Blue Fluorescence in Diamonds

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New Article

Blue Fluorescence in Diamonds


http://journal.pricescope.com/Articles/73/1/Blue-Fluorescence-in-Diamonds.aspxhttp://journal.pricescope.com/Artic...Not-Lie---But-it-Tells-Different-Truths-.aspx


Thank You Garry for an excellent article!

 

[Lorelei]

Its a fantastic article, bravo Garry!

 

[WinkHPD]

Very nice article Garry! I especially liked this comment:

"It is important to remember that it is common for GIA to base studies on populations of diamonds that are submitted to the GIA GTL for grading and these sample assortments may not be representative of all polished diamonds."

It is so easy to get caught up in the belief that what we see is what exists. I am constantly amazed at how different what we see can be. I once did a staff training for a friend in another city on how to sell better cut diamonds and while there asked the staff who liked and disliked fluorescence.

Several of the staff rose their hands that they did not like fluorescence. Several also said they had seen few, if any fluorescent diamonds and none had actually taken them outside to look at. Later in the day I took several of them outside, one by one or in twos, to look at these diamonds. I made no attempt to change their minds as to whether or not they liked them, but I wanted them to at least see them.

It turned out that many disliked the fluorescence because they had been told it was bad and that they had accepted this without ever seeing it. In their universe fluorescence was bad, thus ugly. Once seen it was then an issue for some of them to confront their visual reality with their "learned" bias. One even told me quietly that, "Yes, it is pretty, but I still do not like it."

For good or bad, it had simply been easier to accept that which they were told than to look for themselves.

I freely admit to being in the, "Wow, look at that!" group. I love a nice strong blue fluorescence and what it does to a diamond in the sunlight. Of course I am also known to love stones from D to Z in colour (trying for that Australian spelling to go along with being a jeweller per your article, thanks for the shout out by the way). I know that as a vendor I am supposed to only like the D to G with an occasional H range, but I did poorly in that part of the class. I like sparkle, and I like it in many splendid colours.

Your other comment that I liked was about vendors not denigrating another vendor''s choice of product. That comment probably warrants its own lengthy article, one that few of us would be qualified to write. It seems we all have our biases, and it can be very difficult not to let them influence our thoughts.

Thank you for a well written and thought provoking article, it was a good read this early morning!

Wink

 

[oldminer]

Excellent article putting nearly everything out there on the subject. The trade tends to haggle over anything which the GIA comments on when making reports. Comments on fluorescence engender such haggling among dealers. You only haggle over lowering a price, not paying more, so dealers who want to make a sale knock off a small amouint to make the stone move. More than likely, there is no good reason for most of these "dicsounts" other than the desire to turn over money. The GIA has enhanced the problem recently with quite an about face on the recommended lighting to use in the lab. I agree that face up grading ought to become a standard and whatever the color is with this standardized lighting then that''s all there is. It would make things better for all concerned.

In fancy shapes, those which tend to intensify body color in face-up zones, strong blue fluorescence has a tendency to mitigate tinted body color especially inside these zones of color concentration. The end result is quite a noticeable shift in the color for such diamonds. When the color of fluorecence is yellow rather than blue, the face-up color can readily shift to more tinted than expected. These are the kinds of rather rare reactions which do justify haggling over the value of individual diamonds.

 

[strmrdr]

My opinion is that as long as the trade prices body color as a material rarity factor the only acceptable and repeatable thing to do is filter UV out and table down grading.
Then make a separate UV and "luster" determination.

 

[Garry H (Cut Nut)]

Thanks all

Date: 6/15/2009 11:09:46 AM
Author: strmrdr
My opinion is that as long as the trade prices body color as a material rarity factor the only acceptable and repeatable thing to do is filter UV out and table down grading.
Then make a separate UV and ''luster'' determination.

I do not think it is that easy Storm. I think (don''t know) that not all fluoro diamonds are raised in color by the same amount.

For e.g. does a J Very Strong blue go up one or 2 colours in GIA''s new grading lighting, and does a a F go up 1/2 a grade, or 2 grades?

We need some scientists to help answer such questions

 

[adamasgem]

Besides my commentary at http://www.adamasgem.org/giafluor.html there is and extensive review and updated

information and studies at http://accreditedgemologists.org/currevent.php lighting task force, right hand side of the page..


Not a believer in coincidences, the GIA changed their teaching on UV content, right about the time DeBeers went private (2002?). I wonder what that did to the value of the DeBeers stockpile and were the stockholders informed, somewhat like the true value of that 20 years of IIa brown rough?

