Backite
Backite is an IMA-recognized mineral species in the halide class, with the chemical formula Pb₂AlTeO₆Cl.
It crystallizes in the hexagonal crystal system (space group P312). It is a member of the Backite structural group.
Key properties: Mohs hardness 2–3; specific gravity 5.573; Very pale bluish gray to white streak; Adamantine luster; optically uniaxial.
IMA symbol Bac, IMA status: approved, named in 2013.
Found as a secondary mineral in the oxidation zone of rocks containing Ag- and Au-bearing galena and minor amounts of copper and zinc minerals.
It is found associated with Schieffelinite, oboyerite, rodalquilarite, cerussite, jarosite.
The mineral was named to honor Malcolm A. Back (b. 1951), Department of Natural History (Mineralogy), Royal Ontario Museum, Toronto, Canada.