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. 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 submits to a 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 -- it is just that this phenomenon is induced by the grafter. 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.

The Beginning Of Pearl Culturing In Polynesia

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 the 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 the number one export item in French Polynesia.

The Giant South Sea oysters that are found in the warms waters of the inter-tropical zone belong to the Pinctada family. These are highly sought after and t hey produce pearls of an exceptional size in an infinite range of colors. The shell of the Pinctada maxima with white, silver or golden colored lips and that of the Pinctada margaritifera with green or black lips, have always been prized for their specificity's: 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, exclusively populate 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 Rave 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 to 30 years old, attain the size of 30cm and can weigh 5kgs.
The average life span of the species is estimated to be between 10 and 15 years with a normal size of 15cm.

When selecting a pearl, the following 5 criteria's should be considered:

1 - Shape / 2 - Size / 3 - Color / 4 - Luster / 5 - Surface SHAPE: Round pearls are perfectly spherical and are the most valuable of shapes. They are quite rare and are more expensive. The pear shaped pearls are round pearls extended by a "Queue" at one end. Button-shaped pearls are half-spherical pearls with a flat shape. Baroque-shaped pearls have an irregular shape and are often the source of inspiration for unusual-shaped jewels and accessories. Circled pearls have one or several furrows which encircle the entire pearl. SIZE: The average size of a Tahiti Black Pearl is 8mm to 11 mm in diameter. The larger ones are 12 mm to 14 mm, and it is rare to find pearls that are as large as 15 to 18mm. In assessing the value of a pearl, one takes into consideration the size of the pearl itself, the size of the nucleus -- which is between 6mm and 9mm -- and most importantly, the thickness of the pearl layer. While size is not actually a quality factor, it does have a significant impact on price. COLOR: Tahiti black pearls have a wide range of colors and shades ranging from pearly white to deep black. Other color shades are blue, green, aubergine, silver, copper or gold and amazingly, some pure white or pink-champagne pearls can sometimes be harvested. In selecting a color, the most flattering pearl for any woman is one that compliments her complexion. LUSTER: The formation of a pearl from a tiny bit of sand in an oyster is a fascinating natural phenomena. The natural layering process is not just a defense against an irritant caught in the oyster, but it is also how a pearl gets its luster. The thickness of the layers results from the oyster depositing about 1,000 layers of nacre which is secreted by the oyster. Each layer measures a few microns and the thickness of each layer varies with water temperature. To truly admire the luster of a pearl, one should look at it under sunlight. SURFACE: The surface of a pearl should be free of disfiguration or major blemishes. Slight blemishes or flaws on a pearl are natural and might include small marks or scratches on the surface or perhaps slight bumps or craters. It is often said that "luster is what you see from across the room, not blemishes".

Jewelers and Black Pearls
No matter what the shape, size, color or imperfections of black pearls, jewelers are always able to "show off" the pearl by using clever, yet elegant designs to enhance the good and hide the imperfections. This is why, any black pearl is always valuable.

The cost and purchase of Black Pearls
Obviously there is a very wide range of prices according to the above criteria's of quality. But as an indication, from fair to good, 9 to 12 mm in size, the price can start at $200 to $2500. Larger size and better grades will go to 3, 4000 Dollars and above.

Reading
If you are interested in reading more about the black pearls of Tahiti we recommend the excellent booklet "Pearls of Tahiti" which is very informative and well illustrated. It can be found in Tahiti at the airport and some hotel bookstores, as well as at the Librairie Vaima, 2cd floor of the Vaima Shopping Center in Papeete.
It is publish by SCOOP, phone (689) 43 54 56, fax (689) 42 61 74.