Stibnite

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. == Properties ==

The melting point of Sb2S3 is . The band gap is 1.88 eV at room temperature and it is a photoconductor. Stibnite is also toxic upon ingestion, with symptoms similar to those of arsenic poisoning. ==Uses==

Pastes of Sb2S3 powder in fat or in other materials have been used since c. 3000 BC as eye cosmetics in the Mediterranean and farther afield; in this use, Sb2S3 is called kohl. It was used to darken the brows and lashes, or to draw a line around the perimeter of the eye. Antimony trisulfide finds use in pyrotechnic compositions, namely in the glitter and fountain mixtures. Needle-like crystals, "Chinese needles", are used in glitter compositions and white pyrotechnic stars. The "dark pyro" version is used in flash powders to increase their sensitivity and sharpen their report. It is also a component of modern safety matches. It was formerly used in flash compositions, but its use was abandoned due to toxicity and sensitivity to static electricity. Stibnite was used ever since protodynastic ancient Egypt as a medication and a cosmetic. The 17th century alchemist Eirenaeus Philalethes, also known as George Starkey, describes stibnite in his alchemical commentary ''An Exposition upon Sir George Ripley's Epistle''. Starkey used stibnite as a precursor to philosophical mercury, which was itself a hypothetical precursor to the philosopher's stone. ==Occurrence==

Stibnite occurs in hydrothermal deposits and is associated with realgar, orpiment, cinnabar, galena, pyrite, marcasite, arsenopyrite, cervantite, stibiconite, calcite, ankerite, barite and chalcedony. As of May 2007, the largest specimen on public display (1000 pounds) is at the American Museum of Natural History. The largest documented single crystals of stibnite measured ~60×5×5 cm and originated from different locations including Japan, France and Germany. File:StibineRoumanie.jpg|Stibnite from Herja mine, Romania File:Stibnite-Calcite-203075.jpg|Needles of stibnite within a transparent crystal of calcite (size: 4.5×3.5×1.8 cm) File:Stibnite-21985.jpg|Ray of sharp, striated, iridescent metallic stibnite blades File:Kristallstruktur Stibnit.png|Structure of stibnite == See also ==