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SILICEOUS SINTER. Q2g The fracture is flat conchoids], also coarse-grained un even, and sometimes parallel and promiscuous fibrous. The fragments are angular, and rather blunt edged. The conchoidal varieties occur in fine granular concre tions ; the uneven varieties in thin and curved lamellar concretions. It is more or less translucent on the edges. It is semi-hard. Very brittle. Light. Specific gravity, 1.807, Klaproth. 1.816, Karsien* Chemical Characters. It is infusible without addition before the blowpipe.- Constituent Parts. Silica, - * 08.0 Alumina, - 1.5 Iron, - - 0.5 100 Klaproth, Beit. b. ii. s. 103. Geognostic and Geographic Situations. It occurs abundantly around the hot springs in Iceland.- It is deposited from the water of these springs, in which *t appears to have been held in a state of solution, partly % the alkali the water contains, partly by its high tem perature, which is 212° at the surface, but must be great er in the interior of the earth, where the water appears h) be subjected to a considerable degree of compression. Second