Freshwater pearls are a kind of pearl that comes from freshwater mussels. They were produced in Japan and the United States, but are now exclusive to China. Freshadama grade cultured freshwater pearls. ... Subclasses Pteriomorpha (marine mussels) Palaeoheterodonta (freshwater mussels) Heterodonta (zebra mussels) The term mussel is used for several families of bivalve molluscs inhabiting lakes, rivers, and creeks, as well as intertidal areas along coastlines worldwide. ...

Current and Historic Industry

Although the Japanese freshwater pearl industry has ceased to exist, it does hold special historic value as the first country to cultivate whole freshwater pearls in Lake Biwa, utilizing the Biwa pearly mussel (Hyriopsis schlegeli). The industry attempted a come back with a mussel hybrid (Hyriopsis schlegeli/Cristaria plicata) in Lake Kasumigaura in the last decade, but this venture also met with failure, with production ceasing in 2006. Today China is the only commercial producer of freshwater pearls, producing as much as 1500 tons (2005) ^[1] using the Triangle shell mussel (Hyriopsis cumingii) and several hybrids that have shown heterosis from several mussel species. Lake Biwa ), formerly known as ÅŒmi Lake, is the largest fresh water lake in Japan, located in Shiga Prefecture (west-central Honshu), northeast of the former capital city of Kyoto. ... Heterosis is increased strength of different characteristics in hybrids; the possibility to obtain a better individual by combining the virtues of its parents. ...

Grafting

A technician performing a grafting operation.

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). This mussel produced a high volume of low quality pearls that came to be known as rice crispy pearls in the 1970's and 1980's. Nearly a decade ago the freshwater pearl industry of China shifted production from the Cockscomb to the Triangle shell mussel (Hyriopsis cumingii). While the Triangle shell produced fewer pearls, accepting only 12-16 grafts per valve for a total production of 24 to 32 pearls, the difference in quality was substantial. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ...

The grafting process begins by selecting a suitable donor mussel and cutting a strip of tissue from the mantle. This strip of tissue is then cut into 3mm 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 reverse side of the valve. For other things called pearl, see pearl (disambiguation). ...

Processing

Freshwater pearl harvests are typically purchased while still in the shell. After harvest the pearls are delivered to a first stage factory. This factory 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. These smaller factories perform the treatments ^[2] that are nearly universal to all freshwater pearls. The pearls are pre-treated (maeshori) in a warm and cold chemical solution and then bleached. The pearls that exhibit strong coloration will only go through the maeshori.

After the pearls are bleached they are drilled and then polished with a mixture of cornmeal and wax. 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.

The Product

Freshadama - gem grade cultured freshwater pearls.

Freshwater pearls are seldom perfectly round or even nearly round, more often than not they are baroque. In rare circumstances perfectly round freshwater pearls are produced, and even more rare are the true gems that have recently been designated as freshadama by the trade. Freshadama pearls are visibly round to perfect round, and exhibit orient, and exceedingly rare value factor in cultured pearls. Image File history File linksMetadata No higher resolution available. ... Image File history File linksMetadata No higher resolution available. ...

Many pearls, both natural and cultured, have beautiful color and luster. Freshwater pearls are noted for their wide range of color, they can be found in white, silvery white, pink, salmon, red, copper, bronze, brown, lavender, purple, green, blue, cream, and yellow. Although white, peach, and lavender are the most common colors, the most desirable are the pastel pinks, roses, and purples. The different colors are a function of the genetics, water quality, and the location of the tissue graft in the shell.

References

1. ^ [1] Aquaculture in China - Freshwater Pearl Culture
2. ^ [2] Pearl Treatments

External links

• Pearl-Guide.com on Freshwater Pearls.
• Chinese Freshwater Pearls Modern Jeweler magazine
• Freshwater Pearl Source Locational Map and Gem Information