COMMON SEDIMENT DETRITAL ROCK &gt; 256 mm Boulder 64 - 256 mm Cobble Gravel Conglomerate or Breccia 4 - 64 mm Pebble 2 - 4 mm Granule 1/16 - 2 mm Sand Sand Sandstone 1/256 - 1/16 mm Silt Mud Shale or Mudstone &lt; 1/256 mm Clay Shale Deposition in quiet, non-turbulent waters.