The separation efficiency from water of different-shape particles was studied experimentally using a mini-hydrocyclone. Spherical and flaky (plate-like) aluminum particles with the same particle size distributions were employed. Also, the effects of the feed flow rate and the temperature on the separation performance were studied. The results were investigated in terms of slurry recovery, total efficiency, and partition curves. The separation efficiency of the spherical particles increased with increasing particle size, temperature, and feed flow rate, as expected. The fishhook effect, as a noticeable phenomenon, was observed for the spherical particles. In case of the flaky particles, the separation showed an unusual behavior: The separation efficiency decreased with increasing particle size in the largest particle fraction, which has so far not been reported and addressed in this way.