Conch pearls are one of the most rare and valuable of all natural pearls. It has been estimated that approximately 1 in 10,000 conch produce a pearl and of these only a few possess the color, shape and flame pattern necessary to be considered a gem.
Color & Structure
Conch pearls often exhibit a flame-like pattern due to concentrically arranged calcium carbonate platelets in a lamellar fashion. Flame structure is found mostly in the salmon, pink, and red toned pearls. This significantly increases the value and price of the conch pearl.
Conch pearls contain no nacre, so technically they are not actually pearls at all. Instead, the gems are calcareous concretions. Conch pearls and nacreous pearls have the same chemical composition the only difference between them is their polycrystalline structures.
The principal determinant of value for a conch pearl is its color as well as shape, size and flame vibrancy. Although many tend to be orange, yellow, beige or ivory, enough are pink for these pearls to have been known as "pink pearls" in the trade.
Size, Shape & Care
Most conch pearls have an elongated, oval, or baroque shape, and occasionally they will create a button or round. Round specimens are very rare. Conch pearls weigh significantly more than oyster pearls, with a specific gravity of 2.85; and unlike other pearls, are sized by carat weight. Although conch pearls can be found over 100 carats, larger sizes (above 5 carats) of conch pearls are uncommon, with the average size being less than 3 carats.
Due to the high value of conch pearls, drilling and/or gluing should be avoided in the mounting, as this will devalue the pearl. Prolonged exposure to sunlight (ultraviolet light) can have a dulling and fading effect. Indoor lighting does not seem to have effects on the pearls. Because its an organic gem, therefore, jewelry should be used with care.
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