Treated/Enhanced Pearls

[pearlie]

Questions on how to detect post-harvest enhancements has come up in other threads, so I decided to start a new one dedicated to this topic in order for us to all learn from each other. I am speaking from my own experiences in the pearl world.

Personally, I am in favor of post-harvest treatments - for pearls and colored stones - as long as it''s disclosed.

Problems arise, and our gem markets become destabilized, when uninformed dealers sell treated pearls without disclosure, or those out to deceive succeed in passing off a color as natural when it is enhanced.

So what to look for? In another thread I mentioned treated/enhanced Tahitians can be "pitted". This probably raised more questions than answers, so let me clarify.

We all know that pearls are not perfect. In fact, the best way to determine whether a pearl is real (cultured or natural) from a fake (glass, plastic, etc.) is to look for the imperfections. Born in the body of a living organism, it is extremely rare for a perfectly round and surface clean pearl to be harvested. Even your most expensive and valuable pearls will have blemishes, however minor.

Indentations, crevices, circling, lines, dimples, overgrowths, etc. can all occur naturally. What I refer to as "pitting" is something that occurs post-harvest. A natural indentation, etc., will have somewhat smooth edges, as if something was pressing against the pearl sack during formation, and the layers of pearl nacre continued to be deposited on the nucleus, around that interference. Pitting on the surface of a Tahitian occurs when the pearls have been subjected to harsh chemical agents. The conchiolin (a protien) absorbs most of the chemical agents, "but may suffer damage which can only lead to a decreased durablity of artifically colored pearls" (quote taken from page 656 of Elizabeth Strack''s book Pearls)

It is this damage to the conchiolin that extends to the surface of the pearls, causing pits. The pits can be very small and minor, with uneven, rough edging.

Light colored, low quality Tahitian pearls are sometimes subjected to this treatment to make them darker, more uniform in color, and therefor more saleable. I''ve seen these at major gem shows - and they were not disclosed as treated - they look like the color of black shoe polish.

Chemicals used in this process include silver salts, silver nitrates, and who knows what else. This type of treated pearl can allow a consumer to own a strand of Tahitian pearls of a very large size for a pittance (excuse the pun!). Nothing wrong with this, as long as it''s disclosed.

Having said all this, let me add.......unfortunately, there are no absolutes. If you find pits, it is not diagnostic of post-harvest treaments. If you do not have pits, it does not mean the pearls were not treated. This is just a guideline to go by. The best protection consumers have is to find someone legitimate, and deal only with them.

Hope this helps to clarify what I meant by surface pits and how they happen. Hope others will add to this thread their knowledge of treatments and what to look for.

thanks
julie.

 

[The Old Pearler]

I think this is a good discussion. Btw, it is illegal to treat pearls in French Polynesia and no facilities exist in North America or Europe. So Tahitian pearls are only treated in Japan and China.

I disagree that pitting on Tahitians has anything to do with treatments. Pitting is a normal, natural occurrence in Tahitian pearls. It is a quality factor. There is pitting and there is spotting. Pitting usually refers to a deep spot. The pits are most often lighter in color than the surface of the pearl. This means that pitting can indicate IF a pear has been color treated, because dye can accumulate in these pits, causing them to be darker than the surface. This is because unlike akoya pearls, Tahitian pearls are only color treated using the outer method, not the inner method. The nacre is opaque and thick. The inner method (inserting the dye between the nucleus and the nacre) would not change the color.

Color addition can affect the durability of nacre, but this makes the nacre more brittle and causes cracks, not pits. Chemical treatments also affect nacre durability, causing the nacre to possibly crack or the surface to become chalky and dull. But the damage, when severe, may cause peeling but not pits. Nacre platelets are laid down like bricks in a circular fashion similar to an onion. When the nacre starts to come apart, it peels in chunks.

When Tahitian pearls are color treated, they most often take on a brownish color (see Strack page 652). There are other colors that processors treat for, like pistachio and chocolate, but this is of course disclosed and increases the value of the pearl because of the ''fad'' popularity.

But Tahitian pearls do not, even in China or Japan, go through the same harsh chemical treatments akoya and freshwater pearls are sometimes subjected to. Tahitian pearls do not improve when processed using maeshori or any of the other treatments that use chemicals and heat. Even South Sea pearls will go through this in Japan, but Tahitian pearls never do. The only routine treatment is polishing. The non-routine would be treatment with an organic dye, polymer coating (which can be detected by pricking the surface with a pin) and bleaching to achieve chocolate, which is done by only one company in Japan.

