Cultured freshwater pearls are pearls that are farmed and created using

freshwater mussel Freshwater bivalves are one kind of freshwater mollusc, along with freshwater snails. They are bivalves that live in fresh water as opposed to salt water, which is the main habitat type for bivalves. The majority of species of bivalve molluscs l ...

s. These pearls are produced in Japan and the United States on a limited scale, but are now almost exclusively produced in China. The U.S.

Federal Trade Commission The Federal Trade Commission (FTC) is an independent agency of the United States government whose principal mission is the enforcement of civil (non-criminal) antitrust law and the promotion of consumer protection. The FTC shares jurisdiction ov ...

requires that farmed freshwater pearls be referred to as "freshwater cultured pearls" in commerce. Quality of cultured freshwater pearls is evaluated through a grading system of a series of A values, based on luster, shape, surface, colour and matching.

Current and historic industry

Pearls gathered in the wild from the Holarctic saltwater pearl mussel were important sources of pearls for modern jewelry, with Scotland a major source; this species is now endangered in most areas. Although the Japanese freshwater pearl industry has nearly ceased to exist, it has a normal historic place as the first country to cultivate whole freshwater pearls, which it did in Lake Biwa, using the Biwa pearly mussel ('' Hyriopsis schlegeli''). The industry attempted a comeback with a mussel hybrid (''Hyriopsis schlegeli''/''Hyriopsis cumingi'') in Lake Kasumigaura in the last decade, but this venture also met with failure, with production ceasing in 2006. The pearl farm in Tennessee also holds special historic value as it is the only source of freshwater pearls outside of Asia. Founded by the late

John Latendresse John Robert Latendresse (July 26, 1925 in South Dakota – July 23, 2000) was an American collector, known for being the "father of American cultured freshwater pearls" - USGS. He left home at 13, and lying about his age, joined the U.S. Marin ...

, it continues as a tourist attraction. Today China is the only commercial producer of freshwater pearls, producing 1500 tons (2005) {{cite web , url=https://www.was.org/Meetings/AbstractData.asp?AbstractId=14278 , title=World Aquaculture Society abstract data , accessdate=2008-11-05 , url-status=dead , archiveurl=https://web.archive.org/web/20070927003920/https://www.was.org/Meetings/AbstractData.asp?AbstractId=14278 , archivedate=2007-09-27 Aquaculture in China - Freshwater Pearl Culture using the tetragon shell mussel (''Hyriopsis cumingii'') and several hybrids that have shown heterosis from several mussel species.

Grafting

The grafting process begins by choosing a suitable donor mussel and cutting a strip of tissue from the mantle. This strip of tissue is then cut into three-millimeter squares. These squares are delivered to a technician who performs the operation. Unlike saltwater bead nucleation, this process is not considered difficult, and technicians need only minimum training to perform the operation. The technician creates small incisions on the upper valve, and inserts the tissue piece. A small twist of the tissue upon insertion is believed to create a higher ratio of round pearls. After the maximum number of grafts have been performed, the mussel is flipped, and the procedure is performed once again on the other valve of the shell. Chinese freshwater mussels were once grafted up to 50 times per shell, or 25 times per valve. This practice was common when the industry mussel was primarily the cockscomb pearl mussel (''

Cristaria plicata ''Cristaria plicata'', the cockscomb pearl mussel, is a freshwater mussel, an aquatic bivalve mollusk in the family Unionidae The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometime ...

''). This mussel produced a high volume of low-quality pearls that came to be known as "

raisin A raisin is a dried grape. Raisins are produced in many regions of the world and may be eaten raw or used in cooking, baking, and brewing. In the United Kingdom, Ireland, New Zealand, and Australia, the word ''raisin'' is reserved for the d ...

pearls" in the 1970s and 1980s. More than a decade ago the freshwater pearl industry of China shifted production from the cockscomb pearl mussel to the triangle shell mussel (''Hyriopsis cumingii''). The triangle shell produced fewer pearls, accepting only 12–16 grafts per valve for a total production of 24 to 32 pearls, but produced pearls of better quality.

Processing

Freshwater pearl harvests are typically bought while still in the shell. After harvest the pearls are delivered to a first-stage factory, which is responsible for cleaning and sorting the pearls by size and shape. After this process has been completed, the pearls are considered ready material for processing factories. The pearls are pre-treated (''maeshori'') in a warm and cold chemical solution and then bleached. The pearls that exhibit strong coloration only go through the ''maeshori'' and are not bleached or dyed. After the pearls are treated, they are drilled and then polished with a mixture of

cornmeal Cornmeal is a meal (coarse flour) or a cell membrane ground from dried corn. It is a common staple food, and is ground to coarse, medium, and fine consistencies, but not as fine as wheat flour can be.Herbst, Sharon, ''Food Lover's Companion'' ...

and

wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low ...

. Finally they are matched into temporary strands, which are then matched again into hanks. Hanks are composed of 5 to 10 temporary strands and are considered wholesale-ready.

References

Pearls

Current and historic industry

Grafting

Processing

See also

References