Microstructural evolution during the heat treatment of cement clinker was investigated. Two model specimens, which consisted of faceted tricalcium silicate (C3S) and spherical dicalcium silicate (C2S) grains dispersed in a liquid matrix, were prepared with 5 wt% of large seed particles. The seed particles of faceted C3S grains grew extensively, whereas those of the spherical C3S grains grew rather slowly, relative to the matrix grains. As a consequence, C3S grains exhibited a bimodal size distribution that was typical of exaggerated grain growth, whereas C2S grains retained a uniform and normal size distribution, These results suggest that the growth of faceted C3S grains was controlled by the interface atomic attachment, such as two-dimensional nucleation, and that of spherical C2S grains was controlled by diffusion through the liquid matrix. The dependence of growth mechanisms on grain morphology has been explained in terms of the atomistic structure of the solid/liquid interface.