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A piece of flint 9–10 cm (3.5–3.9 in) long, weighing 171 grams. Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start fires. Flint occurs chiefly as ...
Lynch Quarry Site, North Dakota, NRHP-listed and a U.S. National Historic Landmark, a flint quarry that was "a major source of flint found at archaeological sites across North America, and it has been estimated that the material was mined there from 11,000 B.C. to A.D. 1600."
Fire clay in a furnace. Fire clay is a range of refractory clays used in the manufacture of ceramics, especially fire brick.The United States Environmental Protection Agency defines fire clay very generally as a "mineral aggregate composed of hydrous silicates of aluminium (Al 2 O 3 ·2SiO 2 ·2H 2 O) with or without free silica."
Concretions in Torysh, Western Kazakhstan Concretions with lens shape from island in Vltava river, Prague, Czech Republic Marlstone aggregate concretion, Sault Ste. Marie, Michigan, United States A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary ...
The Lynch site, whose known extent is at least 690 acres (280 ha) has an estimated 20,000 pits from which flint was quarried. The pits range in depth from 3 to 10 feet (0.91 to 3.05 m), and are accompanied by spoil piles. It is located on the banks Spring Creek, a tributary of the Knife River. [8]
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The insoluble eluvium in these limestone layers remained in the soil as flint eluvium.The stone blocks formed between 7 and 2.5 million years ago during the late Tertiary period. The stones are breccias, composed of rough flint, gravel, and fine-grained sand, all cemented together with silica cement. [3] [1]
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