บท 156: Sea Pearl

Pearls are hard, shiny objects that are produced in the soft tissues (particularly the mantle) of living shelled mollusks or other animals, such as fossilized conulariids. Like mollusk shells, pearls are composed of calcium carbonate (mainly aragonite or a mixture of aragonite and calcite) in the form of small crystals, which have been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The finest qualities of natural pearls have been highly valued as gemstones and objects of beauty for centuries. Because of this, pearls have become a metaphor for something rare, good, wonderful, and precious.