The flotation characteristics of enargite have been investigated in a micro-flotation cell in which the solution potential was controlled using hydrogen peroxide (H2O2) and sodium sulfide (Na2S). It was established that the oxidation-reduction potential of the flotation solution can have a pronounced influence on the flotation of enargite. Enargite displayed natural floatability under oxidizing conditions, and non-floatability under reducing conditions. In acidic solutions of pH < 5.5, the hydrophobicty of enargite increased with increasing solution potential due to the formation of elemental sulfur on the mineral surface. However, in alkaline solutions, the hydrophobicity decreased with increasing solution potential due to the formation of CuO. The flotation of enargite was also studied in the presence of ethyl xanthate at pH 10.5. These results showed that enargite floated over a range of 0.2 V in the presence of xanthate. The floatability of the mineral increased with increasing solution potential due to the formation of cuprous xanthate and dixanthogen, then decreased with the decomposition of CuX to CuO under the influence of excess oxygen. (C) 2002 Elsevier Science B.V. All rights reserved.