Purple metallic aggregates of the very rare thallium mineral cuprostibite from the type locality in Greenland (Nakkaalaaq, Ilímaussaq, Narsaq, Kujalleq, Greenland). Ex.Dr.Hartel collection. — Photo: David Hospital · CC BY-SA 4.0
Cuprostibite
A very rare copper-antimony intermetallic compound, sometimes with thallium and tin admixtures.
Intro adapted from Wikipedia (CC BY-SA).
Cuprostibite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Cu₂(Sb,Tl).
It crystallizes in the tetragonal crystal system (space group P4/nmm).
Key properties: specific gravity 8.42; Metallic luster.
IMA symbol Cusb, IMA status: approved, named in 1969.
Occurs as fine-grained aggregates in a vein of ussingite cutting sodalite syenite (Ilı́maussaq intrusion, Greenland); in sulfide veins in metamorphic siliceous dolostone (Långsjön, Sweden).
It is found associated with Löllingite, antimonian silver, chalcopyrite, chalcothallite (Ilı́maussaq intrusion, Greenland); chalcocite, bismuth (Långban, Sweden); sphalerite, galena.
The name refers to copper, CUPRum, and antimony, STIBium, in the composition.