Aluminium oxide, also known as aluminum oxide, is a chemical compound made from aluminium and oxygen. Its chemical formula is Al2O3. It is a normally white, powdery solid. It does not exist in a particular form. It can dissolve in acids and bases. It is used as an abrasive (sandpaper is an abrasive). It comes in bauxite and corundum. It does not melt easily. It is dissolved in a cryolite melt and electrolyzed to make aluminium.