Article Over Grading of Blue Fluorescent Diamonds Revisited

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Karl- maybe you can relate to part of why I've been so dogged on this subject.,
Michael reminds me of a politician.
They make some sort of ridiculous statement, and when pressed, they simply ignore the question and divert to another issue- or post a picture or graph.

Example- at the top of this page Michael tells us other people are also concerned about this and posts an article.
My questions about this study are perfectly legitimate.
Who wrote it?
When and where was it published?
Michael obviously has seen these questions, because he has posted subsequently- but simply refuses to answer them- instead getting indignant that anyone would question AGA. We don't know that AGA endorses Michael's flawed postition in any event.

IN this case, the totally ridiculous statement Michael is making is that GIA is overgrading.
The ONLY evidence presented is a study where Michael himself is making this claim, without any verification.
No answers on that question either.

Garry and I concur on the fact that GIA is doing a good job on these admittedly difficult to grade stones.
Add this to the fact that we both know that we would see more complaints right here on PriceScope if there was a problem.

If you do get the chance to see some higher color MB/SB stones Karl- please take that opportunity and report back to us.

To your comments of late:
Remember that ANY GIA grade is subjective. Every single one needs to be vetted. Period.
In many cases the consumer will be fine accepting the GIA grade, if they have chosen a reputable vendor who should do that vetting. Of course many will want to get a second opinion.
In my mind there's no greater risk in buying an MB stone which is vetted than there is buying an inert.

But as Garry says- the more people who believe there's a problem the greater the discounts we MB/SB lovers enjoy. It's basically a win win for us.
As I said, I have stayed involved partially because of how much I detest the idea of making false claims and not answering valid questions about these false claims.

 

[michaelgem]

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.

Karl,

Thank you for a great summary and for your reasoned conclusions. Your concise summary bears repeating, so as not to be lost in the shuffle:

Karl> “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
.
In some lighting they could look whiter than the letter grade might 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.

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.
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, in the current system, is body color, not the color appearance in consumer lighting .

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.” Karl

Separating a diamond that holds its high white color absent grade whitening UV and VV from one that does not is straightforwardly accomplished either by grading in LED lighting or by the Tashey technique of polycarbonate filtering of current fluorescent grading light.

Either method reveals the diamond’s “material” body color unenhanced by fluorescence. If this color is the color grade arrived at by GIA-GTL, Karl or any consumer has gotten what he paid for. Can’t imagine a consumer who would not want this information to determine if the discount for blue fluorescence is “too high, just right or too low.”

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Consumers are who we are meant to be protecting.
The price cant be too low.

Tom Tashey also initiated the discussion to say diamonds should be graded face up so cut influences are accounted for - you guys are trying to have a Tom "each way" bet. Consumers care about what they see and how good it looks for the money. Investors are another totally separate market.

Michael why on earth should you state that VV should be absent. Have you looked at strong blues and seen the grade whitening that consumers see in light absent UV but still experiencing grade whitening? Surely the effect must be coming from VV? Why should you want ordinary everyday part of the spectrum to be removed?
You never commented on my store photos - where clients do their sit down buying well away from UV daylight?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Talk about tired!
The "evidence" presented by Michael is full of crap and he seems to know it based on his behavior.
He won't answer legitimate questions raised by his statements. The latest: who write the claimed AGA position?- and when and where was it published?
Garry has made countless requests to use hard physical evidence- just look at actual diamonds, as we do every day. They hold these answers- and everyone is free to do their own observation.
Which is all we have from Michael. An observation. His observation is unsubstantiated, and goes against a lot of evidence based on the market, and consumer behavior ( lack of complaints). Plus he refuses to answer reasonable questions about that claim such as methodology- for example he claims to have graded at shoulder height.
Contrary to sound gemological practice there's no second opinion of his grade.

