Bauxite (aluminous soil; bauxite), also known as alumina or bauxite, the main component is alumina, hydrated alumina system containing impurities is an earthy mineral. White or gray, because iron and brownish yellow or pink. Density 3.45g / cm3, hardness 1-3, opaque, brittle. Extremely difficult to melt. Insoluble in water, soluble in sulfuric acid, sodium hydroxide solution. Mainly used for aluminum smelting, manufacture refractories.
