ETYM Latin alumen, aluminis. Related to Alum.
Oxide of aluminum.
Any of various forms of aluminum oxide occurring naturally as corundum; SYN. aluminum oxide, aluminium oxide.
Or corundum; Al2O3 oxide of aluminum, widely distributed in clays, slates, and shales. It is formed by the decomposition of the feldspars in granite and used as an abrasive. Typically it is a white powder, soluble in most strong acids or caustic alkalis but not in water. Impure alumina is called “emery”. Rubies and sapphires are corundum gemstones.
Veoma tvrd mineral iste klase kao rubin i safir, upotrebljava se za čišćenje i glačanja metala (šmirgl). (lat.)