Pearls

Ask whether pearls are natural, cultured, or imitation. Both natural and cultured pearls are made by oysters or other mollusks; imitation pearls are man-made. Naturally-occurring pearls are fairly rare and expensive, so most pearls you’ll see are cultured pearls — pearls made by mollusks with human intervention. An irritant introduced into the shell of the mollusk causes a pearl to grow. A pearl’s cost depends on the size, usually stated in millimeters, and the coating or "nacre", which gives natural and cultured pearls their luster. Imitation pearls are man-made with glass, plastic, or organic materials.