GEMS A pearl primer

Shine, shape, size and surface determine the quality of a pearl.
By KIM NORRIS
KNIGHT RIDDER NEWSPAPERS
Ever since humans figured out how to compel a mollusk to make a pearl, cultured pearls have been prized for jewelry and adornment.
Part of their allure seems to rest in the mystery of creation that makes pearls the only natural gem created by a living organism. Beyond stimulating pearl creation, humans have little control over the end result.
"What separates this from other gems is that it's natural. They're not mined or cut. What an oyster does with it is up to it," said Armand Asher, president of the Cultured Pearl Association of America, a New York trade group representing mostly wholesalers. "There's a lot we don't know about them."
For example, two oysters grown next to each other in the same body of water for the same amount of time can produce pearls of different colors, shapes and size. No one knows why.
Throughout history, pearls have been prized in jewelry. The classic strand of matched round pearls remains one of the most sought-after pieces of jewelry in many women's wardrobes.
In 1917, Mae Plant, wife of New York banker Morton Plant, was so keen to acquire a particular two-strand pearl necklace owned by the Cartier family that she and her husband traded their Fifth Avenue mansion for the pearls, then valued at $1 million. The mansion at 52nd Street now is the New York home of Cartier jewelers.
Natural and cultured
Those pearls supposedly were natural pearls -- often called Oriental pearls. Before the art of culturing existed, the only pearls were those that occurred in nature and found in oysters collected by pearl divers. Perfect round pearls were so rare they commanded prices only royalty could afford.
Culturing made pearls available to the masses.
The art of cultivating pearls began centuries ago but was raised to a commercial venture in the 1920s when Japanese pearl farmers started cultivating pearls in Akoya oysters. Akoya pearls are the ones most commonly seen in classic pearl strands.
Cultured pearls are cultivated on pearl farms in fresh or salt water by people who artificially stimulate the process of pearl creation.
Mollusks make pearls as a defense against an irritant inside their shell. The mollusk secrets thin layers of calcium carbonate -- called nacre -- to coat the irritant. The nacre becomes the pearl.
Irritant inserted
In cultured pearls, that irritant is introduced intentionally -- albeit delicately -- by a person. If it is inserted into the mollusk's soft tissue, it will be completely surrounded by nacre. If the nacre is deposited on the shell, it will create a hemispheric covering (resulting in a mabe pearl).
Traditionally, the core of a cultured pearl has been a bead made from mother of pearl. But Chinese pearl farmers sometimes use a kind of tissue bead that disintegrates over time, leaving just the nacre.
The longer the mollusk is kept in the water, the more nacre it will produce and the larger the pearl will become. But the longer the pearl remains in water the greater the chance that it will grow out of round.
Variety of styles
Today, pearls are as much in demand as ever. Available in a wide range of styles and prices, cultured pearls can be affordable or extravagant, classic or ultra-modern. Necklaces have gone way beyond the traditional strands of creamy matched beads your grandmother donned on formal occasions and Muffy wore with her cashmere twin set.
Now there are more haute creations of giant South Sea and Tahitian pearls of wondrous colors, shapes and sizes. They're being mixed with precious and semiprecious stones, antique accents and even leather and rubber.
Pearls are being worn by everyone from the high-fashion hipster to the classic minimalist. Even classic strands are not out of place with jeans and a T-shirt.
"You can wear pearls every day of the week," says Douglas Schubot, CEO of Jules R. Schubot jewelers in Troy, one of the first jewelers in the country to carry South Sea pearls in the 1960s. "You can't wear a platinum diamond necklace every day. We're getting more casual as a society."
Perhaps more so with pearls than other gems, it is critical that a careful buyer be educated about the product. Pearls vary widely in quality and price. The better the quality, the more you will pay. But you could pay a lot for inferior quality if you don't know what to look for.
"Unfortunately, the education about pearls is behind other gemstones or even metals and semiprecious stones," says Asher of the Cultured Pearl Association. "There's minimal knowledge even among jewelers about pearls."
Asher, who also owns a pearl importing company in New York, says consumers are best advised to look for a reputable jeweler who carries a lot of pearls.
The four S's
"With pearls, an educated consumer is going to do better," Asher says. Asher uses what he calls the four S's for determining pearl quality: shine, shape, size and surface.
UShine. Commonly called luster. Luster refers to the quality of the nacre as determined by the amount of light reflected off the gem's surface. Though it is possible for pearls to have thick nacres and low lusters, high-luster pearls usually have thick nacre. High-luster pearls command a stiff premium over duller pearls that may have the same nacre thickness.
UShape. The rounder it is, the higher the value. Most pearl necklaces are off-round. "An oyster has no reason to make a round pearl," Asher says. Often, natural elements will imbed themselves in the forming pearl, which causes the mollusk to secret nacre around the new irritant. The result is an off-shaped -- or baroque -- pearl. Though consumers might find them appealing, they command a fraction of the cost of round ones.
USize. Other qualities being equal, the larger the pearl, the more it will cost. Freshwater pearls generally range in size from 3 mm to 7 mm, Akoyas from 6 mm to 8.5 mm and South Sea and Tahitian pearls around 15 mm. To put that in perspective, 6 mm is about the size of a pea and is roughly the equivalent of a 1-carat diamond. Fifteen millimeters is the diameter of a quarter.
Asher recommends buying the best quality smaller size rather than the lower quality of a larger size for the same money.
USurface. Like most gems, flaws will affect the value. But, because they are so fragile, pearls often have slight imperfections that don't necessarily reduce the value dramatically. But noticeable spots, pits or ringlike markings should not be present on high-end pearls. Pay particular attention to the drill-hole area and make sure there are no cracks or chipping. They will get worse over time.