Cobaltous oxide, with the chemical formula CoO/Co₂O₃/Co₃O₄, is a metal oxide, which is a black or gray-black powder. It is insoluble in water, alcohol, and ammonia. It is easily reduced to metallic cobalt by carbon monoxide. It easily reacts with diamine at high temperatures. Silicon oxide, aluminum oxide or zinc oxide react to produce a variety of pigments. It is mainly used to produce ternary materials for lithium batteries, enamel pigments, and used for coloring glass and ceramic products. It can also be used to prepare cobalt and cobalt salts, and can also be used as oxidants and catalysts.