|“||These Círdan gave to him, for they were got in great number in the shallow waters about the Isle of Balar; but the Naugrim had not before seen their like, and they held them dear. One there was as great as a dove's egg, and its sheen was as starlight on the foam of the sea; Nimphelos it was named, and the chieftain of the Dwarves of Belegost prized it above a mountain of wealth.||”|
–Of the Sindar, The Silmarillion
Pearls are round, pinkish gemstones.
As with many other materials, you can make a pearl block with nine pearls in a crafting table.
A block of pearl can be found on top of Umbar statues.
Pearls are actually a clam's response to a foreign object inside it's shell, usually a grain of sand stuck inside it's shell. It excretes a coating over the offending object to protect itself.