Dark red-black crystals of laffittite, a very rare silver-mercury mineral of formula AgHgAsS3, associated to orpiment and realgar. From Getchell Mine, Humboldt County, Nevada, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Laffittite
Laffittite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula AgHgAsS₃.
It crystallizes in the monoclinic crystal system (space group Aa). It is a member of the Rocksalt structural group.
Key properties: specific gravity 6.11; Pale cherry-red to brownish red streak; Metallic, adamantine luster.
IMA symbol Lft, IMA status: approved, named in 1973.
With other arsenic sulfides, in hydrothermal deposits.
It is found associated with Smithite, stibnite, pierrotite, parapierrotite, aktashite, realgar, wakabayashilite, sphalerite, pyrite, routhiérite, chabournéite (Jas Roux, France).
The name refers to Pierre Laffitte (1925–), Director, National School of Mines, Paris, France.