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Category Arsenide mineral
(repeating unit)
Strunz classification 2.AA.10b
Crystal system Isometric
Crystal class Hextetrahedral (43m)
H-M symbol: (4 3m)
Space group I43d
Unit cell a = 9.62 Å; Z = 16
Formula mass 265.56 g/mol
Color Tin-white to steel-gray
Crystal habit Reniform, botryoidal; massive
Cleavage None
Tenacity Brittle - sectile
Mohs scale hardness 3-3.5
Luster Metallic
Streak Black gray
Diaphaneity Opaque
Specific gravity 7.2 - 8.1, average = 7.65
Other characteristics Tarnishes pale yellow, then pale brown, and finally to iridescence
References [1][2][3]

Domeykite is a copper arsenide mineral, Cu3As. It crystallizes in the isometric system, although crystals are very rare. It typically forms as irregular masses or botryoidal forms. It is an opaque, white to gray (weathers brassy) metallic mineral with a Mohs hardness of 3 to 3.5 and a specific gravity of 7.2 to 8.1[1][3]

It was first described in 1845 in the Algodones mines, Coquimbo, Chile. It was named after Polish mineralogist Ignacy Domeyko (1802–1889) by Wilhelm Haidinger.[2]


Domeykite, being a minor copper ore is used for obtaining copper. It can also be polished and used for ornamental purposes.[4]

Crystal structure of domeykite
Mohawkite nugget, a mixture of domeykite, algodonite and native copper (50x40x28 mm)

See also[edit]