stibnite

{{Infobox mineral | name = Stibnite | category = Sulfide mineral | boxwidth = | boxbgcolor = | image = Antimonit 02.jpg | caption = | formula = Sb2S3 | IMAsymbol = Sbn | molweight = | strunz = 2.DB.05a | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pbnm | unit cell = a = 11.229 Å, b = 11.31 Å, c = 3.8389 Å; Z = 4 | color = Lead-gray, tarnishing blackish or iridescent; in polished section, white | habit = Massive, radiating and elongated crystals. Massive and granular | twinning = Rare | cleavage = Perfect and easy on {010}; imperfect on {100} and {110} | fracture = Subconchoidal | tenacity = Highly flexible but not elastic; slightly sectile | mohs = 2 | luster = Metallic | refractive = | birefringence = | pleochroism = | streak = Lead grey | gravity = 4.63 | melt = | fusibility = | diagnostic = | solubility = Decomposed with hydrochloric acid | diaphaneity = Opaque | opticalprop = Anisotropic | references = | var1 = Metastibnite | var1text = Earthy, reddish deposits }} Stibnite, sometimes called antimonite, is a sulfide mineral, a mineral form of antimony trisulfide (Sb2S3). It is a soft, metallic grey crystalline solid with an orthorhombic space group. It is the most important source for the metalloid antimony. The name is derived from the Greek through the Latin as the former name for the mineral and the element antimony.

==Structure== Stibnite has a structure similar to that of arsenic trisulfide, As2S3. The Sb(III) centers, which are pyramidal and three-coordinate, are linked via bent two-coordinate sulfide ions. However, some studies suggest that the actual coordination polyhedra of antimony are SbS7, with (3+4) coordination at the M1 site and (5+2) at the M2 site. Some of the secondary bonds impart cohesion and are connected with packing. Stibnite is grey when fresh, but can turn superficially black due to oxidation in air.