Our recent studies on the interaction of oleate with salt-type mineral surfaces have been summarized based on adsorption, infrared and zeta-potential measurements. Monolayer coverage in the case of calcite and a bilayer formation in the cases of fluorite, apatite and scheelite, preceding the precipitation of calcium soap has been suggested for the adsorption mechanism of oleate on these minerals. The monolayer coverage is shown to correspond to a condensed state of oleate with a molecular coverage area of 33 A2 (liquid-crystal state). Depending on the surface potential and its magnitude at basic pH values, oleate is either chemisorbed on the surface calcium or monocoordinated through counter sodium and calcium ions for the monolayer filling.