Article Over Grading of Blue Fluorescent Diamonds Revisited

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

For those who may have gotten the impression that gemologist-appraiser Michael Cowing is a lone wolf crying "wolf", the following position article by the Accredited Gemologist Association may be of interest:

AGA Takes Position Urging Changes In Diamond
Color-Grading Procedures Following Research Showing
Grades For Fluorescent Diamonds May Mislead Consumers

In light of scientific data that shows there are insufficient UV emissions in most indoor lighting
environments—including those using daylight-type fluorescent lighting—to excite a color reaction
in fluorescent diamonds that is comparable to what is seen when the color is graded within a few
inches of a UV-emitting light source, the AGA contends that the use of UV emitting light to colorgrade
diamonds rather than lighting which is devoid of UV emissions results in grades for
fluorescent diamonds that distort the representation of quality and value and which do not
represent the color typically seen in today’s real world.

The AGA contends that in the case of fluorescent diamonds, scientific data shows that color grades based on the color seen when holding a diamond within a couple of inches of an unfiltered, UV-emitting light source is not the same color the diamond will appear when moved a short distance away from the light, and the farther away from the light, the greater the color difference. The color exhibited within a few inches of a UV-emitting light source is a color that will only be seen when held at such close distance, or when viewed outdoors, in natural daylight. Since many people today spend most of their time in indoor environments, and since the color grade indicated on most lab reports for fluorescent diamonds does not represent what people will see when viewed anywhere except in outdoor daylight environments, the AGA contends that the grade now shown on most lab reports for fluorescent diamonds misrepresents the color.

Furthermore, the AGA notes that the actual procedure currently used by major diamond grading
laboratories to color-grade diamonds is scientifically unsound. Current procedure requires that
“master stones” be non-fluorescing and the light source must be a daylight-type fluorescent light
that produces unfiltered fluorescent light containing UV emissions that will excite the fluorescent
reaction of any fluorescent diamond being graded. The color of any non-fluorescing master-stone
will not be impacted by UV emission coming from an unfiltered fluorescent bulb, while the color of
any fluorescent diamond is impacted by the UV emission. To make a fair comparison, the colorgrading
of any fluorescent diamond against a non-fluorescing master-stone would require making
the comparison when the fluorescent diamond is in its “steady state” rather than its “excited state”
(the “excited” state is when its fluorescent reaction is triggered by the UV emission from the
unfiltered fluorescent bulb); a fluorescent diamond’s “steady” state would be its “inherent body
color” and not the color it appears only when it is fluorescing.

The AGA contends that to compare a non-fluorescing “master stone” against a diamond in which the color has been temporarily altered
as a result of the excitation of its fluorescence triggered by the mandated light source is contrary to good scientific procedure. To grade in this way provides an inappropriate comparison resulting in a grade that does not represent the color the diamond will show in its “steady” state, which is the state most frequently observed except when viewed in outdoor daylight.

Furthermore, scientific data confirms that the color shown by a fluorescent diamond in outdoor
daylight is not a constant color because UV emissions in outdoor daylight vary dramatically
depending upon many factors (see Appendices D-F). Therefore the color grade now assigned by
laboratories, using current procedures, does not even represent a constant color that will be seen in
outdoor daylight. Therefore, the AGA contends that the best way to ensure consistent color-grading
and to avoid dramatic color inconsistencies due to the variables found in UV emissions, both
indoors and outdoors, is to use lighting devoid of UV so that the color grade reflects its most
consistent color: the stone’s “steady” color (its inherent body color).

The AGA further contends that while the color of any diamond, fluorescent or non-fluorescent, can
be affected by the wavelengths of light in which it is seen, only fluorescent diamonds may exhibit a
color significantly different from its inherent body color, depending upon the strength of its
fluorescence, and the particular wavelengths of light in which it is viewed. Therefore, the AGA
contends that diamond grading reports would better communicate, and more honestly represent the
unique character of a fluorescent diamond, by providing two color grades that would show the
range of color that may be seen in the particular stone—1) the stone’s “steady” color (its” inherent
body color”) seen in lighting devoid of UV emissions, and 2) the “excited” color seen when graded
with UV-emitting lighting for which a precise standard has been defined.

