by Rose Mueller G.G., CGA
The book 18MM Blue by Gerald Browne was a literary hit. People praised him for his investigation of the subject of pearling. I read the book and immediately realized even Browne missed the origin of the black pearl. He confused the PINCTADA MARGARITIFERA with the PINCTADA MAXIMA. Even so, Browne is correctthat the pearl is rare, exotic, sensuous and mysterious.
The PINCTADA MARGARITIFERA is the mollusk, or oyster, that produces the black pearl. It is of interest that the pearl produced can take on any of the colors of the shell. This particular oyster is commonly referred to as the black-lipped oyster. It can produce pearls that are blue, grayish white, gray, green, purple, bronze, pink, copper, gold and greenish-black. There is no true black. The color of the pearl produced depends on the color of the lining of the shell. The Tahitian word is "poe rava", greenish black.
The black-lipped oyster does not grow off the island of Tahiti. It is found in the outer islands of French Polynesia, including the Gambier islands and the Tuamoto Archipelago.
Many have visions of bare-breasted women diving, risking their lives to recover the black-lipped oyster, hoping for the best of finds, the largest and most luminous of pearls. Until the mid 1800's this was basically the story.
When Isabella gave Columbus a directive to secure pearls from the New World, natural pearls were quickly depleted in the Americas. The Europeans soon discovered French Polynesia where they found the lustrous gifts of the sea. The black-lipped oyster became harder to find. The Ama, or diver, went greater distances from shore and to greater depths to fulfill the new-found need for the pearl. Many died, many became ill with the effects of "the bends". By 1960, only four natural pearls were found in French Polynesia.
A natural pearl forms by chance. There is no scientific evidence to support the grain of sand theory. Most probably, the irritant, or nucleus of the natural pearl, is a parasitic worm. The intruder brings a piece of mantle tissue with it. This secretes the mother of pearl. A pearl is composed of calcium carbonate. By definition it must be formed by a mollusk that has a mother of pearl shell lining. Nacre is on a pearl, mother of pearl is on a shell. A cultured pearl is a direct result of man's assistance. It is likened to artificial insemination. A bead formed from the shell of a pigtoe clam from the Mississippi River is inserted along with a piece of epithelium into the gonad of the oyster to form one cultured pearl. Only X-radiography can definitively determine whether a pearl is natural or cultured.
In 1965, the Rosenthal brothers began the cultivation of the PINCTADA MARGARITIFERA in French Polynesia. This began the most important industry in French Polynesia. and gave us back the black pearl. These oysters can be 8" in diameter, weigh 11 pounds and live up to 30 years. They can be nucleated up to four times in a lifetime.
It seems as though there should be no limit to the number of oysters with pearls. However, as with any form of gardening there are problems. There are the natural predators of the seas, typhoons, red tides, polluted waters, aborted nuclei. The grafting success rate is never greater than 40 percent. It takes 15 years for a pearl farm to become profitable. Although the romance of the growth and harvest is gone, the romance of the pearl itself is not. Now the shells are drilled and hung from ropes in protected areas where scuba diversconstantly monitor the crops, weather systems are watched and red tides infestations monitored.
Pearls come in many shapes. Farmers always tries for a perfectly round pearl. This occurs seldom. There are baroque or circles, semi rounds, drops, and sometimes the coveted round.
The size of the black pearl ranges from 8.00 to 13.00 millimeters. It is rare to find one over 12.00 millimeters. The South Sea Pearl is larger than the Japanese akoya, as a Japanese akoya rarely reaches 9.00mm in size.
The luster is the reflection of a light from the surface of the pearl. It is the glow. If it is free of blemishes, smooth with no pits or scars, it is flawless. Rarely does a perfectly round, flawless, 12.00 mm pearl with high lustre exist. This is the reason they are so costly.
The size, shape and quality of the pearl determine its price. Only a limited number of jewelers have a working knowledge of pearls. Realizing the pearl's importance, the Gemological Institute of America teaches a single course devoted solely to pearls.
French Polynesia produces other pearls. The Keshis are small, natural pearls usually baroque in shape. They are the by- product of the nucleation process. The Mabe is the only assembled, cultured pearl. To make a Mabe Pearl a nucleus or bead is placed on the shell. The nacre forms on the bead. After growth it is extracted with the bead pulled, the cavity filled and a mother of pearl shell is glued to the back. A Blister pearl is the Mabe with part of the mother of pearl shell attached.
The pearl is the oldest of the gemstones. Only the pearl, amber, coral and ivory are classified as organic gemstones. The folklore of all cultures has always associated the pearl with the moon. It is likened to its glow, its roundness. It was once believed to have been born of the moon. It still is used as a beauty aid and for medicinal purposes. Each pearl is unique unto itself. Given the many shapes and sizes of the pearl, an artisan is limited only by his or her imagination.
About the author: Rose Mueller is a Graduate Gemologist (GIA) and Certified Gemologist Appraiser (American Gem Society). She has a BA in Anthropology from the University of Montana. She and her husband, Lornie, own and operate Lithos Jewelry in St. Petersburg, Florida.
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