Copper II oxide (CuO). Molar mass 79.545 g/mol. Also known as cupric oxide and tenorite. Copper(II) oxide is an inorganic compound, a stable oxide of copper. It is used as a pigment to produce a ceramic glaze with a range of colours. It is a component of some wood preservatives. As a precursor, copper oxide is used in chemical reactions to produce many other copper-containing products and chemical compounds.