Aluminium metal and iron oxide mixture. A thermite reaction is a type of aluminothermic reaction in which aluminium metal is oxidized by the oxide of another metal, most commonly iron oxide. The name thermite is also used to refer to a mixture of two such chemicals. The products are aluminium oxide, free elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation. The reaction is used for thermite welding, often used to join railroad rails. Some other metal oxides can be used, such as chromium oxide, to generate elementary metal. (wikipedia)