Bauxite (aluminous soil; Bauxite) is also called the alumina or bauxite, main ingredients are alumina, hydrated alumina containing impurities, is an earthy mineral. White or gray, brown and yellow or light red by iron. From 4 to 3.9 g/cm3 density, hardness, 1 ~ 3 is not transparent, very brittle. Very difficult to melt. Insoluble in water, soluble in sulfuric acid, sodium hydroxide solution. Mainly used for aluminium, refractory material. 
Usage 
2 precision casting. Alumina clinker made after the mould precision casting processed into fine powder. Used in military industry, aerospace, communications, instrumentation, machinery and medical equipment department. 
(4) aluminum silicate refractory fiber. With light weight, high temperature resistance, good thermal stability, low thermal conductivity, heat capacity is small and the advantages of resistance to mechanical shock. Used in iron and steel, nonferrous metallurgy, electronics, petroleum, chemical, aerospace, atomic energy, defense and other industries. 
[6] manufacture alumina cement, abrasive materials, ceramic industry and chemical industry can be aluminum of various compounds