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Formula: Cu6(Cu4Cu2+2)Sb4S13
Sulphosalt, tetrahedrite subgroup,
tetrahedrite group,
antimony-bearing mineral
Crystal System: Isometric
Specific gravity: 5.029 calculated for the empirical formula
Hardness: 3½ to 4
Streak: Black
Colour: Steel-grey
Environments
Tetrahedrite-(Cu) is a new mineral, approved in 2022.
Localities
At the type locality, the Medvedza magnesite body (stope K 401), Bankov magnesite deposit, Košice I, Košice, Košice
Region, Slovakia, hydrothermal-metasomatic bodies of magnesite are hosted in
Carboniferous (358.9 to 298.9 million years ago) shales and
phyllites. Here an interesting hydrothermal ore mineralisation,
represented mostly by copper sulphosalts such as skinnerite,
chalcostibite and various minerals of the
tetrahedrite group, is developed in a small scale on younger
fractures in the magnesite body in the form of crystalline crusts and
fillings. Tetrahedrite-(Cu) is associated with skinnerite,
chalcostibite, famatinite,
tetrahedrite-(Fe), zoned aggregates of tennantite-(Cu) to
tennantite-(Fe) and minor
chalcopyrite and marcasite. This
unusual association of copper sulphosalts has no other equivalent in the whole
Western Carpathians and it is related to hydrothermal solutions strongly enriched in
copper, antimony and
sulphur and later stages of crystallisation also rich in
arsenic as well as minor amounts of
germanium. The primary
ore mineralisation is locally replaced by younger supergene
minerals including chalcocite,
native copper, malachite and
azurite.
Tetrahedrite-(Cu) forms anhedral grains up to 200 × 400 μm. It is steel-grey in colour, with a black streak and
metallic lustre. It is brittle, with a conchoidal fracture and an indistinct cleavage
(MM 88.392–399).
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