Rounding of cobble and boulder
Cobbles and boulders, situated in the tidal zone, are slowly polished to a rounded shape when the waves rocks them under storm. Also on riverbeds and river banks along major rivers and glacial rivers you can see the same phenomenon.
The degree of rounding will, among other factors, be dependent on the size and strength of the grains, the energy in the water and how long they have been exposed to water. Large boulders are, for example, harder to move than cobble and pebble. In some environments as glacier ice, there is little contact between the grains, and therefore a grain transported directly by a glacier has a typical angular shape. Scree material has not been in contact with water, and will therefore hava an angular shape. There are some magnificent talus-cones between locality 1 and 2 and you will see much difference in grain-shape by comparing those two sedimentological environments.