Cobalt is a silver-white metal.Cobalt does not react with water at room temperature and is stable in moist air.When heated to more than 300℃ in air, CoO is oxidized and burned to Co3O4 at white heat.

On October 27, 2017, the world health organization's international agency for research on cancer (iarc) carcinogens released preliminary reference, listing containing tungsten carbide cobalt metal in the list of 2 a kind of carcinogen, excluding tungsten carbide cobalt metal, metal cobalt, nickel and contains 66-67% nickel, chrome 13-16% and 7% of iron alloy powder implanted in the body of the foreign body in the list of 2 class b carcinogens.