In this study, we investigate the effect of drop weight shape, bed mass and drop height on the impact breakage of a run-of-mine platinum group metals (PGM) ore collected from the Great Dyke region in Zimbabwe. The three drop weight shapes used were spherical balls, semi-ellipsoids and cubes. We then applied a model-free optimization tool called the Attainable Region (AR) technique to analyze and optimize the impact energy on a bed of PGM particles. We observed that different drop weight shapes produce products of different levels of fineness, hence an interesting area for research. A higher mass fraction of a preselected desired product fineness (850 + 150 pm) was obtained from use of spherical balls and semi-ellipsoids compared to cubes. We also observed that the bed mass had a significant effect on the impact breakage process and an optimal bed mass gave result to a maximum amount of the desired size class. (C) 2019 Elsevier B.V. All rights reserved.