Outstanding metallic crystal aggregates of the extremely rare Au-Ag selenide mineral fischesserite from a locality in De Lamar mine in Idaho (De Lamar Mine, De Lamar, Owyhee County, Idaho, United States of America), in a partially polished specimen that was probably analyzed by the former owner of the specimen. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Fischesserite
Fischesserite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Ag₃AuSe₂.
It crystallizes in the cubic crystal system (space group I4_132).
Key properties: specific gravity 9.05; Metallic. R: (400) 33.4, (420) 33.4, (440) 33.4, (460) 33.0, (480) 32.3, (500) 31.2, (520) 30.1, (540) 29.8 luster.
IMA symbol Fis, IMA status: approved, named in 1971.
Found in carbonate veins in epithermal precious metal deposits (Předbořice, Czech Republic).
It is found associated with Naumannite, clausthalite, permingeatite, gold, calcite, quartz (Předbořice, Czech Republic).
The name refers to Raymond Fischesser (1911–1991), French mineralogist and crystallographer, Director of the National School of Mines, Paris, France.