Pearls Natural or real pearls are made by oysters and other mollusks. Cultured pearls also are grown by mollusks, but with human intervention; that is, an irritant introduced into shells causes a pearl to grow. Imitation pearls are man-made with glass, plastic, or organic materials.

Because natural pearls are very rare, most pearls used in jewelry are either cultured or imitation pearls. Cultured pearls, because they are made by oysters or mollusks, usually are more expensive than imitation pears. A cultured pearl’s value is largely based on its size, usually stated in millimeters, and quality of its nacre coating, which give it luster. Jewelers should tell your if pearls are cultured or imitation. Some black, bronze, gold, purple, blue and orange pearls, whether natural or cultured, occur that way in nature; some, however, are dyed through various processes. Jewelers should tell you whether colored pearls are naturally colored, dyed or irradiated.