There appears to be several mechanisms affecting the recovery of coarse KCl particles as they flow through the flotation circuit of the Taquari Vassouras mine (Companbia Vale do Rio Doce; CVRD), Aracaju, Brazil in the presence of continually increasing concentrations of carnallite. The increase in carnallite assists in the deposition of fine NaCl and KCl crystals on the surface of the coarse KCl particles. The effect seems to be a slight net improvement in the surface hydrophobicity and therefore flotation recovery of the coarse KCl particles. As the concentration of Mg2+ ions increase, the precipitation of fine crystals of NaCl and KCl starts to increase. These NaCl crystals appear to have fine inclusions of KCl on the surface (and vice versa) which appear to attract collector, thus reducing hydrophobicity and flotation recovery of the coarse KCl feed. It is at this stage that the removal of fine precipitates appears to become critical in order to provide enough collector coverage of the coarse KCl particles to keep them floating. (C) 2007 Published by Elsevier Ltd.