Black shiny crystal aggregates of coiraite, a very rare mineral (a Pb-Sn-Fe-As sulphide) described a few years ago (IMA 2005-024), associated to the rare Pb-Sn-sulphide mineral suredaite, both from the type and only known locality worldwide. From: Pirquitas, Rinconada Department, Jujuy, Argentina. — Photo: David Hospital · CC BY-SA 4.0
Coiraite
Coiraite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula (Pb,Sn)₁₂.₅As₃Sn₅FeS₂₈.
It crystallizes in the monoclinic crystal system (space group P2/m).
Key properties: Mohs hardness 2; specific gravity 5.92; Dark gray to almost black streak; Metallic to dull luster.
IMA symbol Coi, IMA status: approved, named in 2005.
Found as a primary mineral in a telescoped Ag-Sn-Zn polymetallic hydrothermal vein deposit.
It is found associated with Franckeite, cylindrite, pyrite-marcasite, hocartite, Ag-rich rhodostannite, arsenopyrite, galena.
The mineral was named to honor Beatriz Lydia Coira (b. 1941), Professor of Petrology, University of Jujuy, Argentina, for her research on volcanism, regional geology.