Source: The Online Jeweller Magazine
Author: FRANS JONKER, G.G., GIA
Unlike the more common pearl types, Tahitian pearls typically have a much darker body color and they have become some of the most sought-after, and most expensive pearls in the world.
Tahitian pearls are known for their amazing iridescent, vibrant, almost metallic colors, and are unique among saltwater cultured pearls. Though commonly called “black” pearls, Tahitian pearls are actually gray, to lighter or darker degrees.
In addition, Tahitian pearls have the unique ability to display a variety of colors at the same time, shimmering on their surfaces in varying shades — colors such as Peacock, Eggplant — or Aubergine, Green, Olive Green, Blue and Magenta.
Because of their vast color range, matching these pearls into a finished strand is an enormous task requiring thousands of loose pearls to create a single strand.
Tahitian pearls were once the rarest, most valuable cultured pearls in the world, and they are currently still much more valuable than Freshwater and Akoya pearls.
In Tahiti, the story is told of the god Oro, who long ago used his rainbows to visit Earth, giving mother-of-pearl its iridescence and Tahitian pearls their entrancing colors.
Although Tahitian pearls carry the name of the famous Tahiti Island they do not actually come from Tahiti. Tahiti is the main trading post for atolls(small islands) that produce Tahitian pearls.
Tahitian pearls are produced exclusively by the exotic black-lipped oyster which can reach a foot or more in diameter, and produces very large pearls.
They are farmed in French Polynesia, the Cook Islands, and the Micronesian Islands, but only those grown in French Polynesia may be called Tahitian pearls.
With the European discovery of the Pacific Islands in the late 1700’s came a rush of traders and explorers who soon learned of the water’s riches. The pearl oysters quickly became depleted, nearly to the point of extinction.
Then, by 1880, France gained control of the island group we now refer to as French Polynesia and strict regulations were applied to curtail the intense fishing among these islands, including zones designated as off-limits, to allow oyster beds to repopulate.
In the mid-20th century, building on the successful pearl culturing techniques of Kokichi Mikimoto in Japan, experimentation began with the oyster that produces Tahitian pearls.
The Tahitian pearl is now French Polynesia’s largest export, making up over 55 percent of the country’s annual exports of 20 million dollars.
The cultured Tahitian pearl farms are located in the blue lagoons of the Tuamotu-Gambier Archipelago, which is one of the five archipelagos which make up French Polynesia.
The culturing process involves an expert grafter, who inserts a bead made from a mollusk shell into the gonad, or reproductive organ, of the mature Pinctada Margaritifera mollusk.
The whole process takes place very quickly, as oysters cannot survive very long out of the water. It takes around two years for an oyster to be mature enough to even begin producing pearls.
Inserted with the bead is a piece of mantle tissue from a donor mollusk, which influences the color of the pearl being produced and provides epithelial cells to ensure that the oyster produces the all-important nacre around the inserted nucleus.
Compared to harvests at Akoya pearl farms, harvests at Tahitian pearl farms are much smaller, simply because the the supply of oysters used to grow them are far less plentiful.
If, after extracting a pearl, a technician determines the oyster is healthy, he or she will immediately insert another nucleus to produce another pearl. Some oyster may be nucleated up to 4 times.
SIZE: Tahitian pearls generally range in size from as small as 8mm to as large as 16mm, with the average pearl measuring around 13 millimeters. Pearls below 10mm are typically considered small in size.
10mm to 12mm are generally the more popular sizes selected for necklaces, while anything above 13mm is considered to be larger, rarer, and more valuable, especially in the higher qualities. Tahitian pearl necklaces often graduate in size.
SHAPE: Tahitian pearls come in all the shapes cultured pearls are found: “round,” “drop,” “button,” “oval,” “semi-round,” “circle — or “ringed,” “baroque,” and “semi-baroque.” Perfectly round pearls are the most desired and valuable, particularly in larger sizes.
BLEMISHES: Tahitian cultured pearls display a wide range of surface qualities, from “clean” to “heavily blemished.” High-quality Tahitian pearls may occur virtually free of flaws such as spots, bumps, pits, wrinkles and rings.
Tahitian cultured pearl farmers generally use four ratings for surface quality: Clean-Very Lightly Blemished (A), Lightly Blemished (B), Moderately Blemished (C), Heavily Blemished (D).
All surface grading is done with the naked eye (no magnification device like a jeweler’s loop is used in the process).
Quality A: pearls are clean to very lightly blemished (A-). These pearls are entirely smooth or are marred with just one or two tiny ripples or indentations (often hidden later by a drill hole) that are visible to the naked eye but are confined to less than 10% of the surface.
Quality B: pearls are lightly blemished. These pearls are have some imperfections concentrated over less than a third of their surface.
Quality C: pearls are moderately blemished. These pearls have light concentrations of imperfections over less than two-thirds of their surface.
Quality D: pearls are heavily blemished. These pearls have light imperfections over more than two-thirds of their surface and no deep imperfections; or deep imperfections over half of their surface .
*Under Tahitian government regulation, Tahitian pearls below D quality are not allowed to leave Tahiti, but they can be sold in Tahiti.
All things being equal the fewer blemishes the pearl exhibits the higher its value.
LUSTER: is one of the most important quality factors of Tahitian pearls. It is the luster that affects the way in which a pearl reflects the light .
Black pearls will naturally reflect light differently than a lighter colored or white pearl.
However, Tahitian pearls offer their own unique luster that ranges from soft iridescence to a lively, almost metallic shine.
The finest Tahitian pearls also have a green overtone that is called “peacock green”. This is a particular variety which shows an absolutely amazing iridescence, and is highly valued.
A solid black pearl with no overtone is considered less desirable and may cost as much as 50% less than one of similar quality with green overtones.
When the light reflections are weak and fuzzy (or diffused), the pearls are usually described as soft or dull. Dull luster pearls are rejected.
NACRE THICKNESS: affects the durability and sometimes the beauty of a Tahitian cultured pearl. Tahitian pearls have a reputation of having thick nacre due to their long time culturing period.
Under official classification regulations, a Tahitian cultured pearl must have at least 80% of its nucleus’ surface covered with successive layers of pearl material. Thin nacre pearls are rejected.
It is very important to realize that pearls are very susceptible to damage from chemicals and the environment so special care needs to be taken when wearing as well as storing them.
After all, they are the only gemstone that is made by a living creature!