A phenomenological approach to evaluating the agglomeration rate of gr
owing crystals is presented. Crystals larger than the Kolmogoroff micr
oscale collide because of the fluctuating velocity field. Bridges betw
een the crystals form as a result of competition between crystalline g
rowth and the turbulent velocity fluctuations on the opposite sides of
the agglomerate. Crystals smaller than the Kolmogoroff microscale col
lide because of viscous laminar microshear stresses within the same tu
rbulent eddy, are kept close together by Van der Waals forces and are
joined together by crystalline bridges that grow between them. The str
ength of these bridges depends on the supersaturation level during the
moments following the collision. These two sets of phenomena lead to
two different preferential generation mechanisms for agglomerates. One
example involving important agglomeration effects is developed for ea
ch case: the crystallization of adipic acid belongs to the first group
(large crystals), whereas the precipitation of calcium oxalate monohy
drate is typical of the second case (small crystals).