Cultured gem is a term used to describe a PEARL that has been created by human intervention. A PEARL is a hard, round object produced by certain mollusks, typically found in the ocean. Cultured pearls are created when a mollusk is given a nucleus, usually made of mother-of-PEARL, and then returned to the water. The mollusk then coats the nucleus with layers of nacre, which is what gives the PEARL its luster and color. Cultured pearls are often more uniform in shape and size than natural pearls, and they are also less expensive.