Aluminum is the most abundant metal in the earth’s crust (8.1 percent), but it is never found free in nature. It is found in granite, cryolite and other common minerals. The oxide, alumina, occurs naturally as ruby, sapphire, corundum and emery.
Today, however, most aluminum we get is from an artificial mixture of sodium, aluminum and calcium fluorides. Aluminum can also be produced from clay, but the process is not economically feasible today.