Passion for pearls

Fresh water pearls
Although the traditional source of pearls has been oysters which live in saltwater, mollusks which live in freshwater lakes and rivers can also  produce pearls. China has harvested freshwater pearls for many a millennia. The  first record mentioning pearls in China was from 2206 BC. The United States was  also a major source of freshwater pearls from the discovery of the New World up  through the 19th century, when over-harvesting and increasing pollution significantly reduced the number of available pearl-forming mussels.

Freshwater pearls are often somewhat less lustrous than their salt water counterparts. However, they appear in a wide variety of shapes and colors, and they tend to be less expensive than  saltwater pearls, making them quite popular. Freshwater pearls are also quite durable, resisting chipping, wear, and degeneration.

Freshwater pearls differ from other cultured pearls in that they are not bead-nucleated. Freshwater mollusks are nucleated by creating a small  incision in the fleshy mantle tissue and inserting a piece of mantle tissue from another oyster. This process may be completed 25 times on either side of the  mantle, producing up to 50 pearls at a time. 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 round.

In recent years the Chinese have been able to take the art of  culturing freshwater pearls to new levels. In the last decade the quality of  pearls produced have become so high that many pearls in the top percentage of a  harvest are nearly indistinguishable of their saltwater relatives. Gone are the rice-shape seed pearls as they are now being replaced with round, lustrous pearls of sizes as large as 16mm, mimicking large South Sea pearls. This has created a renewed interest in freshwater pearls as an affordable alternative to the higher priced saltwater.

The Japanese have a distinguished history of culturing freshwater pearls as well. Lake Biwa was once world renowned for producing high-quality freshwater pearls. However, in the mid 1970's pearl farming all but came to a  halt due to pollution in this lake that was once synonymous with freshwater  pearls. Today the Japanese are trying once again to farm freshwater pearls in Lake Kasumigaura, utilizing a bead-nucleated hybrid mussel ( Hyriopsis Schlegeli anadonata/plicata hybrid mussels). The resulting pearls have been quite large  and unique. But due to the high prices of such pearls the market remains a niche for collectors.

Fresh water vs. Akoya

Freshwater and Akoya pearls, while both genuine pearls, differ greatly in value and  composition. The three main differences are the culturing process, the nucleus, and the shape.

Fresh water pearls are mantle-tissue nucleated, whereas Akoya pearls are bead-nucleated.  Instead of inserting a mother of pearl bead and a  piece of mantle tissue into the gonad of a freshwater mollusk as is the process  with an Akoya oyster, only a piece of mantle-tissue is used, and this is inserted into the mantle tissue of the freshwater mollusk, not the gonad. The result is a pearl composed of solid nacre, and the mantle tissue is eventually  dissolved or drilled out.

Fresh water pearls are nucleated in the mantle tissue which is on either side of the oyster. This tissue is much larger than the gonad of an Akoya oyster. Therefore the freshwater mollusk can be nucleated up to 25 times on either side, for a total of 50 nucleations. An Akoya oyster, on the other hand, can handle a maximum of 5 nucleations in its gonad, but very rarely is nucleated with more than 2 beads at a time. So upon harvest, a freshwater mollusk may produce up to 50 pearls at a time, while the Akoya oyster has a maximum production of 2.

Freshwater mollusks are also much easier to farm. The mortality rate is much lower than that of the nucleated Akoya oysters, and fresh water farms rarely deal  with natural disasters such as typhoons and red tides that plague Akoya pearl farms.

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 13mm, with most harvests producing a  range of sizes from 9mm up to 20mm.

The South Seas lie between the northern coast of Australia and the southern coast of China. These waters are the native habitat of the large  oyster, the 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 the coloration of the outer edge  of the interior. This shell is also known as mother of pearl, and is  responsible for the coloration of the cultured pearls produced.

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.

There are four reasons South Sea pearls can grow to such large sizes dwarfing many of their other salt water pearl counterparts.  The reasons consist of: the large size of the Pinctada maxima, the size of the implanted bead, the length of time the pearl is left to grow in the oyster, and  the oyster¡¯s environment. Due to the size of the oyster it is able to accept a large bead. The gonad of the Pinctada maxima is several times larger than that of the Akoya. Because of this same reason the South Sea oyster deposits nacre around the nucleus at a much quicker rate, especially in warm water which speeds the oyster¡¯s metabolism. 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  at least 2 years.

South Sea pearls have several distinct characteristics that are  unique to this gem. The nacre is unusually thick, ranging from 2-6mm compared to the .35-.7mm of an Akoya pearl. South Sea pearls  also have a unique, satiny lustre 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.

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