Pearls are highly valued for their wonderful, beautiful luster. Pearls are shiny, hard and rounded. They are translucent and made up of nacre, which is a mankind of chalk called calcium carbonate. Nacre is a kind of secretion of the mollusks like the oysters and mussels. The shell of the oyster looks quite dull and mis-shaped. Inside the shell, the moist body of the oyster is surrounded by flaps of tissue called mantle. This mantle secretes the nacre that covers the inner shell surface in a smooth layer called mother-of-pearl.
Pearls are generally white in color, ranging to delicate pink. Due to different in the nacre, sometimes we get other colors too like black, blue, golden, yellow, lavender, green and mauve. The most valuable pearls are the most perfectly rounded ones and the drop shaped ones with a deep pearly gloss.
Most precious pearls come from the various species of the family Pteriidae found in the tropical waters off north and west Australia, off the California coast, in the Persian Gulf and in the Indian Ocean. Since they are very rare, large mussel pearls of perfect shape are worth more than those from oysters.
The oyster feeds itself by opening its shell slightly to suck in the Plankton. Sometimes a grain of sand or a piece of shell drifts in and the oyster is unable to remove it. The oyster then protects itself from this irritant by covering it with layers of mother-of-pearl. Thus a pearl is formed.
Not all oysters produce pearls. In fact, on an average, in a haul of three tones of oysters only about three of four of the oysters will be having pearls in them. Divers have to go to the depths of the sea to retrieve oysters for their pearls. It is a tiring, risky and thankless job, as most of them will not bear any pearls. Technology and business have combined to alter nature’s product considerably. Today, pearls are cultivated in Japan and in Australia. Artificial pearls were first cultivated in Japan in 1893.
To produce cultured pearls, a tiny bead of shell from a clam together with a small piece of membrane from another oysters mantle is inserted in oysters kept caged in the seabed. This should be done without injury to the oyster. The pearls are ready to be harvested within three to six years. It is almost impossible to make out the difference between natural pearls and cultured pearls. The only way is to dissect the pearls or to x-ray them. The ones with a completely round original centre are the cultivated pearls.
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