Creedite , Gearksutite Locality: Navidad Mine (Mina Navidad; Abasolo Mine; Rodeo Mine), Abasolo , Rodeo , Municipio de Rodeo , Durango , Mexico ( Locality at mindat.org ) Size: 7.8 x 7.0 x 6.0 cm. A striking and very rare orange creedite with gearksutite specimen. Gearksutite is a rare complex aluminum salt, being a late stage, secondary fluoride. The bottom of this creedite pincushion is very richly covered with sharp, dagger-like, frosted, white gearksutite crystals to about 9 mm (second photo). Crystallized gearksutite in itself, is very rare, as it is usually massive or nodular. This specimen is from a brand new lot brought out by Mike New in August of this year (2009), just before the Denver Show. Mike just had this material analyzed and confirmed as gearksutite. Only a couple of dozen of the more than 1000 specimens we obtained have gearksutite on them. Getting back to the creedite, this ball of creedite is covered with gemmy, burnt-orange crystals to 1.7 cm, which is large for the locale. Note that this zone is now inaccessible to a cave-in, and more mining at this new depth is not expected (anytime soon). — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Gearksutite
Gearksutite is an IMA-recognized mineral species in the halide class, with the chemical formula CaAlF₄(OH)·H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 2; specific gravity 2.72–2.77; Dull luster; optically biaxial.
IMA symbol Gak, IMA status: approved, named in 1868.
Found in granite and granite pegmatites; may be formed by low-temperature hydrothermal alteration of aluminous rocks by fluorine-bearing hot springs.
It is found associated with Cryolite, thomsenolite, sellaite, pachnolite, ralstonite, weberite, fluorite.
Its name comes from the Greek ge for Earth, in allusion to the earthy appearance of the mineral, and arksutite (= chiolite).