These are easily distinguished from other pearls due to their generally smaller size, uneven shape and unusual, often pastel, colours. They appeared on the market in the 1950's and the most famous were cultivated in Lake Biwa near Kyoto in Central Japan. Today the lake is heavily polluted and unable to support molluscs, but is still used as a reference for freshwater pearls.
China is now the greatest producer and uses a mollusc called Hyriopsis Sclegeli that can reach a diameter of 130cms after some fifteen years. The main difference between saltwater and freshwater pearl cultivation is that generally only the epithelium fragment is inserted in freshwater molluscs, there is no need for a nucleus. As a result any number of fragments from 15 to 30 can be inserted. These generally produce pearls of 2 to 5 mm but up to 9 mm is achievable.
The percentage of loss is about 20% for non-nucleus inserted
molluscs rising to 80% for nucleus inserted molluscs. Nuclei are inserted to achieve
The insertion procedure is the same as for saltwater molluscs but the cultivation period can be as little as 10 months up to a maximum of 2 to 3 years. Up to 3 harvests can be achieved from the same mollusc without repeating the insertion operation.