What is the aluminum hydroxide formula?

Aluminium hydroxide, Al(OH)3, Alum, is the most stable form of aluminum in normal conditions. It is found in nature as the mineral gibbsite (also known as hydrargillite) and its three, much more rare, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminum oxide hydroxide, AlO(OH), and aluminum oxide, Al2O3, differing only by loss of water. These compounds together are the major components of the aluminum ore bauxite. Freshly precipitated aluminum hydroxide forms gels, which is the basis for application of aluminum salts as flocculants in water purification. This gel crystallizes with time. Aluminium hydroxide gels can be dehydrated (e.g., with the utility of water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminum hydroxide powder, which is readily soluble in acids. Heat-dried aluminum hydroxide powder is known as activated alumina and is used in gas purification, as a catalyst support and an abrasive.