Copper(II) selenideCopper selenide is an inorganic binary compound between copper and selenium, with the chemical formula CuSe.UsesCopper selenide is produced in situ to form a protective black coating on iron or steel parts in some cold-bluing processes. Bluing solutions that operate in this manner will typically be labeled as containing selenous acid or selenium dioxide. It has also been investigated for use in the treatment of colon cancer.Natural occurrencesCopper selenides are the most common selenium minerals. CuSe is known in mineralogy as klockmannite.