Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver metal.
Cobalt, like iron, can be magnetised and so is used to make magnets. It is alloyed with aluminium and nickel to make particularly powerful magnets.
Other alloys of cobalt are used in jet turbines and gas turbine generators, where high-temperature strength is important.
Cobalt metal is sometimes used in electroplating because of its attractive appearance, hardness and resistance to corrosion.
Cobalt salts have been used for centuries to produce brilliant blue colours in paint, porcelain, glass, pottery and enamels.
Radioactive cobalt-60 is used to treat cancer and, in some countries, to irradiate food to preserve it.