CRYOLITE, a mineral discovered in Greenland by the Danes in 1794, and found to be a compound of fluorine, sodium and aluminium. From its general appearance, and from the fact that it melts readily, even in a candle flame, it was regarded by the Eskimos as a peculiar kind of ice, hence it acquired the name of cryolite (from Gr Kpvos, frost and Aikos, stone). Cryolite occurs in colourless or snow-white, cleavable masses, often tinted brown or red with iron oxide, and occasionally passing into a black variety. It is usually translucent, becoming nearly transparent on immersion in water. It cleaves in three nearly rectangular direc tions, and the crystals occasionally found in the crevices have a cubic habit, but they belong to the monoclinic system. The hard ness is 2.5 and the specific gravity 3.
Cryolite occurs almost exclusively at Ivigtut (sometimes written Evigtok), on the Arksut Fjord in south-west Greenland. It has been extensively used as a source of metallic aluminium, and as a flux in smelting the metal. It is largely employed in the manu facture of certain sodium salts, as suggested by Julius Thomsen of Copenhagen, in 1849; and it has been used for the production of certain kinds of porcelain and glass, remarkable for their toughness, and for enamelled ware.