Beads & Baubles Cafe

Black Tahitian pearls are produced by the black-lipped oyster (Pinctada margaritifera) in the islands of French Polynesia. The oyster itself is quite large — sometimes up to 12 inches across and weighing as much as 10 pounds — which often results in much larger-than-average pearls. The pearls are unique because of their natural dark colors. Most “black” Tahitian pearls are not actually black, but are instead gray, silver, charcoal, or similar shades. Truly black pearls are extremely rare. The black-lipped oyster’s mother-of-pearl inner shell is also extremely attractive. Indeed, by the early part of the 20th century, before conservation and repopulation efforts began, the oyster had almost been hunted to extinction for its shell alone.  Although Tahitian pearls are thought my many to be a product of Tahiti this is in fact not true. Tahiti is the commercial center and trading hub for the bulk of the industry, however Tahiti does not have any pearl farms located on the island. The farms are instead scatted throughout French Polynesia, as far east as the Gambier Islands, and beyond French Polynesia to the west into the Micronesian Islands.  Tahitian pearl farming has much later commercial origins than its other cultured pearl cousins. In the early 1960′s a man by the name of Jean-Marie Domard began experimenting with the Pinctada margaritifera using Japanese culturing techniques. In 1962 Mr. Domard successfully nucleated 5000 oysters, and after 3 years harvested more than 1000 high-quality Tahitian pearls.  In an attempt to capitalize on this success, two brothers from the Manihi Atoll founded French Polynesia first Tahitian pearl farm just a year after Mr. Domard’s harvest. They started with the easier-to-cultivate mabe pearls for the first two years, and then switched entirely to spherical cultured pearls in 1968.

So-called “conch pearls” (pronounced “konk”) contain no nacre, so technically they are not actually pearls at all. Instead, the gems are calcareous concretions, similar to kidney stones in humans. They are produced by the Queen conch mollusk (Strombus gigas), which lives primarily in the Caribbean near southern Florida.
 
No one has yet devised a method for culturing conch pearls, so every one you see will be a natural pearl. Therefore, they are extremely rare and valuable. It is estimated that only one in 10,000 conchs produces a pearl, and that less than 10 percent of those are of gem quality.
 
Conch is harvested by fisherman for their meat not for the pearls they occasionally find. The pearls tend to be “by-products,” discovered by the fishermen as they harvest and clean their catch. 

 A pearl is formed when some sort of small object or irritant becomes embedded in the tissue of an oyster or mollusk. In response, the mollusk secretes nacre, a combination of crystalline and organic substances. As the nacre builds up in layers, it surrounds the irritant and eventually forms a pearl. Natural pearls are those pearls which are formed in nature, more or less by chance, by a parasite or a piece of food lodging itself in the gonad or mantle tissue of a host oyster. Cultured pearls, by contrast, are those in which humans give a helping hand. By actually inserting a foreign object into the tissue of an oyster or mollusk, pearl farmers can induce the creation of a pearl. The same natural process of pearl creation takes place. The only difference is that in the one case, the process was begun accidentally; while in the other case, it was begun intentionally. Cultured pearls of today are primarily the result of discoveries made in the late 19th and early 20th centuries by Japanese researchers, most notably Kokichi Mikimoto (see our article on Akoya pearls for more information on Mr. Mikimoto). Although some cultures have long been able to artificially stimulate freshwater mollusks into producing a type of pearl, the pearls produced in this way were generally hemispherical mabes*, rather than actual round pearls. What Mikimoto discovered was a specific technique for inducing the creation of a round pearl within the tissue of an oyster. This discovery revolutionized the pearl industry, because it allowed pearl farmers to reliably cultivate large numbers of high-quality pearls. In contrast to natural pearls — which have widely varying shapes, sizes, and qualities, and which are difficult to find — cultured pearls could be “designed” from the start to be round and primarily flawless. The oysters could be monitored during the several years required for each pearl to become fully formed, thus better insuring their health and survival. And the pearls could be grown by the tens of thousands, thereby bringing their cost down to a point where pearls became accessible to large numbers of people around the world. In short, the development of cultured pearls took much of the chance, risk, and guesswork out of the pearl industry, allowing it to become stable and predictable, and fostering its rapid growth over the past 100 years. Today the cultured pearl industry has effectively replaced the natural pearl industry, turning the natural gems of old into collectors’ pieces.  Cultured pearls can often be distinguished from natural pearls through the use of x-rays, which reveals the inner nucleus of the pearl.  

*mabes - A mabe is a hemispherical shaped pearl which is grown against the inside of the oyster’s shell, rather than within its tissue. Mabes occasionally appear in nature. Cultured mabes are grown intentionally, by using a hemispheric nucleus, rather than a round one; and by implanting it against the oyster’s shell, rather than within its tissue. The pearl then develops in a hemispheric form, with a flat back. While in the oyster a mabe pearl is actually considered a blister pearl not a mabe pearl. After the blister pearl has been ‘worked’ it then becomes a mabe pearl. Blister pearls are worked by cutting the pearl out of the shell with a circle-bit drill. The nucleus is then removed and replaced with a resin. The back of the pearl is capped with a piece of mother-of-pearl to complete the mabe pearl. Cultured mabes are used for such things as rings and earrings, rather than for stringing on necklaces. They tend to be very beautiful with high luster and orient, but are priced much lower than round pearls.