How Do Pearls Grow?
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Internal Makeup
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In order to better understand how a pearl grows inside an oyster, it is helpful to be familiar with the internal makeup of the mollusk. An oyster contains the following parts: mouth, stomach, heart, anus, abductor muscle, mantle, intestines and gills. There are two key parts of an oyster that contribute to pearl formation: the mantle and the nacre. The mantle is the organ that produces the shell of the oyster using minerals from the food the oyster consumes. Nacre is the material produced by the mantle to line the inner layer of the oyster's shell, and is made up of crystals of calcium carbonate. It is these crystals that give pearls their iridescence and shine.
Natural Pearl
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The pearl formation process begins when the oyster gets a foreign particle, such as a piece of sand, dirt or shell, lodged between its mantle and shell. This irritates the mantle, so the oyster begins to produce nacre in order to cover the particle and prevent further discomfort. This process is similar to when a human gets something in his eye, and the eye automatically begins producing tears to lubricate the eye and wash the foreign particle away. Over time, this process produces a pearl inside the oyster. Natural pearls are considered very valuable, and are rare.
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Cultured Pearl
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A cultured pearl is created in the same away as a natural pearl, but it receives assistance from pearl harvesters. A cultured pearl is formed when a pearl harvester cuts a small slit in the mantle of the oyster and inserts a particle in the cut to cause irritation. The oyster then begins its natural process of protecting itself from the irritant, and a pearl is formed. In freshwater pearls, just the small slit created by the pearl harvester is enough to grow a pearl. No additional particle is necessary.
Final Product
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Most pearls are not perfectly round, however they are presented in ways that make them look round. For instance, if a pearl has a flatter side, that part would be placed against an earring back so only the round part will show. Actually finding a perfectly round pearl is very rare. There are many other shapes and sizes of pearls: off-round, button and oval. There are also baroque and keishi pearls, which have an irregular, elongated shape. There are also various colors of pearls ranging from off-white to a pale pink hue and even black. However, black pearls are rarely truly black in color. Black pearls often have blue, green, gray, purple and peacock tints. Green is the primary basis of color for black pearls. Pearls are graded on their shape, lustre, surface quality, thickness of nacre and, in jewelry, how well they match the other pearls on the strand.
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References
- Photo Credit Photo from Anna's Photos on Flickr
