Mineral, Na₃AlF₆; sp. gr. 3.0; hardness 2.5; monoclinic; colourless to white, sometimes brown to reddish; white streak; vitreous to greasy lustre; crystals rare, but cubic-like and hexahedral, also occurs massive; no cleavage, basal parting and poor prismatic parting; occurs in pegmatites that have been enriched with fluorine, and in association with siderite, quartz, galena, chalcopyrite, fluorite, and cassiterite. The powder becomes almost invisible in water due to its low refractive index. Synthetic cryolite is used as a flux in the production of aluminium and enamels.