X-ray photoelectron spectroscopic study of copper minerals

X-ray photoelectron spectroscopy has been used to determine the oxidation state of copper in various kinds of copper minerals. Cuprite Cu2O is found to be stable to air oxidation. Photoelectron spectra of carrollite Co2CuS4, germanite Cu3(Ge, Fe) (S, As)4 and covelline CuS reveal that these minerals contain univalent copper.