China grows far more pearls by volume than any other country, and most of them are freshwater pearls from mussels farmed in lakes, ponds and rivers. Chinese farms use mainly tissue nucleation, grafting many small pieces of mantle tissue into each mussel. The country also has a saltwater pearl history going back about two thousand years around Hepu on the southern coast. In recent decades it has added large, bead-nucleated freshwater pearls to its range.
Two thousand years of pearls
Chinese texts record pearl fishing in the waters off Hepu, in today's Guangxi Zhuang Autonomous Region on the Gulf of Tonkin, from the Han dynasty onward. The pearls there came from wild Akoya-type oysters, and imperial courts collected them as tribute. Pearls from this region came to be called "south pearls" (nanzhu) and were prized for their luster. The old fisheries suffered repeatedly from overharvesting, and imperial officials at times closed them.
The Chinese also experimented with pearl culture long before Japan. By the 13th century at the latest, farmers in the Huzhou area of Zhejiang placed small lead or tin figures, often images of the Buddha, inside freshwater mussels. The mussels coated them with nacre and produced small pearly images attached to the shell. These blister images were sold as curiosities and religious objects, and examples reached European collections in the 18th and 19th centuries.
The modern freshwater industry
Modern freshwater pearl farming in China grew from the late 1960s and 1970s, using methods adapted from Japan's Lake Biwa farms. Early Chinese freshwater pearls were small, wrinkled and shaped like grains of rice. Western buyers in the 1970s and 1980s often called them "rice krispie" pearls. Quality rose steadily as farmers refined their methods and changed the mussels they worked with.
The turning point was a move from the cockscomb mussel, Cristaria plicata, to the triangle shell mussel, Hyriopsis cumingii. Hyriopsis produced smoother, rounder, more lustrous pearls. By the 1990s and 2000s, Chinese farms were turning out round and near-round freshwater pearls that looked much like Akoya pearls at a fraction of the price. Breeders later crossed Hyriopsis cumingii with the Japanese Biwa mussel, Hyriopsis schlegeli, to improve growth and nacre.
How tissue nucleation works
A Chinese freshwater pearl usually starts without a bead. The process works like this:
- Workers cut thin strips of mantle from a donor mussel and slice them into small squares.
- A technician opens the host mussel slightly and makes small incisions in its mantle.
- Each incision receives one square of tissue. A single mussel can take a dozen or more grafts on each half of its mantle, so one animal can carry 20 to 50 pearls in total.
- The mussels hang in nets or baskets in ponds or lakes, often from floating lines held up by plastic bottles or buoys.
- After two to six years, farmers open the mussels and harvest the pearls.
Each graft grows into a pearl sac that fills with nacre, so the finished pearl is solid nacre throughout. That makes Chinese freshwater pearls durable, and they can be drilled and worn without the risk of peeling that thin-coated bead-nucleated pearls carry. The cultured pearls page compares this method with saltwater bead nucleation.
Since the tissue grafts sit in the mantle and not in the gonad, the pearl sacs are free to form irregular shapes. Many freshwater pearls come out oval, button, potato or baroque, and only a small fraction are truly round.
Where the farms are
Zhejiang Province has long been the center of the freshwater industry. Zhuji, south of Hangzhou, grew into one of the world's largest pearl trading hubs, with the Shanxiahu pearl market at its heart. Jiangsu, Anhui, Hubei, Hunan and Jiangxi provinces also farm pearls along their lakes and river systems. The balance between provinces has shifted over time, as local governments limited farming in some areas to protect water quality.
The scale of production is enormous. By the 2000s, Chinese freshwater farms were producing pearls measured in hundreds or even thousands of tonnes a year. Exact figures vary by source and year, and they are hard to verify. The flood of supply made freshwater pearls cheap and widely available, and pushed down prices for low-end pearls of all types.
Colors and treatments
Chinese freshwater pearls come in natural body colors of white, cream, pink, peach, apricot and lavender. The donor tissue strongly affects the color, so farmers select donors to aim for particular shades. Many pearls are bleached to lighten or even out color, and polished to improve luster. Dark colors such as black, deep purple and peacock are almost always dyed or irradiated, since freshwater mussels in China do not naturally produce those shades in quantity. Disclosure rules apply here as with any gem. See gemstone treatments for the wider picture.
Edison and bead-nucleated freshwater pearls
From around the late 2000s, Chinese farms began bead-nucleating freshwater mussels on a commercial scale. Technicians insert a round bead into the mussel's gonad, much as saltwater farmers do with oysters. Grown for several years, these pearls can reach sizes between about 10 and 15 mm or more, with very bright luster and strong metallic colors.
One company marketed them as Edison pearls, and the name spread through the trade as a loose label. Other names, such as ming pearls, also appear. These pearls are large, round to near-round and colorful, so they can compete visually with South Sea pearls and Tahitian pearls. Labs use X-ray imaging and trace element analysis to identify freshwater origin. Freshwater pearls carry more manganese than saltwater pearls, as explained on the pearl composition page.
Chinese Akoya and saltwater pearls
China also farms Akoya oysters along its southern coast, mainly in Guangxi, Guangdong and Hainan, including the old Hepu area. Production grew in the 1990s and 2000s, when Chinese Akoya pearls supplied much of the low and middle market. They were often small and grown for short periods, giving thin nacre. Later problems with pollution, coastal development and typhoons cut Chinese saltwater output. Japan and China have also exchanged Akoya breeding stock at times. The Japanese pearl farming page covers the Japanese side.
Judging Chinese freshwater pearls
Freshwater pearls are graded on the same factors as other cultured pearls. Shape and luster affect value most strongly, since solid nacre makes nacre thickness a minor issue. Many sellers use an A to AAA scale, but grades are not standardized. A AAA strand from one dealer may be much better or worse than one from another. The pearl grading page explains what to look at directly.
Frequently asked questions
Are Chinese freshwater pearls real pearls?
Yes. They are cultured pearls grown by living freshwater mussels, usually from tissue grafts. They are solid nacre and fully genuine pearls.
Why are freshwater pearls cheaper than Akoya pearls?
Each freshwater mussel can produce dozens of pearls at once, and few of them are perfectly round. Akoya oysters usually produce one pearl each, and round shapes are more common, so they cost more per pearl.
What is an Edison pearl?
Edison is a trade name for large, bead-nucleated freshwater pearls from China. They are known for size, round shapes and bright metallic colors.
Are black freshwater pearls natural in color?
Almost never. Black and other very dark freshwater pearls are usually dyed or irradiated. Natural dark colors come from Tahitian pearls.