The societal dilemma of providing adequate mineral supplies from exhaustible resources can only be resolved through advanced technologies, with environmental protection a priority. This report presents research and conclusions in improving mineral recoveries and minimizing waste production in the flotation of sulfide ores. Froth flotation is a widely used, inexpensive process for commercial separation of minerals from gangue and minerals from each other. Extensive research has demonstrated that electrochemistry governs the flotation of sulfide minerals. Flotation often is adversely affected by uncontrolled oxidation, which also is an electrochemical process. Microcell flotation, AC impedance, cyclic voltammetry and spectrophotometry were used to probe the fundamental flotation chemistry of oxidized chalcocite. Tests were conducted in aerated solutions to simulate mill chemistry. Oxidation inhibited chalcocite flotation. Oxidized chalcocite also inhibited flotation of chalcopyrite and pyrite. In contrast, pyrite flotation increased after oxidation. Tetrahedrite was found to float best at reducing conditions in contrast to chalcocite, chalcopyrite, and pyrite, all of which float best under mildly oxidizing conditions. It was also found that xanthate strongly suppresses oxidation of Fe(II) in chalcopyrite and pyrite.