What is a "pearl"?

A pearl is a hard, round object that is produced within the soft tissue of a living shelled mollusk or other similar animals, such as an oyster or clam. It is made up of calcium carbonate and other organic materials that form concentric layers around an irritant, such as a grain of sand, that has made its way inside the shell. Pearls are typically valued for their beauty and rarity and have been used in jewelry for thousands of years. The quality of a pearl is determined by various factors, including its size, shape, color, luster, and surface quality.