Aluminium Oxide is a chemical compound of Oxigen and Aluminium. It's formula is Al2O3. In its most commonly occurring crystalline form, called corundum or α-aluminium oxide, its hardness makes it suitable for use as an abrasive and as a component in cutting tools. Al2O3 is an electrical insulater but has a relatively high thermal conductivity for a ceramic material. Aluminium oxide is insoluble in water.