Laser-induced localized density fluctuations are shown to stimulate primary nucleation of nano-sized aluminum trihydroxide seed crystals in flowing supersaturated industrial sodium aluminate solutions (Bayer liquor). The postnucleation mass deposition rate is greatly increased over rates attainable through more traditional seeding methods. Near-ideal single-crystal gibbsite is formed under diffusion-limited growth conditions. Laser-stimulated nucleation represents an in situ method for the active local modulation of the supersaturation state, so that the stimulated nucleation occurs under macroscopic solution conditions that are unfavorable for spontaneous nucleation.