Talnakhite is a mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 of chalcopyrite

Chalcopyrite

Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.On exposure to air, chalcopyrite...

 group with formula: Cu₉(Fe, Ni)₈S₁₆. It occurs in olivinic

Olivine

The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....

 gabbro

Gabbro

Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....

-dolerite. It was named after the Talnakh

Talnakh

Talnakh was a town located about north of Norilsk at the foot of the Putoran Mountains in Taymyr Peninsula, Krasnoyarsk Krai, Russia. In 2005 the town was merged into Norilsk. Population:...

 ore

Ore

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

 deposit, near Norilsk

Norilsk

Norilsk is an industrial city in Krasnoyarsk Krai, Russia, located between the Yenisei River and the Taymyr Peninsula. Population: It was granted city status in 1953. It is the northernmost city in Siberia and the world's second largest city north of the Arctic Circle...

 in Western Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

 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

Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...

 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

Cubanite

Cubanite is a yellow mineral of copper, iron, and sulfur, CuFe2S3.Cubanite was first described in 1843 for an occurrence in the Mayarí-Baracoa Belt, Oriente Province, Cuba....

 plus bornite

Bornite

Bornite is a sulfide mineral with chemical composition Cu5FeS4 that crystallizes in the orthorhombic system .-Appearance:Bornite has a brown to copper-red color on fresh surfaces that tarnishes to various iridescent shades of blue to purple in places...

.