Researched by Tom Taffel
San Francisco Gem and Mineral Society
Member Since 1975
Protect your pearls from ACID of any kind, including the:
Never allow the string to get wet. If your pearls do become dirty you can, wipe them with a very diluted solution of a mild liquid soap such as Lux Liquid or Ivory.
Never clean your jewelry (containing pearls) ultrasonically or with steam.
Because pearls are extremely soft (2.5 hardness), they should always be protected from contact with hard surfaces such as other jewelry. When storing, always wrap them in a soft cloth to protect their soft surface from being scratched by other jewelry.
The natural beauty of the Black Tahitian Pearl´s nacre cannot be restored if lost, so be careful with your black Tahitian pearls.
Reflection: (luster, reflectivity, glaze sheen, shine, radiance, inner-layer, reflection), light bouncing off the surface of the pearl. The surface of the pearl acts like a mirror. The smoother the surface, the brighter the pearl will appear. This smoothness is part of what gives Tahitian pearls their superior reflective quality known as luster. Cultured Tahitian pearls tend to have a very high luster. Some are so lustrous that they have an almost mirror-like quality. Interestingly, the luster of cultured Tahitian pearls is significantly greater than their natural counterparts.
Size One of the most unique aspects of Tahitian pearls is their large size. Pearls are measured by their diameter in increments of 0.5mm. Small pearls from the black-lipped oyster (Pinctada margaritifera) range from 8mm to 9.5mm. Medium pearls range from 9.5mm to 11.5mm. Large pearls are larger than 11.5mm. Pearls over 16.5mm are very rare, and therefore more valuable. Exceptional specimens include the baroque pearl of 26.95mm in diameter, which can be seen in the Musee de la Perl.
The Shape or form of a pearl depends on many factors, including the biological forces on the environment, which can affect the secretion of the pearl sac, and the nature of mother-of-pearl itself. One can find pearls in round, perfect sphere, symmetrical, button or oval, drop, semi-round, slightly imperfect sphere, semi-baroque, pear, tear drop, oval or button shape. Baroque: irregular forms that don’t fit into the above categories. Ringed or circled, baroque and semi baroque: a subcategory characterized by multiple circles on or near the surface.
Perfectly round and symmetrical pearls are the rarest and most exceptional. They represent at maximum 5% of the harvest. This rarity makes them the most valuable. While round pearls are the most highly sought after for rings and necklaces, the other shapes often inspire designers to create unique jewelry.
There are natural non-nucleated, abstract, artistic, asymmetrical black Tahitian pearls known as keshi (also spelled kashi," "keishe," and "keishi). These pearls are highly prized by jewelry designers for their artistic qualities and uniqueness. Small keshi pearls tend to be less expensive than comparable round pearls, but large keshi pearls are both rare and more expensive than their round counterparts.
Color A pearl gets its color or chroma from the mantle tissue of its parent. “Black” pearls come from the black-lipped oyster, Pinctada margaritifera, hence the name: "black" Tahitian pearls. Despite their name, these pearls, which are called Poe Rava in Tahitian, are not necessarily black. The basic black or gray of the Tahitian pearl
gives rise to a multitude of tones from white to lunar gray/lunar blue, in an amazing palette of tints of the most astonishing hues: rainbow, (peacock), creamy, peacock, pistachio, green, eggplant, (aubergine), blue, pink, cherry, golden, poerava, silver, white, gray, chocolate and black.
Even if peacock green and eggplant are the most sought after for their rarity, all the colors produced by the Pinctada margaritifera have their own originality and richness.
Refraction: light passing through the pearl. The transparent aragonite acts like a prism, bending the light as it passes through the pearl. Some of the light bounces off the layers of aragonite. The more transparent these layers, the easier itis for the light to pass through and reach deeper into the pearl. Orient is the iridescence from the light reflected from the inside of the pearl. If the layers of translucent aragonite are perfectly aligned, they act as a lens, bending the light. This light returns to the surface as the shimmering rainbow aura which is the hallmark of a quality pearl.
Reflection and Refraction combined produces “interference” causing the pearl to radiate iridescent light. The layers of aragonite work as a “diffraction grating” breaking the light into a shimmering spectrum. This is the effect known as “Orient” the moving rainbow of colors so remarkable in Tahitian pearls. Interference increases surface brightness, luster, inner luminosity and orient, giving the impression of a glowing, translucent sphere. The larger the pearl, the more these light phenomena are pronounced. If the layer is too thin, (less than .8mm - taking 18-24 months to develop), the light tends to be diffused rather than reflected resulting in poorer luster and orient. On the other hand, the more layers of aragonite film there are, the larger the pearl and the more exquisite its luminous qualities.
Quality (purity, smoothness), is determined by exterior imperfections and by the brilliance, (shine, sparkle orability to reflect light). The best pearls are nearly featureless, with a high degree of translucency. The cultured pearls of Tahiti are precious jewels of high purity and rare quality which are grown under strict regulation by licensed producers.
Surface imperfections in the nacre layer include: punctures, pits, scratches, deposits, streaks and swellings. Categories are based on luster, and smoothness and run: Top Gem, A, B, C and D.
Top Gem has 0 flaws
It takes one hundred oysters to produce one gem quality pearl. Sea turtles can eat over one hundred and fifty oysters a day!
The temperature of the water dictates both the thickness and the brilliance of the pearl. Warm waters promote the production of layers of pearl, whereas cooler water makes for finer and thus more transparent layers. The Pinctada margaritifera prefers the warm waters of the Pacific. Around the Gambier Islands, the Pinctada produces ultra-fine layers of aragonite; the substance that makes up the inner lining of the shell or the “mother-of-pearl” as well as the pearl itself. The archipelago is situated to the south of Tahiti where the water is cooler, so that the pearls acquire a particularly fine luster and orient. A Tahitian pearl has many thousands of layers of aragonite, depending on the length of time the pearl spends in the oyster. Each one is extremely thin and has the appearance of a transparent film. It takes two to three years before a pearl can be grafted and two years to produce a quality pearl.
In The United States, set pearls appraise at about four times their cost. Tahitian unmounted cultured pearls are exempt from all customs duties and entry taxes in the United States of America (duty free). The duty free status for Tahitian black pearls was restored on Sept. 1, giving them coverage under the General System of Preference as goods considered as having come from an underdeveloped country.
According to The BPGC, the only time duty does not apply is when the
pearls are loose. As soon they are have a clasp or are strung together there
is a 16% local tax applied that you can reclaim before leaving Tahiti.
Upon arrival in the U.S. you are allowed $800.00 per person on duty free
items (set black pearls, perfumes, etc.) or $1,600.00 per couple. Above
this amount, there's a 3% tax per thousand.
Luster or Orient/Orientation
Size
Shape or Form
Color
Surface Purity and Quality
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These standards are as rigorous and precise as those determining the quality of a beautiful diamond.
"A" has 1-2 flaws covering less than 10%
"B" has 2-5 flaws covering 10-33%
"C" has > 5 flaws covering 33-66%
"D" has > 5 flaws covering more than 66%
Photos taken by Tom Taffel on July 25, 2006
m/s Paul Gauguin and Bora Bora Sunrise