This paper describes, in detail, the treatment of a copper/molybdenum sulfide ore (0.94% Cu and 0.05% Me) using emulsified oil extender flotation (Ext-F) at laboratory scale. Results obtained were compared with a "standardized" mill laboratory procedure, measuring concentrate grade and recovery (size by size results included), "true" (bubbles-particles attachment only) flotation recoveries and process kinetics. The Ext-F technique yielded higher metallurgical efficiencies, especially for the fines (<37 mu m), than the mill standard with emulsified diesel oil (>60 g t(-1)). Concentrate recoveries with 60-90 g t(-1) Diesel oil droplets (3-6 mu m) and their process kinetic values were always of the order of 3-6% higher, at similar concentrate grades, either for copper or molybdenum sulfides. Size by size flotation results proved that metallurgical and kinetic gains can be attributed, mainly, to fines (37-5 microns) and ultrafines (<5 mu m) enhancement (8-15% higher). Data obtained are discussed in terms of chemical, physical and physicochemical parameters related to a better oil attachment and capture of particles by bubbles. Thus, it is believed that the emulsified oil droplets interact firstly with the mineral surfaces, then spread out as oil lenses, enhance hydrophobicity and allow aggregation of the very fines. Theses stages do not occur markedly when the oil does not interact properly with the collector-coated sulfides (low chemical affinity) or when the oil was not emulsified. The potential (advantages) of the Ext-F technique for fine ore processing and the practical forms for industrial oil emulsification are envisaged. (c) 2007 Elsevier B.V. All rights reserved.