Finally, the AGA contends that to continue to grade fluorescent diamonds as they are currently
graded results in a situation whereby the interests of the buyer as it relates to value are not being
honestly served. In the case of fluorescent diamonds, the color grades now shown on diamond
grading reports issued by labs using a UV-emitting light source indicate the color the stone appears
in its “excited” state and can be several grades higher than the stone’s inherent body color (the
actual color that will be seen in any light except outdoor daylight, or when held deliberately close to
a UV-emitting light source). The AGA contends that such diamonds are priced higher (and in some
cases, much higher) than prices would be if grades reflected a stone’s inherent body color—the
color normally seen—and that even when “discounts for fluorescence” are factored into the
pricing, prices may still be significantly inflated.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

For those who may have gotten the impression that gemologist-appraiser Michael Cowing is a lone wolf crying "wolf", the following position article by the Accredited Gemologist Association may be of interest:

AGA Takes Position Urging Changes In Diamond
Color-Grading Procedures Following Research Showing
Grades For Fluorescent Diamonds May Mislead Consumers

In light of scientific data that shows there are insufficient UV emissions in most indoor lighting
environments—including those using daylight-type fluorescent lighting—to excite a color reaction
in fluorescent diamonds that is comparable to what is seen when the color is graded within a few
inches of a UV-emitting light source, the AGA contends that the use of UV emitting light to colorgrade
diamonds rather than lighting which is devoid of UV emissions results in grades for
fluorescent diamonds that distort the representation of quality and value and which do not
represent the color typically seen in today’s real world.

The AGA contends that in the case of fluorescent diamonds, scientific data shows that color grades based on the color seen when holding a diamond within a couple of inches of an unfiltered, UV-emitting light source is not the same color the diamond will appear when moved a short distance away from the light, and the farther away from the light, the greater the color difference. The color exhibited within a few inches of a UV-emitting light source is a color that will only be seen when held at such close distance, or when viewed outdoors, in natural daylight. Since many people today spend most of their time in indoor environments, and since the color grade indicated on most lab reports for fluorescent diamonds does not represent what people will see when viewed anywhere except in outdoor daylight environments, the AGA contends that the grade now shown on most lab reports for fluorescent diamonds misrepresents the color.

Furthermore, the AGA notes that the actual procedure currently used by major diamond grading
laboratories to color-grade diamonds is scientifically unsound. Current procedure requires that
“master stones” be non-fluorescing and the light source must be a daylight-type fluorescent light
that produces unfiltered fluorescent light containing UV emissions that will excite the fluorescent
reaction of any fluorescent diamond being graded. The color of any non-fluorescing master-stone
will not be impacted by UV emission coming from an unfiltered fluorescent bulb, while the color of
any fluorescent diamond is impacted by the UV emission. To make a fair comparison, the colorgrading
of any fluorescent diamond against a non-fluorescing master-stone would require making
the comparison when the fluorescent diamond is in its “steady state” rather than its “excited state”
(the “excited” state is when its fluorescent reaction is triggered by the UV emission from the
unfiltered fluorescent bulb); a fluorescent diamond’s “steady” state would be its “inherent body
color” and not the color it appears only when it is fluorescing.

The AGA contends that to compare a non-fluorescing “master stone” against a diamond in which the color has been temporarily altered as a result of the excitation of its fluorescence triggered by the mandated light source is contrary to good scientific procedure. To grade in this way provides an inappropriate comparison resulting in a grade that does not represent the color the diamond will show in its “steady” state, which is the state most frequently observed except when viewed in outdoor daylight.

Furthermore, scientific data confirms that the color shown by a fluorescent diamond in outdoor
daylight is not a constant color because UV emissions in outdoor daylight vary dramatically
depending upon many factors (see Appendices D-F). Therefore the color grade now assigned by
laboratories, using current procedures, does not even represent a constant color that will be seen in
outdoor daylight. Therefore, the AGA contends that the best way to ensure consistent color-grading
and to avoid dramatic color inconsistencies due to the variables found in UV emissions, both
indoors and outdoors, is to use lighting devoid of UV so that the color grade reflects its most
consistent color: the stone’s “steady” color (its inherent body color).

The AGA further contends that while the color of any diamond, fluorescent or non-fluorescent, can
be affected by the wavelengths of light in which it is seen, only fluorescent diamonds may exhibit a
color significantly different from its inherent body color, depending upon the strength of its
fluorescence, and the particular wavelengths of light in which it is viewed. Therefore, the AGA
contends that diamond grading reports would better communicate, and more honestly represent the
unique character of a fluorescent diamond, by providing two color grades that would show the
range of color that may be seen in the particular stone—1) the stone’s “steady” color (its” inherent
body color”) seen in lighting devoid of UV emissions, and 2) the “excited” color seen when graded
with UV-emitting lighting for which a precise standard has been defined.

