Jolliffeite
A rare nickel-arsenic selenide — the selenium counterpart of gersdorffite, often with cobalt.
Intro adapted from Wikipedia (CC BY-SA).
Jolliffeite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula NiAsSe.
It crystallizes in the cubic crystal system (space group P2_13). It is a member of the Ullmannite structural group.
Key properties: Mohs hardness 3; specific gravity 7.1.
IMA symbol Jlf, IMA status: approved, named in 1989.
From a drill core in a fracture zone near a dolomite–peridotite contact.
It is found associated with Clausthalite, Pb–Bi–Ag selenides, gold, “pitchblende”.
The mineral was named to honor Professor Alfred Watson Jolliffe (1907–1988), Canadian geologist, Queen’s University, Kingston, Ontario, Canada.