The detachment of fine particles of silica (0.12 μm) and hematite (0.10 μm) coattached on glass beads (80 μm) in aqueous solution were studied as a function of pH and electrolyte concentration. Detachment occurs at alkaline conditions wherein the surface potentials of the particles and collector are negative. The selective separation of silica particles being governed by the balance of short range forces, which are affected by increasing the pH and electrolyte concentration.