Pronunciation: (pī-rok'sēn, pu-, pī'rok-sēn"), [key]
any of a very common group of minerals of many varieties, silicates of magnesium, iron, calcium, and other elements, occurring as important constituents of many kinds of rocks, esp. basic igneous rocks. Cf. augite, diopside, hypersthene.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.