pearl
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What is a pearl?
A pearl is a lustrous concretion formed within a mollusk's shell, composed of nacre, also known as mother-of-pearl. When a foreign particle enters the shell, the mollusk's mantle tissue secretes nacre layers around the irritant to protect itself, creating the pearl.
Pearls are valued as gemstones and are characterized by their translucence, luster, and orient, a delicate play of surface color. The color of a pearl varies depending on the mollusk and its environment, ranging from black to white, with various shades in between. The finest pearls are produced by saltwater oysters, while freshwater clams also produce valuable pearls. Irregularly shaped pearls are called baroque pearls.
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How are pearls formed?
Pearls form when a foreign particle enters a mollusk's shell, irritating it. In response, the mollusk's mantle tissue, which is responsible for shell formation, coats the particle with nacre, also known as mother-of-pearl. Nacre is made of aragonite (CaCO3) and conchiolin. Over time, layers of nacre build up, forming a lustrous pearl.
Pearls vary in shape, size, and color, depending on the mollusk species and environmental conditions. The most valued pearls are perfectly round, but they can also be irregular and are then known as baroque pearls. Pearl colors range from white to black, influenced by the mollusk's environment and species.
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What makes pearls different from other gemstones?
Pearls stand out from other gemstones because they are formed within a living organism, a mollusk, and consist of nacre, also known as mother-of-pearl, the same material that lines the mollusk's shell. This material gives pearls their unique translucence, luster, and orient, a delicate play of surface color.
Unlike other gemstones that are mined from the earth, pearls are produced by certain saltwater oysters and freshwater clams when a foreign particle enters the mollusk. The mollusk then secretes layers of nacre around the irritant to protect itself, forming the pearl. This natural process and composition distinguish pearls from other gemstones.
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Where are pearls commonly found?
Pearls are commonly found in various locations around the world. The finest Oriental pearls come from the Persian Gulf, specifically in the waters off the great bight from the peninsula of Oman to Qatar. Other notable sources of high-quality pearls include the Gulf of Mannar between India and Sri Lanka, the waters off Celebes, Indonesia, and the islands of the South Pacific. In the Americas, the Gulf of California, the Gulf of Mexico, and the Pacific coast of Mexico have yielded dark-hued pearls with a metallic sheen and white pearls of good quality. Freshwater mussels in the temperate zone of the Northern Hemisphere, such as those from the Mississippi River, have also produced valuable pearls.
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How are natural and cultured pearls different?
Both natural and cultured pearls consist of nacre, or mother-of-pearl, and are valued as gemstones. Natural pearls form when a foreign particle enters a mollusk, which then coats the particle with layers of nacre. Cultured pearls are created through the intentional insertion of a foreign object inside the mollusk to stimulate pearl production. The mollusk is then returned to its bed for pearl formation.
The value of both pearls is based on their shape and luster. The color of a pearl varies depending on the mollusk and its environment.
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What are some common uses for pearls in jewelry and decoration?
Pearls, highly valued gemstones, are commonly used in jewelry. After drilling a small hole through the center, they are often strung into necklaces. The finest pearls come from mollusks with shells lined with mother-of-pearl, such as saltwater oysters and freshwater clams.
Pearls have been used for decorative purposes since at least 2500 BCE. Mother-of-pearl inlays can be found on items including furniture, jewelry, musical instruments, game boards, and trinket boxes. Ancient Egyptians used nacre in furniture and jewelry inlays inside temples and tombs. In the Georgian and Victorian eras, accessories such as brooches, combs, buttons, and lockets made of mother-of-pearl became fashionable.
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pearl, concretion formed by a mollusk consisting of the same material (called nacre or mother-of-pearl) as the molluskās shell. It is a highly valued gemstone. Pearls are often strung into a necklace after a small hole is drilled by hand-driven or electric tools through the center of each pearl (see also jewelry).
Pearls are characterized by their translucence and lustre and by a delicate play of surface color called orient. The more perfect a pearlās shape (spherical or droplike) and the deeper its lustre, the greater its value. Only those pearls produced by mollusks whose shells are lined with mother-of-pearl (e.g., certain species of both saltwater oysters and freshwater clams) are really fine pearls; pearls from other mollusks are reddish or whitish, like porcelain, or lacking in pearly lustre. Jewelers commonly refer to saltwater pearls as Oriental pearls and to those produced by freshwater mollusks as freshwater pearls.
The chief component of the nacre that constitutes the pearl is aragonite (CaCO3). Nacre also contains a small amount of conchiolin, a hornlike organic substance (albuminoid) that is the main constituent of the molluskās outer shell. The shell-secreting cells of the mollusk are located in the mantle, or epithelium, of its body. When a foreign particle penetrates the mantle, the cells attach to the particle and build up more or less concentric layers of pearl around it. Irregularly shaped pearls are called baroque pearls. Pearls that grow attached to the shell are often flat on one side and are called blister pearls.
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The color of pearls varies with the mollusk and its environment. It ranges from black to white, with the rose of Indian pearls esteemed most. Other colors are cream, gray, blue, yellow, lavender, green, and mauve. All occur in delicate shades. The surface of a pearl is rough to the touch. Pearls come in a wide range of sizes. Those weighing less than 1/4 grain (1 pearl grain = 50 mg = 1/4 carat) are called seed pearls. The largest naturally occurring pearls are the baroque pearls; one such pearl is known to have weighed 1,860 grains (121 grams [about 4.3 ounces]).
The finest Oriental pearls are produced by the mohar, the Atlantic pearl oyster (Pinctada imbricata). Found in the Persian Gulf, with the richest harvest taken from the waters off the great bight that curves from the peninsula of Oman to that of Qatar, the pearls come from depths of 8 to 20 fathoms (14.6 to 36.6 meters [48 to 120 feet]). Other notable sources of fine-quality pearls include the Gulf of Mannar between India and Sri Lanka; the waters off Celebes, Indonesia; and the islands of the South Pacific. In the Americas the Gulf of California, the Gulf of Mexico, and the Pacific coast of Mexico have yielded dark-hued pearls with a metallic sheen as well as white pearls of good quality.
Freshwater mussels in the temperate zone of the Northern Hemisphere have produced pearls of great valueāfor example, those from the Mississippi River. Pearling is a carefully fostered industry in central Europe, and the forest streams of Bavaria, in particular, are the source of choice pearls. Freshwater pearling in China has been known from before 1000 bce. In all pearl fisheries, however, production has declined significantly since the widespread introduction of cultured pearls (see cultured pearl).