GEARKSUTITE
Gearksutite is a scarce hydrous calcium
hydroxy-aluminofluoride mineral, CaAlF4(OH)·H2O. It
has a rather unremarkable appearance. It has a dull, nonmetallic luster,
white to clear color, white streak, and is soft (H = 2). It has no
macrocrystalline features, but is reported to have a needle-like
microcrystalline texture. Gearksutite tends to form chalky to earthy
nodules. This mineral is known to be an alteration product of the halide
mineral cryolite, as well as the result of hydrothermal alteration of some
granites and pegmatitic granites.
Gearksutite from the Cresson Open Pit Mine, Cripple Creek Diatreme, Teller County,
Colorado, USA (ER # 2994, 2995, 2996, Ed Raines loan to Colorado School of
Mines Geology Museum, Golden, Colorado, USA).