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Pearl's Common Characteristics
Pearls, which came from the Latin word pernula meaning seashell, are silky, smooth, hard, and shiny calcium carbonate deposits produced inside the shells of bivalve mollusks. Its shape is usually rounded and is used mainly as a gem or jewelry. However, unlike other gems, pearls are not cut or polished. The pearls are formed through the secretion of the epithelial cells of the mantle. As a result, a certain irritating organic matter will be deposited inside the mollusk's shell. This in turn will produce layers of calcium carbonate (CaCO3). It is chiefly composed of aragonite or calcite coatings binded together by conchiolin. This binding process is called as the nacre or most commonly called as the mother-of-pearl. Its typical shapes are rice-shaped, round, pear-shaped, button-shaped, or irregular (also known as the baroque figure). Its usual colors are white, creamy pink, yellow, green, blue, brown, and black. Among these colors the black pearl is considered as the most valuable because of their uncommonness. Because of the pearl's softness, they are delicate to both acids and heat. They are also prone to decay because of their organic material.
Pearl's luster highly depends on the light's reflection and refraction. The extending of the shell's successive layers can cause the pearl its luster and sometimes its quality.
Oysters and freshwater pearl mussels are the most common resource of the pearl specifically the Pinctata and the Hyriopsis genus of the clam family. The Persian Gulf in the Middle East is highly revered as the world's largest natural pearl center. Among its premium item is the saltwater pearl. Other main producers of pearls are India, China, Japan, Australia, the Philippines' Sulu Archipelago, the Pacific islands of Guam, Saipan, and Fiji, Venezuela, and other Central American countries. The bountiful rivers of Europe and North America have also contributed to the production of the pearl industry.
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