Finally, the AGA contends that to continue to grade fluorescent diamonds as they are currently
graded results in a situation whereby the interests of the buyer as it relates to value are not being
honestly served. In the case of fluorescent diamonds, the color grades now shown on diamond
grading reports issued by labs using a UV-emitting light source indicate the color the stone appears
in its “excited” state and can be several grades higher than the stone’s inherent body color (the
actual color that will be seen in any light except outdoor daylight, or when held deliberately close to
a UV-emitting light source). The AGA contends that such diamonds are priced higher (and in some
cases, much higher) than prices would be if grades reflected a stone’s inherent body color—the
color normally seen—and that even when “discounts for fluorescence” are factored into the
pricing, prices may still be significantly inflated.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael,
Can we see where and when this was published please?
Also you have included pictures in your last post that we have seen before- are those photos included in the article you're citing?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Looks like you're just regurgitating something written, somewhere, at some point in the past, maybe 15 or 20 years back.
We don't know when AGA took this position- or if they stand behind this today.
I can't find any reference to it on the AGA site.
Given the gravity of the claim you are making, you'd expect that they'd mention it on thier site.
http://accreditedgemologists.org/index.php

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

In the list of articles here http://accreditedgemologists.org/resources.php there are 2 mentions of diamonds (one is the wrong link) and another is also fear mongering about diamonds.
AGA are a colored gem biased community - it is bleedingly obvious they loath and detest diamonds.

Michael your article which you clearly had a big hand in includes YOUR photo which is totally different to the one in G&G which it was taken for - and again, this article mentions grading very close to lamps - no mention the lamps changed and the doistance changed more than a decade ago.
Give up please!

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It is one thing to impugn the motivations and ethics of one independent gemologist-appraiser trying to make a contribution to consumer knowledge and protection. It is quite another to attack an organization like the Accredited Gemologists Association, the members of which are all about consumer protection.

Established in 1974, AGA was envisioned as a network for sharing gemological information and skills among FGA graduates of the Gemmological Association of Great Britain. Graduate gemologists of the Gemological Institute of America joined in 1975. The international Accredited Gemologists Association of today proudly counts among our members some of the worlds leading independent gemologists.

The AGA is an independent, international, nonprofit organization dedicated to…

Gemological Education & Research 
Identification & Evaluation of Gem Materials 
Development of Professional Standards of Analysis, Practice & Ethics


We are an organization of all beliefs and cultures and share a common bond of the love of gemstones. AGA believes in excellence and is dedicated to establishing the highest professional standards of practice.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, writing things in bold large blue text does not make them more credible

I have asked some simple questions about where you're getting this information regarding AGA's position.
Please show us the article or statement they issued- including when and where it was issued.
But yet again, a simple question is not answered by you.
At this point, all we have is you stating that they agree with your findings.

If anyone needs to apologize to AGA it's you for attempting to pin an untenable position on them.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael, writing things in bold large blue text does not make them more credible

I have asked some simple questions about where you're getting this information regarding AGA's position.
Please show us the article or statement they issued- including when and where it was issued.
But yet again, a simple question is not answered by you.
At this point, all we have is you stating that they agree with your findings.

If anyone needs to apologize to AGA it's you for attempting to pin an untenable position on them.

The bold blue is simply the title of the article which is the AGA position paper on the issue:
http://accreditedgemologists.org/pdf_file/PositionPaperFinal.pdf

It appears to have been published by AGA in 2008:

After reviewing extensive scientific data published by the International Commission on Illumination
(CIE), National Institute of Lighting Technology, Physics Laboratory, Optical Technology Division
(NIST), National Lighting Products Information Program (NLPIP), Pacific University College of
Optometry, Georgia State University Department of Physics and Astronomy, the United States
Department of Energy, and other resources, and articles appearing in the archives of Gems &
Gemology and JCK, and following research by AGA members themselves after presentations given at
their conference in Tucson, in February, 2008, the AGA has concluded that diamond grading
laboratories should change current procedures for color-grading fluorescent diamonds and eliminate
the use of light sources containing UV emissions or filter out UV wavelengths from the light source
being used.

By the way, doing a "locate an AGA member" on the AGA website I notice that most (if not all) of the best appraisers in my area are represented among their membership.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the link Bryan- If it's published, we'd need to see exactly when- and where. The PDF you linked to may never have been offered for public consumption.

Also: There's no supporting evidence newer than 1998.
We all agree standards have changed a lot since 1998

The fact that respected gemologists are members of AGA in no way means they agree with the conclusions of the paper. Which are incorrect in many important regards.

ETA- to your point Byran- about how many respected appraisers are members of AGA:
If GIA was misleading consumers wouldn't these respected appraisers be joining in an attempt to fix such a problem?
Where's the outcry?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the link Bryan- If it's published, we'd need to see exactly when- and where. The PDF you linked to may never have been offered for public consumption.

Also: There's no supporting evidence newer than 1998.
We all agree standards have changed a lot since 1998

The fact that respected gemologists are members of AGA in no way means they agree with the conclusions of the paper. Which are incorrect in many important regards.

ETA- to your point Byran- about how many respected appraisers are members of AGA:
If GIA was misleading consumers wouldn't these respected appraisers be joining in an attempt to fix such a problem?
Where's the outcry?

The position paper of an organization of respected gemologists and appraisers IS the outcry. Tashey's work and commentary is the outcry. Michael's article is the outcry. Rapaport's commentary is the outcry.

