Attempts have been made to develop a mathematical expression on the basis of dislocation theory to describe the effect of intensive milling time on the changes of dislocation density as well as amorphization degree of a mineral substance during intensive milling process. Validity of the proposed expression was verified by the results of experiments performed on a natural chalcopyrite mineral as well as those reported in the literature. It was concluded that the expression satisfied the experimental results with a good accuracy. (C) 2009 Elsevier B.V. All rights reserved.