The present invention relates to flotation of sulfidic copper-molybdenum- and gold-containing minerals. More specifically, the invention relates to sulfoxy reagent-assisted floatation for separating of sulfides of copper, molybdenum and gold from pyrite, marcasite, pyrrhotite, arsenopyrite, and other gangue minerals following aerating by an oxidizing gas and contacting by a sulfoxy reagent. To promote collection and flotation the feed mineral materials are preferably not contacted with an externally generated non-oxidizing gas to lower the dissolved molecular oxygen content prior to flotation.