I was told in Vancouver not to say that too loudly, but as I say, if they can't take a joke.....

 

[strmrdr]

AGA agrees with me:
pdf file of Task force presentation page 44.
"A colorless diamond should be laboratory-graded with the intent of
observing, grading and reporting its True Body Color."

 

[Garry H (Cut Nut)]

Sorry guys, I disagree.
e.g. "Consider UV energy AT NIGHT when consumers are more likely to wear and show off
their most important diamonds?"
You can not see the diamonds body color usually in evening artificial light.

 

[diagem]

Date: 6/15/2009 2:38:11 AM
Author:PS Admin

New Article

Blue Fluorescence in Diamonds




http://journal.pricescope.com/Articles/73/1/Blue-Fluorescence-in-Diamonds.aspxhttp://journal.pricescope.com/Artic...Not-Lie---But-it-Tells-Different-Truths-.aspx




Thank You Garry for an excellent article!

I second that....

Really great article...

It just shows how wide the scope of knowledge and preference is between trade members...
Just surprises me every-time more...

Liked your comment of the existing Ex-Vg polish grades vs. the non-existence grade of transparency on Lab reports.

Priorities----priorities

 

[adamasgem]

Date: 6/15/2009 3:17:29 PM
Author: Garry H (Cut Nut)
Sorry guys, I disagree.
e.g. ''Consider UV energy AT NIGHT when consumers are more likely to wear and show off
their most important diamonds?''
You can not see the diamonds body color usually in evening artificial light.

Garry.. bodycolor is most differentiable in the spectral range between 415nm and 600 nm.... The higher the blackbody color temperature the better the differentiation. The issue with UV is that , as AGA found, there is nil UV in normal indoor lighting, as fluorescent bulbs are sufficiently far away from the diamond to have next to zero effect on the apparent bodycolor, in comparison with GIA showing graders holding the diamonds right up to the UV containing fluoresent light to get a better look..

BTW, even the 4" fluoresecent lights on your microscope generate enough UV to effect apparent bodycolor, that is why I installed a Lexan (polycarbonate) filter) behind the diffuser...

I have seen EGL Israel stones misgraded by FUR(4) color grades because of blue fluor...

Raps discounts are full of s**t, given the grading variability, as in a 1cct stone, one coolor grade can mean $1000 or more, even in the G-H range, not to mention the D/E crossover...


Read the AGA consensus... agrees with what i published 10 years ago... Fuor can be a benefit, providing you are paying for the "correct" grade....Otherwise , you are getting intentionally ripped off...

 

[adamasgem]

Date: 6/15/2009 11:57:25 AM
Author: Garry H (Cut Nut)

Thanks all

Date: 6/15/2009 11:09:46 AM
Author: strmrdr
My opinion is that as long as the trade prices body color as a material rarity factor the only acceptable and repeatable thing to do is filter UV out and table down grading.
Then make a separate UV and ''luster'' determination.

I do not think it is that easy Storm. I think (don''t know) that not all fluoro diamonds are raised in color by the same amount.

For e.g. does a J Very Strong blue go up one or 2 colours in GIA''s new grading lighting, and does a a F go up 1/2 a grade, or 2 grades?

We need some scientists to help answer such questions

Garry, it all depends on the techniques used,as well as the distance to the UV containing light source.. Take the majority of the UV out by using a polycarbonate filter (Lexan)..

 

[adamasgem]

There is nearly a two to one difference in the UV output at the center of a fluorescent tube, to the edges... so if you have a string of non fluorescent masters ... you get the picture...

And yes Garry, the process is non linear, some diamonds will react differently, depending on the N3/N2 balance(which according to GIA, the N2 ceneters quench the N3 generated blue flluor)

 

[adamasgem]

The original Shiley colorimeter used an incandescent light source, with nil UV content, about a 2800 to 3000K black body source, measuring the blue/yellow ratio...

 

[Garry H (Cut Nut)]

Date: 6/16/2009 12:17:50 AM
Author: adamasgem
There is nearly a two to one difference in the UV output at the center of a fluorescent tube, to the edges... so if you have a string of non fluorescent masters ... you get the picture...

And yes Garry, the process is non linear, some diamonds will react differently, depending on the N3/N2 balance(which according to GIA, the N2 ceneters quench the N3 generated blue flluor)

Can you give actual examples of this range Marty?
Have you built a dat base?