For someone shopping for Tahitian pearls in China, I think the only main thing to watch for is polymer coating. Color treatment is just not that common. The polymer coating improves the luster but will eventually wear off. Another way to detect polymer is to check the reflection. An untreated pearl will have reflective luster from the surface. A polymer treated pearl will reflect from under the surface.

 

[pearlie]

Hello Old Pearler, welcome to the discussion.

I did not realize that treatments (you are referring to post harvest enhancements, yes?) are illegal in Fr. Poly. So all the fancy colors, chocolates, etc. are being done in Asia?

To those reading these posts, we have both mentioned Elizabeth Strack''s book, Pearls. It is an extremely well written, and well researched book, and recommended reading for those with a passion for this gem.

You mentioned that the nacre will peel off in chunks, that''s what I''m calling a "pit". I''ll stop using that term so as not to confuse it with naturally occuring surface blemishes. But a compromised nacre will begin to break down, and the resulting blemish can present itself as I described.

However I stand by the statement that some low quality Tahitians are exposed to chemical agents. Maybe a more accurate statement would be low quality p. margeratifera''s are exposed to chemical agents in order to darken them and make them more saleable. Signs to look for include those small chunks Old Pearler spoke of. Keep in mind dear readers, these are not huge chunks of pearl missing from the surface, but are small and seemingly minor blemishes to an untrained eye. But they are an obvious post-harvest blemish, and not one that has occured during pearl formation.

 

[Phoenix]

Thank you very much, Julie, for starting this thread and thanks to Old Pearler for contributing too.

The infor provided is incredibly helpful and I'm very grateful to learn more about pearls.

I have some questions regarding SS pearls.

I have a pair of white round SS earring "jackets" which are though quite expensive are practically perfect, I'd say they'd be rated AA+ or even AAA quality. I boutht these from a jeweweller - a few months ago - whom I've been dealing with for several years and trust they have not and will not deceive(d) me.

However, I also have a white SS slightly off-round SS pearl pendant - bought last week - which I'm wondering about as to whether it's authentic; and I have a pair of golden SS which I also paid quite a bit for and am particularly worried about these.

For a start, my white SS pendant seems very light, though whether it's lighter or heavier than a synthetic pearl I really don't know. It's white so its colour is even throughout and it has some small dimples or "pits". When I look at it under a diamond loupe, I see concentric circles and I also looked at the drill hole whilst I was at the shop and the hole seemed to be even without any ragged edges.

Now, my golden SS pearls are slightly drop-shaped and initially looked to me to be quite genuine. I bought these from a Japanese pearl company at a jewellery exhibition in Singapore recently and i thought since they're Japanese, they should be ok. However, when I look at them these during last couple of days under a diamond 10x times loupe, what I see worries me. Essentially, I see:

- air bubbles which are more concentrated on the bottom and the top of the pearls (not too unlike those on another deep golden SS pearl pendant which I bought from a shop in Shanghai, China and which I subsequently returned). Now, these drop-shapped SS pearls are a lighter golden colour but am not sure if I can describe them as a lemon-golden or lemony/yellow colour;

- there are some slight reddish marks on the surface of the pearls;

- they do feel hefty, but I wonder if they are real SS pearls which have been coated with a polymer coating or have been treated somehow.

They are not drilled so i'm not able to look down the drill holes.

I'd really appreciate some advice as to how I could go about determining if the above SS's are non-fakes and in particular if my golden SS have been treated to enhance their colour?

 

[The Old Pearler]

Pearlie,

Yes, all post-harvest treatments are illegal in French Polynesia, and most Tahitians I know are stoutly opposed to chocolate and pistachio treatment which primarily occur in Japan.

I think our differing opinions in due in part to the vernacular. I understand now that by pitting you meant peeling, but I also disagree on the chemical treatments. Chemical treatments when considered harsh are not color-enhancing treatments. Even cobalt-60 treated (irradiated) akoya are not considered harshly treated, as the only change made to the pearl is manganese-containing freshwater bead in the center.

