The present study is an experimental investigation of the performance of a rubber-lined centrifugal pump when pumping ores and industrial minerals with concentrations by weight of up to 65-70%. The upper limit of particle size was about 8 mm. The clear water head and efficiency were lowered 30-40% by the coarsest iron ore investigated. Most experimental data were correlated to a formula expressing the influence of solid concentration and solid properties on the reduction in pump head. The drop in efficiency was equivalent to the drop in head up to volumetric concentrations of 20-25%. With higher concentrations the drop in efficiency became greater than the drop in head.