The oxidation of some massive sulfide ores (Valentorka (Northern Urals), Letnee and Yaman-Kasy (Southern Urals) deposits) was studied using XRD, DTA, TGA, microscope and chemical analyses. Mineral oxidation was modeled in arid climatic conditions. The influence of structural features of ores on the kinetic processes is revealed. The decreasing of flotation activity of chalcopyrite and sphalerite was found. The selectivity of flotation is reduced.