Acuminite

halide

cryolite

Formula:SrAlF4(OH).H2O
Halide, dimorphous with tikhonenkovite
Specific gravity: 3.295
Hardness: 3½
Streak: White
Colour: Colourless, white, becomes yellow on exposure to x-rays (Mindat)
Environments

Pegmatites

The only reported occurrence of acuminite is at the type locality, the Ivigtut Cryolite deposit, Sermersooq, Greenland, Denmark, where occurs in a small cavity in a specimen from a strontium-rich portion of the cryolite deposit, associated with celestine, fluorite, jarlite, thomsenolite, hydrokenoralstonite, pachnolite and gearksutite (Mindat, Dana, HOM, AM 73.1492).

Common impurities: Ca

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