Article Over Grading of Blue Fluorescent Diamonds Revisited

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There's absolutely no one who ( other than you) who is disputing the grade whitening phenomena exists.
Besides everything Garry just mentioned, I promise, I did not make up the fact Harry Winston used to get a premium for diamonds that had this characteristic.
They were called "Premier"- I can't find a way to look it up, but it's a fact.

To me - a person who has great respect for science, and an inquiring mind- but not to the extent I want to take the effort necessary to understand the nifty graphs that are being displayed.... it's such a moot point as to why.
But I respect those like Garry- and Michael- who take time to research these aspects. Clearly there's a lot to learn- but it all begins with physical observation. As opposed to trying to measure light with tools. Using the tools to verify what we see makes sense.
Trying to interpret them to dispute a physical reality seems off target.

Yes, and if the tools fail to verify what you think you're seeing, then what? There are a few possibilities including that the tools are faulty or that we may not be seeing what have always thought we were seeing.

By the way, where did you ever get the idea that I am "disputing that the grade whitening phenomena exists"? You are not paying attention.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

What we "think we're seeing"?
A woman catches her husband in bed with another woman- he denies it.
"You can't believe your lying eyes" he tells her

A diamond's main utility is how it looks.
If we are all seeing something which a tool can't recognize, we're not using the correct tool.

If you agree with what's been observed by countless people who have observed this, what is the argument Bryan?

Or all these people, we're all being fooled into believing our eyes....

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If we consider yellow diamonds, it will also tell us things about fluorescence in diamonds.
The problem of misgrading is far more likely with MB/SB Yellow diamonds.
The problem for consumers is very real with MB/SB yellow diamonds - and not due to misgrading, There's a fair percentage which actually do show a detrimental effect. Again, in the cases I'm speaking of you don't need direct sunlight. If the lighting is bright enough to see the color, it's affected. It's possible you'd need less light to distinguish a nice inert- or one of the few really nice MB/SB yellow diamonds, from a stone who's color was dulled by MB/SB.
The negative effect I speak of is really easy to see in normal room lighting. I can tell as open the parcel paper- way before I get the stone under a grading lamp.

It's likely some sort of "defect" that causes this- these bad cases look dull- or put another way, the diamond is not allowing the light to flow freely through it.
But it's also interesting to note that some of the purest most Vivid Yellow stone may exhibit fluorescence- sometimes yellow fl, but I've even seen SB Vivid yellow stones that showed no ill affect whatsoever- in fact the opposite.

Not to take the discussion off track, but it's relevant, and goes to my point that the number of potential variations make simple categorization the only choice- that's why not all Medium Blue stones are good, or bad.
It's also why certain white ones look blue in lighting sufficient to determine they are high color. And others don't

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There are really 3 related issues here:
The effect of florescence in the appearance of diamonds in the real world.
The biggest question is of lighting.
With modern lighting and led type lighting(among others) being the future and the push for uv free lighting.
Read the press releases from lighting companies, network control, variable colors, energy use and uv free are all talking points for the next generation of lighting.

Lab color grading:
While a study of 25 diamonds is a good start it is not possible with such a small sample to say it applies to all diamonds.
I have seen one with my own eyes that does not fit the data shown.
It looks like strong florescence in sunlight but is a lab rated none and tested under lab lighting showed none.
My opinion grading with as close to 0 uv would be the more consistent and accurate than using light sources with UV.

lab florescence grading:
The one thing everyone agrees with is that it is a mess.

Karl have you heard about the revival of the tungsten light globe?
Promises to be 1/2 the running cost of LED's by 'recycling' the infra red heat to improve efficiency and retain the same wonderful light.

yes they are working on them and many others, you can bet they will include uv blocking to match the led lights when they come to market.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If we consider yellow diamonds, it will also tell us things about fluorescence in diamonds.
The problem of misgrading is far more likely with MB/SB Yellow diamonds.
The problem for consumers is very real with MB/SB yellow diamonds - and not due to misgrading, There's a fair percentage which actually do show a detrimental effect. Again, in the cases I'm speaking of you don't need direct sunlight. If the lighting is bright enough to see the color, it's affected. It's possible you'd need less light to distinguish a nice inert- or one of the few really nice MB/SB yellow diamonds, from a stone who's color was dulled by MB/SB.
The negative effect I speak of is really easy to see in normal room lighting. I can tell as open the parcel paper- way before I get the stone under a grading lamp.

