Pearls are captivating objects. Though they are widely used for jewelry and decoration, some may not know how they are made or where they come from.
Natural pearls form when a grain of sand, or another foreign object, gets into the shell of a mollusk. Sand is irritating to the mollusk, so it produces layers of iridescent nacre, or mother of pearl, to cover the unknown object. Generally oysters are the mollusks used to produce pearls. Though the process takes a while, sometimes even years, it is well worth the wait. Pearls from oysters in particular are prized for their iridescence.
Countries from all over the world produce pearls. The main producer by volume of pearls is China, but Japan is a notable producer of high-quality pearls. These “cultured” pearls are created by a human controlled procedure: a cut is made in the flesh of an oyster and a graft from another oyster is attached. This process enables consistent formation of high quality pearls.
The most precious of all pearls are white sea pearls and black sea pearls. White pearls are formed in the gold-lip oyster, while black pearls form in black-lip oysters. Black sea pearls are rarely actually black; they typically range in color from a dark gray to peacock green. The production of black sea pearls began in Tahiti over 20 years ago, and continues today.
Pearls can be found all over the world. Natural pearl oyster beds exist in the Persian Gulf , the Bay of Aden in the Red Sea, northwest Sri Lanka, off the northwest Australian coast, and around the South Pacific islands. White south sea pears come from the tropic shores of western and northwestern Australia, and the Mississippi River in North America is a notable source of freshwater pearls.
Whether natural or cultured, pearls are universally admired.
[Source: The Encyclopedia of the Earth: Oceans and Islands]