These people are thoughtful, not hysterical. They are not screaming from the rooftops or stomping their feet. They are simply expressing their understandings, their discoveries and their recommendations. What the labs do with the feedback is up to the labs. In the meantime, consumers should be aware of the legitimate concerns they raise.

Michael's point, I believe, in citing the AGA position, is to refute your repeated suggestions that current practice with regard to fluoro color grading is of concern only to a few "alarmists", while the rest of the trade think everything is just hunky dory. And Garry's characterization of Michael's work as "demagoguery" and 'fear mongering" is most unfortunate and unfair. Shooting the messenger does nothing to promote understanding or progress in our industry.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And yet we can't know when or where this paper was published.
Besides all the other incomplete info, there's no author listed.
Maybe Michael authored the paper himself

Unfortunately Michael's actions make Garry characterizations seem quite accurate.

If AGA stood behind this paper, why is it not possible to find it on their website?

The lack of outcry about GIA grading is not "my position"- it's a fact.
As an example, if we were to try and find problems with EGL grading we'd fall over a mountain of consumer complaints as well as industry objection.

Please show us where we can find any volume of similar discussion of GIA grading as "over-grading".

Bottom line is that I am acting a consumer advocate in this discussion.
Misinformation hurts consumers.
Using statement like "the science suggests" when the statement that follows was not scientifically obtained is misleading.
If there was an issue of GIA grading, I'd be the first one to be mentioning it.
And I'd have seen it based on the volume of stone I personally purhcase on behalf of my company.
And I love MB/SB stones in lower colors like I,J,K,L,M= and also D-E MB/SB stones.
I frequently look at such stones.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael I respect AGA and all other gem associations and would love to attend some of their presentations they hold at the Tucson gem rocks and mineral show.
Is it true that the article you refer to was published 8 years ago? And if so, why is it not in their list of articles that I linked to (the one chock a block full of colored gem articles)

 

[denverappraiser]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the link Bryan- If it's published, we'd need to see exactly when- and where. The PDF you linked to may never have been offered for public consumption.

Also: There's no supporting evidence newer than 1998.
We all agree standards have changed a lot since 1998

The fact that respected gemologists are members of AGA in no way means they agree with the conclusions of the paper. Which are incorrect in many important regards.

ETA- to your point Byran- about how many respected appraisers are members of AGA:
If GIA was misleading consumers wouldn't these respected appraisers be joining in an attempt to fix such a problem?
Where's the outcry?

I’m proud to be a member of AGA, and have been since before 1998 when that paper was written. Although I haven’t read it in a while, I was certainly aware of at the time, and I did and still do agree with much of it. Did Michael write it? It was a committee effort and although I wouldn’t be surprised if Michael served on that committee, I did not.

AGA serves as something of a US alumni association for the Gemmological Association of Great Britain, aka Gem-A. The website needs some work, as is typical of nearly all volunteer organizations, but don’t take that to mean they aren’t serious gemologists (excuse me, gemmologists).

‘Overgrading’ is a tricky concept. In a world where color is a concept that’s reasonably well understood by a lot of people, GIA teaches and describes it rather differently than any other industry. They supply the definition of the grades and they have supplied the definition of the lighting, environment, and methodology to be used to do the grading. They have been teaching their way of doing things for 76 years and has been offering it as a service to the trade for 52 of those years. During that time, the rules have changed more than once, and the procedures in the lab, which have also changed, do NOT match the lessons in the classroom. That causes a litany of problems for gemologists in the field. In order to decide if a stone is ‘overgraded’, it is first necessary to decide what is properly graded. It’s a moving target, and without pinning that down, how can you reasonably decide what’s not properly graded?

I’ve stayed out of this thread because of the above reasons. I see this as a problem of one of defining standards as much as it is one of methodology. I haven't even taken the time to read and consider every post. That said, I find Mr. Cowing to be a capable defender of his own work, and although I don’t entirely agree with everything he’s said, he is a highly skilled and well-respected gemologist. He doesn’t need my assistance. Carry on.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

So glad for your input Neil- thank you!
To be clear- your recollection is that the paper was written and or published in 1998, yes?
We've all agreed that GIA color grading standards have changed since then- do you concur?

I would very much welcome your take on one point which has been particularly difficult: the experience of seeing fluorescent diamonds show an appreciable whitening outside grading lamp environment. Let's call it "consumer lighting". Garry introduced an important qualification. The lighting will have to be intense enough to be able to distinguish the subtle difference of of color grades. In many cases there's a component of sunlight in these environments.
Have you noticed stones of say G-L color that exhibit a whitening in this type of consumer environments?

 

[denverappraiser]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The methodology used in the lab are not the same as what they teach in the classroom. Yes, both have changed over time. More than once.

