Flywing. Eggplant. Champagne. Peacock.

Ingredients in some witch’s mysterious brew? Hardly. They are but a few of the terms used to describe the hues of Tahiti’s impressive and precious jewel of the sea, the black pearl, also known as Poe Rava.

People from all over the world travel to Tahiti and the other French Polynesian islands in search of the perfect black pearl. They come prepared to spend hundreds and perhaps thousands of dollars on a pearl or string of pearls that whispers its secret to them.

One of those secrets is that at the heart of virtually every black pearl lies a spherical pea-sized nucleus fashioned from the shell of a Tennessee or Mississippi River shellfish.

Seeing the fervor of today’s shoppers, it’s hard to believe that little market existed for black pearls a mere 40 years ago. The shell of the black-lipped oyster, Pinctada margaritifera, actually held more value than the pearl the oyster could produce.

Historically, the black-lipped oyster abounded in the crystalline lagoons of French Polynesia, that magical sprinkling of islands about halfway between Australia and South America. Polynesians traditionally used the oyster’s shell for ceremonial jewelry, fishhooks and lures. They later traded the shell to the Europeans, who used it to create mother-of-pearl buttons and pearl-inlaid furniture.

Pearls themselves are nature’s byproduct. If a sand grain or coral fragment lodges in an oyster, the mantle’s epithelial cells secrete a substance to isolate the invader. Layer upon layer of the secretion eventually produces a pearl. Skin divers once descended up to 100 feet to find pearl-producing oysters.

Between 15,000 and 20,000 oysters would be opened before a single pearl was found, and tribal chiefs usually kept the precious item for their own use.

With overexploitation of natural oyster beds and the collapse of the button industry in the 1960s, interest quickly turned to commercial pearl production. By the 1970s, the French Polynesians were using Japanese techniques to culture black pearls.

Here’s the secret of how it’s done.

First, the pearl farmer catches tiny seed oysters known as spat and places them in collectors, which are suspended from rearing lines in a lagoon’s protected waters. The farmer methodically pulls up and cleans the growing oysters, which are ready for seeding when they are about 3 years old.

A technician then sacrifices a healthy donor oyster, snipping its mantle into about 50 pieces. The technician inserts a mantle fragment and the spherical nucleus made of shell into another oyster’s reproductive organ, or gonad. The grafted mantle forms a sac around the nucleus and secretes concentric layers of mother-of-pearl, also called nacre. Nacre is composed of conchiolin, which is a scleroprotein, and calcium carbonate, usually in the form of aragonite.

The seeded oysters are lowered back into the lagoon, and the nacreous layers thicken around the nucleus. The oysters are generally harvested between 18 months and two years after grafting. The longer the growth period, the bigger the pearl.

No two pearls are exactly alike, and farmers still don’t know the secret of how to produce a specific color at will. Color is affected by the graft from the donor oyster, the mineral salts in the water, the degree of salinity, the plankton on which the oysters feed and the temperature of the water.

Although divers no longer jeopardize themselves in search of oysters, modern pearl farming is still a risky business. Of every 1 million oysters raised, only one in five will survive to be seeded. Of every 100 oysters seeded, one-fourth will die and one-fourth will reject the seed. Only 50 of the remaining oysters will produce a pearl, and only five of those pearls will be perfect.

What’s the secret of a perfect pearl? It catches your eye. It calls to you. It whispers your name.

Shape is perhaps the first characteristic that draws the eye. Most people think of the perfect pearl as round, and it is indeed the round pearl that fetches the highest price. Other shapes include semi-round, ringed, semi-baroque and baroque. Semi-round pearls are imperfect spheres, while ringed pearls feature streaks, rings or grooves. Semi-baroque pearls come in drop, button, pear or oval shapes. Baroque pearls are asymmetrical, with no clear axis of rotation. Designers capitalize on the myriad shapes to create unique and dazzling pieces of jewelry, often fashioned in gold and platinum.

Color is more a matter of taste than of real importance, and the “black” of black pearl is generally a misnomer. Colors range from pearly white, metallic silver gray and aubergine to gold, pink, blue and deep purple. Peacock green tends to be the most desirable and the most expensive shade. Po? Rava, the term Tahitians use for the black pearl, means “black with green reflections.”

Size also helps to determine price, and the bigger the pearl the more it costs. The diameter of marketable pearls generally ranges from 7 to 18 millimeters. Anything over 11 is considered large, with pearls over 20 millimeters being the most expensive.

Luster and orient are additional factors that contribute to a pearl’s value. Luster is the pearl’s mirrorlike shine, while orient refers to the pearl’s inner glow. Look for the bright and sharp reflections you would associate with a shiny metal object.

Surface quality, too, is important. You can buy an imperfect pearl and set it to hide its blemishes, but the smoother its skin the more valuable the pearl.

If black pearls don’t turn you on, consider shopping for such lesser known and generally less expensive products such as keshi and mabe.

Keshi is pure mother-of-pearl without a nucleus. An oyster sometimes rejects the nucleus, but its graft continues to secrete nacre. The resulting pearl tends to be baroque in shape and is most often used in earrings, necklaces or bracelets.

Mabe is a blister pearl, formed when a technician attaches a hemispheric nucleus to the inside lip of the mother shell. The half-nucleus may be round, oval, tear drop or heart-shaped. After layers of nacre cover it, the nucleus is removed. Epoxy resin is poured into the hollow mabe, which is sealed with a mother-of-pearl plate. Mabe is generally used for earrings, pendants, brooches and cuff links.

If you choose to buy black pearl, here are some secrets to help you care for them. Pearls require neither cutting nor polishing, but they are not as hard as precious stones. Pearls that are constantly worn can eventually become barrel-shaped and lose their luster. Because they contain protein and water, they can also dry out and crack.

Keep pearl away from chemicals, hair spray, perfume, dishwashing liquid, and such acids as vinegar and lemon juice. Avoid exposure to hard abrasive objects, and store your pearls separately from jewelry pieces that may scratch them.

To keep your pearls fresh and looking new, dampen them occasionally with lightly salted water. Rinse and dry them, then rub them with a soft cloth impregnated with a drop of olive oil.

Should you decide to visit the French Polynesian islands and coral atolls in search of black pearls, here are some secret tips to help you shop.

You might be able to buy pearls at a better price from pearl farmers or shop owners on the islands, but the best pearls tend to go to market in Papeete, Tahiti. Cooperatives offer pearls in lots to be sold at auction to big-name buyers overseas. You will find gorgeous pearl jewelry in Tahiti, but don’t count on getting any real bargains.

Buy from a reputable dealer, not a street vendor. Wherever you buy, get a receipt and certificates of origin and authenticity.

And here’s a final secret that may entice you. Believe it or not, you won’t have to pay import duty on your black pearls when you come home through U.S. customs.

Happy shopping.

Beth Parks lives in Corea. She recently toured in French Polynesia. For more information about black pearls and French Polynesia, visit www.geocities.com/tomcruises.