PEROVSKITE, or PEROFSKITE  , a mineral consisting of calcium titanate, CaTiO3, usually with a small proportion of the calcium replaced by iron . The crystals found in schistose rocks have the form of cubes, which are sometimes modified on the edges and corners by numerous small planes; on the other hand, the crystals occurring as an accessory constituent of eruptive rocks are octahedral in form and microscopic in size . Although geometrically cubic, the crystals 'are always doubly refracting, and they sometimes show evidence of complex mimetic twinning; their structure as shown in polarized light is very similar to that of the mineral boracite, and they are therefore described as pseudo-cubic . There are distinct cleavages parallel to the faces of the cube . The colour varies from pale yellow to blackish-brown and the lustre is adamantine to metallic; the crystals are transparent to opaque . The index of refraction is high, the hardness 5z and the specific gravity 4.0 . The mineral was discovered at Achmatovsk near Zlatonst in the Urals by G . Rose in 1839, and named in honour of Count L . A . Perovsky;at this locality large cubes occur with calcite and magnetite in a chlorite-schist . Similar crystals are also found in talc-schist at Zermatt in Switzerland . The microscopic octahedral crystals are characteristic of melilite basalt and nepheline basalt; they have also been found in peridotite and serpentine .

(L . J .