Hornblende
Hornblende, dark green or black mineral of varied composition, usually including silicates of aluminum and other abundant elements. It forms vitreous glassy rocks. Often found in igneous and metamorphic rock, hornblende is a major constituent of the amphibole group of minerals.
Additional topics
21st Century Webster's Family Encyclopedia21st Century Webster's Family Encyclopedia - Hobbema, Meindert to Human Rights, Declaration of