The flocculation of fine diaspore, kaolinite, illite and pyrophyllite and their artificial mixed minerals and bauxite ore were systematically investigated by the sedimentation tests. The mechanism analyses were performed in combination with examinations through X-ray diffraction (XRD), digital metallographic microscope and infrared spectra. Experimental results showed that the concentrate with A/S (mass ratio of Al2O3/SiO2) 8.9 and the recovery of Al2O3 86.98% were obtained from bauxite ore (A/S 5.68) at pH 9.5-10 by using sodium carbonate 5 kg/t and sodium polyacrylate 7 g/t. Sodium carbonate can act as both pH modifiers and a favorable dispersant for aluminositicates. High performance of sodium polyacrylate on flocculation for diaspore was due to that carboxyl of sodium polyacrylate interacted with active Al sets of diaspore by chemical absorption or formed hydrogen bond via hydroxyl group of macromolecule with surface Al-OH to enhance the sedimentation rate of diaspore. (C) 2007 Elsevier B.V. All rights reserved.