From coarse to fine, sediments range in size from gravel to sand, silt, and clay. These harden into rocks named conglomerate, sandstone, siltstone, and shale. Being in rushing water is like being tossed in a washing machine. As the grains knock against each other and the rocks at the sides of the stream, their rough edges smooth. The roundness of grains reflects the energy of the transporting agent.
Roundness also reflects the amount of time the sediment traveled, indicating the distance as well.
The farther a sediment travels, the smoother and more rounded it becomes. Inc. All rights reserved.