Talnakhite

Talnakhite
Talnakhite and putoranite
General
Category	Sulfide mineral
Formula (repeating unit)	Cu9(Fe, Ni)8S16
Strunz classification	2.CB.10b
Crystal system	Isometric
Crystal class	Hextetrahedral (43m) H-M symbol: (4 3m)
Space group	I4 3m
Identification
Color	Brass-yellow, tarnishes to pink or brown tints, then iridescent
Luster	Metallic
Diaphaneity	Opaque

Talnakhite is a mineral of chalcopyrite group with formula: Cu₉(Fe, Ni)₈S₁₆. It was named after the Talnakh ore deposit, near Norilsk in Western Siberia, Russia where it was discovered as reported in 1963 by I. Budko and E. Kulagov. It was officially named "talnakhite" in 1968. Despite the initial announcement it turned out to be not a face centered high-temperature polymorph of chalcopyrite, but to have composition Cu₁₈(Fe, Ni)₁₈S₃₂. At 80 °C (176 °F) to 100 °C (212 °F) it decomposes to tetragonal cubanite plus bornite.