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Updated: May 7, 2025
I have found in it neither amphibole nor pyroxene, but some small white points, which seem to be feldspar. None of the obsidians of the Peak appear in those grey masses of pearl or lavender-blue, striped, and in separate wedge-formed pieces, like the obsidian of Quito, Mexico, and Lipari, and which resemble the fibrous plates of the crystalites of our glass-houses, on which Sir James Hall, Dr.
The grunsteins, which begin again to the south of these slates, appear to me to differ little from those found north of the ravine of Piedras Azules. I did not see there any pyroxene; but on the very spot I recognized a number of crystals in the amygdaloid, which appears so strongly linked to the grunstein that they alternate several times.
This conclusion is not deduced from the observations I made at the southern declivity of the littoral Cordillera, between the Morros of San Juan, Parapara and the Llanos of Calabozo. The greyish blue amygdaloid contains fendilated crystals of pyroxene and mesotype. It forms balls with concentric layers of which the flattened centre is nearly as hard as basalt.
Karsten, to the pyroxene augite. With respect to this last substance, which has hitherto been observed only at Vesuvius and in the environs of Rome, it exists perhaps at the peak of Teneriffe, in the old currents of lava now covered by more recent ejections.
This young scientist, too, cherished loving thoughts about Angelina, thoughts of a more earthly and volcanic tinge; certain definite projects which made him forget, at times, his preoccupation with biotite, perlite, magnetite, anorthite, and pyroxene. "Denis," said Keith, in his usual pompous fashion. "Do put down that absurd tray and let people help themselves. Listen to me for a moment.
2-Quartz Biotite Schist. Contact between above dike and amphibolite. A coarse black rock carrying magnetite and pyrites in considerable quantities. Under the microscope some of the biotite has a green coloration from decomposition and is surrounded by strong pleochroic halos. Small grains of secondary pyroxene are numerous. 3-Grand Lake.
In order to pass from the town of Laguna to the port of Orotava and the western coast of Teneriffe, we cross at first a hilly region covered with black and argillaceous earth, in which are found some small crystals of pyroxene. The waters most probably detach these crystals from the neighbouring rocks, as at Frascati, near Rome.
They form a set of dikes of a fine-grained dark greenstone or dolerite, composed of feldspar and pyroxene, with occasional scales of mica and grains of pyrites. Their width varies from a few feet to a hundred yards, and they have a columnar structure, the columns being truly at right angles to the plane of the dike. Some of the dikes send off branches.
The talus now narrowed; the side-walls of dark trachytic blocks pinching it in. At this grisly hour they showed the quaintest figures towers and pinnacles, needles and tree-trunks, veiled nuns and monstrous beasts. Amongst them were huge bombs of obsidian, and masses with translucent, vitreous edges that cut like glass. Most of them contained crystals of felspar and pyroxene.
5-Mica Granite Gneiss Country Rock near Caribou Ridge. In the hand specimen the rock has the same appearance as No. 4, if anything, it is somewhat more compact. The principal minerals are, plagioclase, biotite and microcline, with smaller quantities of quartz, iron oxide, pyroxene and garnet. The feldspar is decomposed with the resulting formation of epidote, which is quite prominent.
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