Applied to minerals whose chemical composition includes the OH radical, and often to those with water molecules, whose presence gives hydrated oxides. Among the important hydroxide minerals are: brucite, Mg(OH)2; gibbsite, Al(OH)3; diaspore, α-AlO(OH); boehmite, γ-AlO(OH); limonite, FeO(OH).nH2O; and goethite, α-FeO(OH).