The interactions between particles in the processed ore are a key feature in copper hydrometallurgical beneficiation. The formation of aggregates reduces the performance of some of the stages of the hydrometallurgical trains, in particular solvent extraction. In the case of copper hydrometallurgy, the most abundant colloids are silica and some clays, mostly kaolinite, which are difficult to separate under the typical conditions of low pH and 300 mM ionic strength. In this work a thorough electrokinetic investigation of concentrated suspensions of the two kinds of particles is presented, both individually and in mixtures, in conditions of pH and copper sulfate concentrations typical of the hydrometallurgical processes. The technique used was ESA (Electrokinetic Sonic Amplitude), whereby an alternating field is applied to the suspension and the generated pressure wave is analyzed. In the case of silica, it is found that the (dynamic or ac) electrophoretic mobility is quite low, and so is the best-fit zeta potential of the particles, as the pH gets close to the isoelectric point while the ionic strength is very high (80 mM copper sulfate). Our experiments also reveal that there are no specific interactions between silica and either copper or sulfate ions, which appear to have no other influence than compressing the double layers of the silica/solution interface. In the case of kaolinite, the dynamic mobility results indicate a large effect of the complex structures which are possible in suspensions of this clay (through face-to-face and face-to-edge interactions). Finally, a study was carried out of realistic mixtures of silica and kaolinite, with the aim of possibly predicting mixed structures, which were also ascertained by electron microscope observations. The results at low pH cannot be justified by a simple averaging between the mobility of silica and kaolinite alone, but by a non-trivial association between kaolinite and silica particles, being the latter attached to the former. At pH 5, the silica spheres do not show any preference for edges, and we can expect a predominant attraction towards positive alumina faces. Sedimentation experiments indicate that the conditions described at low pH slow down the sedimentation rate of kaolinite-silica as compared to silica alone, contrary to findings at pH 5.