Freshwater cultured pearls are typically between two and 13 millimetres in diameter; examples which are larger than 13 millimetres are rare, and above 15 millimetres extremely rare.
The main areas of production are the Yangtze delta in China, and Lakes Kasumigaura and Biwa in Japan.
Their colour ranges from rose tinted white, rose-tinted orange and golden brown, to purple/lilac and steel grey.
The colour of Japanese Kasumigaura cultured pearls ranges from pink to violet and slightly rose-tinted shades.
The freshwater pearl oyster, Hyriopsis cumingii, grows to 30 centimetres in size and is oval in shape.
Freshwater pearls are predominantly cultivated without the use of an artificial nucleus. Cultivation takes between two and four years for small pearls, or between seven and eight years for larger ones.
Pearls cultivated in Lakes Kasumigaura and Biwa in Japan are cultured by planting an artificial nucleus into a pearl oyster. They reach up to 16 millimetres in size, and cultivation takes between three and four years.