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Updated: May 20, 2025
From Point Hansborough the canyon widens, "the marble benches retreat, new strata of limestone, quartzite, and sandstone come up from the river," writes Stanton, "and the debris forms a talus equal to a mountain slope.
Excavations near them have brought to light fragments of charcoal, masses of cinders, chips of silicate of flint, with numerous fragments of pottery, and tools made of quartzite, granite, schist, and diorite, similar to those met with under all the other megaliths of Morbihan.
But just as a silicious deposit may be metamorphosed into opal or quartzite, and chalk into marble, so known metamorphic agencies may metamorphose clay into schist, clay-slate, slate, gneiss, or even granite.
At Porton, east of Truxillo, the same metamorphism which has changed the ridge of sandstone to a hard quartzite has also changed the ordinary bituminous coal into an anthracite, which is here vertical in position. The coals of Peru usually rise to more than 10,000 feet above the sea, and they are practically inaccessible.
Whether such a metamorphosis as this occurs in submarine deposits, as well as in those formed in fresh water, does not appear; but there seems no reason to doubt that it may. And hence it may not be hazardous to conclude that very ordinary metamorphic agencies may convert these polar caps into a form of quartzite.
Thirty, or even forty, tons was no very unusual weight for these blocks of smooth, water worn quartzite. Every one, no matter how large, had to be shifted, the reason being that whatever gold there was lay on the bedrock, and thus beneath all the wash. The bedrock was granite, but was so decomposed and friable that one could dig it out like so much cheese.
So, for a dozen miles of river through the gneiss, there may be a hundred miles of wall on either side. Climbing to the summit of the black gneiss and following the wall in the variegated quartzite, it is found to be stretched out to a still greater length, for it is cut with more lateral gorges.
So these quartzites are aslant, and though of great geologic thickness, they make but 800 feet of the wall. Your books may have many-colored bindings and differ greatly in their contents; so these quartzites vary greatly from place to place along the wall, and in many places they entirely disappear. Let us call this formation the variegated quartzite.
We must cursorily refer to some other fortifications which really scarcely belong to our subject, though certain archaeologists claim for them a prehistoric origin. We refer to the vitrified forts, which are strange structures in which stones, such as granite and gneiss, quartzite and basalt, have been subjected to a heat so intense as to produce vitrification.
You just listen to me, my boy. You and me figure to be pretty hard, don't we? Well, soft pine stacked up agin' quartzite, is what we are compared to Kate." Lee Haines gaped at him, too astonished to be angry. He suggested softening of the brain to Buck, but the latter waved aside the implications.
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