Outstanding small orange crystals of the rare Cl-Br-I mineral perroudite from Coppin Pool, Ashburton Shire, Western Australia, Australia, on a contrasting matrix. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Perroudite
Perroudite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ag₄Hg₅S₅(I,Br)₂Cl₂.
It crystallizes in the orthorhombic crystal system (space group P2_12_12).
Key properties: specific gravity 6.928; Reddish orange streak; Vitreous to adamantine luster; optically biaxial.
IMA symbol Pro, IMA status: approved, named in 1986.
An alteration of tennantite in sandstones and conglomerates (Cap Garonne mine, France); in a quartz vein carrying oxidized galena (Coppin Pool, Australia).
It is found associated with Mercurian and argentian tennantite, secondary copper minerals (Cap Garonne mine, France); iodargyrite, gold, kaolinite (Broken Hill, Australia); anglesite.
The mineral was named to honor Professor Pierre Perroud (b. 1943), Voltaire College, Geneva, Switzerland, for his work on Cap Garonne mine minerals.