Heterocoagulation and dispersion of diaspore and rutile fines in aqueous suspensions have been studied through the measurements of aggregation efficiency, zeta potentials, particle hydrophilicity and IR spectra. This study was performed on 2.7-mum rutile and 3,7-mum diaspore in volumetric mean diameter. The experimental results have demonstrated that around pH 5.0 sodium fluorosilicate (SFS) can induce a selective dispersion of diaspore fines in a diaspore-rutile suspension, leaving rutile fines to coagulate. This finding would be very helpful in developing a new process for the separation of rutile and diaspore fines. The mechanism by which SFS selectively dispersed diaspore fines in a diaspore-rutile suspension has been found to be due to the adsorption of SiF62-on diaspore surfaces instead of rutile particles. This adsorption strongly increased the negative zeta potential and the hydrophilicity of the particles, and thereby the electrical double layer and the solvation repulsive forces. The latter plays a predominant role in the selective dispersion.