It's likely some sort of "defect" that causes this- these bad cases look dull- or put another way, the diamond is not allowing the light to flow freely through it.
But it's also interesting to note that some of the purest most Vivid Yellow stone may exhibit fluorescence- sometimes yellow fl, but I've even seen SB Vivid yellow stones that showed no ill affect whatsoever- in fact the opposite.

Not to take the discussion off track, but it's relevant, and goes to my point that the number of potential variations make simple categorization the only choice- that's why not all Medium Blue stones are good, or bad.
It's also why certain white ones look blue in lighting sufficient to determine they are high color. And others don't

You probably have more experience with fancy yellow's than me or most David.
I would note that the grading environment that GIA use for fancy colors is very different to that used for D-Z.
Firstly it is face up, not table down, secondly they use a Judge or similar light box where the lamps (of various sorts) are about 18 inches / 45cm away from the base. There was a mention in a G&G article on grading fancy yellows a few years back.
The relevance here is that yes, it is known in the trade that blue fluoro can reduce the perceived color of fancy's in various light, not just daylight rich in UV.
Variablitiy could well be a result of many factors David.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

By the way David, where did you ever get the idea that I am "disputing that the grade whitening phenomena exists"? You are not paying attention.

Bryan what is your opinion from your personal experience and communications with consumers about the effects you and others report about the grades of strong blue diamonds graded GIA and their face up color appearance in various lighting?

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Garry,
Your argument seems to rest on a notion that the wavelengths in visible light capable of activating fluorescence somehow behave differently than those in the UV range. That is, you seem to be saying that the UV in an overhead fluorescent light is not strong enough to stimulate grade whitening fluorescence, but somehow the VV in the light is. On what are you basing that? I have not seen anything in either of the studies mentioned here that supports that. In fact, the 3D profile done by Hainshwang in Cowing study shows the fluoro strength caused by the VV wavelengths to be weaker than those in the UV.

If they drop off in intensity proportionately, and UV is no longer capable of activating fluoro, then VV are similarly incapable. If no fluoro activation is taking place , then fluoro-driven grade whitening cannot be either. And any surveys or expressed preferences that suggest otherwise would have to be the result of something other than fluorescence.

Simply Bryan, Michael and others have shown that UV from various light sources drops off to almost nil in most indoor lighting.
I accept their testing and dtat.
Regarding VV - I can see for myself that this light is present - because I can see violet things in my surroundings and my new little 415 nm camera lens can take (somewhat blurry) indoor photo's with my point and click Samsung Tough camera.

Edited later:
https://en.wikipedia.org/wiki/High-energy_visible_light
"A 2013 in vitro study using shorter blue band spectrum LED lights indicated that prolonged exposure may permanently damage the pigment epithelial cells of the retina. The test conditions were the equivalent of staring at a 100 watt blue incandescent source from 20 cm (8 in) for 12 hours."
Bryan as you know, there is not a lot of VV in an incandescent light. This is not 'proof' but it leads that way

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

By the way David, where did you ever get the idea that I am "disputing that the grade whitening phenomena exists"? You are not paying attention.

Bryan what is your opinion from your personal experience and communications with consumers about the effects you and others report about the grades of strong blue diamonds graded GIA and their face up color appearance in various lighting?

I clearly see effects in sunlight, especially direct sunlight. I would say that diffuse sunlight (like bright overcast) has a more positive effect on appearance than direct sun--- color masking with nice overall brightness. In direct sun there is a definite blue hue which is very nice, but there is a darkness that accompanies it that is not so attractive. I think that can be said of non-fluoro diamonds to some extent as well, but it seems to not play well with the blue hue of the strong fluoro. Direct sun in general is not the optimal lighting environment for diamond beauty - however, with the right background you can see some awesome fire (if the diamond has good fire potential).

