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Formula: CaAlF4(OH).H2O
Halide
Crystal System: Triclinic
Specific gravity: 2.768 measured, 2.771 calculated
Hardness: 2
Streak: White
Colour: white, colourless (including in transmitted light)
Solubility: Readily soluble in dilute acid.
Environments
Plutonic igneous environments
Volcanic igneous environments
Pegmatites
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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