Jarlite

jarlite

gearksutite

cryolite

thomsenolite

Images

Formula: Na₂(Sr,Na)₁₄(Mg,☐)₂Al₁₂F₆₄(OH)₄
Fluoride
Crystal System: Monoclinic
Specific gravity: 3.78 to 3.93 measured
Hardness: 4 to 4½
Streak: White
Colour: Colourless, grey-white, white; colourless in transmitted light.
Solubility: Soluble in AlCl₃ solution; easily fusible, with effervescence (Dana).
Common impurities: Ca
Environments

Pegmatites

At the type locality, the Ivigtut Cryolite deposit, Sermersooq, Greenland, Denmark, jarlite occurs growing with thomsenolite in vugs in a pegmatitic cryolite deposit in granite. Associated minerals include cryolite, gearksutite, chiolite, thomsenolite, hydrokenoralstonite, prosopite, stenonite, acuminite, bøgvadite, jørgensenite, fluorite, topaz and baryte (AM 34.383, Dana, Mindat, Webmin, HOM).

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