Freshwater Pearl

Freshwater pearls are a kind of pearl that comes from freshwater mussels. They are produced in Japan and the United States on a limited scale, but are now almost exclusive to China The U.S. Federal Trade Commission  requires that freshwater pearls are referred to as "freshwater cultured pearls" in commerce.
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A pearl produced by a mollusk that inhabits freshwater, usually these pearls are shaped like an uneven grain of rice. There is also a variety called Tennessee fresh water pearls that taper like a long tooth, as in the illustrated 1940's brooch.