'Consumer lighting' is a difficult thing to define as well. Most indoor lighting, meaning incandescent lamps, halogen lamps, fluorescent lamps, and modern LED bulbs, have effectively zero UV component. Even sunlight can be tricky. Light filtered through glass is subject to the optics of the glass, the dirt on the glass and even the air outside. It's different at different times of day, different levels of cloud cover, and even at different altitude.

Yes, there is a difference in visible color appearance of highly fluorescent diamonds in UV rich environments, which normally means direct sunlight. Even THAT is tricky to pin down. Direct sunlight is significantly brighter than nearly all indoor environments for example, even rather bright ones. That changes the way your eyes work.

Yes, with artificial lights, for example fluorescent lamps, the UV component varies with the distance from the bulb. Air is not equally transparent to all frequencies.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the link Bryan- If it's published, we'd need to see exactly when- and where. The PDF you linked to may never have been offered for public consumption.

Also: There's no supporting evidence newer than 1998.
We all agree standards have changed a lot since 1998

The fact that respected gemologists are members of AGA in no way means they agree with the conclusions of the paper. Which are incorrect in many important regards.

ETA- to your point Byran- about how many respected appraisers are members of AGA:
If GIA was misleading consumers wouldn't these respected appraisers be joining in an attempt to fix such a problem?
Where's the outcry?

I’m proud to be a member of AGA, and have been since before 1998 when that paper was written. Although I haven’t read it in a while, I was certainly aware of at the time, and I did and still do agree with much of it. Did Michael write it? It was a committee effort and although I wouldn’t be surprised if Michael served on that committee, I did not.

AGA serves as something of a US alumni association for the Gemmological Association of Great Britain, aka Gem-A. The website needs some work, as is typical of nearly all volunteer organizations, but don’t take that to mean they aren’t serious gemologists (excuse me, gemmologists).

‘Overgrading’ is a tricky concept. In a world where color is a concept that’s reasonably well understood by a lot of people, GIA teaches and describes it rather differently than any other industry. They supply the definition of the grades and they have supplied the definition of the lighting, environment, and methodology to be used to do the grading. They have been teaching their way of doing things for 76 years and has been offering it as a service to the trade for 52 of those years. During that time, the rules have changed more than once, and the procedures in the lab, which have also changed, do NOT match the lessons in the classroom. That causes a litany of problems for gemologists in the field. In order to decide if a stone is ‘overgraded’, it is first necessary to decide what is properly graded. It’s a moving target, and without pinning that down, how can you reasonably decide what’s not properly graded?

I’ve stayed out of this thread because of the above reasons. I see this as a problem of one of defining standards as much as it is one of methodology. I haven't even taken the time to read and consider every post. That said, I find Mr. Cowing to be a capable defender of his own work, and although I don’t entirely agree with everything he’s said, he is a highly skilled and well-respected gemologist. He doesn’t need my assistance. Carry on.

Thanks for weighing in Neil.

Re: "I’m proud to be a member of AGA, and have been since before 1998 when that paper was written. Although I haven’t read it in a while, I was certainly aware of at the time, and I did and still do agree with much of it."

It is important to correct the date. The AGA position paper entitled: "AGA Takes Position Urging Changes In Diamond Color-Grading Procedures Following Research Showing Grades For Fluorescent Diamonds May Mislead Consumers" along with a presentation by the AGA Task Force on Lighting and Color-Grading was presented at the annual AGA Conference in Tucson on February 4, 2009.

This was a few weeks after the G&G Winter 2008 article was published detailing how GIA labs color grade “D-to-Z” diamonds. The AGA position paper and presentation, which included discussion of the new GIA lighting standard based on the DiamondDock, represent the Task Forces position and recommendations from that time to today.

"Did Michael write it? It was a committee effort and although I wouldn’t be surprised if Michael served on that committee, I did not."

I served on the committee, but did not write either the position paper or the Tucson Presentation. From that presentation here are the main lighting recommendations:

Task Force Proposed Standards for Lighting and Color Grading Colorless Diamonds in a Laboratory

1. A colorless diamond should be laboratory-graded with the intent of observing, grading and reporting its True Body Color. A colorless diamond’s True Body Color is defined as the color of a diamond observed when its fluorescence is not stimulated.

2. A white artificial lighting environment should be created which is free from reflections, distractions, ambient interferences, and any ultraviolet energy (wavelength below 400nm) which may be emitted from the illumination source. In a professional color grading laboratory, any negligible ultraviolet energy remaining in the color grading environment should not exceed 3µW/cm².

3. The artificial lighting environment should also be properly diffused to further remove any possible reflections resulting from the illumination source, and to provide the most consistent pattern of illumination within the diamond viewing area.

