Formula: CaAlF4(OH).H2O
Specific gravity: 2.768
Hardness: 2
Streak: White
Colour: white, colourless (including in transmitted light)
Solubility: Readily soluble in dilute acid.

Plutonic igneous environments
Volcanic igneous environments
Hydrothermal environments

Gearksutite is an alteration product of cryolite (Webmin). It occurs in granite and granite pegmatites, and may be formed by low-temperature hydrothermal alteration of aluminous rocks by fluorine-bearing hot springs. Associated minerals include cryolite, thomsenolite, sellaite, pachnolite, hydrokenoralstonite, weberite and fluorite (HOM).

At the type locality, the Ivigtut Cryolite deposit, Sermersooq, Greenland, Denmark, gearksutite is an alteration product of cryolite associated with thomsenolite and cryolite (AM 34.383-397). Gearksutite is one of the last formed secondary fluorides here (Mindat).

At the Gallagher-Manila properties, Cochise county, Arizona, USA, gearksutite appears to be associated with baryte, anglesite and other minerals in quartz-hosted vugs (R&M 90.4.343).

At Saint Peter's dome, Pikes Peak area, El Paso county, Colorado, USA, gearksutite occurs in a cryolite pegmatite (Dana).

At Wagon Wheel gap, Pikes Peak area, El Paso county, Colorado, USA, gearksutite occurs in wall-rock alteration of a fluorite-baryte vein in rhyolite (Dana).

At the Cresson open pit, Cripple Creek mining district, Teller county, Colorado, USA, gearksutite occurs with rhodochrosite, celestine and creedite, and is the last mineral in this assemblage to form. (MinRec 36.2.170)

At a locality midway between Hot Springs and Warm Springs, Bath county, Virginia, USA, gearksutite has been found in a clay bed in limestone, associated with gypsum (AM 14.281-285).

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