A comparative study of the electrochemical behavior of different copper sulfide minerals (chalcopyrite, bornite and chalcocite) in sulfuric acid solutions was performed. Carbon paste electrodes (CPE) containing mineral particles with nonconducting binder were used. The comparative study shows that the chalcopyrite oxidation process does not produce covellite as claimed by some authors. Chalcopyrite oxidation has been found to produce a nonstoichiometric sulfide, Cun-1Fen-1S2n. On the other hand, it is apparent that bornite is not an intermediary species formed in the chalcopyrite reduction; the reduction of chalcopyrite directly produces chalcocite. (C) 2002 Elsevier Science B.V. All rights reserved.