Tahitian Cultured Pearls

It’s hard to imagine, but the first commercial harvests of black Tahitian cultured pearls occurred just 37 years ago, in 1965. Only the Tahitian pearl has the very dark gray (black) body color with orient. Grown from the black-lipped oyster, the Pinctada margaritifera cumingi, Tahitian cultured pearls grow from 8 mm up to 18 mm, beautifully round, with high luster and durable thick nacre. Only now are other South Pacific Islands beginning to harvest black pearls that could rival the Tahitian cultured pearl.

History and romance. There isn’t a gemstone on earth found in a more exotic place than the Tahitian cultured pearl. Known to Western civilization since the mid-1700s, the Tahitian pearl was first seen by European explorers navigating their way through what is now called French Polynesia.

Tahiti … Bora-Bora … Moorea. The approximately 120 exotically named islands and atolls played host to plenty of pearl-bearing oysters. The natives, not having the tools to drill pearls, wore the shells; mother-of-pearl became a chief export of the islands up until the 1960s, when over-harvesting brought the pearl oyster to near-extinction. Natural pearls were harvested and traded for centuries but now are quite rare. It wasn’t until after World War II that pearl culturing began to take hold in earnest.

All pearls are the birthstone for those born in June. But by the time one gets to wear an 18-in. strand of 18-mm peacock-green Tahitian cultured pearls, many birthdays have more than likely passed.

Qualities. The clean ocean waters of the lagoons in and around the islands and atolls contain much warmer waters than the pearl-oyster beds in and around Japan. This warmer water allows the giant mollusk to thrive and allows nacre deposition to be fast and thick—and it’s this thick nacreous layering that is responsible for the pearl’s durability. Pure water with plenty of plankton is critical for growing oysters, and the waters of French Polynesia are still close to perfect. However, increased production and bigger harvests over the past decade have sparked concern that pollution may be hindering the production of the larger top-quality pearls.

The Tahitian cultured pearl is a bead-nucleated product; there are no all-tissue-nucleated Tahitian pearls. Typical sizes for Tahitian cultured pearls range from 9 mm to 14 mm, but they can grow smaller and larger—up to 20 mm. Size depends on the size of the bead and the length of time it’s left in the oyster. At one time, only one pearl was harvested from a mollusk, which grew 2 mm of nacre (an increase of 4 mm to the diameter) around the implanted bead. It took about three years.

Today, two or three harvests will be made from the same mollusk in the same amount of time, yielding more pearls, but with thinner nacre. Since .6 mm of nacre is the minimum required by Tahitian governmental policies, a pearl might be harvested as early as 12 months after implantation. This has led to the recent oversupply of loose Tahitian cultured pearls (more than 10 tons in 2001) and accounts for the major decline in prices over the past five years—from $32 per gram in 1995 to $13 per gram in 2000. (See “Too Many Tahitians?” JCK, Oct. 2001, p. 98.) New regulations beginning July 1, 2002, set the minimum thickness at .8 mm, adding four months to the growth process. The government suggests that oysters remain in the lagoon for a minimum of 18 months.

Like all pearls, the Tahitians are graded on a number of factors, including size, orient (iridescent colors), luster (shine), color (cream, peacock green, aubergine [eggplant], blue, pink, golden, silver, copper, and, of course, black), shape (round, semi-round, baroque, drop, circled, or ringed), and surface (smoothness).

Enhancement. Most Tahitian pearls have all natural color and luster. Sometimes luster is enhanced by tumble polishing. Faceting Tahitian pearls is becoming popular now that lower-quality pearls are available, but you wouldn’t dream of faceting a high-quality Tahitian pearl.

Pricing. Tahitian cultured pearls are priced as single pearls. Prices for necklaces are said to be negotiable. For fine-quality strands, figure that it will be priced per pearl, times the number of pearls. For single pearls of 12 mm to 12.5 mm in fine quality, prices range from $425 to $600 per pearl. Matching pearls will cost more than just doubling the single pearl price.

Care and cleaning. As with all pearls, only a soft cleaning cloth, a chamois, should be used to wipe them clean. Washing pearls is no longer recommended. Typically, it’s the silk string that is dirty, so the strand should be restrung rather than cleaned.

All pearls can be damaged by chemicals, so the rule is that when getting ready for an evening out, pearls go on last, after cosmetics, hairspray, and perfume. Pearls also should be the first to come off, and then should be wiped clean. And even though you see native Tahitians wearing pearls and swimsuits, pearls should never be worn to the pool or to the beach. Perspiration, as well as body oils containing natural acids, can damage the luster of a pearl. Remember, swimming pools are chlorinated: Chlorine is an acid and will dissolve a pearl.

Protect pearls from other jewelry, including other pearls, even on the same strand. Nacre is made up of tiny crystals of aragonite and calcite. This makes them gritty like sandpaper—and thus potentially damaging to each other—and is the reason for the old “tooth test.” Pearls are individually knotted on strands for two reasons: First, to keep the pearls from sliding off if the strand breaks, and second, to protect them from rubbing against their neighbors.

Bench repair and setting. Always remove the pearl before doing any type of work. Pearls are easily scratched and can be damaged by harsh chemicals used at the bench.

Recommended reading. For more information, see: GIA’s Pearls Course, 1999, GIA, Carlsbad, Calif.