Aluminum is named from the Latin alumen, alum and was used by the Greeks and Romans in medicine as an astringent, and as a mordant in dyeing. The metal was isolated in 1827. Aluminum is the third most abundant metal to be found in the earth's crust (8.1%), but is never found free in nature. The Bayer process is most commonly used today to refine bauxite so it can be accomodated in the Hall-Heroult refining process, used to produce most aluminum. Pure aluminum, a silvery-white metal has many desirable characteristics. It is light, non-toxic, has a pleasing appearance can easily be formed, machined or cast, has a high thermal conductivity and has excellent corrosion resistance. It is nonmagnetic, nonsparking, stands second among metals in the scale of malleability and sixth in ductility. It is extensively used for kitchen utensils, outside building decorations and in thousands of industrial application where a strong, light easily constructed material is needed. Although pure aluminum lacks strength, it can be alloyed with copper, magnesium, silicon, manganese and other elements to impart a variety of useful properties. These alloys are of vital importance in the construction of aircraft and rockets.