What is "amphibole"

Amphibole \Am"phi*bole\ ([a^]m"f[i^]*b[=o]l), n. [Gr. 'amfi`bolos doubtful, equivocal, fr. 'amfiba`llein to throw round, to doubt: cf. F. amphibole. Ha["u]y so named the genus from the great variety of color and composition assumed by the mineral.] (Min.) A common mineral embracing many varieties varying in color and in composition. It occurs in monoclinic crystals; also massive, generally with fibrous or columnar structure. The color varies from white to gray, green, brown, and black. It is a silicate of magnesium and calcium, with usually aluminium and iron. Some common varieties are tremolite, actinolite, asbestus, edenite, hornblende (the last name being also used as a general term for the whole species). Amphibole is a constituent of many crystalline rocks, as syenite, diorite, most varieties of trachyte, etc. See Hornblende.

n. (context geology English) A large group of structurally similar hydrated double silicate minerals, containing various combinations of sodium, calcium, magnesium, iron, and aluminium/aluminum

n. a mineral or mineral variety belonging to the amphibole group

Amphibole is the name of an important group of generally dark-colored, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.