It has a mohs hardness of 2.5 to 3 and a specific gravity of about 2.95 to 3.0. It is translucent to transparent with a very low refractive index of about 1.34, which is very close to that of water; thus if immersed in water, cryolite becomes essentially invisible. It is used as a solvent for bauxite in the electrolytic production of aluminum and has various other metallurgical applications, and it is used in the glass and enamel industries, in bonded abrasives as a filler, and in the manufacture of insecticides.

A large amount of synthetic cryolite is made from fluorite. Cryolite has a lower melting point than aluminum oxide and acts as a solvent to create an electrolyte mixture of molten cryolite and alumina. This mixture melts at about 900 degrees celsius instead of over 2000 degrees celsius, as in the case of pure alumina. Less energy or less electricity is therefore used.