The first harvest of Biwa pearls was in August 1925 and they had a shell bead nucleus like Akoya pearls. By the 1930's they were being sold overseas. Some merchants from India would buy these Lake Biwa pearls from Fujita and then resell them to the Middle East as highly valuable Persian pearls for huge sums of money. One day, it was accidentally discovered that a shell bead is not necessary for the cultivation of a freshwater pearl. All that is needed is the insertion of a piece of mantle (a membranous tissue which secretes nacre and lines the inner shell surface of mollusks). This is a lot less trouble than inserting both a bead and mantle tissue. Also, it was noticed that after the first harvest, mussels can spontaneously grow pearls a second and third time. What this means is that cultured freshwater pearls usually have more pearl nacre than cultured Akoya pearls because most do not have a shell bead nucleus.
Pearls that are cultivated using just mantle tissue are called tissue-nucleated pearls in America and non-nucleated pearls in Britain and Commonwealth countries. When a shell bead is implanted along with a graft of mantle tissue, the resulting pearl is called a nucleated pearl or a headnucleated pearl (The bead can be any shape; it isn't necessarily round). The general term for any pearl cultivated in a lake, pond or river area is freshwater cultured pearl. For the sake of brevity, this book usually omits the word "cultured" since practically all pearls today are cultured.
Biwa pearls (pearls from Lake Biwa) have enjoyed a great deal of prestige. This is because they tend to have a smooth surface and a high, even luster. Unfortunately, production almost came to a halt in the early 1990's due to the death of most of the Biwa mussels. It is now being resumed. Some dealers still have old stocks of pearls from Lake Biwa to sell, but many pearls which are identified as Biwa pearls are actually from China.
Most freshwater pearls today are produced in China. Their quality has been steadily improving since 1991 and their sizes have been increasing. At the end of 1992, semi-round Chinese freshwater pearls made their appearance on the market and now offer an attractive, lower priced alternative to the round Akoya pearls. Some of the larger pearls are even becoming alternatives to South Sea pearls.
China and Japan are not the only places where freshwater pearls are found. There are many historical accounts about the natural freshwater pearls of Europe and North America. These pearls are still being sold, but in decreasing quantities. Overfishing, flooding and pollution has either dwindled or, in some areas, eliminated the supply of these natural pearls.
