Gearksutite is a scarce hydrous calcium hydroxy-aluminofluoride mineral, CaAlF4(OH)ĚH2O. 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).