Most pearls today are cultured. There are two main processes employed: Nucleated Cultivation used for saltwater pearls and Non-Nucleated Cultivation, used for freshwater pearls.
Freshwater pearls being harvested
from a Mussel
The process involves inserting into the oyster a nucleus and a tiny piece of mantle cut from a donor oyster; the nucleus is made with shell taken from a North American mussel grown in the Mississippi River and the mantle is the part of the fleshy oyster lip that secretes the nacre.
Oyster shells are then suspended from culture systems and tended daily by workers who carry out the intensive husbandry required for the next 20 to 24 months.
Pearls are harvested during the months of June and September. Once they have been taken out of the oysters, they are initially sorted, usually by shape and size. The oysters are seeded anew and the cycle begins again.
A healthy oyster can be reseeded as many as four times with a new nucleus.
As the oyster grows and it can accommodate progressively bigger pearl nuclei. Therefore, the biggest pearls are most likely to come from the oldest oysters.
http://www.costellos.com.au/pearls/cultivation.html
Freshwater pearls differ from other cultured pearls, in that the great majority of them are not bead-nucleated. Freshwater mollusks, scientific name Margaritifera margaritifera, are nucleated by creating a small incision in the fleshy mantle tissue of a 6 to 12 month old mussel, then inserting a 3mm square piece of mantle tissue from a donor mussel. Upon insertion, the donor or graft tissue is twisted slightly, rounding out the edges. Some believe that this tissue acts as a catalyst in producing a pearl sac thus making the 'nucleation' actual 'activation'. Others believe the tissue molds with the host to create a pearl sac, while still others maintain the tissue is the actual nucleus. Although it is said that a freshwater mollusk can withstand up to 25 insertions per valve, it is common industry practice to perform only 12-16 insertions in either valve, for a total production of 24-32 pearls. The mollusks are then returned to their freshwater environment where they are tended for 2-6 years. The resulting pearls are of solid nacre, but without a bead nucleus to guide the growth process the pearls are rarely perfectly round.
Bleaching, dying, and polishing do occur. Except for the old Arabic practice of sun-bleaching in the Persian Gulf, naturals were practically never processed. Chinese pearls that are nearly white or mottled are usually bleached to make them whiter and more uniform. With the same methods perfected by the Japanese, the Chinese use a mild bleach, bright fluorescent lights, and heat. They polish surfaces by tumbling pearls in pumice or similar substances. The idea, as always, is to facilitate matching pearls for strands.
The Chinese are nucleating mussels with their own tissue-cultured freshwater pearls, which result in all-nacre round or almost round pearls. Aiming for an even higher percentage of rounds, the Chinese are even reshaping reject freshwater pearls into spheres, then nucleating mussels with them.
http://www.costellos.com.au/pearls/cultivation.html
http://www.costellos.com.au/pearls/cultivation.html
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| The array of natural colors of freshwater pearls |
Bleaching, dying, and polishing do occur. Except for the old Arabic practice of sun-bleaching in the Persian Gulf, naturals were practically never processed. Chinese pearls that are nearly white or mottled are usually bleached to make them whiter and more uniform. With the same methods perfected by the Japanese, the Chinese use a mild bleach, bright fluorescent lights, and heat. They polish surfaces by tumbling pearls in pumice or similar substances. The idea, as always, is to facilitate matching pearls for strands.
The Chinese are nucleating mussels with their own tissue-cultured freshwater pearls, which result in all-nacre round or almost round pearls. Aiming for an even higher percentage of rounds, the Chinese are even reshaping reject freshwater pearls into spheres, then nucleating mussels with them.
http://www.costellos.com.au/pearls/cultivation.html
| Tahitian Pearls | |
Tahitian pearl farming has much later commercial origins than its other cultured pear. Sometime around 1963 the black lipped Pinctada margaritifera was first seeded for pearls. The resulting pearls harvested two years later, were of reasonable quality. This sparked considerable interest in the culture of black pearls and quite a lot of experiments by biologists of growing them in various lagoons of Tahiti and also Bora Bora.
Although Tahitian pearls are thought by many to be solely 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 actually located on the island. The farms are instead scattered throughout French Polynesia, as far east as the Gambier Islands, and beyond French Polynesia to the west into the Micronesian Islands. Australia, the Seychelles and Vietnam have all produced black pearls as well, but those cannot be referred to as Tahitian pearls.
South Seas Pearls
South Seas Pearls are primarily black or white and are grown in the species Pinctada Maxima in deep ocean waters. White pearls are grown in the water of Indonesia, the Northern Coast of Australia and the Philippines. Their colors range from white and silvery blue to pale gold - the golden or light-yellowish varieties abound in Philippine and Indonesian waters while white or silvery hues occur mainly in Australian waters.
Pearls from the black group, among which is the legendary black pearl of the South Pacific, are most frequently found over a wide area stretching from the Cook Islands, eastward through Tahiti to the Tuamotu Archipelago and the Gambier Islands in French Polynesia.
Golden Pearls
The highly esteemed golden pearl commands an even higher price than their Tahitian and Japanese counterparts primarily because of its rarity.
The mantle of this bivalve shell, the gold lipped Pinctada Maxima, gives the pearl its rich color. Depending on where it was cultivated, the shell produces pearls of various colors, from silvery white to golden yellow.
After the nucleation procedure, the oysters, placed inside baskets, are returned back to the waters at a depth of 10 feet so as to protect them from predators. It takes two to three years to produce a pearl. During this period, the oysters are turned everyday to achieve the roundness of a gem, and the baskets are cleaned every month.
For pearl farming, it is absolutely crucial to cultivate pearls in pristine waters, so as to maintain stability in the ecosystem.The constant culturing of pearls in an area will eventually weaken its environment so sites must be frequently relocated. It takes approximately six years to produce a quality harvest.
Akoya Pearls
Akoya pearls are formed by Akoya oysters from Japan,
Fucata Martensi. Relatively small, measuring only 6 to 8 centimers across, Akoya pearls range from about 2 millimeters to 11 millimeters in size with the most common pearl size at 7 millimeters. Akoyas are known for their luster which is said to be caused by the cooler waters that the molluscs are grown in. Because the cooler waters promote slower growth the nacre’s luster is particularly impressive compared to other types of pearls.
Pearl farmers implant a “bead” of mother-of-pearl ( the stuff that covers the inner surface of the mollusc ) together with some mantle tissue into the mollusc’s gonads. This will irritate the mollusc and will begin to cover the irritant with layer after layer of nacre. Nacre is the pearly substance the constitutes most of the pearl. Only about half of the mollusks survive this operation. Akoys Pearl Mollucks in farms may also die well before the 9 t 18 months required for them to produce a normal sized pearl. Disease, storms and other factors contribute to the high mortality rate. For those that survive long enough only about 3% produce high quality pearls. Japanese Akoya pearls maintain this very high standard of quality while Chinese made Akoyas may be less stringent about quality.
Pearls from the Sea of Cortez
 http://youtu.be/qKhbuaPH-_8 http://youtu.be/rVjnnYtdego With special thanks to Perlas del Mar de Cortez http://perlas.com.mx/en/ |
