<p>The competence of mined rock is a key property determining both the amount of energy required to grind the ore and the throughput of the process plant. Existing empirical geometallurgical models cannot predict outside the tested ore base or account for changes to the grinding circuit. A new approach is introduced which provides a precise measure of rock fracture energy distribution related to the rock mineralogy, specifically the degree of alteration of a porphyry copper. A relationship between mineralogy and rock strength allows the rock crushing and milling energy to be mapped into the orebody based on the geological map of the deposit, rather than requiring extensive, and expensive, breakage testing and the use of unreliable proxy values. This study presents a viable method to quantify the distributed and widely varying rock properties of mineral resources in a more cost-effective manner than traditional independent rock-strength testing methods, by using automated core-scanning technology to relate mineralogy and texture to rock strength. Recent developments in more rapid and cheaper but still accurate ore breakage characterisation may help propel this methodology into standard geometallurgical modelling practice.</p>