The kinetics of vaterite (CaCO3) crystallization in the presence of leucine was investigated by the constant composition technique. The presence of leucine in the supersaturated solution stabilizes this carbonate polymorph by a modulation procedure. The number of ions forming the critical nucleus was found to be two and a surface energy of 23 mJ m(-2) was estimated. The apparent order was found to be 1, typical for a surface diffusion controlled spiral growth mechanism. (C) 2004 Elsevier B.V. All rights reserved.