Not many. A few hundred will do in a tiny rocky cove.
The main feature of a pebble beach is not that there are many pebbles, but that there is no sand. If there is sand, it cannot be a pebble beach.
The pebbles are flint deposited in the chalk cliffs adjacent to Brighton. Through natural erosion the flints are released from the cliffs and slowly make their way through natural process to Brighton where the groynes are in place to "capture" the pebbles. You can see this in action as you can see a higher level of pebbles to the west of a groyne than on the easterly side.
Brighton Beach - BMT Brighton Line - was created in 1878.
Brighton Beach was created in 1868.
A beach made of pebbles is often called a "shingle" beach.
Mahattan beach aka Brighton Beach Mahattan beach aka Brighton Beach
Beach pebbles are smooth as they are eroded by the waves
The address of the Brighton Beach is: 16 Brighton 1St Road, Brooklyn, 11235 8002
the pebbles at the front of the beach get eroded by the water
Brighton Beach railway station was created in 1861.
Brighton Beach Race Course was created in 1879.
Brighton Beach Range Lights was created in 1890.
Live on Brighton Beach was created on 2001-07-07.