Nimphelos
In J. R. R. Tolkien's The Silmarillion, Nimphelos was a valuable pearl given by Thingol to the Dwarves from Belegost as a reward for building Menegroth.
It was probably fished from Belegaer by CĂrdan's folk, who gave it to the King of Doriath as a gift.
The pearl was said to be as big as a dove's egg. Beren took it from the Dwarves.