 

[Indira-London]

Date: 6/15/2009 6:48:25 AM
Author: Lorelei
Its a fantastic article, bravo Garry!

That's just what I wanted to say Lorelei!
Well done to Garry on writing THE defiinitive article on fluorescence and tackling many commonly held misconceptions - useful and informative for consumers and professionals alike.

As to the measurement of fluorescence itself: I believe that there is room for improvement in awarding grades/consistemcy not just between different labs but within any given lab too.

 

[Garry H (Cut Nut)]

Date: 6/16/2009 2:20:32 AM
Author: Indira-London
Date: 6/15/2009 6:48:25 AM
Author: Lorelei
Its a fantastic article, bravo Garry!

That''s just what I wanted to say Lorelei!
Well done to Garry on writing THE defiinitive article on fluorescence and tackling many commonly held misconceptions - useful and informative for consumers and professionals alike.

As to the measurement of fluorescence itself: I believe that there is room for improvement in awarding grades/consistemcy not just between different labs but within any given lab too.

Thanks Indira.

I do believe that GIA''s Antwerp based research unit might be working on a solution Indira. Not sure if it would be commonly available or lab only.

 

[Indira-London]

Date: 6/16/2009 2:29:00 AM
Author: Garry H (Cut Nut)

Date: 6/16/2009 2:20:32 AM
Author: Indira-London
Date: 6/15/2009 6:48:25 AM
Author: Lorelei
Its a fantastic article, bravo Garry!

That''s just what I wanted to say Lorelei!
Well done to Garry on writing THE defiinitive article on fluorescence and tackling many commonly held misconceptions - useful and informative for consumers and professionals alike.

As to the measurement of fluorescence itself: I believe that there is room for improvement in awarding grades/consistemcy not just between different labs but within any given lab too.

Thanks Indira.

I do believe that GIA''s Antwerp based research unit might be working on a solution Indira. Not sure if it would be commonly available or lab only.

Thanks Garry - do you know what timescale they are working to? Without more stringency/consistency in grades, it only adds further haziness (oops no pun intended) to the whole subject.

 

[adamasgem]

Date: 6/16/2009 12:41:57 AM
Author: Garry H (Cut Nut)

Date: 6/16/2009 12:17:50 AM
Author: adamasgem
There is nearly a two to one difference in the UV output at the center of a fluorescent tube, to the edges... so if you have a string of non fluorescent masters ... you get the picture...

And yes Garry, the process is non linear, some diamonds will react differently, depending on the N3/N2 balance(which according to GIA, the N2 ceneters quench the N3 generated blue flluor)

Can you give actual examples of this range Marty?
Have you built a dat base?

1) All you have to do is measure the output of any fluorescent tube, as I have, and has AGA, I believe. The plasma in the center of the tube emits the most UV, and tails off to the edges by a factor of about two, as I remember from my Spectroline UV measurements.

2) On my website SAS2000 page there is my normalized graph of the spectra of NON Fluorescent diamond masters which indicate a correlation between the relative absorption at N3 and N2 , although I have never plotted it, vis a vie fluor stones.. I do also have EPR data on a lot of these stones (N3 center concentrations), measured by Bruker.

I had a GIA split I/J master once, with "robbed N2 centers", as the late Dr. Vince Manson termed it.

All diamonds fluoresce to some extent, believe it or not "none" does not mean "none", by GIA''s Clintonesque definition. You need to pump up the UV (365 or othere wavelengths) to "see it.

In a 1990''s (I believe) G&G (mine are packed away right now), there was an excellent article on the fluorescence spectroscopy of one particular diamond, showing the three dimensional contour map of an amplitude response versus wavelength versus monoenergetic excitation wavelength. I on''t know how the data were corrected for all the error contributors. In the AGA papers, Thomas H. used quazi mono energetic sources to show the relative response, with the peak N3 sideband response due to the ~405nm Hg lines, if I remember right.

No two diamonds are the same, and the absolute trace concentrations of the aggregates are very difficult to measure, because of the pathlength issue, as my masters are not flat plates, nor is there any really perfectly collimated source,nor "perfect" monochromatic source, which you need for the experiment, along with a lot of math correctins for slit smearing, detector sensitivity, excitation purity and stability,etc, etc, etc.. Ask DeBeers if you don''t believe me
I believe all you can get, without a lot of complex work, is somewhat qualitative data, with probably significant error bars!