4. The intensity of the white light at the location of the diamond should be between 200 and 500 fc (approx. 2000 – 5000 lux). By controlling the intensity of the white light within the grading environment, the subtle colors of the diamond will not be overcome by the artificial light source. In addition, reducing the artificial light intensity will reduce fluorescence-stimulating energy in the narrow visible-violet band of 400nm – 420nm.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

David I need to qualify my position that you explained wrongly to Neil. It is a new position that arose from this discussion.
The GIA 2013 G&G paper, plus the evidence Michael included from Thomas Hainsweng (sp? sorry) shows that near Ultra Violet but still visible Blue and Violet light can and does excite the 415 nm that causes grade whitening. Since this light is very common in consumer lighting, it seems to bean equally main reason that grade whitening is apparent in many Medium and strong blue fluorescent diamonds.
I have left out VST in all my posts because this is a consumer forum and I would not want consumers to think they can select those stones for themselves.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the link Bryan- If it's published, we'd need to see exactly when- and where. The PDF you linked to may never have been offered for public consumption.

Also: There's no supporting evidence newer than 1998.
We all agree standards have changed a lot since 1998

The fact that respected gemologists are members of AGA in no way means they agree with the conclusions of the paper. Which are incorrect in many important regards.

ETA- to your point Byran- about how many respected appraisers are members of AGA:
If GIA was misleading consumers wouldn't these respected appraisers be joining in an attempt to fix such a problem?
Where's the outcry?

I’m proud to be a member of AGA, and have been since before 1998 when that paper was written. Although I haven’t read it in a while, I was certainly aware of at the time, and I did and still do agree with much of it. Did Michael write it? It was a committee effort and although I wouldn’t be surprised if Michael served on that committee, I did not.

AGA serves as something of a US alumni association for the Gemmological Association of Great Britain, aka Gem-A. The website needs some work, as is typical of nearly all volunteer organizations, but don’t take that to mean they aren’t serious gemologists (excuse me, gemmologists).

‘Overgrading’ is a tricky concept. In a world where color is a concept that’s reasonably well understood by a lot of people, GIA teaches and describes it rather differently than any other industry. They supply the definition of the grades and they have supplied the definition of the lighting, environment, and methodology to be used to do the grading. They have been teaching their way of doing things for 76 years and has been offering it as a service to the trade for 52 of those years. During that time, the rules have changed more than once, and the procedures in the lab, which have also changed, do NOT match the lessons in the classroom. That causes a litany of problems for gemologists in the field. In order to decide if a stone is ‘overgraded’, it is first necessary to decide what is properly graded. It’s a moving target, and without pinning that down, how can you reasonably decide what’s not properly graded?

I’ve stayed out of this thread because of the above reasons. I see this as a problem of one of defining standards as much as it is one of methodology. I haven't even taken the time to read and consider every post. That said, I find Mr. Cowing to be a capable defender of his own work, and although I don’t entirely agree with everything he’s said, he is a highly skilled and well-respected gemologist. He doesn’t need my assistance. Carry on.

Thanks for weighing in Neil.

Re: "I’m proud to be a member of AGA, and have been since before 1998 when that paper was written. Although I haven’t read it in a while, I was certainly aware of at the time, and I did and still do agree with much of it."

It is important to correct the date. The AGA position paper entitled: "AGA Takes Position Urging Changes In Diamond Color-Grading Procedures Following Research Showing Grades For Fluorescent Diamonds May Mislead Consumers" along with a presentation by the AGA Task Force on Lighting and Color-Grading was presented at the annual AGA Conference in Tucson on February 4, 2009.

This was a few weeks after the G&G Winter 2008 article was published detailing how GIA labs color grade “D-to-Z” diamonds. The AGA position paper and presentation, which included discussion of the new GIA lighting standard based on the DiamondDock, represent the Task Forces position and recommendations from that time to today.

"Did Michael write it? It was a committee effort and although I wouldn’t be surprised if Michael served on that committee, I did not."

I served on the committee, but did not write either the position paper or the Tucson Presentation. From that presentation here are the main lighting recommendations:

Task Force Proposed Standards for Lighting and Color Grading Colorless Diamonds in a Laboratory

1. A colorless diamond should be laboratory-graded with the intent of observing, grading and reporting its True Body Color. A colorless diamond’s True Body Color is defined as the color of a diamond observed when its fluorescence is not stimulated.

2. A white artificial lighting environment should be created which is free from reflections, distractions, ambient interferences, and any ultraviolet energy (wavelength below 400nm) which may be emitted from the illumination source. In a professional color grading laboratory, any negligible ultraviolet energy remaining in the color grading environment should not exceed 3µW/cm².

3. The artificial lighting environment should also be properly diffused to further remove any possible reflections resulting from the illumination source, and to provide the most consistent pattern of illumination within the diamond viewing area.

4. The intensity of the white light at the location of the diamond should be between 200 and 500 fc (approx. 2000 – 5000 lux). By controlling the intensity of the white light within the grading environment, the subtle colors of the diamond will not be overcome by the artificial light source. In addition, reducing the artificial light intensity will reduce fluorescence-stimulating energy in the narrow visible-violet band of 400nm – 420nm.

