Amphibole
any of a group of double chain inosilicates (mineralogy) / From Wikipedia, the free encyclopedia
Amphibole is a group of inosilicate minerals. They form prism or needlelike crystals.[1]
They are double chain SiO
4 tetrahedra, linked at the vertices. Usually they contain ions of iron and/or magnesium in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown.[2]