Brighton & Hove has a natural pebble beach with a flat sandy part that you can only see when the tide is out. The reason why it has pebbles and not sand is because the rocks in this area are chalk containing flint.
Flint is very hard does not break down into sand but does get worn away into pebble shapes. Apparently there are over 614,000,000 pebbles on Brighton beach.
There’s also a Brighton Beach in New York City