gravel

The gravel is formed by small fragments of stone: when very thin it is called sandy beach, on the other hand it takes the name of paving. The gravel is commonly found walking on country or mountains path, on beach and on river beds. sea pebbles have irregular shapes and sharp edges because of the waves smash them; the river ones are more smoothed and spherical since the water flow is regular.

photo -> nature -> stone -> gravel