The Beer''s Law math suggests non linear response... The ratios of N3/N2 centers for "zero" fluor has not been published, to my knowledge. Complex issue to "correctly" solve.

No dat base available....

 

[oldminer]

Marty:

"All diamonds fluoresce to some extent, believe it or not "none" does not mean "none", by GIA''s Clintonesque definition. You need to pump up the UV (365 or othere wavelengths) to "see it."


I have been told that ALL diamonds fluoresce provided sufficient UV is directed at them. However, the wavelength of emitted fluorescence may not be visible to the human eye. Of course, this means that if we can''t see it, it isn''t there. Nicely simplistic, but surely does not cover all the possible issues with perception of the color that we do end up seeing with our rather miserable receptors (our eyes).


I believe you have always been in the camp of no UV in color grading light. GIA was thought to be in this same camp for years due to their many statements to that effect, but now have admitted that they might never have been there and have sent us all notice that they now reside in the camp of "some UV". I sort of think this is where they have been all along under an assumed identity. Teaching one thing and doing it at the lab a bit differently.


Do you or anyone else have a comment or two about the effect of 400 to 420 wavelength light which is at the low end of visible, but which also apparently has some drastic potential effect on our perception of a diamond''s body color. How should we handle the amount of this range of light?

 

[Garry H (Cut Nut)]

Marty I do not think you read my conclusion.

I am not interested in screening out ALL UV for color grading.

I prefer the industry find a solution that represents some balance and realism. In the G&G article that was published concurrently with my article, they suggest that a CIE standard that is being developed is used. I also believe face up color and transperency are far bigger related issues.

For your benefit - here is part of my conclusion:
A review of the literature indicates that there are no clear guidelines on the type of lighting used for grading diamond colour. Should ultra violet light be present, if so what frequency and strength, and how far from a lamp should a diamond be held? This writer believes the answer lies in digital or spectrophotometer machine based colour grading, in the face up position, with perhaps half the radiation strength of long wave ultra violet light as found in shaded daylight. lf industry standards bodies like CIBJO could agree on an appropriate standard light source for face up colour grading, then the industry may not need to price fluorescent diamonds differently. Certainly consumers would prefer that the face up colour of a diamond was reported on lab diamond grading reports or certificates because differences in face up colour can also be caused by factors other than fluorescence.

 

[adamasgem]

Date: 6/16/2009 4:06:03 PM
Author: oldminer
Marty:

''All diamonds fluoresce to some extent, believe it or not ''none'' does not mean ''none'', by GIA''s Clintonesque definition. You need to pump up the UV (365 or othere wavelengths) to ''see it.''


I have been told that ALL diamonds fluoresce provided sufficient UV is directed at them. However, the wavelength of emitted fluorescence may not be visible to the human eye. Of course, this means that if we can''t see it, it isn''t there. Nicely simplistic, but surely does not cover all the possible issues with perception of the color that we do end up seeing with our rather miserable receptors (our eyes).


I believe you have always been in the camp of no UV in color grading light. GIA was thought to be in this same camp for years due to their many statements to that effect, but now have admitted that they might never have been there and have sent us all notice that they now reside in the camp of ''some UV''. I sort of think this is where they have been all along under an assumed identity. Teaching one thing and doing it at the lab a bit differently.That is called FRAUD, in my book


Do you or anyone else have a comment or two about the effect of 400 to 420 wavelength light which is at the low end of visible, but which also apparently has some drastic potential effect on our perception of a diamond''s body color. How should we handle the amount of this range of light?

If you look at the AGA data, you will see the extreme influence of 405nm excitation, present in all fluorescent lights.

 

[adamasgem]

Date: 6/16/2009 5:20:27 PM
Author: Garry H (Cut Nut)
Marty I do not think you read my conclusion.

I am not interested in screening out ALL UV for color grading.

I prefer the industry find a solution that represents some balance and realism. In the G&G article that was published concurrently with my article, they suggest that a CIE standard that is being developed is used. I also believe face up color and transperency are far bigger related issues.

For your benefit - here is part of my conclusion:
A review of the literature indicates that there are no clear guidelines on the type of lighting used for grading diamond colour. WRONG see below! Should ultra violet light be present, if so what frequency and strength, and how far from a lamp should a diamond be held? This writer believes the answer lies in digital or spectrophotometer machine based colour grading, in the face up position, with perhaps half the radiation strength of long wave ultra violet light as found in shaded daylight. lf industry standards bodies like CIBJO could agree on an appropriate standard light source for face up colour grading, then the industry may not need to price fluorescent diamonds differently. Certainly consumers would prefer that the face up colour of a diamond was reported on lab diamond grading reports or certificates because differences in face up colour can also be caused by factors other than fluorescence.