The whole issue of VV/UV is redonkulous.
JUST LOOK AT THE DIAMONDS

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Talk about tired!
The "evidence" presented by Michael is full of crap and he seems to know it based on his behavior.
He won't answer legitimate questions raised by his statements. The latest: who write the claimed AGA position?- and when and where was it published?
Garry has made countless requests to use hard physical evidence- just look at actual diamonds, as we do every day. They hold these answers- and everyone is free to do their own observation.
Which is all we have from Michael. An observation. His observation is unsubstantiated, and goes against a lot of evidence based on the market, and consumer behavior ( lack of complaints). Plus he refuses to answer reasonable questions about that claim such as methodology- for example he claims to have graded at shoulder height.
Contrary to sound gemological practice there's no second opinion of his grade.

The whole issue of VV/UV is redonkulous.
JUST LOOK AT THE DIAMONDS

I have used the "report concern" button twice now in this thread. If such personal attacks from a tradesperson are not policy violations, they are certainly violations of etiquette. If you are not interested in civil discussion, at least have some common decency.

Here are snippets of your vitriol just from just of few of your most recent posts. Let alone that for 17 pages in this thread you have actively engaged in what can only be described as a smear campaign:

The "evidence" presented by Michael is full of crap...

Michael reminds me of a politician.
They make some sort of ridiculous statement, and when pressed, they simply ignore the question and divert to another issue- or post a picture or graph.

I have stayed involved partially because of how much I detest the idea of making false claims and not answering valid questions about these false claims.

There should be no room for character assassination here. I find it completely unprofessional for a trade person to behave this way. And I cannot understand why a forum that should want to encourage participation would ever tolerate it.

I am sure there is a good reason that Mr. Cowing is not responding to your rabid and undignified assault. And I am sure that other potential contributors to the forum would have no interest whatsoever in exposing themselves to such utterly appalling treatment.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

IMO the bigger issue is that there should be no room for misleading consumers.
Every statement of mine you quote has merit.
Michael is making claims- then not responding to legitimate questions. This does remind me of politicians lately.
All of my questions have been initially posted in a polite dialog
I am sorry if my language has gotten strong of late- but it's just gotten really frustrating how Michael will not respond to valid criticism and questions, which have been presented in a respectful dialog.

Also frustrating how you will not look at diamonds as Garry has repeatedly requested.

 

[denverappraiser]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Has anyone else noticed that in the last YEAR, the journal has had a total of 3 articles published by only two authors, one of which is this one. Perhaps this treatment is part of the reason.

This particular one has been nailed to the front door of the forum since January.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To anyone offended by my tone or choice of words, I apologize.
To those who think that a lively discussion discourages writing an article: it's quite possible that a discussion like this is more likely to inspire new studies as opposed to one of the other 3 articles written over the last year. There were 5 the year prior. I believe this discussion is the most extensor one related to any article over the past few years. It's a hard stretch to peg this discussion as causal to a slowdown in published articles/ Studies
Peace

 

[Sagebrush]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael,

Great articles well researched and argued.

Richard

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael,

Great articles well researched and argued.

Richard

Hi Richard,
Welcome! Great to have you pop in.

I recently read your book The French Blue. Wonderful, wonderful piece of work.

Not to hijack the thread, but the book is something that every pricescoper would thoroughly enjoy. The story of Tavernier ultimately finding what would become the most famous diamond in the world, the Hope diamond, is just the icing on the cake of the fascinating stories of his travels and adventures which you bring to life so very well.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I recently came across a very interesting GIA article on graining. Although the subject is different than the current topic, the article takes the reader through a timeline of grading practices at the lab as it evolved over many years. What we are discussing here, and what Michael and others have documented, is a similar evolution of grading practice with regard to fluorescence.

For anyone who thinks GIA grading is monolithic or done in a vacuum, or is not subject to change, this article is quite instructive. Clearly, GIA is adaptive to new information and attitudes. This is a good reason for continued robust debates within the trade on grading practices and philosophies.

