The first cultured freshwater pearls to become well known were originally from Lake Biwa, Japan, and grown in the Hyriopsis schlegeli mussel. However, because of environmental changes as well as geographical advantages, China has taken over as the world’s main supplier. The Hyriopsis cumingi mussel is now mainly used for freshwater pearl cultivation in China, replacing the previously used Cristaria plicata. A small quantity of pearls is also cultivated in Japan’s Lake Kasimiguara using a Hyriopsis schlegeli x cumingi hybrid that produces Kasumiga cultured pearls.
The majority of freshwater cultured pearls do not have a bead nucleus, but consist purely of nacreous layers, which means that they can grow into an interesting variety of shapes: teardrops, buttons, twins, rice, ovals and even crosses are common, as are spherical pearls. However, the use of a solid nucleus for cultivation has increased in recent years. Up to around 40 pearls can be cultivated in a single shell.
Freshwater cultured pearls occur in five main hues: white (not a hue sensu stricto), cream, grey, pink, orange and purple. However, various combinations of hue, tone and saturation yield a broad range of appearances.
