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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 9:42 am 
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For the record, BE treatment can be ruled out by several other methods and thus it is not always necessary to use LIBS or LA-ICP-MS. If a gem is determined NOT to have been diffused there is no need for further testing. Thus if your report from AIGS simply says HT without reference to light elements or diffusion etc...then you can rest assured that it is traditional heat only.

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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 10:17 am 
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Excuse please my lack of knowledge about beryllium diffusion. I understand if a sapphire is examined and determined not to be heated, then beryllium diffusion can be ruled out. But if the gem shows signs of the heat treatment, how does the lab determine that it has not also been beryllium diffused without testing for the presence of the element beryllium? Is there some other indication of diffusion treatment that does not require testing for beryllium? Maybe this is obvious but I am not expert about this.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 10:18 am 
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If you can, go at the GIT in Bangkok. It,s not so far from AIGS

http://www.git.or.th/index_en.html

That is the University lab:
http://www.git.or.th/testing_center_en01.html

GIT's CIBJO registered laboratory (officially accredited by the World Jewellery Confederation since May 2000) has several highly experienced gemologists and is equipped with the world-most advanced instruments. Its gem testing services include
• Distinguishing natural, synthetic and imitation gemstones
• Analyzing the enhancement methods of gemstones
• Distinguishing natural, seawater cultured pearls and freshwater cultured pearls; pearl treatments
• Distinguishing natural, synthetic and imitation diamonds
• Identifying treatment types of diamonds
• Ruby & Sapphire grading
• Diamond grading
• Determining Gemstone’s country of origin especially rubies, sapphires and emeralds
• Identifying the variety of jade and quality enhancement method applied
• Laser inscription on gemstone girdle

Good luck

Oli.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 10:23 am 
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The only information I found on how to check if a sapphire is not diffused are specific inclusions that look like circles. However, that is being thought of as inconclusive in some recent material I read. Can someone point me to an up-to-date reference that indicates, based on using standard gemological equipment, if a sapphire can be determined as not diffused? Thank you in advance. :D


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 10:47 am 
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We know today there are many other light elements than “Be” that could be diffused into gems. So the problem today for a lab is to distinguish between those elements. It is no enough to say if the stone have been diffused using a visual analysis because it can give you clue but no proof.
When you write a report, you need to have all the proof about what you are saying and if the stone have been treated you need to know with what.
I made myself long time ago a doc with all the GRS http://www.gemresearch.ch/ treated corundum, side by side pictures of natural untreated and beryllium treated, sapphire and ruby, the heated one etc, even by origin. That’s my best friend in lab but that will only give me clues about the treatment. That do not give me the right to write diffused on a report because you need at least to bring the proof of it. In science, inductive method of reasoning is not accepted.

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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 10:55 am 
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Often, standard gemological tools are not sufficient to determine diffusion treatments.

In the early days, there were clues one could determine with microscopic observation, but the sophistication of the treaters (and treatment methods) have made it necessary to rely on very sophisticated tools for positive determination of treatment(s). Of course if one sees clear examples of treatment with microscopic observation (circles, surficial color concentrations), further testing may not be necessary. BUT, if one just observes evidence of high heat treatment, it may be prudent to take the stone to the next level.

Richard Hughes wrote an excellent early article: Vampire Blues

G&G's article in Be Diffusion in Ruby & Sapphire is insightlful, albeit an earlier article.

The most recent paper I can find, from 2009 is Beryllium Treated Blue Sapphires: Continuing market observations and update including the emergence of larger size stones by G. DuToit, J.Thanachakapad and K.Scarratt: (June 25th, 2009)

This study, raises some excellent points. Such as, some blue sapphires have been sold as Be diffused, but upon testing with LA‐ICP‐MS, no beryllium was found. :?


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 12:00 pm 
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Thank you for the links Barbra, and thanks to everyone that has responded to this thread.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 3:13 pm 
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As Jason pointed out, Be diffusion can be ruled out without expensive equipment in some instances. Others require the equipment though. If there is no evidence of high heat, then you can safely say there has been no Be diffusion, unless there is a new method I have not heard about.

IMHO, currently, I prefer a couple inclusions in some stones, like sapphires/rubies, so I can get examine them and see if high heat was used or not, versus a perfectly clean stone. Same with quartz products, give me a natural inclusion or two, lol.

