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“Fine Pearls,” from a "Modest Maker"

Natural Pearls are formed in Marine Pearl Oysters or Freshwater Mussels by a living process. These humble organisms live in recluse, while they make the magnificent Iridescent pearl that lights up the person it adorns. Pearl oysters and mussels belong to the Bivalvia class of organisms in the phylum, Mollusca.
Most mollusks with shells can produce pearls, but only certain species of bivalve mollusks, produce fine nacreous pearls, which have high commercial value.


Iridescence, that Dispels the Darkness of Ocean Caves!
A nacreous pearl is made from layers of nacre secreted by the bivalve mollusk. When a tiny object gets trapped in the mantle folds inside the shell, the oyster covers this foreign object with nacre, as a protective measure. The outer layer of pearls and the inside layer of the shells of pearl bivalves are made of nacre. Nacre (also known as Mother of Pearl ) is secreted by the bivalve and consists mainly of layers of aragonite ( a mineral formed of calcium carbonate crystals) separated by sheets of organic matter(called conchiolin). With visible light, this multi layered, intricate and strong structure of Nacre creates its characteristic Iridescence that lights up its surroundings in many colors and hues. Fine layer upon layer of nacre is secreted around the irritant object, and after years of this living process a pearl is formed. Natural pearls come in many sizes, colors and shapes depending on the nacre secretions.

Pearl Oysters, Pinctada margaritifera and Pinctada mertensi, which live in the sea produce fine natural pearls of superior quality. In Pearl farming, cultured pearls are made by inserting “irritants” such as tiny bits of shells or beads within the mantle tissue of the oysters and mussels, to stimulate the secretion process.

Please visit the site given below and search for "Pearls" if you wish to know more about this topic.

http://www.livescience.com

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