In some ore deposits, such as Sediment hosted Stratiform Copper deposits, Epithermal Copper deposits and Volcanic associated massive sulfide deposits, the assemblage of pyrite, copper (iron) sulfides, iron oxides often occurs. The study of this assemblage is important to understand the genesis of the ore mineral in those types of ore deposit. In this paper, we consider the theory of mineral—fluid interaction. This process may involve dissolution—reprecipitation reaction giving rise to transformation of some ore formation elements. We use pyrite as the parent mineral and Cu(I)—Cl as the cupreous speciation to study the assemblage and reaction mechanism on the interface between mineral and fluids.Methods: We conduct our reaction in a 10 mL PTFE tube. Every 6mL pH buffer solutions and a cubic pyrite were used. The cubic pyrite can record morphological changes before and after reaction. The hydrothermal reaction occurred in anaerobic conditions. And the reactions are in different temperature, different pH, different reaction time and different concentration of Cu(I)—Cl solution. X ray Diffractometry (XRD), Electron Probe Microanalysis (EPMA), Scanning Electron Microscopy (SEM) and Laser Raman Microprobe (LRMP) were used to study the transformation of the product and the structure during the reaction.Results: The results show that the species of the reaction product differs at different temperature, different pH and different reaction time. The main products are chalcopyrite, bornite, digenite, anilite, hematite and magnetite. The hematite can form in different temperature and different pH. There would be more in low temperature and most of the hematite nucleate on the bottom and wall of the PTFE tube. Chalcopyrite and bornite can form in mild acid conditions while digenite forms in mild basic conditions. At low temperature (about 100℃ ) the pyrite mainly converts to hematite. Furthermore, the results show that the trace element of parent mineral can be inherited by daughter phase and the processes are pseudomorphic reactions.Conclusions: The mineral assemblage obtained in our experiment is similar to the one in some deposits in nature. This may suggest that this type of copper deposits has a similar forming conditions to our experiment.