A member of the clinopyroxene group of minerals and the iron-rich end-member of the diopside series, with formula CaFeSi2O6; sp. gr. 3.7; hardness 6; black; forms short, prismatic crystals or lamellar masses; occurs in metamorphosed iron-rich sediments, skarns and eulysites, and in some igneous ferrogabbros and granophyres along with fayalitic olivine.