Originally Posted by
STBCypriot
Alumina is the only form of aluminum oxide. Alumina , or alpha-alumina, is AL2O3. Alumina is also called corundum in it's most common crystalline form. There are other crystalline forms of alumina, but all aluminum oxide is Al2O3 (oxidation state of Al is +3).
Abundance---- natural occurrence. As far a I know rubies and sapphires are naturally occurring aluminium oxides too. And they are not as abundant as alumina.
