Pachnolite

halide

cryolite

Formula: NaCaAlF6.H2O
Halide, dimorph of thomsenolite, which is epitaxial on pachnolite
Specific gravity: 2.98
Hardness: 3
Streak: White
Colour: Colourless, white; colourless in transmitted light.
Solubility: Soluble in sulphuric acid, easily fusible (Dana)
Environments

Pegmatites

Pachnolite occurs as as alteration product of cryolite and other alkali aluminium fluorides, most commonly in pegmatites. Associated minerals include cryolite, thomsenolite, chiolite, elpasolite, hydrokenoralstonite, sellaite and fluorite (HOM).

At the type locality, the Ivigtut Cryolite deposit, Sermersooq, Greenland, Denmark, pachnolite occurs as an alteration product of cryolite (Dana), associated with thomsenolite (Mindat).

At Saint Peter's dome, El Paso county, Colorado, USA, pachnolite occurs with thomsenolite, elpasolite and other fluorides (Dana).

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