Amphibole

Amphibole is a group of inosilicate minerals, forming prism or needlelike crystals. 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.

Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. In chemical composition and general characteristics they are similar to the pyroxenes. Amphiboles are the primary constituent of amphibolites.

The name amphibole derives from Greek amphíbolos, implying ambiguity. The name used by René Just Haüy to include tremolite, actinolite and hornblende. The group so named by Haüy in allusion to the protean variety, in composition and appearance, assumed by its minerals. This term has since been applied to the whole group.