Aluminum content distribution

Aluminum content in the earth's crust is second only to oxygen and silicon, the content of 8.3%, ranking third, is the most abundant metal element in the earth's crust, its reserves in the second place in the metal. In the metal varieties, second only to steel, for the second major category of metal. It mainly exists in aluminosilicate ores, as well as bauxite and cryolite. Alumina is a white amorphous powder that comes in many variants, the most familiar of which are α-Al2O3 and β-Al2O3. Corundum that exists in nature belongs to α-Al2O3, its hardness is second only to diamond, high melting point, acid and alkali resistance, commonly used to make some bearings, manufacturing abrades, refractories. Such as corundum crucible, can withstand 1800℃ high temperature. Al2O3 has a variety of colors due to the presence of different impurities. For example, a trace of Cr(III) is red and is called ruby; Those containing Fe(II), Fe(III) or Ti(IV) are called sapphires.