You can google the pdf on graining to see what I am talking about. It's also a good opportunity to learn more about graining!
THE IMPACT OF INTERNAL WHITISH AND REFLECTIVE GRAINING ON THE CLARITY GRADING OF D-TO-Z COLOR DIAMONDS AT THE GIA LABORATORY

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I recently came across a very interesting GIA article on graining. Although the subject is different than the current topic, the article takes the reader through a timeline of grading practices at the lab as it evolved over many years. What we are discussing here, and what Michael and others have documented, is a similar evolution of grading practice with regard to fluorescence.

For anyone who thinks GIA grading is monolithic or done in a vacuum, or is not subject to change, this article is quite instructive. Clearly, GIA is adaptive to new information and attitudes. This is a good reason for continued robust debates within the trade on grading practices and philosophies.

You can google the pdf on graining to see what I am talking about. It's also a good opportunity to learn more about graining!
THE IMPACT OF INTERNAL WHITISH AND REFLECTIVE GRAINING ON THE CLARITY GRADING OF D-TO-Z COLOR DIAMONDS AT THE GIA LABORATORY

Yes Bryan,
An excellent article - I read it at the time. It has contributed to my belief that GIA try to do the right thing and do change their practices to keep up with changes in the real world.
Just as they did with blue fluorescence after Marty Haske et al caused a ruckus about their grading lamps that GIA changed about they year 2000 - thereby making a realistic lab grading lighting that reflects what consumers see in the real world.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The 2010 study findings reinforced what was known from Shipley's time and known even back to 1915 from Wade's writing.

The color the consumer sees in the real world depends upon the lighting and how close to the lighting the diamond is viewed. The study reinforces what the pre-2000 GIA knew and taught, that grading in fluorescent lighting results in strongly blue-fluorescent diamonds being graded higher than their inherent body color, which is the color seen at normal viewing distances from most all sources of artificial illumination in the home or office.

The Study's 25 diamond Data-base illustrates real, not hypothetical color change, along with the amounts of UV and VV that bring about that improvement in color.

For example, the 1.13ct VST Blue pear brilliant (study diamond #4) was graded in the DiamondDock lighting by GIA-GTL, AGSL and myself as an H.

In artificial illumination , which was absent blue fluorescence stimulating UV and VV, the pear's color dropped two grades to a J, its true body color. Although this drop of two grades in artificial light may not be noticed, the consumer of this diamond would have paid based upon a color grade that needs the boost of UV and VV to appear an H.

Had the consumer paid based on the unenhanced true color of J she would find her diamond looking as white or whiter than her friend's H color stone when viewed at 7 inches from a jewelry store's fluorescent desk lamp.

If the jeweler takes her near a store window on a sunny day she would find that the diamond looks like its F color as it was graded in the DiamondLite in 150uW of UV and 600fc of illumination. Around noon outside where there is over 1500uW of UV the perceived color would rise past D and into the realm of blue-white. That is over 6 grades of change.

This continuum of color change due to the varying degrees of UV and VV and varying strengths of blue fluorescence that this Study documents is well known and understood.

With the inconsistency and variability of color grading in fluorescent lighting such as the two tubes in the DiamondDock, it is logical to assume that the savvy consumer would agree with SharonP who said:

"Michael has addressed the applicability of his study fairly and he isn't reporting all VSB diamonds will whiten 4 grades +/- 2 he kept it more general as a trend recognizing the inherent reading error. The trend in my mind is enough to want to seek a solution as he has proposed."

"If you admit that 2 grades of whitening is very likely (in the post-2000 DiamondDock) than the real question is why should that be the acceptable status quo? Consumers will never know if its 0, 1 or 2 grades of whitening, will you?"

"I'd rather GIA-GTL reports its true unenhanced body color and consumers can only 'Win', as certain lighting can only improve it, as can cut, but it would then be no lower in any lighting than what is printed on the grading report."

