Polished section of the intermediate member of the series hollingworthite and irarsite in a completley analyzed specimen. From: Goodnews Bay, Bethel Borough, Alaska, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Irarsite
Irarsite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula IrAsS.
It crystallizes in the cubic crystal system. It is a member of the Pyrite structural group.
Key properties: specific gravity 11.92; Metallic. R: (400) 47.6, (420) 47.3, (440) 47.0, (460) 46.8, (480) 46.6, (500) 46.4, (520) 46.2, (540) 45.9 luster.
IMA symbol Irs, IMA status: approved, named in 1966.
Found in chromite in hortonolite dunite (South Africa); as inclusions in chrompicotites (Bulgaria); and as rims around Pt-group alloys.
It is found associated with Platinum, ruthenian hollingworthite, sperrylite, laurite, iridarsenite, ruthenarsenite, rutheniridosmine, chalcopyrite, chalcocite, pyrrhotite, cobaltite.
The name refers to IRidium and ARSenic in the composition.