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South Sea Pearls’ Nacre Thickness

Some questions on South Sea Pearls’ Nacre Thickness :

1) I understand that the minimum nacre thickness for akoyas is .25mm and .8mm for tahitians. What is the minimum for south sea pearls? Anything official? Whati s currently being applied in the industry?

2) Thick nacre makes good luster. However, I recently saw a thin nacre coating in a small baroque south sea pearl (it’s in a strand) through the drill hole (I’m estimating about .5-.8mm) but the luster of the pearl is great. If I’m not mistaken, good luster also may be produced by good nacre quality aside from nacre thickness. I’m assuming the pearls were still untreated as the strand is composed of bi-colored pearls and the overtone was a bit greenish to greyish but the luster is great and looks natural. Not sure though if there is a nice polishing agent that’s been applied. Any thoughts?

3) Is Indonesia still producing much of the indicator pearls?

Nacre – cross section

There are no standards for nacre thickness in South Sea pearl production, at least not in the way there is in French Polynesia. But the nacre is typically very thick (2-4mm), at least when not dealing with indicator pearls, which I have not seen around in a while.

If the pearl is baroque it could definitely have thinner nacre on one side than the other, and thinner nacre does not mean the luster will always be bad (think akoya). This is a problem in Tahiti right now, with so much production going to waste because of thin areas (of baroques), even though the nacre is thick everywhere else around the pearl.

The south sea that I saw was around 8.5mm. What’s the smallest nucleus typically used in south seas? 6mm?

May I also add that why is thick nacre associated with luster? Isn’t it a reasonable assumption that luster depends on the nacre quality, not the nacre thickness?

Think of freshwater pearls. They are almost all nacre yet there are a lot of freshwater pearls that are not lustrous at all.

May I also add that why is thick nacre associated with luster? Isn’t it a reasonable assumption that luster depends on the nacre quality, not the nacre thickness?

Both… I think. Structure and thickness – as you say with the example.

And treatment is obviously more reliable way to get lustre than scouring for natural quality.

nacre – diagram

I don’t think there is any natural counterpart to the mirror shine of fake or (some) inexpensive treated pearls. Not sure how to ‘show’ what I am talking about here, but I am quite sure everyone has seen such examples somewhere. Think cheap!

Anyway, just an opinion (the same as yours, I guess).

Would add a question: It seems reasonable to think that a lower limit for nacre thickness that may produce the very same visual effect as on an all-nacre pearl could be determined – it should be a matter of how deep through the nacre does reasonably strong light get into the pearl. Which can’t be all that deep… no matter how much more desirable all-nacre pearls might be

Does anyone know what this thickness is for any type of pearl? (would imagine that candling half a pearl would give such result; Don’t have a microscope with darkfield at hand…).

This is the only relation I see in nacre thickness and luster — the bead nucleus maybe seen in thin-nacred pearls. And since a thin nacre is translucent/transparent, the pearl may have a chalky appearance.

On the other hand, I’ve smashed a chalky south sea with good nacre thickness!

A lot of written resources always say good luster is indicative of thick nacre.

However, if we think of good nacre quality/structure, maybe a thin-nacred pearl is possible to have great luster even without treatment. Doesn’t great luster hide blemishes? Why can it hide a nucleus?

Also, as I’ve seen in fwps, in some pearls (they’re usually in the multi-colored strands), there can be that mirror-like shine when placed in incandescent/ pearl lights.. they can have that metallic mirror shine (but in daylight, you can see some depth unlike in overly treated and fake pearls).

… if we think of good nacre quality/structure, maybe a thin-nacred pearl is possible to have great luster even without treatment. Doesn’t great luster hide blemishes? Why can it hide a nucleus?”

Haven’t yet found any measure of what is ‘too thin’ to allow lustre naturally… in mm, for any type of pearl (= nacre structure) or quality. That’s where the question in the previous post comes from. Since nacre is translucent… it should have different properties from different thickness. Anyone knows how this works exactly?

Nacre cross section

The south sea that I saw was around 8.5mm. What’s the smallest nucleus typically used in south seas? 6mm?

The smallest nucleus I’ve seen used in South Sea pearls is 5mm.

Haven’t yet found any measure of what is ‘too thin’ to allow lustre naturally… in mm, for any type of pearl (= nacre structure) or quality. That’s where the question in the previous post comes from. Since nacre is translucent… it should have different properties from different thickness. Anyone knows how this works exactly?