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The 2010 study findings reinforced what was known from Shipley's time and known even back to 1915 from Wade's writing.

The color the consumer sees in the real world depends upon the lighting and how close to the lighting the diamond is viewed. The study reinforces what the pre-2000 GIA knew and taught, that grading in fluorescent lighting results in strongly blue-fluorescent diamonds being graded higher than their inherent body color, which is the color seen at normal viewing distances from most all sources of artificial illumination in the home or office.

The Study's 25 diamond Data-base illustrates real, not hypothetical color change, along with the amounts of UV and VV that bring about that improvement in color.

For example, the 1.13ct VST Blue pear brilliant (study diamond #4) was graded in the DiamondDock lighting by GIA-GTL, AGSL and myself as an H.

In artificial illumination , which was absent blue fluorescence stimulating UV and VV, the pear's color dropped two grades to a J, its true body color. Although this drop of two grades in artificial light may not be noticed, the consumer of this diamond would have paid based upon a color grade that needs the boost of UV and VV to appear an H.

Had the consumer paid based on the unenhanced true color of J she would find her diamond looking as white or whiter than her friend's H color stone when viewed at 7 inches from a jewelry store's fluorescent desk lamp.

If the jeweler takes her near a store window on a sunny day she would find that the diamond looks like its F color as it was graded in the DiamondLite in 150uW of UV and 600fc of illumination. Around noon outside where there is over 1500uW of UV the perceived color would rise past D and into the realm of blue-white. That is over 6 grades of change.

This continuum of color change due to the varying degrees of UV and VV and varying strengths of blue fluorescence that this Study documents is well known and understood.

With the inconsistency and variability of color grading in fluorescent lighting such as the two tubes in the DiamondDock, it is logical to assume that the savvy consumer would agree with SharonP who said:

"Michael has addressed the applicability of his study fairly and he isn't reporting all VSB diamonds will whiten 4 grades +/- 2 he kept it more general as a trend recognizing the inherent reading error. The trend in my mind is enough to want to seek a solution as he has proposed."

"If you admit that 2 grades of whitening is very likely (in the post-2000 DiamondDock) than the real question is why should that be the acceptable status quo? Consumers will never know if its 0, 1 or 2 grades of whitening, will you?"

"I'd rather GIA-GTL reports its true unenhanced body color and consumers can only 'Win', as certain lighting can only improve it, as can cut, but it would then be no lower in any lighting than what is printed on the grading report."

Thanks Michael.
You totally support what I have been saying all along.
A diamond Very strong Blue fluoro graded H by GIA will have a color range of J to D depending on the lighting that it is viewed under.
The consumer will expect a big discount for the fluoro making it a J priced diamond that in various lighting looks WAY BETTER.

Of course this is an example of a rarity - a VST - and there are not many. So for the strong and medioum stones the color shift is a lot less.
But you do agree that GIA made a huge chamge to their grading lighting and that really in most cases the shgifts are small, but as you wrote - more likely to shift more grades higher than they shift lower.
game set and match

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The 2010 study findings reinforced what was known from Shipley's time and known even back to 1915 from Wade's writing.

The color the consumer sees in the real world depends upon the lighting and how close to the lighting the diamond is viewed. The study reinforces what the pre-2000 GIA knew and taught, that grading in fluorescent lighting results in strongly blue-fluorescent diamonds being graded higher than their inherent body color, which is the color seen at normal viewing distances from most all sources of artificial illumination in the home or office.

The Study's 25 diamond Data-base illustrates real, not hypothetical color change, along with the amounts of UV and VV that bring about that improvement in color.

For example, the 1.13ct VST Blue pear brilliant (study diamond #4) was graded in the DiamondDock lighting by GIA-GTL, AGSL and myself as an H.

In artificial illumination , which was absent blue fluorescence stimulating UV and VV, the pear's color dropped two grades to a J, its true body color. Although this drop of two grades in artificial light may not be noticed, the consumer of this diamond would have paid based upon a color grade that needs the boost of UV and VV to appear an H.

