Cobalt is a brittle, hard, transition metal with magnetic properties similar to those of iron.
Cobalt is present in meteorites.
Cobaltite is metallic steel grey. The colour of erythrite varies from adamantine to pearly crimson red. Finally, skutterudite is also metallic white. Hardness of these minerals is about 5 to 6 except for the erythrite around 2. Minerals containing cobalt were of value to the early civilisations of Egypt and Mesopotamia for colouring glass deep blue.