Amphibole (/ˈæmfəboʊl/ AM-fə-bohl) is a group of inosilicate minerals, forming prism or needlelike crystals,[1] composed of double chain SiO
4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is Amp.[2] 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.[3]