Black metallic crystal aggregates of the very rare Au-Ag-Sb-Bi-Pb telluride montbrayite from the type locality in Montbray, Quebec, Canada, associated to quartz. Ex. F. Bauer collection (Munich). Ex. C. Rewitzer specimen. — Photo: David Hospital · CC BY-SA 4.0
Montbrayite
A very rare, complex gold-silver telluride allied to krennerite and calaverite, named for a Canadian locality.
Intro adapted from Wikipedia (CC BY-SA).
Montbrayite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula (Au,Ag,Sb,Bi,Pb)₂₃(Te,Sb,Bi,Pb)₃₈.
It crystallizes in the triclinic crystal system (space group P1).
Key properties: Mohs hardness 2.5; specific gravity 9.94; Metallic luster.
IMA symbol Mnb, grandfathered status — known before the IMA’s founding, named in 1946.
With other tellurides, sulfides, and gold in coarsely crystalline masses almost free from gangue (Robb-Montbray mine, Canada).
It is found associated with Calaverite, gold, tellurobismuthite, altaite, petzite, melonite, frohbergite, chalcopyrite, pyrite, sphalerite, chalcocite, covellite.
The name refers to the Robb-Montbray mine, Canada.