Pearls and Lab Reports

[Zeide Erskine]

Hi Jeremy,

The production of the bead nucleated freshwater pearls (with about 35% coin pearls and 65% rounds) was 4-5t in 2001 and was projected to reach 30t (that's metric tons or 1000kg) by the end of 2005. If you consider the amount of truely round tissue-nucleated pearls, you see that 65% of 30t corresponds to about 20t or 20% of total output in fine rounds (estimated at 100t). I posted the name of company before but here I go again: Chenghai Xinxi Pearl Culturing Factory and Guangdong Hin Qing Pearl Culturing Company JV, Technical Director: Xie Shao He. I do not know whether these pearls are always declared to be nucleated (except for the obvious case of coin pearls), but they probably put out even more than that considering the lively franchise business.

Zeide

[Zeide Erskine]

Hi Bogus,

The largest nuclei used in Chenghai are 17mm and will get a 2mm or so absolute cultivation (that means nacre thickness measured from the radius) for a grand total of a 21mm final pearl. These round pearls are almost exclusively sold to Hong Kong dealers and heaven knows what they will be declared to be. The typical nucleus size is only 9-10mm, though. The Chenghai operation is getting their rounds already very round most of the time. The new franchisees in Zheijiang still have tail problems. The Chengai growers are using a hybrid mussel but I do not know exactly what went into that particular genetic mix. A sizeable share of their output are yellow goldens and have already been found mixed in with golden South Sea strands. These pearls are by no means cheap. So, you are not getting cheated by having any of these mixed in with your South Sea cultured pearls. Actually you are getting a substantially better value due to their greater nacre thickness.

Zeide

[jshepherd]

Prejoected, yes, but they did not produce rounds. To date, no farms have perfected rounds with a bead. The GIA tested this back in 2004, sampling thousands of rounds because comsumers were hearing rumors, based on the earlier plans. But they did not find a single round with a nucleus. I have never seen one either. Those that claim to be producing rounds are very, few and farm between. Certainly not accounting for any percentage of total production.
On the ground in Zhejiang they have said it is because of the incision. It does not heal fast enough, and the mantle secretes into it - they all have some sort of tail. This is why you could buy them cheap just a couple of years ago. Now they are trying to make money on their investments by artificially inflating prices with the help of HK pearl houses like Rio, and selling them with fancy names and descriptions at the shows.

[Zeide Erskine]

Hi Jeremy,

It seems that Elisabeth Strack got enough rounds without a tail to photograph and show in her 2001 book. Fred Ward also seems to have found some and so does Antionette Matlins. The real difference is that these pearls are not marketed in China but in Hong Kong and Japan where they are being sold as Kasumigauras and South Seas depending on color. I consider them a better deal than South Seas and definitely on a par with Kasumigauras but nowhere near a tissue-nucleated round from Zheijiang or Heilongjian.

Zeide

[Bogus]

Oh, dear...I'm afraid a lot of this is going over my layperson head!

Actually I've become interested in big freshwater pearls...not South Seas. When I said 'big' I was thinking 10-11mm.

Perhaps I should explain myself a bit. My first love is natural, untreated/heated gemstones. Until I found this website, I've never been too interested in cultured pearls because I've always thought of them as 'nacre coated beads".

Since natural pearls out of my league, I'm intrigued with these "big" FWPs.

I'm still having trouble picturing how these bigger roundish FWPs can be grown from a small irregular "tissue" nucleus. What is the "tissue"? Is it round? Does it come in different sizes?

Thanks.
Bogus

[Kevin Canning]

The mantle tissue used is just a small piece of tissue and they can place up to 50 in a mussel at one time. Most of the resulting pearls do not come out round or even close to round, but the sheer numbers of freshwater pearls produced makes round freshwater pearls possible.

[Zeide Erskine]

Hi Bogus,

The mantle tissue is the part of a mussel that forms the shell. If you transplant a piece of this mantle tissue someplace else within the same animal or into an open wound of another animal it will bond into the local blood circulation, the connective tissue disintegrates and the conchiolin producing and calcium carbonate secreting cell islands will multiply and grow together to form a three dimensional pearl sac. The shape of the original tissue implant determines the final shape of the pearl sac although available body cavity space may cause indentations that then lead to changes in the shape of the pearl being created.

In contrast to what one often hears, there is no residual tissue inside the pearl that forms. There may be an original conchiolin clump at the center of a pearl if the nucleation was done while the mussel was active and secreting more conchiolin. If the mussel was nucleated in the dormant months, there will be no measurable conchiolin clump at the core. The aragonite crystals grow along the folds of the conchiolin protein. As such, a tissue nucleated pearl is indeed a true pearl albeit a cultured one. The final size of the pearl is due to cultivation time and available ambient calcium.

