Fig. 1.

Schematics of the scenario of this model. (a) Size evolution of silicate particles. Silicate molecules (small circles) dissolve into water from the small silicate particle and precipitate onto the large particle. (b) Evolution of a series of grains. Silicate molecules precipitate onto the necks between grains because of its concave surface. (c) After the necks are filled with silicate molecules, the thickness reflects the initial size of the grains. (d) Splitting occurs at the thin section because of the variation in the surface curvature.