Dufrénoysite from the Legenbach Quarry, Binnetal , Switzerland. Held at the A. E. Seaman Mineral Museum . — Photo: Chris857 · CC BY-SA 3.0
Dufrénoysite
Dufrénoysite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Pb₂As₂S₅.
It crystallizes in the monoclinic crystal system (space group P2_1). It is a member of the Sartorite structural group.
Key properties: Mohs hardness 3; specific gravity 5.5–5.57; Reddish brown to chocolate-brown streak; Metallic luster.
IMA symbol Duf, grandfathered status — known before the IMA’s founding, named in 1845.
An uncommon mineral of medium- to low-temperature hydrothermal origin.
It is found associated with Chalcopyrite, sphalerite, realgar, orpiment, tetrahedrite.
The mineral was named to honor Professor Ours Pierre Armand Petit-Dufrénoy (1792–1857), French mineralogist, National School of Mines, Paris, France.