A fine black powder which when used in conjunction with cobalt and iron produces black. In lead and low alkaline glazes it produces a dull brown, while in high alkaline glazes along with tin, the colour is purple. In magnesium and barium glazes, colours ranging from lilac to violet will develop. With small amounts of cobalt oxide, a deep violet can be obtained. Other interesting colour effects are obtained with copper in crystalline glazes (2-5%).