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"White quartzose sand," Paul rattled off, "sodic carbonate, slaked lime, cutlet, manganese peroxide there you have it, the finest French plate glass, made by the great St. Gobain Company, who made the finest plate glass in the world, and this is the finest piece they ever made. It cost a king's ransom. But look at it! You can't see it. You don't know it's there till you run your head against it.
Formations of quartzose porphyry, pyroxenic porphyry and trachyte, of grauwacke, muschelkalk and quadersandstein, which are frequent towards the west, have not yet been seen in Venezuela; but it may be also observed that in the system of secondary rocks of the old continent muschelkalk and quadersandstein are not always clearly developed, and are often, by the frequency of their marls, confounded with the lower layers of Jura limestone.
Both the quartzose sand, of which it chiefly consists, and the included shells, are most commonly distinguished by a deep ferruginous or ochreous colour, whence its name.
In the Shark Mountain, near Pottsville, in that State, there are thirteen seams of anthracite coal, some of them more than six feet thick, separated by beds of white quartzose grit and a conglomerate of quartz pebbles, often of the size of a hen's egg.
But some of these same porphyries are partially unconformable, as b, and may lead us to suspect that the others also, notwithstanding their appearance of interstratification, have been forcibly injected. Some of the porphyritic rocks above mentioned are highly quartzose, others very feldspathic.
The smallest fish are visible in them at a depth of twenty or thirty feet; and most commonly the bottom of the river may be distinguished, which is not a yellowish or brownish mud, like the colour of the water, but a quartzose and granitic sand of dazzling whiteness. Nothing can be compared to the beauty of the banks of the Atabapo.
A curious observation of Professor Forchhammer suggests an explanation of another peculiarity in the structure of the sandstone of Mount Seir. He describes dunes in Jutland, composed of yellow quartzose sand intermixed with black titanian iron. When the wind blows over the surface of the dunes, it furrows the sand with alternate ridges and depressions, ripples, in short, like those of water.
On the contrary, in addition to old granitic and other igneous rocks, all explorers find only either innumerable undulations of sandstones, schistose, and quartzose rocks, or such tufaceous and ferruginous deposits as would naturally occur in countries long occupied by lakes and exuberant jungles, separated from each other by sandy hills, scarcely any other calcareous rocks being found except tufas formed by the deposition of landsprings.
After riding 17 miles, the first eight through thick scrub, we came into a more open and elevated country where we saw pigeons, as sign that water was not distant on some side of us. The hills were covered with a quartzose soil, containing angular fragments. The Callitris pyramidalis and the Sterculia heterophylla were among the trees.
Millstone grit: a coarse quartzose sandstone passing into a conglomerate, sometimes used for millstones, with beds of shale; usually devoid of coal; occasionally above 600 feet thick. Mountain or Carboniferous Limestone: a calcareous rock containing marine shells, corals, and encrinites; devoid of coal; thickness variable, sometimes more than 1500 feet.
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