These river mixed aggregates are mined, and then transported to the stone quarry for crushing. River stone screening plant can separate sand, granule, pebble, cobble in the mixture. The final grain sizes of river stone crushing plant are: Coarse sand: 0.6 mm - 2 mm Fine gravel: 2 mm - 6 mm Medium gravel: 6-20 mm Coarse gravel: 20-60 mm.