Bauxite

Bauxite is mainly composed of alumina, hydrated alumina containing impurities, and is an earthy mineral. White or off-white, brownish yellow or light red due to iron. Density 3.45g / cm3, hardness 1-3, opaque, brittle. Extremely difficult to melt. Insoluble in water, soluble in sulfuric acid and sodium hydroxide solution. Mainly used for smelting aluminum and making refractory materials.