Cryolite
Image: Didier Descouens (CC BY-SA 3.0)
Mineral NameCryolite
Chemical FormulaNa₃AlF₆
Mohs Hardness2.5
Crystal Systemmonoclinic
Streak Colorwhite
Cleavagepoor/indistinct in three directions
Fractureuneven to conchoidal
Specific Gravity2.95
Colorswhite, colorless, brownish, reddish
Transparencytransparent to translucent
Type LocalityIvigtut Cryolite deposit, Ivittuut (Ivigtut), Arsuk Firth, Arsuk, Kitaa (West Greenland) Province, Greenland
Mineral GroupHalides
Usesindustrial (synthetic), collector
Associated Mineralsquartz, siderite, galena, chalcopyrite, fluorite
Rarityrare
Description
This is a massive, off-white to translucent white specimen of cryolite, exhibiting a somewhat waxy or greasy luster on its uneven surfaces. A small area shows a faint yellowish tint.
Geological Context
Cryolite typically forms in granite pegmatites or hydrothermal veins, often associated with alkaline igneous rocks. The Ivigtut deposit was a unique, large cryolite-rich pegmatite.
