Very nice specimen of steropesite, a exceptionally rare thallium mineral (IMA 2008-014) of formula Tl3BiCl6 from La Fossa Crater (Vulcano Island, Aeolian Islands, Sicily, Italy). — Photo: David Hospital · CC BY-SA 4.0
Steropesite
Steropesite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Tl₃BiCl₆.
It crystallizes in the monoclinic crystal system (space group Cc).
Key properties: specific gravity 5.737; White streak; Vitreous to adamantine luster.
IMA symbol Strp, IMA status: approved, named in 2008.
Forms as a sublimate at an active high-temperature volcanic fumarole (~450 flC).
It is found associated with Bismuthinite, lafossaite.
The name commemorates Steropes, one of the three Cyclops and a son of Uranus. These mythological half-gods were helpers of Hephaistos (Hephaestus), the ancient Greek god of fire.