Spherical particles of calcium dioleate were successfully prepared to measure the interaction force of a calcium dioleate collector colloid at calcite and fluorite surfaces. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and electrophoretic mobility measurements were used to characterize the specially prepared calcium dioleate spheres. FTIR spectra show that the spheres have the same spectral properties as untreated (freshly precipitated) calcium dioleate. SEM imaging of the sphere surface and AFM roughness measurements indicate that these spheres can be used as colloidal probes for interaction force measurements. AFM interaction force measurements between calcium dioleate spheres and mineral surfaces were conducted at selected pH values from pH 5.2 to pH 10.0. The attractive force and adhesion force between the calcium dioleate sphere and the fluorite surface were found to be much stronger and longer-range than those measured between the calcium dioleate sphere and the calcite surface. The range and magnitude of these attractive forces were found to be pH dependent in the case of fluorite. These results are discussed in conjunction with streaming potential measurements, contact angle measurements, and the flotation behavior of calcite and fluorite with oleate as the collector.