Exactly. I was however wondering whether there is a quantitative model/measure of the effect explained on the page down your ling… fully recognizing that it would be a rather ‘hot’ if not controversial thing (depending on where it came from).

Love the ‘deep lustre’ wording; new to me. It sounds suggestive in the right way, appreciate the relation with the nature of the phenomenon, clear as two words can get, etc…

It wuld be extremely complex to find an equation to describe the relationship between nacre thicknes and luster. In the case of thinly coated pearls it is a no-brainer: just surface luster, mainly due to polishing.

But when we talk about thick-coated pearls (Cortez, SSP, FWP) then we have to take into account too many variables. Each animal is said to deposit some 1-3 nacre layers per day. The amount depends on: the environment (food availability, temperature=metabolic rate, stress, etc.), the oyster’s health (also influenced by the environment, but also having to do with parasites, predators, handling, etc.) and the organism’s genetic make-up.

If we were to cut a pearl in half, and inspect the nacre layers you can find all sorts of interesting data…just as dendrochronologists (the people that can “read” tree-rings) use tress and old logs-wood at archaelogical sites. Each pearl can tell a story of good times and times of sorrow. The longer the pearl was grown, the more complete its story can be.

The pearl layers can also be of different substances, not only nacre (aragonite), but also chalky calcite, brown conquiolin, and all these will interact with each other…so every pearl bearing mollusk will have a personal story to tell, the story unfolds in its pearl and we can see that each pearl is unique…

If we were to cut a pearl in half, and inspect the nacre layers you can find all sorts of interesting data…just as dendrochronologists use tress and old logs-wood at archaeological sites.

…so every pearl bearing mollusk will have a personal story to tell, the story unfolds in its pearl and we can see that each pearl is unique…

Leaving any cold judgement aside, what you describe is so …. beautiful! All self-respecting pearls should feel flattered.

Sure there’s no exact science here, just like the one scientific method you mentioned (dendrochonology) isn’t working with the same concepts of ‘precision’ as material science or whatever.

My understanding was that a greater number of thinner layers refract light better than fewer thicker layers and as such, lustre is vastly improved. Some farmers have been known to drop their oysters to deeper (colder) depths just prior to harvest to partly achieve this.

Re nuclei size, I would doubt anything smaller than about 6mm is used regularly.

Perhaps…but when i buy from this reputable farm they insist on this fact. They use it regularly because their oysters are virgin and cannot accommodate bigger nuclei..i believe they have a high mortality rate and actually produce smaller-sized specimen. This is actually due to shabby management..and also accounts for a lot of their oysters being stolen from right under their noses…

This is one of the major decisions for farmers; seed early (small shells) or harvest early (thin layers) to initiate cashflows. Easy for me to say but not sure i’d recommend either path. To my mind, in an ideal world, bigger shell for first seeding, thus resulting in bigger pearls. With all new clients of mine, when asked, i offer the advice….always focus on larger size and better quality. Again, easy for me to say.

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South Sea Pearls’ Nacre Thickness

Just some questions…

1) I understand that the minimum nacre thickness for akoyas is .25mm and .8mm for tahitians. What is the minimum for south sea pearls? Anything official? Whati s currently being applied in the industry?

2) Thick nacre makes good luster. However, I recently saw a thin nacre coating in a small baroque south sea pearl (it’s in a strand) through the drill hole (I’m estimating about .5-.8mm) but the luster of the pearl is great. If I’m not mistaken, good luster also may be produced by good nacre quality aside from nacre thickness. I’m assuming the pearls were still untreated as the strand is composed of bi-colored pearls and the overtone was a bit greenish to greyish but the luster is great and looks natural. Not sure though if there is a nice polishing agent that’s been applied. Any thoughts?

3) Is Indonesia still producing much of the indicator pearls?

There are no standards for nacre thickness in South Sea pearl production, at least not in the way there is in French Polynesia. But the nacre is typically very thick (2-4mm), at least when not dealing with indicator pearls, which I have not seen around in a while.

If the pearl is baroque it could definitely have thinner nacre on one side than the other, and thinner nacre does not mean the luster will always be bad (think akoya). This is a problem in Tahiti right now, with so much production going to waste because of thin areas (of baroques), even though the nacre is thick everywhere else around the pearl.

The south sea that I saw was around 8.5mm. What’s the smallest nucleus typically used in south seas? 6mm?

In akoyas, it is plausible to attribute the luster to treatment for thin- nacred pearls. I understand that a thinner side than the other is typical in pearls esp. baroques, but the current lack of standard for nacre thickness in south seas concerns me about the durability of the product.

