What Makes a Black Pearl Black?
The pearl, treasured since the days of the ancient Chinese Emperors, begins with the gemological equivalent of spinach between teeth. All mollusks create pearls as part of a defensive mechanism using the same process that they use to coat the inside walls of their shells. The finest pearls grow in oysters; only a few oysters grow perfect pearls and of those, only one type grows black pearls. Does this Spark an idea?
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The Pearl Oyster
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Pearl oysters are bivalve, filter-feeding mollusks from the family Pinctada. Pinctada Margaritifera is the pearl oyster that parents black pearls. These tender little marine animals have a two-piece shell connected by a bit of muscle that separates its edges so that water can flow inside. The creature filters out plankton and other organic fare as the seawater washes through.
Mother of Pearl
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The pearl oyster builds its shell with minerals digested from seawater and coats the inside of its shells with several layers of materials. The luminous inner lining is called nacre and is often used for buttons. Each type of mollusk creates a slightly different coloration of nacre that is genetically determined. Color is not the result of environment; conches, for example, create pink pearls. The mollusk attacks bits of organic matter that catch on the lining by coating them with nacre. The foreign object grows as nacre is layered on and irritates the creature further; the irritant becomes a pearl in two to three years.
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The Black Pearl Oyster
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Pinctada Margaritifera pearl oysters produce an iridescent black nacre radiating from the valve and lining the lips around the shell. Colors of finished pearls range from silver-gray to anthracite black. Natural black pearls are each unique; "seed" objects (irritants) differ and the pearl’s coloration varies according to where they lodge.
Geography
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P. Margaritifera live in Pacific Ocean waters around Papua New Guinea, Australia, French Polynesia, Indonesia and Japan. They also live in the Southwestern part of the Indian Ocean near the Andaman Islands, Persian Gulf and Red Sea. Cooperatives in French Polynesia and the Cook Islands specialize in black pearl production; the semi-annual auctions in Tahiti export about 60,000 pearls. The entire area produces about a million pearls a year.
Culturing Black Pearls
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Because of scarcity due to over-harvesting, culturing programs began in Bora Bora in the 1960s. Cultured black pearls are seeded with mussel pearls harvested on the Upper Mississippi. The exclusive use of the mussel pearls allows growers to start a crop of pearls with seeds chosen for uniform size and perfect shape, ensuring a profitable harvest. Oysters are seeded at the same time, and send their lives in baskets where pearl farmers can control their diets and keep them clean. The delicacy of the black pearl oyster and high level of skill required to culture black pearls limits the number of pearls produced.
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References
Resources
- Photo Credit golden bracelet and black pearl necklace on white image by Steve Mann from Fotolia.com
