An investigation of the species present on the surface of natural enargite and the effects of X-ray radiation on the surface after electrochemical oxidation at pH 10 has been carried out using X-ray photoelectron spectroscopy. Surface species present on fractured and polished unoxidized enargite have been compared with those present on the polished surface after oxidation at pH 10. The effect of X-ray irradiation time as a function of temperature on the forms and intensities of the photoelectron signals from the enargite surface was studied. High binding energy (BE) components and shake-ups of the Cu 2p signals, characteristic of a copper (II) hydroxide surface layer: reduced in intensity with increasing X-ray exposure time. Associated changes in the relative concentrations of surface oxygen species were also observed. Comparing a surface exposed to X-rays at 35 degrees C with that maintained at -135 degrees C, temperature was shown to significantly influence the rate of change. The observed changes were evaluated in terms of a proposed two-stage mechanism involving the dehydration of Cu(OH) to CuO, followed by photoreduction of CuO to Cu2O. The photoreduction effects of X-ray irradiation should be significantly reduced by sample cooling for consistent analysis of the enargite surface using XPS. (c) 2013 Elsevier Ltd. All rights reserved.