The industrial processes of water clarification often imply flocs of millimeter length. The principal motivation of this work relates to the characterization of these large flocs with laser diffractometry, for which the authors propose particular experimental approaches. In addition, a reformulation of the various properties of the flocs accessible by laser diffractometry is presented, in particular for the determination of the size, density, porosity, volume fraction, and fractal dimension. By way of illustration, these experimental and theoretical developments are applied to the characterization of flocs obtained by flocculation of a commercial kaolin. The size, fractal dimension, and density of kaolin floc were examined under various flocculant concentrations. Measurements reveal important variations of the granulometric and textural properties of large flocs in response to flocculation, opening ways of optimization for the associated industrial processes.