"Stratified stone that splits into pieces suitable for paving", says the dictionary. This effect is simulated by the Flagstone function.

Increase the Octaves value to add smaller stones. Each octave features stones, that are two times as small as the preceding octave's ones. Persistence controls the reduction of the stones' height as they get smaller. Decrease the value to fade out the smaller ones. Increase the Resolution value to capture a wider stone field, similar to a zoom-out effect.

Use the Amplify value to adjust the stones' maximum height. Flatten the top of the stones by increasing this value until their heights exceed the valid ranges.

Tip: By using the functions Filter/Smooth and Color/Black and White by turns on the flagstone pattern, you can create the shape of round stones.