Alacránite
An arsenic sulfide discovered in the Uzon caldera in Kamchatka, named after the Alacrán silver-arsenic mine.
Intro adapted from Wikipedia (CC BY-SA).
Alacránite is an IMA-recognized mineral species in the sulfide class, with the chemical formula As₈S₉.
It crystallizes in the monoclinic crystal system (space group P2/c).
Key properties: Mohs hardness 1.5; specific gravity 3.43; Yellow-orange streak; Adamantine, vitreous, resinous, greasy luster; optically biaxial.
IMA symbol Acr, IMA status: approved, named in 1985.
Found in hydrothermal As-S veins (Alacrán mine, Chile); in the condensation zone of a hydrothermal Hg-Sb-As system as cement in a sandy gravel (Uzon caldera, Russia).
It is found associated with Realgar, orpiment, smithite, arsenic, sulfur, stibnite, pyrite, greigite, arsenopyrite, arsenolamprite, sphalerite, acanthite, barite, quartz.
The name refers to the occurrence in the Alacrán deposit, Chile.