CRYOLITE, so named from κpvo<i, ice, and λι'0oς, stone, on account of its ready fusibility, is a massive, usually granular or indistinctly crystalline, cleavable, translucent to transparent, brittle mineral, of a snow-white (sometimes reddish or brownish) colour, vitreous lustre, hardness 2 ’ 5, and specific gravity 2 ’ 9-3O77. Its transparency is increased by immersion in water. Before the blowpipe it fuses easily to an opaque white enamel. It is a double fluoride of aluminium and sodium, with the percentage composition—aluminium 13, sodium 32 ’ 8, fluorine 54 ’ 2, answering to the formula Al 2 F 6 ,6NaF. Cryolite is used in the manufacture of soap, soda, aluminium sulphate, alum, and cryolite glass; and, till superseded by bauxite, was the chief source of aluminium. That metal was first obtained from it, early iu 1855, by Allan Dick, who fused the mineral with alternate layers of small pieces of sodium in a magnesia-lined crucible. Rose, in September of the same year, published a method of producing aluminium by heating together cryolite, potassium chloride, and sodium. According to Μ. Gauduin a mixture of equal parts of cryolite and barium chloride forms a flux superior to borax for soldering iron, or brazing copper, brass, and bronze. Cryolite was discovered and named by Abildgaard about the year 1800, and was subsequently described by D’Andrada and Karsten, and accurately analyzed by Klaproth. Giesecke in 1822 first made known its occurrence at Ivigtot, in the colony of Frederikshaab, South Greenland. It is found there associated with galena, pyrites, and chalybite, and forms a vein 80 feet in thickness. At Miask in the Urals it occurs with chiolite, lepidolite, and fluor. In 1875 thirty-three cargoes of the mineral, representing a total of 5076 ...