This paper presents the results of investigations concerning the influence of magnesium, copper, aluminum and ferric cations on the coagulation and electrokinetic behaviors of clinoptilolite suspension. While clinoptilolite exhibited a negative surface charge over a broad pH range and had no isoelectric point (iep), especially the trivalent ions strongly changed the sign and magnitude of the zeta potential of the mineral depending on pH and cation concentration. The coagulation of clinoptilolite particles with these metal cations also showed sharp dependences on pH and cation concentration. That is, the coagulation process significantly took place in the pH and concentration ranges in which metal hydroxides existed in the suspension. Moreover, the coagulation behavior of clinoptilolite at pH values below the iep of metal hydroxides was usually consistent with its zeta potential variation, indicating a coagulation process by the charge neutralization mechanism. However, at pH values larger than the iep of these hydroxides, sweep coagulation of clinoptilolite suspension occurred and a clear correlation between surface charge and the onset of coagulation was not determined.