seed pearl

A seed pearl is a very small and often irregular pearl. Pearls themselves are concretions formed by mollusks, consisting of nacre, also known as mother-of-pearl. These are highly valued gemstones characterized by their translucence, luster, and a delicate play of surface color called orient.12

The value of a pearl increases with its perfect shape and deep luster. Pearls are composed primarily of aragonite, a form of calcium carbonate, along with a small amount of conchiolin, an organic substance. They form when a foreign particle enters the mollusk's mantle, and the cells build concentric layers of pearl around it. Irregularly shaped pearls are called baroque pearls, and those attached to the shell are known as blister pearls. Pearls come in various colors, with black to white being common, and their size can range significantly, with those under 1/4 grain being classified as seed pearls.2