Black crystal aggregates of the rare selenide mineral weibullite from the TL in Falun mine (Falun Mine, Falun, Dalarna County, Sweden). Ex. Erich Laskowski collection. — Photo: David Hospital · CC BY 4.0
Weibullite
Weibullite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Ag₀.₃₃Pb₅.₃₃Bi₈.₃₃(S,Se)₁₈.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Kobellite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 6.73; Metallic luster.
IMA symbol Wbl, IMA status: approved, named in 1910.
Intimately intergrown with laitakarite and bismuthinite in a “hornblende” rock.
It is found associated with Laitakarite, bismuthinite, gold, chalcopyrite, bismuth, pyrrhotite, quartz.
The name refers to Mats Weibull (1856–1923), who first described the mineral.