Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth's crust. It makes up about 8% by weight of the Earth's solid surface. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. The chief ore of aluminum is bauxite.
It is a silvery white, soft, ductile metal. It is nonmagnetic and does not easily ignite. A fresh film of aluminum serves as a good reflector of light visible by humans, and an excellent of medium and far infrared radiation. Aluminium is a good thermal and electrical conductor. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 K and a critical magnetic field of about 100 gauss. Aluminium is theoretically 100% recyclable without any loss of its natural qualities.
Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Aluminium is the most widely used non-ferrous metal. Structural components made from aluminum alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminum, at least on a weight basis, are the oxides and sulfates.
Despite its prevalence in the environment, no known form of life uses aluminum salts metabolically. In keeping with its pervasiveness, aluminum is well tolerated by plants and animals. Owing to their prevalence, potential beneficial (or otherwise) biological roles of aluminum compounds are of continuing interest.