Separation of the slightly soluble minerals, ksp 10-10, is one of the more difficult tasks confronting flotation engineers. This study focused on means of separating such prominent members of this class as scheelite, fluorite, and calcite from one another. Some experimental work was also done on magnesite, dolomite, and apatite. Four techniques were evaluated for separation of the minerals: (1) control of potential determining ions, (2) use of stereo-specific collectors, (3) use of flotation rate differences, and (4) use of selective activating and depressing compounds. Each of these techniques was found to be a possible method of achieving selectivity between scheelite, fluorite, and calcite. The use of stereospecific fatty acid or sulfonate collector appears to be a particularly promising method of achieving selectivity between minerals of the slightly soluble class.