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South Sea and Tahitian Pearl Grading

Grading South Sea and Tahitian Pearls
While there is no internationally recognized number or letter system for pearl grading, there are best-grading practices that are accepted and recognized by all professional pearl dealers within the industry. Understanding grading attributes and quality characteristics of South Sea and Tahitian pearls is imperative to properly shop and compare.

Pearl Grades Are Combinations Of Many Different Value Factors
As pearls have many differing value factors such as shape, luster, size and surface quality combining together to produce a unique gem, grading pearls can become very difficult. Although it is possible to grade each value factor individually, most purveyors of this gem rely on a simple letter-grade system.

The grading assigned by a retailer or producer is specific only to that source. In other words, grades assigned by different companies are subjective to those companies and cannot be compared with grading from different sources.

Super-fine Tahitian pearl strands

Which System Is Correct? The AAA-A System Or The A-D System?
Confusion abounds regarding the use of the A-D system (the Tahitian System) or the AAA-A system, popularized by the late Kokichi Mikimoto. While some pearl dealers swear by one method, another seller may use the other. So which is correct? The answer is simple – they both are.

As there is no International mandated system for grading pearls, nor is there an absolute alphabetical system, both systems are used interchangeably. Their use is largely based on location, but even this is a general rule of thumb, by no means absolute.

Both Systems Are Correct
In the USA both systems are often used by different pearl companies, which is considered completely acceptable if the seller makes it known what system is being used, and has an accurate representation of the quantified qualities.

In producing countries such as French Polynesia and Australia the A-D system is nearly universally used by producers of Tahitian and South Sea pearls. However, when the pearls are auctioned in Hong Kong , these same producers utilize the AAA-A system when selling to wholesalers.

Courtesy of Cultured Tahitian Pearl Grading by PearlParadise.com

A-D (Tahitian) GradingAAA-A GradingGrading Description and Criteria
Top GemGem GradeFlawless pearl with excellent luster
Pearl exhibits no inclusions or imperfections prior to setting or drilling
AAAAFlawless on at least 90% of pearl’s surface
Only 10% of pearl’s surface may exhibit slight, concentrated imperfections
Only a single deep inclusion allowable
Pearl should drill or set clean to virtually clean
Luster is very high
A/BAA+Flawless on at least 80% of pearl’s surface
Only 20% of pearl’s surface may exhibit slight, concentrated imperfections
Only one or two deep inclusions allowable
Pearl should drill or set clean to nearly clean
Luster is high to very high
BAAFlawless on at least 70% of pearl’s surface
Only 30% of pearl?s surface may exhibit slight, concentrated imperfections
Only one or two deep inclusions allowable
Pearl should drill or set nearly clean
Luster is high to very high
CA+Flawless on at least 40% of pearl’s surface
Up to 60% of pearl?s surface may exhibit slight, concentrated imperfections
Deep inclusions are limited to 10% of pearl?s surface
Luster is medium to very high
DAAt least 60% of pearl’s surface will exhibit flaws
Deep inclusions and/or white spots within inclusions on up to 20% of pearl?s surface
Luster is poor to very high

*Cultured Tahitian pearls that do not fall into a category above, or do not meet the minimum nacre depth requirements of 0.8 mm per radius, do not pass the mandatory examination of the Ministere de la Perliculture of Tahiti. Those pearls are refused for export and destroyed.

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South Sea Pearl

South Sea Pearls Defined

A South Sea pearl is pearl produced by the Pinctada maxima mollusk. They are currently cultured in areas throughout the Indian and Pacific Oceans, primarily in Australia, the Philippines, Indonesia and Myanmar.

The South Seas lie between the northern coast of Australia and the southern coast of China. These waters are the native habitat of a large oyster known as Pinctada maxima. This oyster grows up to 12 inches in diameter, and can be nucleated with a much larger bead than other saltwater pearl oysters such as the akoya.

south sea pearl
Golden south sea pearl

South Sea Pearls Come From Two Varieties Of Pearl-Producing Mollusks

There are two varieties of Pinctada maxima, the silver-lip and the gold-lip. The two are distinguished by their distinct coloration of the outer edge of the interior shell. This type of shell is also known as mother-of-pearl, and is responsible for the coloration of the cultured pearls produced, therefore the name.

Unlike the akoya pearl oyster, the South Sea pearl oyster will only accept one nucleation at a time. The oyster is nucleated when it is only about half developed, from 4.7 inches to 6.7 inches in size, or about 24 months old. Although the South Sea oyster will only handle one nucleus at a time, this oyster (like the Tahitian pearl producing Pinctada margaritifera) can be nucleated up to three times over the course of many years.

Why South Sea Pearls Grow So Large

There are four reasons South Sea pearls can grow to such large sizes, dwarfing many of their other saltwater pearl counterparts. These reasons are: the large size of the Pinctada maxima, the size of the implanted bead, the length of time the pearl is left to grow in the oyster, and the oyster’s environment.

Due to the size of the oyster, it is able to accept a large bead. The gonad of the Pinctada maxima is several times larger than that of the akoya. Because of this larger gonad, the South Sea oyster deposits nacre around the nucleus at a much quicker rate, especially in warm water, which speeds the oyster’s metabolism.

The South Seas are also extremely clean, and filled with plankton – the Pinctada maxima’s favorite food source. The clean waters and abundant food supply also speeds the nacre production. The growth period for South Sea pearls is also substantially longer than that of the akoya. Akoya pearls are harvested after only 9-16 months, where as South Sea pearls are harvested after a minimum of two years allowing for a larger size.

What Makes South Sea Pearls So Unique?

South sea pearl of Indonesia

South Sea pearls have several distinct characteristics that are unique to this gem. The nacre is unusually thick, ranging from 2 to 6 mm, compared to the 0.35 to 0.7 mm of an average akoya pearl.

South Sea pearls have a soft, satiny luster that comes from large aragonite platelets and rapidly deposited nacre due to the warm waters of the South Seas. South Sea pearls also have a subtle array of colors; typically white, silver, and golden – colors that are rare in other pearl types.