Coagulation is one of the most important processes for aggregating the fine particles in a dispersed system via different mechanisms. Many factors such as particle size, morphology, pH, coagulant type, and concentration may affect particle-particle interactions, which will then be effective on their coagulation characteristics. In this study, the effect of grinding type on the roughness of magnesite particles under 38 microns was evaluated for its role in the coagulation of particles under different salt types and concentrations. The results of grinding tests showed that rougher particles could be obtained with a rod mill compared to the particles ground in a ball mill. After grinding of particles, an increasing trend was obtained in terms of settling rate for different salts in an order of NaCl < CaCl₂ < AlCl₃ during coagulation tests under all concentrations (10^-3, 10^-2, 10^-1 and 1 M) at a constant pH value as 8.01±0.2. In sum, the results of this study clearly showed that adjusting the grinding conditions is not only effective on the size and morphology of the particles but also plays a significant role in particle-particle interactions and accordingly their coagulation characteristics.