Although freshwater pearls can be grown in mussels and other mollusks, saltwater pearls are always grown in oysters. Most saltwater pearls are harvested in the Red Sea, the Persian Gulf, and the coastal waters of India and Japan. Generally, saltwater pearls are higher in quality than freshwater pearls. They often have a smooth, round, regular shape—freshwater pearls tend to be more irregular. Saltwater pearls have a glossy surface with moderate luster. Their color is most often white or light.
Because a saltwater oyster can produce only one pearl, while a freshwater mollusk can produce several at once, saltwater pearls are more rare than freshwater—and thus more expensive. The most common saltwater pearls found on the open market are Tahitian pearls, South Sea pearls, and Akoya pearls.