Had the consumer paid based on the unenhanced true color of J she would find her diamond looking as white or whiter than her friend's H color stone when viewed at 7 inches from a jewelry store's fluorescent desk lamp.

If the jeweler takes her near a store window on a sunny day she would find that the diamond looks like its F color as it was graded in the DiamondLite in 150uW of UV and 600fc of illumination. Around noon outside where there is over 1500uW of UV the perceived color would rise past D and into the realm of blue-white. That is over 6 grades of change.

This continuum of color change due to the varying degrees of UV and VV and varying strengths of blue fluorescence that this Study documents is well known and understood.

With the inconsistency and variability of color grading in fluorescent lighting such as the two tubes in the DiamondDock, it is logical to assume that the savvy consumer would agree with SharonP who said:

"Michael has addressed the applicability of his study fairly and he isn't reporting all VSB diamonds will whiten 4 grades +/- 2 he kept it more general as a trend recognizing the inherent reading error. The trend in my mind is enough to want to seek a solution as he has proposed."

"If you admit that 2 grades of whitening is very likely (in the post-2000 DiamondDock) than the real question is why should that be the acceptable status quo? Consumers will never know if its 0, 1 or 2 grades of whitening, will you?"

"I'd rather GIA-GTL reports its true unenhanced body color and consumers can only 'Win', as certain lighting can only improve it, as can cut, but it would then be no lower in any lighting than what is printed on the grading report."

Thanks Michael.
You totally support what I have been saying all along.
A diamond Very strong Blue fluoro graded H by GIA will have a color range of J to D depending on the lighting that it is viewed under.
The consumer will expect a big discount for the fluoro making it a J priced diamond that in various lighting looks WAY BETTER.

Of course this is an example of a rarity - a VST - and there are not many. So for the strong and medioum stones the color shift is a lot less.
But you do agree that GIA made a huge chamge to their grading lighting and that really in most cases the shgifts are small, but as you wrote - more likely to shift more grades higher than they shift lower.
game set and match

Game, set, and match? Possibly. But for who?

You seem to be acknowledging that there is inherent inaccuracy in the current color grading practice. But you dismiss it as a problem for consumers because (paraphrasing) it's not as bad as it used to be, and because the market discounts these diamonds.

I don't think Michael is at all supporting your view. He is arguing that the consumer is best served by grading diamonds accurately for their true un-enhanced body color. If anything, your comments are supporting his view, at least to the extent that grading accuracy is an issue. Where you differ is in whether the status quo adequately serves the interests of the consumer.

You may be right that market forces generally account for the variability in grading. But how is the consumer to know where their particular stone really stands? Doesn't the consumer rely upon the lab for this very knowledge ? And how is the consumer to know if the price truly reflects the appropriate compensation for grading uncertainty?

Do you believe that the consumer market is even aware of this particular issue? I don't. In fact, from my discussions with colleagues, I know that many in the trade are not even aware of it. Most think the discounts for fluoro stones revolve around the milkiness issue. So if the consumer is not aware of this potential issue, they don't even know the right questions to ask of their jeweler. You see this play out here on the forum every day- a poster asks for opinions on their strong blue under consideration, and the typical response is "ask your vendor if the stone is milky. If not, you're good to go."

The graining issue I referenced is relevant to this discussion in the sense that the leadership at the labs grapple with these questions, periodically re-considering how best to report so that the consumer has an understanding of important issues. In that case, if a stone is otherwise flawless but has transparency deficits due to graining, there is a need to communicate that on the report, either through dropping the clarity grade or notes in comments or both. Similarly, if the color grade on a flurorescent diamond is not the same as the body color that the consumer is likely to observe most of the time and the consumer is unaware of it, that is a problem that needs to be addressed somehow.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

....... if the color grade on a flurorescent diamond is not the same as the body color that the consumer is likely to observe most of the time and the consumer is unaware of it, that is a problem that needs to be addressed somehow.

