Silvery metallic blades of cuprobismutite associated with bismuthinite from Utah (Tunnel Extension No. 2 Mine, Utah, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Cuprobismutite
Cuprobismutite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Cu₈AgBi₁₃S₂₄.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: specific gravity 6.36; Metallic. Anisotropism: Distinct. R1 –R2: (400) 31.8–35.2, (420) 32.4–35.8, (440) 33.1–36.4, (460) 34.4–37.6 luster.
IMA symbol Cbit, grandfathered status — known before the IMA’s founding, named in 1884.
Rare, of hydrothermal origin with other sulfides and sulfosalts.
It is found associated with Emplectite, aikinite, wittichenite, benjaminite, berryite, cupropavonite, paděraite, hodrushite, wolframite, bismuthinite.
The name refers to copper, CUPRum, and BISMUTh in the composition.