Aluminium oxide is an amphoteric oxide with the chemical formula ₂O₃. It is commonly referred to as alumina (α-alumina), or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry. Its most significant use is in the production of aluminium metal, although it is also used as an abrasive owing to its hardness and as a refractory material owing to its high melting point. There is also a cubic γ-alumina with important technical applications.