SO we now have these questions- Neil remembers the paper from 1998. He's generally a pretty accurate guy. Is he wrong, or is it possible the paper was written in 1998?
Since you're denying authorship, who authored the paper Michael?

Would you agree that simply presenting the paper, and AGA "taking a position" are two different things?
If AGA has taken a position, it's an awfully quiet one- especially given the gravity of the charge.

Garry- bottom line is that for whatever reason of technical light measurement, we agree that whitening is relatively common for consumers, yes?

Bottom line aside from all the noise- who is warning consumers, and what is the effect of it?
Neil- given that you're a member of AGA do you agree with the position that GIA is overgrading to the detriment of consumers, and do you warn consumers that there's a problem with GIA grading?


Michael- it's eminently clear GIA is not going to take your recommendations- I did bring up this discussion with a GIA rep the other day.
They appreciated my input and scoffed at the idea they are issuing G on stones that are actually J color.
What is your recommendation to consumers Michael?
Since you're intent on alerting us of a problem, should consumers simply avoid all MB/SB diamonds in your opinion?

 

[denverappraiser]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It's entirely possible I"m misremembering the schedule. As I said, I wasn't involved in it even though I was present for the presentation. Time flies when you're having fun and I've read a LOT of various papers. Michael is a reliable source for the date of this one. I am not.

Do I warn customers that GIA grading isn't 'carved in stone' as sellers tend to suggest? Absolutely. Again, I try to avoid terms like 'overgraded', but the fact that grades describe overlapping ranges and that stones can look quite different under various lighting conditions is a common subject for discussion. Yes, I discuss that there's more to consider about the grades than is printed on the reports and yes, fluorescence is part of that discussion.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

We all agree that color grades are subjective and there's plenty of cases where a stone GIA graded J might be whiter than another stone graded I.
But we may agree that using the term "overgraded" might not be the best choice of words.
From my perspective, it's absolutely the wrong word.
Do you feel misgrading is systematic at GIA Neil?

I feel like we're beating that dead horse and I have no desire to insult Michael or anyone else, but if this claim has substance, it's serious.
If ( as I'm saying) there's no systematic overgrading coming out of GIA the claim is not helpful to consumers IMO

 

[denverappraiser]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Systemic? No.

People think they know what the grades mean, for example that a stone that appears darker than another will do so under all lighting conditions, and this is not the case. Price gets into it because G's generally cost more than otherwise similar I's, and folks feel they've been treated badly when what they thought they understood as 'facts' turn out to be otherwise.

Dead horse? Yes.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Two gemologists walk into a bar and argue about GIA grading....lol
Maybe we can frame it like this- discussing this paper as a theoretical discussion may be interesting. But it's not a practical issue which is relevant to consumers.
Consumers need to realize that not all G/SI1's are equal- and that if the G/SI1 in question is MB/SB there's far more variation likely.
That makes your job as an appraiser more vital- and from my perspective, my job as a seller.

 

[smitcompton]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi,

I want to thank the people who are trying to understand what variables go into grading B/FL diamonds. I am just a consumer and want Michaelgems to know that his work is appreciated. It seems like common sense to me that what you have found in GIA lighting
conditions might give rise to over grading of the SB/FL diamond. I don't think overgrading is a terrible word to use.

Complaints about EGL diamond grading does not come from the consumer, it comes from a lab, most probably GIA after someone checks out the EGL diamond. Consumers don't know to complain until they are told. So you cannot have complaints against GIA for SB/FL grading until this is brought to the attention of the GIA by the gemology folks themselves. If the grading standards change, then some may question an old grading report.

Thanks for trying to improve standards.

Annette

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Annette,
Complaints about EGL grading certainly do imitate with consumers.
Someone buys an EGL graded G color to find out it's a K color- there's many cases where the consumer themselves notice the color difference when comparing to a friends diamond- or when shopping.
In other cases the consumer learns when they take the stone for an appraisal- or sadly when they try to sell it.

I can assure you that if GIA was doing a bad job grading MB/SB stones, there would be a lot of fuss made by dealers and consumers.

I'm all for making things better- but first we need to establish if there's a problem to fix- and in this case, there's not.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I promised myself i was going to stay out of this thread but here I am.
David would you buy a D color strong blue stone off the lists no return without inspecting it first for color?
Really that is the bottom line.... confidence. How confident are you?
Personally I would want to inspect it or much better yet have it inspected since my color perception is not that great.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I promised myself i was going to stay out of this thread but here I am.
David would you buy a D color strong blue stone off the lists no return without inspecting it first for color?
Really that is the bottom line.... confidence. How confident are you?
Personally I would want to inspect it or much better yet have it inspected since my color perception is not that great.

