Bauxite（aluminous soil； Bauxite, also known as alumina or bauxite, is mainly composed of alumina, which is a hydrated alumina containing impurities and is a soil like mineral. White or grayish white, brownish yellow or light red due to iron content. Density 3.45g/cm3, hardness 1-3, opaque, brittle. Extremely difficult to melt. Insoluble in water, soluble in sulfuric acid and sodium hydroxide solutions. Mainly used for refining aluminum and making refractory materials.