Friedrichite
Friedrichite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Cu₅Pb₅Bi₇S₁₈.
It crystallizes in the orthorhombic crystal system (space group Pb2_1m). It is a member of the Meneghinite structural group.
Key properties: specific gravity 6.98; Metallic. Anisotropism: Strong in oil, distinct in air. R1 –R2: (470) 41.0–46.7, (546) 40.1–46.2, (589) 39.9–45.8 luster.
IMA symbol Frd, IMA status: approved, named in 1977.
Occurs as aggregates of granular crystals, in boulders of vein quartz which occur in the scree of a landslip (Salzburg, Austria); in magnesian and calcic skarn deposits (Apuseni Mountains, Romania).
It is found associated with Chalcopyrite, covellite, cerussite, chlorite, mica, quartz (Salzburg, Austria); cuprobismutite, cupropavonite (Apuseni Mountains, Romania).
The mineral was named to honor Professor Dr.-Ing Otmar Michael Friedrich (1902–1991), Austrian geologist of the Mining University, Leoben, Styria, Austria.