And, of course, you cannot grow 50 at a time if you intend to grow big rounds. The ambient calcium limits the amount of nacre a mussel can precipitate. Also in 50 nucleations the pearls would all grow together into a clump if you did not harvest them at around 6mm. So for the big rounds, you need space in the mussel and patience. It happens by accident when a multi-nucleated mussel dissolves most of the other implants and only lets 1 or 2 grow at the same time. You can greatly increase your yield of big rounds by only implanting one or two tissue grafts. The size of the tissue graft also influences the speed of pearl growth. This technique of implanting just one or two large, round tissue grafts has already been making inroads in China for years. The multiple nucleation thing with 20 or even 50 grafts will only yield beading grade pearls with too much conchiolin that renders them murky, off-round shapes because their pearl sacs touch, and more often than not grown together pearls called peanuts.

I hope this helps,

Zeide

[Caitlin]

Hi Bogus
I felt exactly the same when I came here. I am so happy I found out about QUALITY cultured freshwater pearls.
Anyway, let me take a stab and see If I understand. The experts will correct me as needed.

The mantle tissue that is inserted in CFWP is roughly shaped as the desired pearl shape. Hoewever it seems that the inserted tissue stimulates the growth of a pearl sac and then it shrivels and is gone leaving the nacre-producing sac. In a bead nucleated pearl, the sac surrounds the bead and thus the bead is covered with nacre. In the CFWP the sac just fills up with nacre. That is why it is harder to get a really round tissue nucleated pearl.

[Caitlin]

Well, I got beat to it.

I think I just said the same thing as Zeide, but mine is a probably over-simplified version

[Caitlin]

There may be an original conchiolin clump at the center of a pearl if the nucleation was done while the mussel was active and secreting more conchiolin. If the mussel was nucleated in the dormant months, there will be no measurable conchiolin clump at the core.

Hi Zeide
what is the difference in the pearl with and w/o the conchiolin clump at the core?
Was my saying the sac "Fills up with Nacre" too far off?

[Zeide Erskine]

Hi Caitlin,

Your term of filling it up with nacre would be inside out. Such original conchiolin clumps are about 2mm in cristaria plicata and rarely more than 0.3mm in hyriopsis cumingii. The calcium carbonate precipitates from the pearl sac fluid and the aragonite crystals grow onto the conchiolin protein folds.

Zeide

[Caitlin]

Hi Zeide
And in the ones that don't have the clump in the center? I have been consulting Strack, 2006 since I first tried to answer Bogus. There is a diagram on p.414.

It appears that a few injected epithelial cells will multiply and form a sac. Now does the pearl form on the outside of the sac or the inside? It looks like the inside.

[jshepherd]

Returning to the large bead-nucleated rounds, I would really like to know who is selling them in Hong Kong. I would also like to see a strand. I am having a really hard time believing it simply because I have not seen any, high quality, bead nucleated round freshwater pearls - in China or Hong Kong, and I know most of the large wholesalers in Hong Kong as well.
I also want to reitterate my early post about the 80% mantle and 20% bead nucleated larger rounds - this is not correct. I just do not want another run on the same rumor we dealt with a couple of years ago, when everyone was certain if they were large and round they were bead-nucleated, asking us if we used x-ray to be certain they weren't (this is why the GIA did their research). If there are larger, nucleated rounds out there, they do not even come close to making up .01% of the production. They would be a definite exception to the rule.

[Zeide Erskine]

Hi Caitlin,

Both the initial conchiolin secretion and the aragonite accretion occur inside the pearl sac. That's why there is no tissue remnant inside the pearls.

Hi Jeremy,

Caitlin can probably answer that question better since she has the newer edition of the Strack book. In my edition it is right before the chapter on American freshwater cultured pearls.

From all I heard the sellers in Hong Kong are marketing them as saltwater cultured if they are round. So they would not impact the freshwater cultured pearl market at all.

Zeide

[Caitlin]

Hi Zeide and Jeremy
There is a section in Strack called, Freshwater Cultured Pearls With Nucleus .pp446-448. There is a picture of perfectly round pearls with a high gloss.

This is just a wild guess- these are not being marketed as CFWP, but as "BABY Suth Sea pearls! Voila! 2 mysteries solved in one swipe. (nacre thickness, "in range of .5mm-3mm"!)