Formula: Na₂NaAlF₆

Species:

Colour: Colourless, white, brown, grey, black; colourless in transmitted light.

Lustre: Vitreous, Greasy, Pearly

Hardness: 3 – 3½

Specific Gravity: 2.96 – 2.98

Crystal System: Monoclinic

Member of: Cryolite Subgroup > Stoichiometric Perovskites Group > Perovskite Supergroup

Name: From the Greek κρύος, frost, and λίθος, stone, meaning “ice-stone” in allusion to its appearance.

Type Locality: Ivigtut Mine, Ivittuut town (formerly Ivigtût), Arsuk Fjord, Sermersooq – Greenland

A curiosity mineral. Colourless samples of this sodium-aluminium-fluoride mineral seemingly disappear in water due to the proximity of their refractive indices. Historically, cryolite was used as an aluminium ore and later in the electrolytic processing of the aluminium ore bauxite.