Description
CULTIVATED / FRESHWATER PEARLS
Below is a brief story about the production of freshwater pearls. At Timmersgems, you will find the best quality pearls from Japan, China, and other regions, always harvested and produced in an eco-friendly way, with a heart for nature and people. Cultured freshwater pearls are pearls that are cultivated and created using freshwater mussels. These pearls are produced on a limited scale in Japan and the United States, but are now produced almost exclusively in China. The U.S. Federal Trade Commission requires that cultured freshwater pearls be labeled as “freshwater cultured pearls” in trade. The quality of cultured freshwater pearls is evaluated through a rating system of a range of values, based on luster, shape, and other factors. Pearls collected in the wild from the Holarctic freshwater mussel were important sources of pearls for medieval jewelry, with Scotland being a major source; this species is now threatened in most areas.
CURRENT AND HISTORICAL INDUSTRY
Although the Japanese freshwater pearl industry has nearly ceased to exist, it holds a special historical place as the first country to produce whole freshwater pearls. They achieved this by cultivating mussels in Lake Biwa, using the Biwa pearl 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 unfortunately failed and production ceased in 2006. The pearl farm in Tennessee also holds special historical
value, as it was the only one to produce freshwater pearls outside of Asia. Founded by the late John Latendresse, it remains a tourist attraction. Today, China is the only commercial producer of freshwater pearls, with production of 1,500 tons (2005) using the triangle mussel (Hyriopsis cumingii).
GRAFTING
The grafting process begins with selecting 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 processes them. This process is not difficult, and the technician requires only minimal training to
perform the procedure. The technician makes small incisions on the top valve and inserts the piece of tissue. The tissue is rotated slightly during insertion to create proportionally rounder pearls. After the maximum number of grafts has been performed, the mussel is turned over, and the procedure is performed 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. The cockscomb pearl mussel (Cristaria plicata) is a popular example. This mussel produced a high volume of low-quality pearls that became known as "Crispy Rice pearls" in the 1970s and 1980s. More than a decade ago,
China's freshwater pearl industry shifted production from the cockscomb pearl mussel to the triangle shell mussel (Hyriopsis cumingii). The triangle mussel produces fewer pearls, accepting only 12-16 grafts per valve for a total production of 24 to 32 pearls, but produces pearls of better quality.
PROCESSING
Harvested freshwater pearls are usually purchased while still in the shell. After the pearls are harvested, they are delivered to a first-stage factory, which is responsible for cleaning and sorting the
pearls by size and shape. Once this process is completed, the pearls are considered ready for processing in factories. The pearls are pretreated (maeshori) in a hot and cold chemical solution and then bleached. Pearls showing strong discoloration pass through the maeshori and are not bleached or dyed. After the pearls
have been treated, they are drilled and then polished with a mixture of cornmeal and wax. Finally, they are aligned into temporary strands, which are then aligned again into twists. Strands are composed of 5 to 10 temporary strands and are considered ready for wholesale.
