A part of the Bureau of Mines mission is to help improve the nation's mineral posture by providing the technology for utilizing low-grade ores. In this regard, laboratory testing by the Bureau of Mines has shown that the removal of insoluble slimes using selective flocculation and flotation is a viable method for treating low-grade potash ores that have a high content of water-insoluble impurities. Results indicated that over 82 percent of the insoluble slimes could be removed from sylvinite ore containing 5 percent water insolubles and 13 percent k2o by using nonionic or cationic polyacrylamide flocculants and cationic, anionic, and/or nonionic collectors. Subsequent potash flotation recovered 87 percent of the potash in rougher concentrates containing 57 percent k2o. Sizing and cleaner flotation of the rougher concentrates upgraded the products to 60 percent k2o. Filtration of the water-leached insoluble-slimes flotation concentrates on a bed consisting of leached insoluble- slimes concentrate mixed with potash flotation tailings recovered 80 percent of the brine. Filtration rates using the mixed bed were nine times faster than filtration rates obtained when the insoluble- slimes flotation concentrates were filtered separately.