
The gneiss near the Cross of La
Guayra, half a league from Caracas, presented also vestiges of
azure copper-ore* (* Blue carbonate of copper.) disseminated in
veins of quartz, and small strata of plumbago (black lead), or
earthy carburetted iron. This last is found in pretty large masses,
and sometimes mingled with sparry iron-ore, in the ravine of
Tocume, to the west of the Silla.
Between the spring of Sanchorquiz and the Cross of La Guayra, as
well as still higher up, the gneiss contains considerable beds of
saccharoidal bluish-grey primitive limestone, coarse-grained,
containing mica, and traversed by veins of white calcareous spar.
The mica, with large folia, lies in the direction of the dip of the
strata. I found in the primitive limestone a great many
crystallized pyrites, and rhomboidal fragments of sparry iron-ore
of Isabella yellow. I endeavoured, but without success, to find
tremolite (Grammatite of Hauy. The primitive limestone above the
spring of Sanchorquiz, is directed, as the gneiss in that place,
hor. 5.2, and dips 45 degrees north; but the general direction of
the gneiss is, in the Cerro de Avila, hor.
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