Photo: The famous Pearl Market in Beijing, dated March 24, 2006. Dimension: 1600 x 1200 pixels, size: 373 KB. Click on photo for an enlarged view and save the photo.
A pearl is a hard, generally spherical substance formed within the soft tissue, specifically the mantle, of a living shelled mollusk, and made up of calcium carbonate (CaCO3) in minute crystalline form, which has been deposited in concentric layers. The finest natural pearls have been highly valued as gemstones for many centuries.
Precious pearls occur in the wild but they are very rare. Cultured or farmed pearls from pearl oysters make up the major chunk of pearls sold in the market. Seawater Pearls are more valuable than freshwater pearls.
Imitation or fake pearls are also widely sold in inexpensive jewelry. Pearls have also been crushed and used in cosmetics, medicines, or in paint formulations.
In 1914 pearl farmers began growing cultured freshwater pearls using the pearl mussels native to Lake Biwa, the largest and most ancient lake in Japan, near the city of Kyoto. Japanese pearl farmers recently developed a hybrid pearl mussel, a cross between Biwa Pearl Mussels and a closely related species from China, Hyriopsis cumingi, in Lake Kasumigaura.
Japanese pearl producers also invested in producing cultured pearls with freshwater mussels in Shanghai, China, which is currently the world's largest producer of freshwater pearls, producing more than 1,500 metric tons per year.