Perovskite occurs as an accessory mineral in low silica igneous rocks such as nephelinites, carbonatitites and kimberlites.  It is moderately to strongly coloured in shades of yellow, brown and green in plane polarized light and has extreme positive relief.  It commonly occurs as equant, euhedral to subhedral grains.  The euhedral grain in A encloses several euhedral grains of apatite.  It has extremely low interference colours (first order grey), but this is usually masked by the strong absorption colours.  The common complex lamellar twinning is visible under crossed nicols in B.  In plane polarized light, perovskite has superficial similarities to rutile, but the latter has high order interference colours, and perovskite is restricted to silica-poor alkaline rocks.  Sample is from a wolgidite from West Kimberley, Australia.  Both fields of view are 5.5 mm.  A ppl, B x-nicols.