In order to describe temporal evolution of BET surface area of a mineral substance during an intensive milling process, a mathematical model in the form of S = a + b e-(mt) + c e(-nt) has been developed based oil well-established phenomena in mechanical activation processes Validity of the proposed model was verified by the results of experiments performed on a natural chalcopyrite mineral as well as those reported in the literature on a variety of sulfide minerals. It was shown that the model could fit different types of surface area variation with a very good accuracy. (C) 2009 Elsevier B.V All rights reserved