blister pearl

A blister pearl is a pearly growth found on the inside of a mollusk's shell, often enclosing a foreign object like mud or a parasite. These pearls are typically hemispherical and attached to the shell. While natural blister pearls occur, they are also produced through cultivation. In cultured pearls, a foreign object is intentionally placed inside the mollusk to stimulate pearl formation. Chinese cultivation historically focused on blister pearls, which were then enhanced with resin and mother-of-pearl to create mabe pearls or pearl doublets. Pearls, in general, are formed from nacre, the same material that lines a mollusk's shell, and are valued as gemstones for their luster and color.123