pyroxene

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of a group of crystalline silicate minerals common in igneous and metamorphic rocks and containing two metallic oxides, as of magnesium, iron, calcium, sodium, or aluminum.

Century Dictionary and Cyclopedia

1. n. An important mineral species, embracing many varieties differing in appearance and chemical composition. It occurs in monoclinic crystals, often short prismatic in habit, and with an angle in front of nearly 90°, so that these crystals resemble square prisms. Granular forms are common, and also massive varieties, the latter being usually coarsely laminated in structure, rarely fibrous or columnar. The color varies from white to gray, green, brown, and black, and the composition from the simple metasilicate of calcium and magnesium to kinds containing, with calcium or magnesium, or both, iron, manganese, and aluminium. The different varieties are usually divided into two groups, the non-aluminous and the aluminous. Of the former the prominent kinds are — diopside or malacolite, which contains only calcium and magnesium, and is white to gray or light-green in color, with the subvarieties called alalite or mussite (the diopside proper, from the Mussa Alp in the Ala valley in Piedmont, occurring in beautiful slender crystals), traversellite, canaanite, and white granular coccolite, and those containing iron, namely the grayish-green to deep-green or black salite, occurring in laminated masses, the crystallized baikalite, the granular green coccolite, and the deep-green diallage, which is characterized by a distinct parting parallel to the orthopinacoid plane and often by a pearly to metalloidal luster on this surface; also the lime-iron variety, hedenbergite, and the manganesian schefferite. The aluminous kinds include fassaite, which is light- to dark-green in color, and the common augite, which is dark-green to black and contains considerable iron. Augite is characteristic of many eruptive rocks, especially those of a basic character, as diabase, basalt, etc. Diallage is an essential constituent of the gabbros, of norite, etc. Besides the above varieties or subspecies belonging to pyroxene proper, the pyroxene group includes the related species enstatite or bronzite and hypersthene, which are orthorhombic in crystallization (hence called rhombic pyroxenes); also the mono clinic species wollastonite, ægirite and acmite, spodumene, and the triclinic rhodonite and babingtonite. Jadeite probably also belongs here. All these are characterized by the same prismatic angle of 87°. This group is closely related to the analogous amphibole (or hornblende) group, the species of which are characterized by a prismatic angle of 124½°; and several of the kinds under the two groups correspond exactly in composition — for example, diopside to tremolite, etc. A change of pyroxene to hornblende by a process of paramorphism is often observed, especially in certain igneous rocks. See uralite and uralitization.

Wiktionary

1. n. mineralogy Any of a group of crystalline minerals containing silicates of iron, magnesium and calcium.

GNU Webster's 1913

1. n. (Min.) A common mineral occurring in monoclinic crystals, with a prismatic angle of nearly 90°, and also in massive forms which are often laminated. It varies in color from white to dark green and black, and includes many varieties differing in color and composition, as diopside, malacolite, salite, coccolite, augite, etc. They are all silicates of lime and magnesia with sometimes alumina and iron. Pyroxene is an essential constituent of many rocks, especially basic igneous rocks, as basalt, gabbro, etc.

WordNet 3.0

1. n. any of a group of crystalline silicate mineral common in igneous and metamorphic rocks