So what you are saying is sometimes, but mainly on Very Strong stones, GIA's color grade is a grade or two higher than what the stone would be if graded in some light that has no purple or UV.
What I am saying is that in that lighting no one can ever see such slight grade differences.
What Michael just wrote is that there can be a huge shift up grades from G or H to D in light that has purple and UV - and what I am saying is every consumer can see the difference in that light between a +1ct H and a non fluoro H.
So therefore some people could argue GIA should raise the grades of fluoro stones. I am not making that claim - I am happy with where gIA have set their standard.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Dead. Horse. Beating.
I admire your patience Garry
You have one guy desperately defending an article based on authorship. He wrote it he'll defend it to the nines, regardless of silly facts.
Another guy basing his arguments on theoretical principles, and refusing to look at actual diamonds.....

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

nm

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Garry:
game set and match

Bryan:
Game, set, and match? Possibly. But for who?

You seem to be acknowledging that there is inherent inaccuracy in the current color grading practice. But you dismiss it as a problem for consumers because (paraphrasing) it's not as bad as it used to be, and because the market discounts these diamonds.

I don't think Michael is at all supporting your view. He is arguing that the consumer is best served by grading diamonds accurately for their true un-enhanced body color. If anything, your comments are supporting his view, at least to the extent that grading accuracy is an issue. Where you differ is in whether the status quo adequately serves the interests of the consumer.

Michael:
Well said Bryan. This is not a game to be won or lost. If there are winners and losers it is the consumer depending upon her/his take away from this contributed article ( https://www.pricescope.com/journal/blue-fluorescent-diamonds-color-grading-issues ) and the ongoing discussion it has generated.

There is a competition worth pointing out. It is between the GIA teaching for 60 years prior to 2000 and the GIA teaching after 2000 when they switched their prescribed grading light from the DiamondLite to the DiamondDock.

Contrast the before 2000 teaching by GIA in their Diamond Courses with their 2008 article on D-Z color grading both found at the end of the article:

The GIA Diamond Course, Assignment #19, 7-9 :
“One of the primary requirements for effective diamond color grading is standard lighting. Although daylight, at its best, provides excellent illumination for distinguishing faint nuances of color, it is not a satisfactory standard light source for diamond color grading for reasons (among which) is that the presence of ultraviolet in sunlight will make some stones that exhibit blue fluorescence appear higher in color. Fluorescent diamonds should be graded at their color in artificial light devoid of ultraviolet radiation, rather than at their daylight appearance.”

Contrast that with their post-2000 teaching in “Color grading “D-to-Z” diamonds at the GIA Laboratory”, Gems & Gemology, 2008, 44(4), 296–321 where GIA states that the basic technical specifications for the lighting used for D-Z color grading includes:

“An emission for long-wave UV (between 315 and 400nm, close to the reference spectrum of D55-D65.”

Regarding this UV in the GIA standardized fluorescent light source GIA says:
“We have learned that for some fluorescent diamonds the distance between the lamps and the grading tray can influence the final color grade. For consistency, we use a distance of 8-10 in. between the lamps and the diamond. Bringing a fluorescent diamond closer to the lamps may result in a stronger fluorescent impact.”

With the change in standard lighting at the Laboratory to the 20-watt fluorescent lamps in the DiamondDock, GIA has gone from requiring that diamonds be graded in light with a minimum of UV to obtain the true unenhanced color to requiring that “the lamp should emit long-wave UV, which is an important characteristic of daylight.“

Prior to 2000, this is the lighting that GIA said “causes fluorescent diamonds to be graded higher than is actually warranted, due to the neutralizing, or masking, effect of the fluorescent color on the true body color.”

