Freshwater pearls are the most commonly produced pearls, with China being the undisputed leader in its commercial production. Although traditional freshwater pearls are grown without a bead nucleus, they are the result of a culturing method known as “tissue-nucleation.” The grafting process involves implanting a small piece of suitable donor mantle tissue into the mantle of the host. Freshwater mussels can be grafted with up to 25 insertions per valve, or 50 times per shell, but industry practice limits it to only 12-16 insertions in either valve to produce pearls of better quality. The resulting pearls are composed of solid nacre, making them very durable, but without a bead nucleus, the shapes of these gems are rarely perfectly round.
TRADITIONAL FRESHWATER PEARLS
The triangle shell mussel Hyriopsis cumingii is used to cultivate freshwater pearls. This bivalve mussel lives in lakes, riverbeds, ponds, and man-made bodies of water. Varieties of freshwater mussels produce pearls in a host of natural colors, not only in white but pastel shades of pink, peach, lavender, orange, yellow and silver. The shapes of freshwater pearls are distinctive, too. Because a bead nucleus is absent, they can grow in various shapes such as round, semi-round, potato, rice (long or short), and even flat.
Freshwater pearls may be the most common type of pearl, but they do not have the same sharp luster and shine of fine quality Akoya or South Sea pearls. Luster ranges from dull and chalky to high. For the most part, freshwater pearls have a more muted luster. They are also generally the least expensive of all cultured pearl types. Freshwater pearls with brilliant, metallic, mirror-like luster do exist but are rare.
NEW FRESHWATER PEARLS
There is a relatively new type of freshwater pearl being marketed today. Chinese pearl farmers have begun inserting a bead within the soft inner tissue of the mussels, rather than in the mantle, producing pearls reaching 20mm in diameter and 40mm in length. These new bead-nucleated freshwater pearls are more symmetrical in shape, larger and more spectacular. They are produced in a wide spectrum of natural colors in a whole variety of shapes.
A universal name for this new type of freshwater pearl has yet to be coined. They are locally called “nuclear” pearls, from the word “nucleus” and “nucleated”. At times, they are loosely branded as “Edison” pearls (a backhanded tribute to American inventor Thomas Edison). They are also known as “Ming” or “Ikecho” pearls, referencing a specific company that produces them. Strictly speaking, though, they should refer only to beaded pearls produced by each particular company.