Iron is a shiny, bright white metal

Iron is a shiny, bright white metal that is soft, malleable, ductile and strong. Its surface is usually discolored by corrosion, since it combines readily with the oxygen of the air in the presence of moisture. In absolutely dry air, it does not rust. The oxide that is produced is crumbly and soft, giving no protection to the base metal, which eventually rusts away. It is found in nature as the metal only in meteorites and in very rare circumstances where iron minerals have been reduced by environmental factors. Masses up to 25 tons in weight have been found in West Greenland. Practically, it is always obtained from ores that are usually the oxides, and occasionally the carbonate, as low in sulphur and phosphorus as possible. The plentiful iron pyrite, FeS2 is not an acceptable ore because sulphur is a deleterious impurity in iron, and expensive to remove in refining. Iron is the fourth most plentiful element in the earth's crust (4.6%), but is so widely disseminated that it can be obtained only from ores in which iron has been specially concentrated. Much of this concentration, incidentally, occurred very early in the earth's history when iron removed from the atmosphere the little oxygen that it then contained, possibly with the help of the earliest forms of life.



A clean surface of cobalt is tinged with pink, nickel with yellow. Neither rusts as vigorously as iron, since the oxide layers are more protective and adherent. Nickel displays a resistant bright surface that takes a high polish. It is generally used as an undercoat for chromium plating, since chromium is not suitable by itself on iron, as the electrodeposited film is not continuous.