Thursday, March 12, 2009

Akoya Pearls

Akoya pearls are cultured in the Pinctada fucata martensii, also known as the akoya oyster. This mollusk is found and farmed primarily in Japan and China. Renowned for their luster, akoya are considered the classic pearl. They are generally white or cream colored, with overtone colors of rose, silver, or cream. The akoya oyster is the smallest pearl-producing oyster used in pearl culture today, so akoya pearls also tend to be small, ranging in size from about 2 to 11 millimeters. They also tend to be the most consistently round and near-round pearls, making them ideal in terms of matching for multi-pearl jewelry such as strands and bracelets.

Thursday, March 5, 2009

Freshwater Pearls

Freshwater Pearls differ from other cultured pearls, in that the great majority of them are not bead-nucleated. Freshwater mollusks 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, (graft) tissue is twisted slightly, rounding out the edges. What happens after this point is really just speculation. 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.

Saturday, February 28, 2009

South Sea Pearls

South Sea pearls are among the largest commercially harvested cultured pearls in the world. The average size of a South Sea pearl is 13 mm, with most harvests producing a range of sizes from 9 mm to 20 mm. The South Seas lie between the northern coast of Australia and the southern coast of China. These waters are the native habitat of a large oyster known as Pinctada maxima. This oyster grows up to 12 inches in diameter, and can be nucleated with a much larger bead than other saltwater oysters such as the akoya. There are two varieties of Pinctada maxima, the silver-lipped and the gold-lipped. The two are distinguished by their distinct coloration of the outer edge of the interior. This type of shell is also known as mother-of-pearl, and is responsible for the coloration of the cultured pearls produced, therefore the name. Unlike the akoya oyster, the South Sea oyster will only accept one nucleation at a time. The oyster is nucleated when it is only about half developed, from 4.7 inches to 6.7 inches in size, or about 24 months old. Although the South Sea oyster will only handle one nucleus at a time, this oyster (like the Tahitian pearl producing Pinctada margaritifera) can be nucleated up to three times over the course of many years.The South Seas are also extremely clean, and filled with plankton – the Pinctada maxima's favorite food source. The clean waters and abundant food supply also speeds the nacre production. The growth period for South Sea pearls is also substantially longer than that of the akoya. Akoya pearls are harvested after only 9-16 months, where as South Sea pearls are harvested after a minimum of two years allowing for a larger size. South Sea pearls have several distinct characteristics that are unique to this gem. The nacre is unusually thick, ranging from 2 - 6 mm, compared to the 0.35 - 0.7 mm of an akoya pearl. South Sea pearls have a unique, satiny luster that comes from the rapidly deposited nacre and warm waters of the South Seas. South Sea pearls also have a subtle array of colors; typically white, silver, and golden, that are rare in other pearl types.

Tahitian Pearls

Tahitian pearls are produced in the black-lipped oyster ‘Pinctada margaritifera’, in and around Tahiti and the French Polynesian islands. This oyster itself is quite large - sometimes over 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 silver, charcoal, or a multitude of colors with the dominant color being green. Truly black pearls are among the most beautiful pearls in the world, and are extremely rare. Not only are the pearls beautiful, but the black-lipped oyster's mother-of-pearl inner shell is also extremely attractive. 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.


Almost any shelled mollusk can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within the mollusk's mantle folds, but the great majority of these "pearls" are not valued as gemstones. Nacreous pearls, the best-known and most commercially-significant pearls, are primarily produced by two groups of molluscan bivalves or clams. A nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell. A "natural pearl" is one that forms without any human intervention at all, in the wild, and is very rare. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened, and thus killed, in order to find even one wild pearl, and for many centuries that was the only way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. A cultured pearl, on the other hand, is one that has been formed on a pearl farm. In modern times however, almost all the pearls for sale were formed with the aid of human pearl farmers. The great majority of pearls on the market are cultured pearls.