Relationships between microstructure, fracture mechanism and mechanical response of rocks under stressing have been intensively investigated in the last couple of decades. However, only limited work has been carried out that sheds light on the role of microstructure on particle breakage and crushing response of rocks. The paper analyzes these relationships for rock samples from four quarries that produce crushed aggregate in Brazil. The breakage and crushing characteristics are analyzed in light of the rock internal structure and fabric. It is found that the appearance of non-normalizable single-particle breakage functions and the effect of particle size on strength may be explained on the basis of a number of microstructures identified. (C) 2008 Elsevier B.V. All rights reserved.