Pearls don’t need polishing or faceting to reveal their natural beauty. That’s why pearls were among the first gems worn by humans. The oldest known pearl necklaces graced the necks of women more than 4,000 years ago.
Some early stories say pearls grew from the tears of a goddess. Others tell of oysters swallowing raindrops or dewdrops that fell into the ocean. Round and lustrous, pearls symbolize the moon, and mortals have universally assigned feminine characteristics to them. Those who value gems for their powers wear pearls to attract love and good health.
Pearls are classified as organic gems because they are made by animals called mollusks. Mollusks have shells and most of them live underwater. They secrete a natural substance called nacre (rhymes with “acre”).
Nacre consistes mainly of aragonite, a mineral crystal from the calcium carbonate family. The aragonite is combined with a natural “glue” called conchiolin and small amounts of water to form nacre. Nacre is also known as mother-of-pearl. The purpose of nacre is to make the inside of the shell smooth so that it doesn’t irritate the soft body of the mollusk. A pearl is simply an abnormal growth of nacre.
Natural pearls are formed when something such as a grain of sand gets inside the shell and irritates the mollusk. To reduce the irritation, the animal covers it with thousands of smooth layers of nacre. The process is similar to what your body does when it forms a callus to protect irritated skin. It takes about three years to grow a small pearl.
Cultured pearls differ from natural pearls in that the irritant, usually a bead, is placed in the oyster by man. As cultured and natural pearls look alike, only an expert with special X-ray equipment can distinguish between them. Cultured pearls may not be sold as natural; however, they are regarded as “real” pearls and not fakes. Nearly all pearls on the market today are cultured, with most of them coming from Japan.
Pearls grow in many shapes, with round being the most highly prized. Some other symmetrical (even) shapes are pear, bell, and drop. A baroque pearl is one that is irregular in shape. Skilled jewelers often take advantage of the odd shapes of baroque pearls to make unique jewelry. Most popular are those shaped like animals or humans. If a pearl is rounded on one side, but flat on the other, it is known as a bouton. Blister or button pearls are other names for boutons.
Because the nacre is deposited in overlapping layers, it doesn’t reflect light evenly. This creates iridescence and the lustrous inner glow of pearls. The quality of the luster depends on how many layers of nacre have been deposited, which depends on how long the pearl has been in the mollusk. The more layers of nacre, the greater the luster of the pearl. The water trapped between the layers also adds to the luster.
Iridescence is also known as orient. The most beautiful pearls are prized because of their high orient. Saltwater pearls, which are grown in pearl oysters, usually have more orient than those from freshwater mollusks. Because of this, saltwater pearls have become generally known as orientals, regardless of where they are harvested.
The pearl oyster is found in several seas. The oldest fisheries are in Sri Lanka, but pearls from the Persian Gulf are often regarded as the highest quality. Each pearl oyster, which is not edible, normally produces only one pearl and dies when the pearl is removed.
The mussels that produce freshwater pearls are found in lakes and rivers throughout the world.
Both cultured and natural pearls range in color from white through rose, yellow, and blue to dark gray. Black pearls are rarely a true black. They are usually dark gray, but may also be bronze or gun-metal colored. An even or deep black pearl is often the result of “treating” the pearl with silver nitrate. Some “black pearls” are really polished hematite. While shiny, hematite lacks the glow of a true pearl.
All pearls may be dyed or stained, although coloring is more common with freshwater than saltwater pearls. Dying is usually undectable, except under strong magnification. Peroxide is sometimes used to bleach out surface discoloration on cultured pearls. Bleaching cannot be detected.
Fake pearls have been made for more than 400 years. Fish scales are used to prepare pearl essence. The essence is used to coat glass or plastic beads to manufacture simulated, imitation, or artificial pearls. Fakes are easy to detect. They feel smooth if gently drawn across the edge of your teeth. Natural and cultured pearls will always feel gritty or rough.
Pearls are soft and easily scratched. Wipe them with a soft cloth after wearing, then store them in a soft leather or cloth bag where they can “breathe.” Pearls stored in plastic or in dry and airless places like safe deposit boxes will soon lose their special glow. Body oils, perfumes, hair spray, and make-up will stain pearls. Never put pearls in an ultrasonic cleaner or expose them to strong chemicals. Even mild acids will dissolve them. Because natural and cultured pearls are so soft, the drill holes will become enlarged if they are loosely strung and allowed to slide on the thread. Necklaces should have a knot between each pearl, and should be restrung professionally every year or so to prevent excessive wear on your treasures from the ocean.
By Sandra I. Smith, Writer