This article presents the results of performance evaluation studies performed at the grinding circuit of a pyrite flotation plant. A detailed sampling survey was conducted at the grinding circuit and also at the main streams in the beneficiation circuit. By using the solids content, size distributions and chemical assays of all streams, the mass balance of the full plant was calculated. A series of gravity concentration tests were performed at two different periods to evaluate the possibility of obtaining a concentrate at coarser sizes. Using the data obtained, models for the SAG mill, trommel screen, cone crusher, ball mill and hydrocyclones were developed. The alternatives, which include both operational and flowsheet changes, were then investigated by simulations. As a final flowsheet, a gravity concentration circuit is proposed for the particles coarser than 0.2 mm, while any particles liberated after ball mill grinding will be caught by flash flotation. This circuit enables precise classification of the ore for both gravity and flotation, reduces all overgrinding possibilities and would be the most flexible circuit when the ore characteristics change. Since the gravity circuit would recover 20-30 percent of the valuable minerals, flash flotation would perform much more smoothly.