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Antoinette Matlins, PG, FGA

This is an issue of such paramount importance it surprises me that more people are not commenting. I think, unfortunately, that this is a reflection of how many people have no idea of the importance of the lighting used for color-grading diamonds, and ANY light that permits ANY amount of UV emission will result in a color grade that will NOT be the color seen in most environments in which the diamond will be worn/seen!

I don't have time to go into all the particulars here, but anyone who wants the facts, should go to the AGA website (www.accreditedgemologists.com) to read about the extensive research done on this topic...by people with NO "VESTED" interest.

In the latest editions of my 2 most popular books (Diamonds: The Antoinette Matlins Buying Guide; and Jewelry & Gems: The Buying Guide) I have added extensive sections to discuss this important issue.
Continued.,.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Antoinette Matlins, PG, FGA

The reality is that any diamond being sold today, with any lab report indicating the presence of blue fluorescent ranging in intensity from medium to very strong, has a color-grade that is 1-4 grades whiter than its inherent body color.

This means that in ANY lighting environment EXCEPT outdoor lighting, during daylight hours, the color seen will be less white than indicated on the report. Even though prices for the rarest colors (D-H) have been adjusted for the presence of medium/strong/very strong blue fluorescence, they have NOT been adjusted enough to compensate for the color actually seen MOST of the time.

For my own clients, the first thing I do is check the true colot/intensity of the fluorescence (also often WRONG on the report depending on the output of the UV lamp and the proximity of the stone to the UV output from the lamp.)

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Antoinette Matlins, PG, FGA

Another reality is that few people today even know how to properly check whether or not a diamond exhibits fluorescence, and how to judge its intensity, and most important, to what degree it affects the color seen in the lighting in which most people are seeing their diamonds, most of the time (indoors).

Many people, even at major labs, believe that if you are using "daylight" type fluorescent lighting, this is the best light for grading. This is true, but ONLY FOR NON-FLUORESCENT stones. For those who are now completely confused, please go to the AGA website -- accredited gemologists.org -- or if you have one of my books, please read the sections on fluorescence.

Blue fluorescence is not a BAD thing at all, and can be a very GOOD thing, but NOT if a stone you are buying is over-priced for the color you will see MOST of the time!

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Uninterested appraisers, page down.

Consumer advocate gemologists read on:

From gemologist-appraiser Robert LaPrad on the switch from DiamondLite to DiamondDock in 2000: Does this mean fluorescent diamonds should be re-graded? The trade seems to discount fluorescence a lot because of the "blue-white" effect. Are they going to change their minds and accept fluorescence or even give it a premium? When GIA changes their standards this radically, they should explain how if the standard is now (north) daylight, why don't we just sit by the window instead of buying their latest incarnation of a color grading tool?

Good point Robert: why don't we just sit by the window instead of buying their latest incarnation of a color grading tool?

According to GIA, Digital radiometer readings revealed a similar long wave UV content in each source of fluorescent lighting including the standard DiamondLite. They also found “indirect daylight through our windows has about as much UV radiation as the fluorescent light sources”.

The key fact left out is that the amount of UV in these sources falls off with distance from the fluorescent lighting dropping below a negligible one microwatt three or more feet away. At three feet there is no fluorescence whitening. At 2" to 10" in the Diamondlite and DiamondDock there is plenty of UV which causes blue fluorescence whitening and leads to inconsistency and overgrading.

 

[DiamondsbyRaymondLee]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

So would it be safe to say that although fluorescents have a negative stigma, customers are more drawn to them, and will save money buying a diamond that has them? Thank you in advance for any clarification on this.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

So would it be safe to say that although fluorescents have a negative stigma, customers are more drawn to them, and will save money buying a diamond that has them? Thank you in advance for any clarification on this.

In a very narrow sense, each of the statements you cite is true. But the subject is much more complicated than that. To understand the various impacts of fluoresce, you must dig deeper. As the saying goes, ''the devil is in the details'!

