GEOLOGY & PLANETARY SCIENCE A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site alumina Aluminum oxide, Al2O3, a mineral used as an abrasive, electrical insulator, and furnace lining. The impure hydrated form of alumina, bauxite, is the chief ore of aluminum. Other forms of alumina include corundum, two impure varieties of which are the gemstones ruby and sapphire. Related category    • GEOLOGY AND PLANETARY SCIENCE Source: U.S. Geological Survey Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP