Copper(II) sulfide?

Reference to covellite as copper(II) sulfide has been challenged. To support the nominally Cu(I) formal oxidation state for covellite suggested by X-ray photoelectron spectroscopy, the Cu L2,3 near-edge X-ray absorption fine structure spectrum for unoxidised covellite has been determined in fluorescence yield mode. Interpretation of the Cu L3-edge spectrum has been effected with the assistance of ab initio calculations of the density of unfilled states and the simulation of spectra from both Cu sites in the covellite structure. An alternative explanation has been provided for a covellite Cu L2,3-edge spectrum determined in electron yield mode that had been rationalised previously in terms of the presence of both Cu(I) and Cu(II) in the covellite structure. The relevance to mineral processing of the Cu(I) formal oxidation state in copper sulfides and other sulfide minerals has been discussed.