Coarsening of self-organized clusters in binary mixtures of particles.

Experiments on patterned particle segregation in binary granular mixtures which are subjected to horizontal shaking have been performed. A novel mechanism for separation is found, where random forcing of one species by the other causes clustering. A pattern is formed which contains a series of stripes aligned orthogonal to the direction of the periodic forcing. The pattern coarsens with time and shows a power law behavior which is consistent with simple models of the geological process of "stone striping."