An extremely rare thallium mineral in crystallized form (IMA 2013-58) as light red crystals. From: Monte Arsiccio Mine, Apuan Alps, Tuscany, Italy — Photo: David Hospital · CC BY-SA 4.0
Arsiccioite
Arsiccioite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula AgHg₂TlAs₂S₆.
It crystallizes in the tetragonal crystal system (space group I-42m). It is a member of the Routhierite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 5.989; Orange streak; Metallic to submetallic luster.
IMA symbol Asi, IMA status: approved, named in 2013.
Found in a lens of microcrystalline barite near the contact between schist and pyrite-rich dolostone. The assemblage interpreted as crystallized from a sulfide melt during greenschist-facies metamorphism.
It is found associated with Protochabournéite, cinnabar, laffittite, pyrite, realgar, Hg-bearing sphalerite, stibnite, barite.
The name refers to the mine that yielded the first specimens.