Ores are the form in which most metallic elements are mined. They are rocks that contain the elements found in compounds. Ores are refined and the elements are extracted, often by a chemical reaction or an electrochemical process. Few metals are found in their pure form in nature, due to the tendency of most to react with other substances.
Some examples of commonly occurring ores are iron ores (Fe2O3, FeO and Fe3O4), lead ore (galena, PbS), silver ore (Ag2S), copper ore (CuS and Cu2S) and aluminum ore (bauxite, Al2O3.) Gold is found in its elemental form but usually in small deposits that must be removed from crushed rock.
The metals that are extracted from ores must be reduced, which means converted from the positively charged ionic form to the neutral metallic form. Smelting is a process in which the ore is heated and reacted with a reducing agent to produce the reduced metal. Carbon is used to reduce iron. Reduction of aluminum is accomplished by electrolysis of the molten ore.