Garry, you can''t control the UV, so you take it out. I''m hearng the merchant in you speaking.

BTW, "shaded daylight", under a tree for example, is about 8000 degrees Kelvin black body color temperature.

How about going BACK to the ORIGINAL premise: "Diamonds should be graded at their poorer color, in artificial light, devoid of ultraviolet"...

You can control that easily, and grading technique doesn''t influence the results.

 

[strmrdr]

Date: 6/16/2009 6:39:05 PM
Author: adamasgem
Garry, you can''t control the UV, so you take it out.
BTW, ''shaded daylight'', under a tree for example, is about 8000 degrees Kelvin black body color temperature.


How about going BACK to the ORIGINAL premise: ''Diamonds should be graded at their poorer color, in artificial light, devoid of ultraviolet''...



You can control that easily, and grading technique doesn''t influence the results.

Agree 100%
The only consistent lighting you can have among multiple locations is blocking UV.

 

[Garry H (Cut Nut)]

Date: 6/16/2009 6:39:05 PM
Author: adamasgem


How about going BACK to the ORIGINAL premise: ''Diamonds should be graded at their poorer color, in artificial light, devoid of ultraviolet''...

You can control that easily, and grading technique doesn''t influence the results.

The original premise was that Blue White diamonds sold at a premium until merchants abused the term and applied it to lower coloured diamonds.
Any other construct based on GIA is not an international rule. it is one (albeit huge) Labs opinion. It is not an original anything.

I am less interested in GIA and more interested in beautiful diamonds.
Sure, blue fluoro changes the color grade. But the face up color of many diamonds changes more because of variances in cut quality.
And what about transperency?

I understand your focus on GIA color Marty, but it is a rather narrow topic especially since it is done upside down anyway.

From a consumer protection and benefit point of view, the main aim from this boards perspective, what can or should we do and can we do from here (Pricescope)?

 

[Garry H (Cut Nut)]

Date: 6/16/2009 6:58:20 PM
Author: strmrdr

Agree 100%
The only consistent lighting you can have among multiple locations is blocking UV.

Even AGS has fallen in line with GIA. It seems to me the only answer will come from digital color grading done face up.

DiamCalc can enable this when the spectrum in non banded stones is taken from the rough diamond (something which we believe will become a commercial reality in larger better equipped factories dealing with larger rough, simply because it makes good economic sense as DiamCalc can show what the face up color will be (as well as side graded color)).

 

[strmrdr]

Date: 6/17/2009 2:11:47 AM
Author: Garry H (Cut Nut)

Date: 6/16/2009 6:39:05 PM


From a consumer protection and benefit point of view, the main aim from this boards perspective, what can or should we do and can we do from here (Pricescope)?

One answer is push for government regulation and file class action lawsuits.
Not a very popular answer.

 

[strmrdr]

Date: 6/17/2009 2:15:35 AM
Author: Garry H (Cut Nut)
It seems to me the only answer will come from digital color grading done face up.

Only if the current color and pricing system is tossed out and replaced.
Upgrading stones under the current system is criminal.

 

[Garry H (Cut Nut)]

Date: 6/17/2009 2:29:26 AM
Author: strmrdr

Date: 6/17/2009 2:11:47 AM
Author: Garry H (Cut Nut)

Date: 6/16/2009 6:39:05 PM


From a consumer protection and benefit point of view, the main aim from this boards perspective, what can or should we do and can we do from here (Pricescope)?

One answer is push for government regulation and file class action lawsuits.
Not a very popular answer.

Storm!!!!
US govt got us into the mess we are in back in the 1930''s.
And sorry, but there is life outside USA.

 

[Garry H (Cut Nut)]

Date: 6/17/2009 2:33:04 AM
Author: strmrdr

Date: 6/17/2009 2:15:35 AM
Author: Garry H (Cut Nut)
It seems to me the only answer will come from digital color grading done face up.

Only if the current color and pricing system is tossed out and replaced.
Upgrading stones under the current system is criminal.

Who said anything about only upgrading stones. What about the huge # that would fall because of bad proportions and symmetry?

One thing is for sure however, that if color was done face up then there would be a new business opportunity to RE-cut and polish a huge number of existing stones out there! And that would make me very very happy!