A natural gemstone formed when a oyster is irritated by a substance that gets into its shell or mantle. Most jewelry pearls are cultured pearls, created by purposefully inserting a tiny mother-of-pearl bead. Pearls, like other gemstones, come in a variety of shapes and forms. A blister pearl is a pearl that forms attached to the shell. A half-dome shaped pearl is a mabe (pronounces mah-bay) pearl. Irregular shaped pearls are called baroque.
Mother of pearl