Grinding ball fragments discharging from SAG mills and ball mills cause extreme wear to downstream processing equipment. These ball fragments, circulating in a milling circuit, will cause excessive wear to sumps, pumps, hydrocyclones and interconnecting piping. Grinding ball fragments contribute very little to the grinding process while consuming power. Magnetic separation applied to milling circuits to remove the recirculating grinding media has evolved over several years. Magnetic separation techniques have been successfully applied to ball mill circuits as well as SAG mill circuits. The Trunnion Magnet separator was developed and improved over the years to remove grinding ball fragments directly from the mill discharge. The removal of grinding media from the ball mill discharge has resulted in several benefits in the milling circuit. Reported benefits taken from various installations are: Extended the pump life and the hydrocyclone life of approximately 250%. An increase in mill throughput of a nominal 5%. A nominal 8% reduction in mill power consumption. More efficient grinding resulting in a nominal 10% reduction in the mill work index. Magnetic separation has also been recently applied to the SAG mill discharge. Suspended electromagnetic and rotating drum type magnetic separators have been designed to "pick-up" the grinding media in the coarse oversize recirculating product. In addition, rotating drum type magnetic separators have been developed to remove grinding media in the fine undersize product that that reports to the sump. (C) 2004 Elsevier Ltd. All rights reserved.