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PostPosted: Tue Apr 24, 2007 9:58 pm 
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For more information on jade:

Richard Hughes site has an outstanding series of articles beginning here:
http://www.ruby-sapphire.com/jade_burma_part_1.htm

Fred Ward Hosts a Site called Friends of Jade:
www.friendsofjade.org/

Please feel free to add any information you can on any of these topics. :P


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 Post subject: motled vs web like appearance in jade
PostPosted: Mon May 07, 2007 7:13 am 
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hi everyone, I am new at this place , simply great. Being a hobbyist sitting several hrs flight from the nearest gemologist, I have a collection of un identified gems , some were acquired as jadeite , look like it , excellent green color, semi transparent, have the typical text book description of motling.

1.I need to know the chances of my confusing moteling (specks of green and colorless Portions) with the web like formation of treated stones. can i get to see the pics of the web somewhere?

2. How reliable are these two different characteriscs indicative of treatment

Thx


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PostPosted: Mon May 07, 2007 8:22 am 
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How reliable are these two different characteriscs indicative of treatment


Welcome.

They are not reliable. The only thing that is reliable in an infrared spectrographic analysis. Contact Mason Kay and arrange sending a piece or two of your jade to them. They will to the analysis very reasonably.

Sadly almost all jade available on the market today is B or C jade: Polymer impregnated and dyed.


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PostPosted: Mon May 07, 2007 10:24 am 
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Barbra,
Thx for guidance , seems rational thing to do.


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PostPosted: Mon May 07, 2007 1:12 pm 
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hi Barbra

Where can I find specific information about FTIR spectra of the different types of jadeite?

In this mineral collection at my uni, there is a piece of jadeite. The collection was donated 15 years ago, but it was put together over the man's lifetime. So the piece of jadeite might be A, or B, or C type. I thought it would be an interesting exercise to subject it to FTIR.

I spoke with my chemists, and they can run a FTIR spectrum on a solid. And they even said they would run one for me. But they'd rather not re-invent the wheel... they'd like to know about sample preparation and about the expected differences between spectra.

Thanks,
Brian


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PostPosted: Mon May 07, 2007 8:47 pm 
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We have all heard of translucent emerald green jade but I have never seen any faceted, it always seems to be cabbed. Is there any facet grade out there or is there simply no demand for faceted or what? It would seem that a stone that rates with the finest rubies and red diamonds would have to be better than cab grade, right? Of course, I could be missing something. Best regards, Lee

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PostPosted: Tue May 08, 2007 12:01 am 
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Oops, a little google research with keywords "FTIR jadeite" and I find typical spectra. These organic chemists should recognize hydrocarbon signatures in the spectra... fingers crossed that I can get around to trying this out.


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PostPosted: Tue May 08, 2007 11:01 am 
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Hi

A lot of nice information you can find in G&G Spring 1982 (you can download it from GIA) and the beautiful book "Jade" by Roger Keverne
ISBN 0-442-30847-7

Ciao


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PostPosted: Tue May 08, 2007 11:10 am 
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"Jade" by Roger Keverne
(ISBN 0-442-30847-7 ) is available on the Jade page of our Bookshop.

Thanks, Fozzie, for the reference to the G&G, 1982 article. I am holding the copy now.
Excellent and in depth!!!


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PostPosted: Wed May 09, 2007 5:51 am 
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Lee Little wrote:
We have all heard of translucent emerald green jade but I have never seen any faceted...



Well, even the most translucent jade is still quite hazy/textured compared to usually faceted materials and even in theory RI is low (1.6 or so). Why bother? The (mercifully) few pieces of faceted jade seem like a crime to me :?

Since it came to it: is there a point to the 'cab grade' concept? That's just another cut with an esoteric following, not a grade.


Last edited by valeria102 on Wed May 09, 2007 7:44 am, edited 1 time in total.

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PostPosted: Wed May 09, 2007 6:35 am 
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Hi All,
Anyone seen 01May report by AGTA GTC . Richard Hughes and Dr. Lore Kiefert have presented a pic of Jadeite FTIR , within the same text they have pointed out an easy to spot differentiating characteristic of black pits and microfracture of bleached mtrl and absence of these on natural surface .

Anyone used this feature to separate natural from bleached . Any comments pls.

Thx

Mazhar


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PostPosted: Wed May 09, 2007 9:53 am 
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The above reference can be found here:
http://www.agta.org/consumer/news/20070 ... tm#jadeite

The spectra shown is for treated jadeite.
Does anyone have the data for untreated?

It is also my understanding that not all treated jadeite will display a series of micro fissures, which is why FTIR is the most reliable indicator.


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PostPosted: Wed May 09, 2007 10:42 am 
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The link below is a .pdf file of a single page that presents FTIR spectra of "A" and "B" jadeite:

http://www.spectroscopymag.com/spectros ... rticle.pdf

It seems the presence of structure between 3200 - 2800 cm-1 identifies the presence of hydrocarbons (and thus indicates "B" jadeite), while the absence of structure in this wavenumber range indicates "A" jadeite.



I hate wavenumbers, but chemists use 'em a lot. Wavenumbers are the inverse of wavelength, with a bunch of conversion factors thrown in. So, when wavenumber decreases, wavelength increases. To avoid the annoying calculation, you can use the following link to convert from wavenumber to the wavelength, or vice-versa. http://www.impublications.com/convert.php


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PostPosted: Wed May 09, 2007 3:26 pm 
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Valeria102 said

Since it came to it: is there a point to the 'cab grade' concept? That's just another cut with an esoteric following, not a grade.


My response:
When I buy rough I am very interested in whether something is graded as cab vs. facetable material. It has great influence on the cost, and therefore affects a buying decision, such as whether I would even want to look at it. I'd say that "grade" in this context has meaning only for rough and its suitability for a particular form of lapidary; it has nothing to to with the grade of finished gems.

Lee Little's question on faceting reminded me of milky chalcedony or opal that had been faceted (often for beads), perhaps with the intent to provide reflective surfaces all over the stone, I think that placing facets on cabs only gets in the way of the color. Considering something like the imperial jadeite I once saw in Kobe back in '63, facets would definitely be a crime, like valeria102 so eloquently stated.

Dick


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PostPosted: Wed May 09, 2007 10:41 pm 
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valeria102 wrote:
Lee Little wrote:
We have all heard of translucent emerald green jade but I have never seen any faceted...



Well, even the most translucent jade is still quite hazy/textured compared to usually faceted materials and even in theory RI is low (1.6 or so). Why bother? The (mercifully) few pieces of faceted jade seem like a crime to me :?

Since it came to it: is there a point to the 'cab grade' concept? That's just another cut with an esoteric following, not a grade.


I don't know if the most translucent jade could be described properly as hazy or not. I bet the owners of it would strongly disagree. The RI doesn't stop faceting from occurring in tourmalines, topaz and many others that have a lower RI than Jadeite.
Certainly have to disagree with cab grade being 'just another cut with an esoteric following'. That is actually a funny statement. When preparing to facet stones a cutter will always sort out those that have less clarity and more inclusions as cabbing material rather than wasting his time faceting the lower grade material. It is most definately a grade, however, my question is more in the direction of wondering if this very expensive gemstone is indeed all cab grade or is it simply cabbed for traditional reasons or for some other reason? To show the color off the best still points to heavy inclusions/cab grade. The color of other faceted stones is not compromised but is enhanced by faceting.
If it is all cab grade then I find it even more remarkable that it has achieved such a high value. This would indicate that it has some qualities, perhaps beyond current science, that other stone does not since no other cab grade material can come even close to rivaling it in value. Best regards, Lee

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