Pearl
A pearl is a hard, shiny object produced within the soft tissue of a living shelled mollusk. Like the shell of a mollusk, a pearl is composed of calcium carbonate in a crystalline form, which is deposited in concentric layers. More commercially valuable pearls are perfectly round and smooth, but many other shapes, known as baroque pearls, can occur. The highest quality of natural pearls have been highly valued as gemstones and objects of beauty for many centuries. In literature, pearls have become a metaphor for something rare, fine, admirable, and valuable.
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