Cobalt carbonate should be a pink-violet or lavender color. During storage and exposure to air, some of the basic material converts to cobalt oxide, thereby reducing its biological value significantly As the basic material oxidizes, the cobalt carbonate becomes more grey in color and can turn almost black. If you buy imported material, be sure to specify that the basic material is not acceptable, unless the company nutritionist gives his approval. Very stable at room temperature. In general, cobalt metal is produced as a byproduct of copper mining.
Most cobalt comes from Central Africa.
Zaire and Zambia are leading producers. Availability has become a problem due to political problems in Central Africa. There is some cobalt produced in Canada. Cobalt is required in the diets of ruminants for the production of vitamin B-12.