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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 4:23 pm 
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What is evidence of high heat vs low heat though? I know there are some tell tale signs to see if a s gem is unheated like silk or needles, but what are the signs that indicate low heat vs high heat?


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Tue Jun 01, 2010 6:37 pm 
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tudortwo wrote:
What is evidence of high heat vs low heat though? I know there are some tell tale signs to see if a s gem is unheated like silk or needles, but what are the signs that indicate low heat vs high heat?


UPDATE thanks to Vince Pardieu:
Vince Pardieu wrote:
Titanium will start to diffuse rapidly in corundum around 1000 degres. Then my experience is that if you heat a sapphire or a ruby with rutile needles at about 1000 to 1200 degres then the rutile wioll be affected. Most heat treatment to remove the silk is about 1400 and then they cool rapidly until less than 1000 in order to avoid the needles to form again...
Then they cool quietly in order for the stone not to develop fissures...



In order to improve the blue color of sapphire, it is necessary for the titanium in the rutile to be disseminated into the lattice of the sapphire. This will NOT happen unless the corundum is heated minimally to 1000ºC-1400ºC .

Claims of "low" heat in sapphire treatment have always made me laugh a little.*

More info: Identification of heat treated corundum

*exception: glass filling can be done at quite low temperatures, leaving mineral inclusions intact.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Wed Jun 02, 2010 11:15 pm 
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I agree with Barbra. I only use the term high heat, meaning to separate natural heating that occurs form the extremely high heat it takes to diffuse corundum. If rutile is intact but slightly damaged, one can safely assume it was NOT high heat.

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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Wed Jun 02, 2010 11:26 pm 
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LOL, if the rutile is damaged it's still very high heat, in my opinion....but I guess, nothing much happens at lower temps. :|

Diffusion occurs at temperatures just shy of the melting point of corundum.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Thu Jun 03, 2010 12:28 am 
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Hello,

Wonder what difference that would make if the stone have been heated at one or another temp.?
If the stone is treated, the only difference will be on the price whatever the temp. the stone was heated.

From 800 to 1900 degree with O rich to get better color (to much Fe2+ then looking for Fe3+)
From 1600 to 1900 degree with O rich to get better yellow or pink become orange
From 1600 to 1900 degree with O poor stone with Fe3+ and Ti4+ induce Fe2+ to get bluer sapphire and if cool down slow that will let the Ti crystallize to get needles and asterism. Mostly used for Geuda sapphire
From 1600 to 1900 degree O poor with cool down fast t get ride of the Ti needles
From 1100 to 1400 degree O rich on rough with cool down slow from 1 to 14 days to help Ti to crystallize.

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Oli.


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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Fri Jun 04, 2010 1:36 am 
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Barbra Voltaire wrote:
LOL, if the rutile is damaged it's still very high heat, in my opinion....but I guess, nothing much happens at lower temps. :|

Diffusion occurs at temperatures just shy of the melting point of corundum.

Very true, and thanks for correcting my mistake, I guess I choose a bad inclusion as an example, lol. Should have thought that one through a bit more. It was the only inclusion known in sapphire I could think off of hand, lol. Sorry. :(

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 Post subject: Re: AIGS ability to test for diffused corundum
PostPosted: Mon Jun 07, 2010 12:16 am 
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Jason wrote:
For the record, BE treatment can be ruled out by several other methods and thus it is not always necessary to use LIBS or LA-ICP-MS. If a gem is determined NOT to have been diffused there is no need for further testing. Thus if your report from AIGS simply says HT without reference to light elements or diffusion etc...then you can rest assured that it is traditional heat only.

J-


I don't know that is true Jason. I'm trying to find out, but when I emailed the lab, and asked them if my gem was only heat treated without beryllium because it said HT only, they just said that the "issue of beryllium was not addressed." I'm unsure what that means so I emailed for clarification, but I never heard back. Right now, I'm assuming it could be a be-treated stone based on the lack of information after three emails back and forth. I feel, in my honest opinion, they are skirting my question.

If that's true, they should remove their HT codes from their webpage because it is misleading. I could potentially sell this gem, which might be be-treated, as traditional heat only by referencing that web page to a buyer.


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