Best beaches?

Trying to find out which islands in the caribbean tend to have volcanic black sand beaches. Is there a certain group/area e.g. eastern/western/southern??

St Kitts does. I believe there might be some in St Lucia as well .... if I remember right our guide said they imported the white sand from Guyana to cover the beach I was on in St Lucia because tourists didn't like the black sand as much......

They are scattered across the Carib. Many throughout the Lesser Antilles include

Black Bay Beach Grenada, several beaches on Monserrat, Rosalie Beach Dominica, Plage de Salee a Bananier Beach Guadeloupe, Anse Chastanet St Lucia, Black Point St Vincent, Saint Pierre Beach Martinique (historic Mont Pelee).

Also many in central Smerica like The beaches of Cahuita, Costa Rica.