PYROXENITE

dark-coloured, intrusive igneous rock that consists chiefly of pyroxene. Pyroxenites are not abundant; they occur in discrete inclusions, in layered sills (tabular bodies inserted between other rocks) and lopoliths (laccoliths with basin-shaped bases), in branching veins, in narrow dikes (tabular bodies injected in fissures), and at the edges of silica-poor plutons (intrusive igneous rock bodies). Many of the pyroxenites have been named according to their dominant pyroxene minerale.g., diopsidite, which occurs in the Pyrenees, and bronzitite, which occurs in the Bushveld of South Africa. Others occur at Newry, County Down, Ire. (biotite pyroxenite); in the province of Quebec, Can. (hornblende pyroxenite); and at Ben More Assynt, Scot. (melanite pyroxenite).