Black corundum, also known as low alumina corundum, is in the arc furnace, the bauxite smelting and made of a kind of α-Al2O3 and iron spinel as the main mineral phase of the gray black crystal, which is characterized by low Al2O3 content, and a certain amount of Fe2O3 (10% or so), so it has moderate hardness, high toughness, high temperature resistance, hot state performance temperature characteristics. Mainly used for free grinding, such as rough grinding before electroplating products, mainly used for stainless steel, metal products, optical glass, bamboo and wood products polishing and sandblasting, is also the manufacture of resin grinding wheel, cutting pieces, emery cloth novel abrasive.