The study extends previous fundamental modelling work on the influence of surface microtopography on enhanced dissolution (mechanical activation) of milled particles. Specifically, it analyses quantitatively the conjoint effects of particle size and the fraction (alpha) of dissolution sites associated with steps on the overall mass dissolution behaviour of fine particles. The study shows clearly that microtopography-enhanced dissolution is likely to be most evident for leaching processes exhibiting high activation energies of dissolution (similar to70 kJ mol(-1) or higher) and unlikely to be evident in particle sizes larger than a few pm. Experimental determination of representative alpha-values obtained from scanning electron micrographs of three crushed minerals (sphalerite, ilmenite and chalcopyrite) suggest that the limiting milled particle size for significant microtopography-enhanced dissolution lies within the range from similar to 0.2 to similar to 0.4 mum. (C) 2002 Elsevier Science Ltd. All rights reserved.