I read a hardback book, in the ’70s, about a girl on a coast, Ireland or Britain, who finds a piece of jewelry, a ring or broach or a necklace (in the ruins of an ancient building maybe?) She has dreams that reveal the life of the girl who had the piece a long (centuries?) time ago. The dream girl was maybe Spanish.
There were dolphins, and an island that figured very large in the story.
It didn’t seem like a new book at the time. Looking back I would guess that it was written after ww2. It had a sad tragic feel to it.
Does this ring any bells?