Harsh treatments are luster-enhancing treatments (when not properly applied). This would include heat treatment and maeshori, both of which are chemical treatments. Tahitian pearls never go through this treatment, only occasional color treatment and possibly coating. Color treating is done with organic dye. Polymer could be considered a chemical treatment, but it does not imbue itself to the aragonite platelets, it is only a surface treatment. This is why I maintain treatment has nothing to do with pitting, or even peeling of a Tahitian pearl. A peeling Tahitian is a rare sight, and is a pearl that cannot pass export control in Papeete, so will only reach the market illegally.

Harsh chemical treatments like those used on freshwater and akoya pearls in "family" processing factories can and do affect the nacre quality of the pearls. Freshwater pearls may oxidize in as little as six months, and the chemical treatment applied to akoya removes the water from the nacre, tightening it and increasing the luster, but making it more brittle and prone to breakage and peeling. The larger processing factories with the better "science" as they call it, have much better processing and these factors aren't as important. They also usually deal with a higher grade of pearl.



Pheonix,

I would not be concerned with the bubble-like inclusions you see. This are not atypical with South Sea pearls. If the pearls are oval, those flaws will usually be on the far ends of the pearl, not in the body. I would be concerned, however, with any red discoloration on your gold pearls. This is one possible (but not definitive) sign of treatment. For the pearls you are unsure of whether they are genuine, try the simple-but-effective tooth test.

 

[Phoenix]

Date: 9/13/2009 8:56:38 PM
Author: The Old Pearler


Pheonix,

I would not be concerned with the bubble-like inclusions you see. This are not atypical with South Sea pearls. If the pearls are oval, those flaws will usually be on the far ends of the pearl, not in the body. I would be concerned, however, with any red discoloration on your gold pearls. This is one possible (but not definitive) sign of treatment. For the pearls you are unsure of whether they are genuine, try the simple-but-effective tooth test.

Thank you so much.

Actually, the red is not so much red discolouration all over, they''re just tiny little marks on the pearls which are not eye-visible, only on the diamond 10xtimes loupe. Does that make a difference?

 

[The Old Pearler]

It sounds like the pearls might be color treated. When the dye agent bonds with conchioline it will often turn red. Because conchioline is the glue holding the aragonite platelets together, it is in clumps. So when color treated, one might find small red specks on the pearl.

You should also check for rings, concentric rings like a fingerprint, just under the surface. That is an indication of color treatment.

 

[pearlie]

Phoenix,

maybe it''d be a good idea to find a gemologist who specializes in pearls. They can best look over your questionable pearls. Jewelers are helpful, gemologists are helpful, one who is specialized would be ideal.

In Feb. of 2006 I attended a conference on pearl treatments. The subject was deceptive based post-harvest treatments of south sea and Tahitian pearls. The lecturer spoke extensively on this subject, I have written about that treatment on this forum, and I stand behind that. I am not just copying paragraphs out of a book, I am speaking from personal knowledge and experience.

Consumer protection and a healthy pearl market are what motivates me, therefor I think it very important for consumers to be aware of chemically treated black pearls. They''re being sold on the market, I''ve seen them for sale at trade shows in the US.

Signs to look for, dark, even color throughout the pearl, and small ''divots'' on the surface of the pearls with uneven edges, signs of a compromised nacre. And price, price will be a huge factor. For example, if you come across a round, 15mm black pearl necklace that has some or similar characteristics that have been described, at an unheard of price, this is no deal.

Also, there are no synthetic pearls. There are only real pearls (cultured or natural); fake pearls (plastic, glass, etc.) and I suppose shell beads could fall under the heading of immitation pearls. But there are no synthetics, so don''t let anyone try to sell you synthetic pearls, there is no such thing.

Majorca pearls (glass beads coated in fish scales, basically) shell beads, and some fakes, will feel rough when rubbed against the surface of your teeth, just like a real pearl can. While the "tooth-test" can be helpful, it is not a definitive test by any means. And you run the risk of scratching a pearl, staining it with lipstick for example, and it''s just plain gross to put jewelry in your mouth. So don''t do it. View pearls on a light colored background with good strong light, sunlight is best. Use your powers of observation, look for the imperfections, look down the drill hole to see how thick the nacre is. Feel the weight of the pearls. This will help you distinguish real pearls from fakes.

