Freshwater pearls are created by freshwater mussels. Cultured freshwater pearls are formed when the irritant is surgically implanted into a mussel by pearl farmers. These ‘seeds’ (‘nuclei’ or a ‘nucleus’ for singular) are most often a small polished shell bead and piece of mantle tissue in each. As a defense mechanism the mantle tissue of the mollusk secretes nacre layer upon layer around nucleus until a pearl is formed.
The culturing process usually takes several years. Mussels must reach a mature age and only then can be implanted with an irritant. It can take up to another several years for the pearl to reach its full size and nacre thickness. Freshwater pearls can take between 1 and 6 years to form. The longer a pearl stays in the shell, the more nacre that forms and the larger the pearl is.
Quality of pearls is evaluated through a grading system based on luster, shape, surface, colour and matching. They come in many shapes and sizes, but the most rare is a round one as it is most difficult to culture.
Nugget/ Freeform – irregularly shaped pearls
Oval – also known as rice pearls
Button – symmetrical pearls that appear to be flattened
Keshi/Biwa – it is used in Japanese for all pearls that grew without a nucleus, Keshi and Biwa pearls are composed entirely of nacre and have no nucleus.
Baroque – general term for pearls with an irregular non-spherical shape
Edison – these cultured pearls are nucleated with tiny beads instead of tissue. “Edison” pearls are new technology bead nucleated pearls from China that producers will not reveal. They have an astounding luster and deep vibrant colours.
Round/ Nearly round – the rounder the pearl, the more valuable it is