A method of predicting breakage properties of a particulate material when subjected to impact, the method including: calculating a breakage index for the particulate material using the following equation: Breakage Index=M{I−exp[−fmatxk−E]} where: M represents the maximum breakage of particles for the particulate material; fmat is a material parameter that is a function of the particulate material being broken and particle size; x is the initial particle size of the particulate material prior to impact; E is a measure of the specific energy applied to the particulate material; and k is the number of impacts with specific energy E.