Pearl core leakage is a rare form in shellfish. Its appearance is generally round or oval, its diameter is about 1-6 mm, and its surface is smooth without obvious defects and bad spots. Its interior is a regular sphere or ellipse, and its color is light yellow to light gray, pearlescent and usually opaque. Pearls are full of defects, usually due to virus and bacterial infection, environmental pressure and other factors leading to incomplete growth, and are easily regarded as useless waste. However, some people attach importance to their processing and utilization, such as creating works of art and jewelry according to their shapes and textures.