黑剛玉又名低鋁剛玉是于電弧爐中，將鋁礬土熔煉而制得的一種以 α- Al2O3 和鐵尖晶石為主礦相的灰黑色結晶體，其特點是Al2O3 含量較低，并有一定量的Fe2O3（10%左右）存在，因而具有硬底適中、韌性高、耐高溫、熱態性能溫定的特點。特別適合做高速公路、機場跑道、大橋路面等的耐磨防滑材料，適合做耐磨防滑地坪材料。是優質的拋光研磨材料。具有硬度適中，韌性、自銳性、粘結性良好，經久耐用等特點。磨削時發熱量小，不易劃傷工件表面，不易引起工件表面變色，加工后工件表面光潔度高、色差極小。主要用于金屬工件等研磨拋光，特別適合于不銹鋼工件的研磨拋光，亦適用于光學玻璃、木材等材料的拋光，也大量用于制成樹脂磨具，砂帶等涂附磨具。
Black fused alumina is also known as low aluminum corundum. It is a dark gray crystal body with α- Al2O3 and ferropicotite as main ore by smelting the bauxite in the electric arc furnace. Black fused alumina is characterized by low Al2O3 and a certain amount of Fe2O3 (10% more or less) content, so it has characteristics of moderate hardness, high toughness, high temperature resistance, and stable thermal stability. It is mainly suitable for wear-resisting and antiskidding materials in expressway, airport pavement, bridge pavement. It is a high-quality polishing and abrasive materials with the characteristics of moderate hardness, toughness, self-sharpening, and good cohesiveness, durable in use. It is mainly used for polishing and sandblasting of stainless steel, fabricated metal products, optical glass, bamboo products, and it is widely used in manufacturing the resin abrasives and coated abrasive tools, with the characteristics of strong cutting power, high toughness, high flexibility, good abrasion resistance.
黑剛玉指標：Black Fused Alumina indexes
| 化學成分chemical composition | Al2O3% | SiO2% | Fe2O3% | TiO2% |
| 黑剛玉black fused alumina | ≥60% | ≤30 | ≤5-13 | ≤2.0-4.0 |
