The main source of aluminum is bauxite, a sedimentary rock that is formed from the weathering of certain types of aluminum-containing minerals, such as gibbsite, boehmite, and diaspore. These minerals are typically found in tropical and subtropical regions, where they are formed by the chemical weathering of rocks such as granite and syenite. Bauxite is the primary source of aluminum because it contains a high concentration of aluminum oxides, which can be easily extracted and refined to produce pure aluminum.