A pearl begins as a defense mechanism. When an irritant—such as a grain of sand or a parasite—becomes lodged in the soft mantle of a mollusk (typically an oyster or clam), the animal responds by secreting (mother-of-pearl).
Despite the name, these are not limited to Tahiti, but the islands of French Polynesia. These pearls are famous for their exotic dark hues—peacock green, aubergine (eggplant), blue, and charcoal gray. No Tahitian pearl is perfectly black; their beauty lies in the overlapping overtones of color that shimmer across the dark surface. A pearl begins as a defense mechanism