Pyroxenes

Pyroxenes, a group of minerals, comprising both monoclinic and rhombic forms. The monoclinic pyroxenes are silicates of lime, magnesia, and iron—alumina being absent or sparingly present in some, while others contain a larger percentage. The more important monoclinic forms are Augite (q.v.) and Diallage (q.v.), both being constituents of igneous rocks. The rhombic pyroxenes are silicates of iron and magnesia. There are three: Enstatite (q.v.), which contains less than 5 per cent. of ferrous oxide; Bronzite (q.v.), in which the percentage is from 5 to 15; and Hypersthene (q.v.), containing 15 per cent. and upwards. All these are important constituents of igneous rocks.