Geerite Field of view: 3 mm Locality: Clara Mine, Oberwolfach, Ortenaukreis, Freiburg Region, Baden-Württemberg, Germany — Photo: Henk Smeets – tomeikminerals.com · CC BY 4.0
Geerite
A copper sulfide (Cu₈S₅) named for Adam Geer, the Utica, New York collector who first gathered it.
Intro adapted from Wikipedia (CC BY-SA).
Geerite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Cu₈S₅.
It crystallizes in the cubic crystal system (space group F-43m).
Key properties: Mohs hardness 3.5; specific gravity 5.61; Metallic luster.
IMA symbol Gee, IMA status: approved, named in 1978.
Replacing sphalerite along cleavage traces (DeKalb Township, New York, USA); in a serpentine-hosted magnetite–chromite deposit (Eretria, Greece).
It is found associated with Spionkopite, sphalerite, tetrahedrite, chalcopyrite, malachite, azurite, brochantite, chrysocolla, cervantite, stibiconite, hemimorphite.
The mineral was named to honor the collector of the original specimens, Adam Geer (1895–1973), of Utica, New York, USA.