If you have some questionable pearls in your collection, ask on this forum and maybe we can help you, or find someone qualified who can identify them for you. If you are in a jewelry store and are uncertain if the salesperson is being truthful, leave. Find someone who''s legitimate, deal only with them. Legitimate retailers want to help you, want you to be educated about the jewelry, and will spend all the time you require answering your questions.

Julie.

 

[The Old Pearler]

Was that the Tucson Strack lecture on treatment identification? Funny! I was there. Maybe we met

I don''t think we are going to agree on this, and I''m not just trying to argue. My experience comes from selling and trading Tahiitian pearls in both China and Japan. I have a lot of first-hand experience in processing factories in both. I am explaining what I''ve seen first hand and have intimate knowledge of. I just think the signs you mention to look for are going to have a lot people questioning their untreated pearls. Dark, even color is quite normal. Small divots are almost universal. An uneven edge is relative. And what is an unheard of price? It''s relative.

But is the question of the color treatment? Is this what you are referring to when you describe a chemical treatment?

 

[Phoenix]

Date: 9/14/2009 7:23:13 PM
Author: pearlie
Phoenix,

maybe it''d be a good idea to find a gemologist who specializes in pearls. They can best look over your questionable pearls. Jewelers are helpful, gemologists are helpful, one who is specialized would be ideal.

In Feb. of 2006 I attended a conference on pearl treatments. The subject was deceptive based post-harvest treatments of south sea and Tahitian pearls. The lecturer spoke extensively on this subject, I have written about that treatment on this forum, and I stand behind that. I am not just copying paragraphs out of a book, I am speaking from personal knowledge and experience.

Consumer protection and a healthy pearl market are what motivates me, therefor I think it very important for consumers to be aware of chemically treated black pearls. They''re being sold on the market, I''ve seen them for sale at trade shows in the US.

Signs to look for, dark, even color throughout the pearl, and small ''divots'' on the surface of the pearls with uneven edges, signs of a compromised nacre. And price, price will be a huge factor. For example, if you come across a round, 15mm black pearl necklace that has some or similar characteristics that have been described, at an unheard of price, this is no deal.

Also, there are no synthetic pearls. There are only real pearls (cultured or natural); fake pearls (plastic, glass, etc.) and I suppose shell beads could fall under the heading of immitation pearls. But there are no synthetics, so don''t let anyone try to sell you synthetic pearls, there is no such thing.

Majorca pearls (glass beads coated in fish scales, basically) shell beads, and some fakes, will feel rough when rubbed against the surface of your teeth, just like a real pearl can. While the ''tooth-test'' can be helpful, it is not a definitive test by any means. And you run the risk of scratching a pearl, staining it with lipstick for example, and it''s just plain gross to put jewelry in your mouth. So don''t do it. View pearls on a light colored background with good strong light, sunlight is best. Use your powers of observation, look for the imperfections, look down the drill hole to see how thick the nacre is. Feel the weight of the pearls. This will help you distinguish real pearls from fakes.

If you have some questionable pearls in your collection, ask on this forum and maybe we can help you, or find someone qualified who can identify them for you. If you are in a jewelry store and are uncertain if the salesperson is being truthful, leave. Find someone who''s legitimate, deal only with them. Legitimate retailers want to help you, want you to be educated about the jewelry, and will spend all the time you require answering your questions.

Julie.

Julie,

Thanks again for your detailed reply.

I used the word "synthetics" myself to refer to fakes. The jeweller insists that the pearls are real. Unfortunately, there are no reputable appraisers or none that I know of in Shanghai that I can to go. I''d also like to know as much as I can, for my own educational purposes.

What do you mean by "divots"?

I''ll try and take pics of both the Tahitians and the SS and post them here. Perhaps that''d give you a better idea as to whether they may be fakes and/ or real pearls which have been subject to some colour treatment.

Thanks very much.

 

[Phoenix]

Date: 9/14/2009 9:52:28 AM
Author: The Old Pearler
It sounds like the pearls might be color treated. When the dye agent bonds with conchioline it will often turn red. Because conchioline is the glue holding the aragonite platelets together, it is in clumps. So when color treated, one might find small red specks on the pearl.

You should also check for rings, concentric rings like a fingerprint, just under the surface. That is an indication of color treatment.

The red specks are not in clumps. They''re just few red specks. I''ll try and post pics so you can see.

