Aluminum hydroxide, Al(OH)3, commonly referred to as hydrate of alumina or alumina trihydrate (Al2O3·3H2O), is a non-abrasive powder having a Mohs hardness index of 2.5-3.5 and a specific gravity of 2.42. It can be heated to 200 ° C, and hydrated alumina can be broken down into 66% alumina and 34% water.