Freshwater Pearls

The Chinese were the first to culture a product from freshwater mussels, though their centuries-old Buddhas are not true pearls but shell mabes. The first cultured freshwater pearls originated in Japan. Quite soon after their initial success with cultured saltwater pearls, Japanese pearl farmers experimented with freshwater mussels in Lake Biwa, a large lake near Kyoto. Initial commercial freshwater pearl crops appeared in the 1930s. The all-nacre Biwa pearls formed in colors unseen in saltwater pearls. Almost instantly appealing, their lustre and luminescent depth rivaled naturals because they, too, were pearls throughout.

Unlike the seawater-cultivated pearls, most of today's freshwater-cultivated pearls do not have a mother of pearl nucleus. 95% to 98% of these pearls are composed only of nacre. For seeding , the oyster is gently opened. Tiny slits are cut into its Mantle ( flesh) and small pieces of living tissue from a donor oyster are then carefully inserted into the slits. Depending on the age and size of the oyster, between 20 to 60 pieces of tissue are used to seed it. Soon after seeding, pearl sacs begin to form around the soft irritants that, as time passes, dissolves away and pearls grow.

After about a year and half, they grow to about 3mm in diameter. After three years approximately 80% of the pearls reach sizes up to 7mm. There is a direct correlation between the nacre thickness and the luster. The thicker the nacre the higher the luster. After harvesting, the oysters can be seeded again and put back in the water to produce again. The oysters generally provide fewer pearls the second time around and the pearls may be flatter in shape but they do have a better luster and stronger colors than the first time.

Growth slows and quality declines for the few oysters that are harvested a third time.

The nucleated oysters are suspended from rafts such as these in order to provide the best growing conditions. Pearl technicians check water temperatures and feeding conditions daily at various water depths and then move the oysters up or down to take advantage of the best growing conditions.

Jerry Smith, Beads
Gemstone Beads -- Serving the Beading Community..Since 1999