The effects of pyrite and bornite on bioleaching of two different chalcopyrite samples by Leptospirillum ferriphilum were studied for the first time. Results showed that bioleaching behaviors of the two chalcopyrite samples were extremely different. Bornite decreased the redox potential (ORP) and maintained it at an appropriate range (380-480 mV vs. Ag/AgCl) to promote chalcopyrite (A) dissolution, but caused the redox potential out of the optimum range and inhibited chalcopyrite (B) dissolution. Large amount of pyrite decreased the redox potential and maintained it at an optimum range to promote chalcopyrite (A) dissolution, while increased the redox potential and kept it at appropriate range for a longer period of time to enhance the dissolution rate of chalcopyrite (B). Chalcopyrite (B) had significantly higher values of conductivity and oxidation-reduction rate when compared with those of chalcopyrite (A). The work is potentially useful in interpreting the inconsistence of the researches of chalcopyrite hydrometallurgy. (C) 2015 Elsevier Ltd. All rights reserved.