This thesis investigates the effect of ore blends on milling and flotation performance. Anglo Platinum's Waterval UG2 concentrator in Rustenburg processes ore from various shafts. The thesis was initiated to gain a better understanding of the type of interactions between the ores that consequently affect metal accounting at the concentrator. Four ores were sourced from the following shafts: Salene ore (x 1 ), Waterval UG2 ore (x 2 ), Paardekraal ore (x 3 ) and Townlands ore (x 4 ). The literature review indicates various experimental mixture designs that could possibly be used. The mixture designs that are most evident in the literature are the simplex centroid design, the simplex lattice design and the axial (augmented) design. The simplex lattice design was selected for this research as it is commonly used in, for example, the pharmaceutical industry, chemical industry and the food industry. None of these mixture designs has ever previously been applied to the field of mineral processing and the thesis aimed to establish the experimental mixture design as a foundation for a methodology to evaluate and interpret the effect of ore blends.The thesis involved the characterization of four pure ores. Laboratory milling and flotation tests were conducted in order to standardize a milling time and quantify the uncertainty around the test work. Laboratory batch milling tests were performed using a standard Yaskuwa 0.25 kW rod mill, and laboratory batch flotation tests were performed using a standard Denver laboratory flotation cell. The simplex lattice experimental mixture design was then used to generate design points where ore from the four sources were blended in specified proportions. Ten-ton bulk samples of each ore were collected and sub sampled. The material was crushed to -12 mm using a cone crusher and split 12 ways with a rotary bulk splitter. The subsamples from splitting were combined and resplit for homogenization. Material was then crushed to -3 mm using a jaw crusher and 40 kg of this material was split 8 ways with a rotary splitter to render 5 kg portions.Each 5 kg portion was split 10 ways using a rotary splitter to render 500 g portions, which were used to make up the experimental design points.Laboratory milling and flotation experiments were conducted on these ore blends for each design point. Different polynomial models were fitted to the design and the special cubic model was found to describe the data adequately. By evaluating the coefficient for binary and ternary terms, the polynomial model was then used to interpret antagonistic and synergistic interactions between the various ores. Binary and ternary plots were further used to visually interpret interactions. A was also accentuated by the significant synergistic interaction of the ternary terms containing both Paardekraal (x 3 ) and Townlands (x 4 ). It was found that the quality of ore as well as the relative proportion on the blend will affect grade. This model is therefore a useful tool to detect the effect of blending on cumulativ...