A significant problem of thermal pre-treatment methods is that of assessing the influence of these methods on the ore strength. Single particle breakage tests may be used to determine the effect of thermal pre-treatment on intrinsic strength parameters of the material as opposed to bulk parameters. In order to test the validity and sensitivity of a new method, the Three-point bend test experiments were conducted on a heterogenous carbonatite ore and a homogenous shap granite which were thermally pre-treated. The rest successfully detected the sharp strength decrease (up to 87%) due to quartz phase inversion within the granite as well as reductions of up to 80% in the carbonatite due to the thermal pre-treatment. Results correspond well to those of the Berry and Bruce method. Overall the Three point bend test is sensitive enough to detect changes in rock strength whilst being a much simpler method than conventional grinding tests.