Pearls

 

Tahitian Black Pearl

A cultured pearl is a true jewel of the sea. It owes its beauty to the creative forces of nature. While precious stones must be polished before they sparkle, pearls already have a warm natural glow.

The birth of a pearl begins when a foreign substance, such as a grain of sand, finds its way into the oyster's body and causes an irritation. The oyster then takes a defensive action by secreting a substance called nacre which builds up around the irritant object. The layers of nacre secreted onto the irritant develop into a smooth, hard substance. After many years of this process, a pearl is formed.

Cultured pearls are made in much the same way as natural pearls by utilizing a technique known as grafting.

The grafting technique consists of introducing a perfectly round nucleus, fashioned from the shell of a mussel cultivated in the Mississippi , into the gonad of an oyster.
A small piece of mantle from another oyster is inserted along with the graft. The cells from the sacrificed oyster develop around the implanted nucleus thus forming a pearl sack which, once closed, will secrete pearl material.

Before undergoing this grafting process, the oyster is put to fast for several days in order to slow down its metabolism which decreases the risk of rejection.

Many people still make the mistake of believing that cultured pearls are imitations or fake ones. In fact, cultured pearls result from the same natural phenomenon as natural pearls - the only difference is that this phenomenon is induced by the grafter and does not happen randomly. In other words, man plays the part of nature by introducing the irritant or nucleus into the oyster and then steps aside to allow nature to create its miracle.




Robert Hervé was the first to experiment with pearl culturing in Polynesia . He settled in the Tuamotus and built a fare or bungalow on piles over the lagoon of Apataki where he carried out his studies. After failing to produce large numbers of pearls in the 1930s, he brought in Japanese grafting specialists to help perfect the art of culturing pearls in Polynesia. Today, the Tahitian black pearl is French Polynesia's number one export item.

The Giant South Sea oysters that are found in the warm waters of the inter-tropical zone belong to the Pinctada family. These are highly sought after and they produce pearls of an exceptional size in an infinite range of colors. The shell of the Pinctada Maxima, which have white, silver or golden colored lips and that of the Pinctada margaritifera, which has green, black or silver lips, has always been prized for its specificities: thickness and quality of the nacre, depth and brilliance of color.

The Pinctada margaritifera, variety Cumingi, named for the scientist who first described them in 1820, populate exclusively the coral reefs of Polynesian lagoons. Their giant shells are streaked with black lines on a gray background and the lips are black. The inside edge of the shell is splashed with iridescent glints of greens and blacks that are absolutely unique and from which they take their Tahitian name of Poe Rava or green black. In fact, they offer a fascinating diversity of shades.

This aristocrat of turquoise-blue lagoons loves waters of between 24 and 29 C degrees. At 18 degrees C its growth stops and at 11 degrees it dies. Such low temperatures are nonexistent around Tahiti and its archipelagos.

Water density, the nature of the sea bottom and currents exert a notable influence on its
growth. A strong Polynesian oyster will live for as long as 30 years, attain a size of 30 cm and get to weigh as much as 5 kgs (11 pounds).

The average life span of the species is estimated to be between 10 and 15 years with an average diameter size of 15cm.


  Tahitian Pearls Classification

When harvesting pearls, the farmer performs an initial sort of this crop, discarding all the rejects. He then performs a more detailed separation of his crop sorting out pearls by size, shape and quality.
  Size

Pearl size is most commonly measured in millimeters. Tahitian cultured pearls generally range in size from 8 mm to 16 mm.
  Shape

There are four basic shapes that Tahitian cultured pearls come in:

  Round and Semi Round
Round pearls are almost-perfect spheres whose diameter variation rate is less than 2 %. Semi round pearls are slightly imperfect spheres whose diameter variation rate is greater than 2 % but less than 5 %.
01
  Semi-Baroque
Semi-baroque exhibits at least one axis of rotation and are subdivided into drop, button, and oval shapes.
02
  Baroque
Baroque pearls do not have any axis of rotation and are non-symmetrical in shape.
03
  Circled
Circled or ringed pearls are characterized by regular streaks or concave rings, perpendicular to an axis of rotation of over more than one third of the pearl's surface.
04
 

Quality

This is determined by observing the special features of the pearl's surface and luster. Special surface features are considered to be any flaw in the nacre that is visible to the naked eye such as pits, bumps, scratches, deposits, ridges and cracks.
Luster is evaluated according to reflection of light on the pearl's surface. The brighter the reflection, the higher the luster.

Tahitian cultured pearls are defined by four basic qualities:
A, B, C, D.
  Quality A 
An "A Quality" pearl is one that has no surface flaws or very slight flaws that are visible to the naked eye and confined to less than 10% of its surface. All "A Quality" pearls exhibit a very high luster.
05
  Quality B
A "B Quality" pearl is one that exhibits high or medium luster with some flaws visible to the naked eye and distributed over less than one third of the surface.
06
  Quality C
A "C Quality" pearl is one that exhibits several visible flaws, distributed over more than one third of the surface and exhibits a medium quality luster.
07
  Quality D
A "D Quality," pearl is one that exhibits a large amount of visible flaws over more than two thirds of the surface, regardless of luster.
08

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