Torrecillasite
Torrecillasite is an IMA-recognized mineral species in the halide class, with the chemical formula Na(As,Sb)³⁺₄O₆Cl.
It crystallizes in the orthorhombic crystal system (space group Pmcn).
Key properties: Mohs hardness 2.5; specific gravity 4.056; White streak; Adamantine luster; optically biaxial.
IMA symbol Trc, IMA status: approved, named in 2013.
Forms secondarily through oxidation of native As and As-bearing minerals in hydrothermal veins followed by later alteration by saline fluids derived from evaporating meteoric water under hyperarid conditions.
It is found associated with Anhydrite, cinnabar, gypsum, halite, lavendulan, magnesiokoritnigite, marcasite, quartz, pyrite, scorodite, wendwilsonite, leverettite, canutite.
The name refers to the locality from which the first specimens were obtained.