The nature and basic kinetics of the hydrothermal reactions of bornite, covellite and pyrite with copper sulfate solutions were investigated, as a previous study on the behavior of the bulk Chilean copper concentrates. The reaction of bornite produced digenite at < 160 degrees C and djurleite above this temperature. The reaction products formed a continuous, non porous layer. The rates were of zero order with respect [Cu(2+)]((aq)), and the activation energy was similar to 100 kJ/mol. Covellite was transformed to digenite at <200 degrees C and to chalcocite (Q and M) at> 200 degrees C. The reaction was characterized for an irregular nucleation and growth of the products, which were non-protective. The order with respect the [Cu(2+)]((aq)) was 0.6 and the activation energy similar to 110 kJ/mol. The pyrite reaction was significant at >200 degrees C and extensive at 240 degrees C. It produced a mixture of digenite/chalcocite-Q, with small amounts of djurleite. The transformation has a high Philling-Betworth ratio (similar to 1.6), causing the break of the product layers. The reaction order and the activation energy were also 0.6 and similar to 110 kJ/mol, respectively. The rate of the bornite reaction should be controlled by solid-state ionic diffusion, whereas for covellite and pyrite the rates should be limited by electrochemical processes. Towards the hydrothermal transformation, the reactivity of the main phases present in Chuquicamata-type concentrates was: bornite > chalcopyrite > covellite > sphalerite > pyrite. (C) 2008 Elsevier B.V. All rights reserved.