May I also add that why is thick nacre associated with luster? Isn’t it a reasonable assumption that luster depends on the nacre quality, not the nacre thickness?

Think of freshwater pearls. They are almost all nacre yet there are a lot of freshwater pearls that are not lustrous at all.

Both… I think. Structure and thickness – as you say with the example.

And treatment is obviously more reliable way to get lustre than scouring for natural quality.

I don’t think there is any natural counterpart to the mirror shine of fake or (some) inexpensive treated pearls. Not sure how to ‘show’ what I am talking about here, but I am quite sure everyone has seen such examples somewhere. Think cheap!

Anyway, just an opinion (the same as yours, I guess).

Would add a question:

It seems reasonable to think that a lower limit for nacre thickness that may produce the very same visual effect as on an all-nacre pearl could be determined – it should be a matter of how deep through the nacre does reasonably strong light get into the pearl. Which can’t be all that deep… no matter how much more desirable all-nacre pearls might be 

Does anyone know what this thickness is for any type of pearl? (would imagine that candling half a pearl would give such result; Don’t have a microscope with darkfield at hand…).

This is the only relation I see in nacre thickness and luster — the bead nucleus maybe seen in thin-nacred pearls. And since a thin nacre is translucent/transparent, the pearl may have a chalky appearance.

On the other hand, I’ve smashed a chalky south sea with good nacre thickness!

A lot of written resources always say good luster is indicative of thick nacre.

However, if we think of good nacre quality/structure, maybe a thin-nacred pearl is possible to have great luster even without treatment. Doesn’t great luster hide blemishes? Why can it hide a nucleus?

Also, as I’ve seen in fwps, in some pearls (they’re usually in the multi-colored strands), there can be that mirror-like shine when placed in incandescent/ pearl lights.. they can have that metallic mirror shine (but in daylight, you can see some depth unlike in overly treated and fake pearls).

It wuld be extremely complex to find an equation to describe the relationship between nacre thicknes and luster. In the case of thinly coated pearls it is a no-brainer: just surface luster, mainly due to polishing.

But when we talk about thick-coated pearls (Cortez, SSP, FWP) then we have to take into account too many variables. Each animal is said to deposit some 1-3 nacre layers per day. The amount depends on: the environment (food availability, temperature=metabolic rate, stress, etc.), the oyster’s health (also influenced by the environment, but also having to do with parasites, predators, handling, etc.) and the organism’s genetic make-up.
If we were to cut a pearl in half, and inspect the nacre layers you can find all sorts of interesting data…just as dendrochronologists (the people that can “read” tree-rings) use tress and old logs-wood at archaelogical sites. Each pearl can tell a story of good times and times of sorrow. The longer the pearl was grown, the more complete its story can be.
The pearl layers can also be of different substances, not only nacre (aragonite), but also chalky calcite, brown conquiolin, and all these will interact with each other…so every pearl bearing mollusk will have a personal story to tell, the story unfolds in its pearl and we can see that each pearl is unique

From my scientist-pearl-farmer friend, she harvests her pearls in the cool months of December-Feb (Philippines). The oysters coat the pearls with a thinner layer of calcium carbonate which is shinier than a thicker coating. So whether your nucleus is big or small then that accounts for the luster, unless its treated or coated artificially.And the smallest nucleus that can be used is 2mm. I know of a philippine farm that uses 2-6mm for their virgin oysters. When they are inserted, the oysters are held in baskets where they are held upright (as in with the lips looking up) so that the oysters do not spit out or reject the nucleus. There is also a 50% mortality rate among spats in the pearl farm, so in culturing, one must really pick the spats which display the best “healthy” attributes. This assures for better genes the next time it’s their turn to produce their own spat. Veddy veddy interesting huh? You should really visit a pearl farm and see for yourself.

My understanding was that a greater number of thinner layers refract light better than fewer thicker layers and as such, lustre is vastly improved. Some farmers have been known to drop their oysters to deeper (colder) depths just prior to harvest to partly achieve this.

Re nuclei size, I would doubt anything smaller than about 6mm is used regularly.

Perhaps…but when i buy from this reputable farm they insist on this fact. They use it regularly because their oysters are virgin and cannot accommodate bigger nuclei..i believe they have a high mortality rate and actually produce smaller-sized specimen. This is actually due to shabby management..and also accounts for a lot of their oysters being stolen from right under their noses.

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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.