An aluminium hydrate α‎-AlO(OH), forming a continuous series with its polymorph boehmite γ‎-AlO(OH); sp. gr. 3.3–3.5; hardness 6.5–7.0; white; massive or foliaceous or as orthorhombic prismatic crystals; it is a constituent of bauxite and laterite deposits along with emery and corundum.