kermesite

{{Infobox mineral | name = Kermesite | category = Oxysulfide | boxwidth = | boxbgcolor = | image = Mineraly.sk - kermezit.jpg | alt = | caption = | formula = (Sb2S2O) | IMAsymbol = Kem | molweight = | strunz = 2.FD.05 | dana = 02.13.01.01 | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | color = Red to cherry red, purple | habit = Acicular, fibrous, radial | twinning = | cleavage = Perfect {100}, parting on {010} | tenacity = Sectile | fracture = Brittle | mohs = 1–2 | luster = Adamantine to semimetallic | refractive = nα = 2.720 nβ = 2.740 nγ = 2.740 | opticalprop = Biaxial (+) | birefringence = | pleochroism = None | streak = Brownish red | gravity = 4.5–4.8+ | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent, Opaque | other = | references = }}

Kermesite (also known as antimony oxysulfide, red antimony, or purpur blende) is a mineral with the chemical formula Sb2S2O. Its color can range from cherry red to a dark red to a black. Kermesite is the result of partial oxidation between stibnite (Sb2S3) and other antimony oxides such as valentinite (Sb2O3) or stibiconite (Sb3O6(OH)). Under certain conditions with oxygenated fluids the transformation of all sulfur to oxygen would occur but kermesite occurs when that transformation is halted.