What do you mean by rings "just under the surface"? Do you have a pic or pics you can post so I can see what you mean?

Thanks very much.

 

[The Old Pearler]

Conchioline clumps between the aragonite platelets. This are very, very tiny. The would look like tiny red flakes. The red splotches would not look like clumps. It is difficult to describe the rings under the surface and quite beyond my photographic capabilities. Strack describes it well as almost finger print like.

I am going to do my best to attach a picture to this post. The pearl on the left is a dark pearl with even color. The next pearl is one with small spots. The third has mild to moderate pitting, and the last pearl has deep pitting. None of these pearls have been treated, and the flaws are consistent with A grade, to C, to C, to D grade. All are very typical of any give lot within that range.

If the picture does not post, my apologies. This is my first.

 

[The Old Pearler]

It works! I am going to try another two.

This image is of two pearls that have been treated. The pearl to the left is a treated chocolate, and the pearl to the right, a treated pistachio. Both are rarely found in natural color lots. If you look closely at the coloration you can see a difference between the play of color on a treated Tahitian versus a Tahitian of natural color.

 

[The Old Pearler]

I don''t know why that picture seems pixelated. It makes it more difficult to see the difference in color I was referring to.

This last image is of two Tahitian pearls that have serious nacre issues. They are starting to peel. These have not been treated either. The peeling is natural, and this pair does not fall within the A-D grading scale. These are throw-aways.

 

[Phoenix]

Date: 9/15/2009 11:32:32 PM
Author: The Old Pearler

It works! I am going to try another two.

This image is of two pearls that have been treated. The pearl to the left is a treated chocolate, and the pearl to the right, a treated pistachio. Both are rarely found in natural color lots. If you look closely at the coloration you can see a difference between the play of color on a treated Tahitian versus a Tahitian of natural color.

Thank you very much for posting the infor and the pictures. Mine, I'd say are closer to the one to the further left in yr first pic.

I'm afraid I still don't know what you mean by the "difference between the play of color"! Sorry, I'm being really dense here!

 

[Nacre]

Hi Phoenix,

I think TOP is referring to the photo above the one of the treated Tahitians. Treated Tahitians have an even skin colour that is ''too'' even. I think TOP has addressed the effects of treatments in another post.

Untreated Tahitians will show a variety of colour due to the laws of light and the nature of the nacre, I think this is what TOP is calling ''play of colour'' a phenomenon usually used to explain what is seen when looking at an opal (effect of light from beneath the surface), but it is a good term to use in this instance. It is also very difficult to photograph pearls and the colours that they show in different lights.

I strongly advise you to go and visit a local Gemmologist who specialises in Pearls whom you trust. Getting your eye in with colour in real life is something you can only really teach yourself over time. The terms a Gemmologist uses to explain the nature of light when it comes to pearls is very different from the descriptive words used (by the seller) to sell a pearl, just like with any gemstone. It''s science versus creative marketing...and sometimes science doesn''t sound very sexy!

I hope that helps!

 

[Phoenix]

Date: 9/21/2009 5:48:50 AM
Author: Nacre
Hi Phoenix,

I think TOP is referring to the photo above the one of the treated Tahitians. Treated Tahitians have an even skin colour that is ''too'' even. I think TOP has addressed the effects of treatments in another post.

Untreated Tahitians will show a variety of colour due to the laws of light and the nature of the nacre, I think this is what TOP is calling ''play of colour'' a phenomenon usually used to explain what is seen when looking at an opal (effect of light from beneath the surface), but it is a good term to use in this instance. It is also very difficult to photograph pearls and the colours that they show in different lights.

I strongly advise you to go and visit a local Gemmologist who specialises in Pearls whom you trust. Getting your eye in with colour in real life is something you can only really teach yourself over time. The terms a Gemmologist uses to explain the nature of light when it comes to pearls is very different from the descriptive words used (by the seller) to sell a pearl, just like with any gemstone. It''s science versus creative marketing...and sometimes science doesn''t sound very sexy!

I hope that helps!

Thank you so much, Nacre.

I am going to see my trusted gemologist in Singapore next time I''m there.

Buuuuuttt, I''m confused by the terminology you used (highlighted in yellow above). Sorry, I''m being really dense.

And who says science is not sexy!?

I come from a science background and I think it''s plenty sexy, LOL!