Accidental activation is a function of metal ion production, transfer and resultant flotation response. In Part I copper ion production from chalcocite and chalcopyrite was determined for single minerals and ores as a function of particle size using an EDTA extraction method. Copper ion production was inversely proportional to particle size. For single minerals, chalcocite produced about 50 times more Cu than chalcopyrite. The chalcopyrite-bearing ores gave higher copper ion production than for mineral alone, ascribed to galvanic interaction. A model was derived to predict surface concentration of Cu. The Cu production is compared to the resultant flotation effect in Part II. (C) 2002 Elsevier Science Ltd. All rights reserved.