A method of forming aggregate abrasive grains for use in the production of abrading or cutting tools comprises providing abrasive core particles; coating these particles with adhesive, the adhesive comprising a binding agent and a solvent for the binding agent; separately dropping the adhesive-coated core particles onto a layer of abrasive peripheral particles and covering the dropped core particles with further peripheral particles, in such a way as to form aggregate particles, each of which comprises a core particle having peripheral particles attached to it; consolidating the aggregate particles by causing the solvent to evaporate, i.e. by letting the adhesive set.