Colusite , Quartz Locality: Butte District (Summit Valley District), Silver Bow County , Montana , USA ( Locality at mindat.org ) Size: 5.3 x 4.1 x 2.5 cm Brassy-metallic colusite in quartz-rich matrix. Colusite was not named until 1932. Charles Velte Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Colusite
Colusite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Cu₁₃VAs₃S₁₆.
It crystallizes in the cubic crystal system (space group P-43n). It is a member of the Sphalerite, Germanite structural group.
Key properties: Mohs hardness 3–4; specific gravity 4.2; Black streak; Metallic. R: (400) 25.1, (420) 25.5, (440) 25.9, (460) 26.4, (480) 27.0, (500) 27.7, (520) 28.6, (540) 29.6 luster.
IMA symbol Col, grandfathered status — known before the IMA’s founding, named in 1914.
Widespread in small amounts with other sulfides and sulfosalts, typically in hydrothermal vein and disseminated copper deposits.
It is found associated with Pyrite, tetrahedrite–tennantite, enargite, luzonite, stannoidite, goldfieldite, germanite, reniérite, bornite, chalcocite, covellite, chalcopyrite, sphalerite.
The name refers to the Colusa claim, Butte, Montana, USA, near which it occurs in the Leonard mine.