Aluminum content distribution 

The most abundant metallic element in the crust, with a content of 8.3%. Mainly existing in aluminosilicate ores, as well as bauxite and cryolite. Aluminum oxide is a white amorphous powder with various variants, among which the most well-known is α－ Al ₂ O æ and β－ Al ₂ O æ. Corundum, which exists in nature, belongs to α Al ₂ O ₂, second only to diamond in hardness, has a high melting point and is resistant to acid and alkali. It is commonly used to make bearings, abrasives, and refractory materials. Like a corundum crucible, it can withstand high temperatures of 1800 ℃. Al ₂ O æ comes in various colors due to the presence of different impurities. For example, a red color containing trace amounts of Cr (III) is called ruby; Sapphire contains Fe (II), Fe (III), or Ti (IV).

Aluminum is a light metal with the chemical symbol Al and atomic number 13. Aluminum is the most abundant metallic element in the Earth's crust, ranking third only to oxygen and silicon, and its reserves rank second among metals. Among metal varieties, it is the second largest category of metals, second only to steel.