Cultured Freshwater Pearls - Grafting

Grafting

The grafting process begins by choosing a suitable donor mussel and cutting a strip of tissue from the mantle. This strip of tissue is then cut into three-millimetre squares. These squares are delivered to a technician who performs the operation. Unlike saltwater bead nucleation, this process is not considered difficult, and technicians need only minimum training to perform the operation. The technician creates small incisions on the upper valve, and inserts the tissue piece. A small twist of the tissue upon insertion is believed to create a higher ratio of round pearls. After the maximum number of grafts have been performed, the mussel is flipped, and the procedure is performed once again on the other valve of the shell.

Chinese freshwater mussels were once grafted up to 50 times per shell, or 25 times per valve. This practice was common when the industry mussel was primarily the cockscomb pearl mussel (Cristaria plicata). This mussel produced a high volume of low-quality pearls that came to be known as "Rice Krispie pearls" in the 1970s and 1980s. More than a decade ago the freshwater pearl industry of China shifted production from the cockscomb pearl mussel to the triangle shell mussel (Hyriopsis cumingii). The triangle shell produced fewer pearls, accepting only 12-16 grafts per valve for a total production of 24 to 32 pearls, but produced pearls of better quality.