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  • 2015.04.22 Wednesday
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  • by スポンサードリンク

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Nacreous pearls

Pearls that are considered to be of gemstone quality are almost always nacreous and iridescent, wild or cultured, like the interior of the shell that produces them. However, almost all species of shelled mollusks are capable of producing pearls (formerly referred to as "calcareous concretions" by some sources) of lesser shine or less spherical shape.jewelry factory Although these may also be legitimately referred to as "pearls" by gemological labs and also under U.S. Federal Trade Commission rules,and are formed in the same way, most of them have no value, except as curios.


Pearl is the official birthstone for the month of June as adopted by the American National Association of Jewelers in 1912. It is also the birthstone for the Sun Signs of Gemini and Cancer. See the birthstone tables for additional references to this stone. Fresh water pearls are given on the 1st wedding anniversary. Pearls are also given on the 3rd, 12th and 30th anniversaries.


Almost any shelled mollusk can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within the mollusk's mantle folds, but the great majority of these "pearls" are not valued as gemstones. Nacreous pearls, the best-known and most commercially-significant pearls, are primarily produced by two groups of molluscan bivalves or clams. A nacreous pearl is made from layers of nacre,golden south sea pearl by the same living process as is used in the secretion of the mother of pearl which lines the shell.


An organic gem, pearls are formed inside mollusks such as oysters and mussels. They are formed when an irritant such as a tiny stone or bit of sand gets inside the mollusk's shell. A lustrous substance, called nacre, is secreted around the object to protect the soft internal surface of the mollusk. As layer upon layer of nacre coats the irritant, a pearl is formed. Light that is reflected from these overlapping layers produces a characteristic iridescent luster. This process of building a solid pearl can take up to seven or eight years.

A "natural pearl" or "wild pearl" is one that forms without any human intervention at all, in the wild, and is very rare. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened, and thus killed,tahitian pearl in order to find even one wild pearl, and for many centuries that was the only way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. A cultured pearl is formed in a pearl farm, using human intervention as well as natural processes.

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  • 2015.04.22 Wednesday
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  • 11:37
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  • by スポンサードリンク

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