HI Karl,
Of course not.
But then again I would not buy an inert D color sight unseen. And I'd never buy sight unseen with no possibility of return.
There's risk in buying any diamond sight unseen.
The fact is internet consumers may have to purchase a stone without looking at it - but they are getting a money back guarantee so they take the risk and buy it. The inspection takes place when the stone arrives. I'd think the money back guarantee is what gives most consumers confidence.


But let's look at your question from a different perspective.
Say I was shopping for a D color diamond off a list.
Say an inert stone was $11k, a MB was $9k, and a SB was $8k.

Given the opportunity to view them all, I certainly would.
If I loved the SB best, it would be a bargain.
My hypothetical example is pretty much what you'll find shopping nowadays- MB/SB stones are discounted heavily.
So even if the assumption about overgrading was true ( it's not) then the market has adjusted.
So what we currently have is MB/SB colorless stones being graded relatively accurately, given the fact it can never be perfect- yet they are discounted as though they were overgraded.
This equals a big win for consumers willing to purchase MB/SB diamonds.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

But let's look at your question from a different perspective.
Say I was shopping for a D color diamond off a list.
Say an inert stone was $11k, a MB was $9k, and a SB was $8k.

Given the opportunity to view them all, I certainly would.
If I loved the SB best, it would be a bargain.
My hypothetical example is pretty much what you'll find shopping nowadays- MB/SB stones are discounted heavily.
So even if the assumption about overgrading was true ( it's not) then the market has adjusted.
So what we currently have is MB/SB colorless stones being graded relatively accurately, given the fact it can never be perfect- yet they are discounted as though they were overgraded.
This equals a big win for consumers willing to purchase MB/SB diamonds.

[/quote]
Yes consumers can win sometimes how often is up for debate but without grading training or hiring an expert how can they know if they won or lost? The discount may be too high, just right or too low.
The grade and price are not based on how it looks as a consumer would look at it.
It is based on a trained trade person looking at it under specific conditions looking for a material color grade.
AS I said earlier in higher colors it bugs me, in lower colors I see it as having less effect due to the width of the grades and the amount of whitening needed to move out of the 1 grade industry accepted accuracy range.(too high if you ask me but that's another post.)

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

But let's look at your question from a different perspective.
Say I was shopping for a D color diamond off a list.
Say an inert stone was $11k, a MB was $9k, and a SB was $8k.

Given the opportunity to view them all, I certainly would.
If I loved the SB best, it would be a bargain.
My hypothetical example is pretty much what you'll find shopping nowadays- MB/SB stones are discounted heavily.
So even if the assumption about overgrading was true ( it's not) then the market has adjusted.
So what we currently have is MB/SB colorless stones being graded relatively accurately, given the fact it can never be perfect- yet they are discounted as though they were overgraded.
This equals a big win for consumers willing to purchase MB/SB diamonds.

Yes consumers can win sometimes how often is up for debate but without grading training or hiring an expert how can they know if they won or lost? The discount may be too high, just right or too low.
The grade and price are not based on how it looks as a consumer would look at it.
It is based on a trained trade person looking at it under specific conditions looking for a material color grade.
AS I said earlier in higher colors it bugs me, in lower colors I see it as having less effect due to the width of the grades and the amount of whitening needed to move out of the 1 grade industry accepted accuracy range.(too high if you ask me but that's another post.)[/quote]

Consider this:
Medium and Strong blue diamonds are under graded because in light that is good enough to make small grade distinctions they look better than their graded color. No one has thus far challenged me on this point of view.
And no one has been prepared to say "I took some diamonds and looked at them and Garry and David are wrong".

And also consider this:
Michael - keep banging the drum because maybe we Fluoro lovers will get even better buys!!!!

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Consider this:
Medium and Strong blue diamonds are under graded because in light that is good enough to make small grade distinctions they look better than their graded color. No one has thus far challenged me on this point of view.
And no one has been prepared to say "I took some diamonds and looked at them and Garry and David are wrong".

In some lighting they could look whiter than the letter grade night imply but there are a lot of things that could make that happen, cut for example.
My point is that lab color grading is advertised as a material grade of rarity not the color a consumer will see in consumer lighting. Anything that gives a false reading of body color is therefore bad in some ways.
The problem is not with the diamonds themselves but potentially with the grading.
I am still not sure how big an issue it is with current grading practices at GIA but there is some uncertainty there causing lower values.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

And also consider this:
Michael - keep banging the drum because maybe we Fluoro lovers will get even better buys!!!!

I love it also and think it is a kewl thing but on the other hand as long as pricing is based on body color I want to make sure I get what I am paying to get based on good grading. Which is body color not consumer lighting appearance color in the current system.
I would like to see them fairly graded, a strong or vstrong blue that holds its grade without uv should not be discounted but first it must be separated from one that does not hold its grade in no uv lighting.
Its a bigger issue in higher colors. I am not that worried about it in lower colors.