The sulfur oxidation activities of four pure thermophilic archaea Acidianus brierleyi (JCM 8954), Metallosphaera sedula (YN 23), Acidianus manzaensis (YN 25) and Sulfolobus metallicus (YN 24) and their mixture in bioleaching chalcopyrite were compared. Meanwhile, the relevant surface sulfur speciation of chalcopyrite leached with the mixed thermophilic archaea was investigated. The results showed that the mixed culture, with contributing significantly to the raising of leaching rate and accelerating the formation of leaching products, may have a higher sulfur oxidation activity than the pure cultures, and jarosite was the main passivation component hindering the dissolution of chalcopyrite, while elemental sulfur seemed to have no influence on the dissolution of chalcopyrite. In addition, the present results supported the former speculation, i.e., covellite might be converted from chalcocite during the leaching experiments, and the elemental sulfur may partially be the derivation of covellite and chalcocite. (C) 2010 Elsevier Ltd. All rights reserved.