The naturally occurring chemical substances in form of which the metal occur in the earth along with impurities are called minerals. The minerals from which the metal can be extracted conveniently and economically is called an ore. Thus, all ores are minerals but all minerals are not ores. For example iron is found in the earth’s crust an oxides, carbonates and sulphides. Out of these minerals of iron, the oxides of iron are employed for extraction of the metal. Therefore, oxides of iron are the ores of iron. Similarly, aluminium occurs in earth’s crust in form of two minerals, i.e, bauxite (Al2O3. x H2O) and clay (Al2O3.2SiO. 2H2O). Out of these two minerals, Al can be conveniently and economically extracted from bauxite the ore of aluminium.
