A mineral with flat shiny grey (usually) orthorhombic crystals, calcium titanium oxide, chemical formula CaTiO3. It is also used as the family name of related minerals, such as latrappite, lueshite, tausonite, and macedonite, where the calcium place varies over similar elements such as sodium, strontium, or cerium, and the titanium may be replaced by niobium. The general formula is ABO3 for some A2+ and B4+.

It was discovered by Gustav Rose in 1839 and named after the Russian mineralogist, Count Lev Alexevich von Perovski (1792-1856). It is commonly found in the Urals on a base of chlorite, talc, or serpentine, but can also be found from Brazil to California to Greenland. Its hardness on the Mohs scale is 5.5, its specific gravity is 4.0, and its streak is greyish-white.

The colour may be dark grey like galena, to which it has a similar cubic appearance, but may also vary to brown, orange, and yellow depending on the exact composition. The perovskite family taken as a whole are said* to be the most abundant minerals on earth.

Perovskites in the wider sense are valuable for their rare earth content, as well as the titanium. The rare earths are now very important for high-temperature superconductor research. In 1986 the Swiss researchers Alex Müller and Georg Bednorz at IBM labs found that a perovskite ceramic consisting of lanthanum, barium, copper, and oxygen was superconducting at 30 K, the highest temperature yet attained, and this was surprising because ceramics are normally insulators. In 1987 the use of yttrium instead of lanthanum gave a perovskite ceramic caled YBCO that superconducted at 92 K, higher than the temperature of liquid nitrogen, a readily available coolant.

http://webmineral.com/data/Perovskite.shtml (general data)
http://mineral.galleries.com/minerals/oxides/perovski/perovski.htm (general)
http://micro.magnet.fsu.edu/micro/gallery/perovskite/perovskite.html (beautiful high magnification micrographs!)

* Said in the micro.magnet.fsu.edu site above. I have read this assertion before and was surprised by it then too, since perovskite is not a household name. Are they excluding things like silica?