Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
- Page 732 of 779 - First - Home
I remember
having seen similar balls filling a vein in transition-slate, near
the castle of Schauenstein in the margravate of Bayreuth.
I sent
several balls from Antimano to the collection of the king of Spain
at Madrid.) These balls are composed of lamellar feldspar and
hornblende closely commingled. The feldspar approximates sometimes
to vitreous feldspar when disseminated in very thin laminae in a
mass of granular diabasis, decomposed, and emitting a strong
argillaceous smell. The diameter of the spheres is very unequal,
sometimes four or eight inches, sometimes three or four feet; their
nucleus, which is more dense, is without concentric layers, and of
a very dark green hue, inclining to black. I could not perceive any
mica in them; but, what is very remarkable, I found great
quantities of disseminated garnets. These garnets are of a very
fine red, and are found in the grunstein only. They are neither in
the gneiss, which serves as a cement to the balls, nor in the
mica-slate, which the veins traverse. The gneiss, the constituent
parts of which are in a state of considerable disintegration,
contains large crystals of feldspar; and, though it forms the body
of the vein in the mica-slate, it is itself traversed by threads of
quartz two inches thick, and of very recent formation. The aspect
of this phenomenon is very curious: it appears as if cannon-balls
were embedded in a wall of rock. I also thought I recognized in
these same regions, in the Montana de Avila, and at Cabo Blanco,
east of La Guayra, a granular diabasis, mixed with a small quantity
of quartz and pyrites, and destitute of garnets, not in veins, but
in subordinate strata in the mica-slate.
Enter page number
PreviousNext
Page 732 of 779
Words from 198888 to 199178
of 211363
