Metallic crystal aggregtaes of the very rare thallium mineral pierrotite from the type locality in Jas Roux (La Chapelle-en-Valgaudemar, Hautes-Alpes, Provence-Alpes-Cote d'Azur, France). — Photo: David Hospital · CC BY-SA 4.0
Pierrotite
Pierrotite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Tl₂(Sb,As)₁₀S₁₆.
It crystallizes in the orthorhombic crystal system (space group Pna2_1). It is a member of the Sartorite structural group.
Key properties: specific gravity 4.97; Metallic, lively. Anisotropism: Moderate. R1 –R2: (400) 35.9–39.6, (420) 35.2–38.8, (440) 34.5–38.0, (460) 33.7–37.2 luster.
IMA symbol Pie, IMA status: approved, named in 1969.
Found in quartz veins (Jas Roux, France).
It is found associated with Stibnite, realgar, pyrite, an unnamed amorphous mineral of composition Tl(As, Sb)10 S16 (Jas Roux, France); chabourneite, parapierrotite (Alšar, Macedonia).
The mineral was named to honor Roland Pierrot (1930–), French mineralogist, Head of Mineralogy, B.R.G.M., Orléans, France.