A number of previous researchers have noticed that the degree of mineral liberation in a given size fraction is the same regardless of where in a comminution circuit a sample is collected. This behaviour has been observed for a range of ore types, and was found to be independent of the mode of breakage. This provides a useful heuristic for modelling the particle characteristics in mineral comminution and separation circuits. However, the published research does not explicitly consider the effect on the liberation behaviour of minerals of the amount of energy applied to break the ore. In this study, a gold-bearing pyrite ore and a copper sulphide ore were comminuted over a wide range of energy levels, using impact breakage. The liberation properties of the product particles were characterised using a Mineral Liberation Analyser (MLA). It was found that that the amount of impact energy applied did not significantly affect the degree of liberation of the minerals in a given size fraction, measured using particle sections. This provides sound experimental evidence to support the heuristic model.