If you read this entire thread, and other fluoro threads here on pricescope, you will get plenty of details as well as opinions. You can find a brief overview of the topic here: https://www.pricescope.com/wiki/diamonds/diamond-flourescence

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

So would it be safe to say that although fluorescents have a negative stigma, customers are more drawn to them, and will save money buying a diamond that has them? Thank you in advance for any clarification on this.

I think you've really written a great summary Raymond.
Some customers are indeed drawn to fluorescent diamonds- especially in lower colors. Although there's not a big savings on "silver stones" in that regard, the tendency to show color improvement is why I-J-K-L stones that are MB/SB may trade at the same price or higher than inert stones.
In higher colors, consumers will see large discounts. I feel it's a question of perception and demographics causing this.
Articles like the one this thread is based on, as well as the link Bryan posted are misleading, and draw incorrect assumptions- which may be part of the perception problem I mention.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Have not stopped thinking and reading about this topic.

A few updates.
It seems GIA have been using more accurate and narrow banded LED UV sources for a long time in their lab - first patents were granted in 2004 for digital grading systems. I wish they were more forthcoming with GTL processes.
The most recent application is for an adaption and new instrument for fancy shapes. Just as fancy shaped diamonds generally increase the amount of color we see in the same material used for round cuts - so too does the intensity of fluorescence in fancy shapes appear more apparent.
http://patft.uspto.gov/netacgi/nph-...d=PTXT&s1=7,102,742&OS=7,102,742&RS=7,102,742 Note they have crept a little higher to 370nm in the LED light source. Wish they would go higher to 400nm.


http://www.gia.edu/gems-gemology/summer-2013-luo-fluorescence-optical-defects states that there is twice as much blue created by just visible light slash Ultra Violet light (400nm) than at the Long Wave UV standard that is used simply because that Mercury vapour tube lights were once apon a time (in a far away land) the only source of UV light.
Quote " For example, the intensity of N3 luminescence (measured at 439 nm) when excited by 400 nm excitation is approximately double that of the same emission measured at 360 nm excitation (figure 6)."
This is also evident in the Thomas Hainschwang, Gemlab chart MC used in his article. A point I have made before that was ignored is that ordinary visible light produces a strong N3 blue fluorescence too. The range of the Solarmeter that MC used does not go to the near visible spectrum. Also note that there are no window materials that block the wavelengths we really now should be discussing.

Unless I am mistaken GIA has not disclosed they have a digital fluorescence grading system, and given they have digital color grading patents, I do not think we know how GIA color grades diamonds. Since Michael never provided a full disclosure of the dates and grading reports on the stones he used in his study, I have no confidence that the "Over Grading" problem is a problem.

It may well be that Strong Blue fluorescent diamonds are now under graded by GIA for most lighting environments where there is adequate illumination to make small color grading distinctions possible.

 

[StevL]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Steve still upsetting the apple cart....

Enjoyed the article, well done Michael!


Steve

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Steve still upsetting the apple cart....

Enjoyed the article, well done Michael!


Steve

Hi Steve!
You may not remember me but I have called on your store, back in the late '80's when I worked for M Fabrikant and Sons
Good to see you here!

About the subject at hand- based on your post... do you discourage anyone from buying an SB or MB stone because of the misgrading Michael is claiming? Or is there another strategy you propose for consumers who want to buy a fluorescent diamond?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Steve still upsetting the apple cart....

Enjoyed the article, well done Michael!


Steve

Hi Steve,
It appears Michael asks people in the trade to come here and support his case. But I wonder if you read the article, and bothered to read any of the rebuttals (including one a few posts above)?
It certainly appears that your business does not agree with Michael from the education page on your website: http://www.demsjewelers.com/jewelry/diamond-education-part-2/
"it would be a wise choice to purchase diamonds with no more than medium fluorescence"
and
"Many believe that an H or I color diamond can actually appear whiter (more colorless) than it is because of this effect. Many years ago jewelers would refer to colorless diamond that had blue fluorescence as a blue-white diamond."