Over several decades in the business I have seen and bought and sold a fair number of fluoro diamonds. And for much of that time I have been operating under the presumption that blue fluoro provides color whitening in any lighting environment that has a UV component. And so, I have never questioned the notion common in the trade that fluoro is a benefit to diamonds lower on the color scale. In light of recent research I am quite skeptical of that proposition today.

While some of it may very well be suggestibility, clearly part of it is the fact that as diamond dealers we spend a great deal of time studying our goods very close to fluoro lights. So we DO see some positive effects. However, I have serious doubts that the consumer is getting much benefit in terms of improved appearance. Unless of course they are spending a good deal of time outdoors. They do presumably get the benefit of lower price, and fluoro stones can potentially represent a bargain because of the market stigma. But that also presumes the stone has not been overgraded and does not have transparency issues. And the same market stigma that may benefit them on the front end, causes a liquidity problem for them on the back end.

I know the last few remarks where not specifically what you asked, but they do relate to the issue at the center of the article being discussed here, in that there is a need to ensure that fluoro stones are being graded accurately. That protects both the consumer and at the same time keeps fluoro diamonds from being unfairly punished by the market.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If we consider yellow diamonds, it will also tell us things about fluorescence in diamonds.
The problem of misgrading is far more likely with MB/SB Yellow diamonds.
The problem for consumers is very real with MB/SB yellow diamonds - and not due to misgrading, There's a fair percentage which actually do show a detrimental effect. Again, in the cases I'm speaking of you don't need direct sunlight. If the lighting is bright enough to see the color, it's affected. It's possible you'd need less light to distinguish a nice inert- or one of the few really nice MB/SB yellow diamonds, from a stone who's color was dulled by MB/SB.
The negative effect I speak of is really easy to see in normal room lighting. I can tell as open the parcel paper- way before I get the stone under a grading lamp.

It's likely some sort of "defect" that causes this- these bad cases look dull- or put another way, the diamond is not allowing the light to flow freely through it.
But it's also interesting to note that some of the purest most Vivid Yellow stone may exhibit fluorescence- sometimes yellow fl, but I've even seen SB Vivid yellow stones that showed no ill affect whatsoever- in fact the opposite.

Not to take the discussion off track, but it's relevant, and goes to my point that the number of potential variations make simple categorization the only choice- that's why not all Medium Blue stones are good, or bad.
It's also why certain white ones look blue in lighting sufficient to determine they are high color. And others don't

You probably have more experience with fancy yellow's than me or most David.
I would note that the grading environment that GIA use for fancy colors is very different to that used for D-Z.
Firstly it is face up, not table down, secondly they use a Judge or similar light box where the lamps (of various sorts) are about 18 inches / 45cm away from the base. There was a mention in a G&G article on grading fancy yellows a few years back.
The relevance here is that yes, it is known in the trade that blue fluoro can reduce the perceived color of fancy's in various light, not just daylight rich in UV.
Variablitiy could well be a result of many factors David.

Very good points Garry.
The main take away regarding this discussion is that the variability is ...variable.
That is to say- sometimes the fluorescence will make a stone look more yellow in normal lighting. I mean lighting that is bright enough to determine color, yet not direct sunlight.
For this reason, many dealers feels GIA downgrades stones with MB/SB
SO it's possible to find a Fancy Yellow MB that faces up just like a Fancy Intense Yellow inert. But many times not. And in many cases the MB/SB produces an ugly tint of yellow.
For these reasons I advise consumers to stay away from most MB/SB yellow diamonds.

Totally different if we're speaking of other colors BTW......

 

[queradas2]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I clearly see effects in sunlight, especially direct sunlight. I would say that diffuse sunlight (like bright overcast) has a more positive effect on appearance than direct sun--- color masking with nice overall brightness. In direct sun there is a definite blue hue which is very nice, but there is a darkness that accompanies it that is not so attractive. I think that can be said of non-fluoro diamonds to some extent as well, but it seems to not play well with the blue hue of the strong fluoro. Direct sun in general is not the optimal lighting environment for diamond beauty - however, with the right background you can see some awesome fire (if the diamond has good fire potential).

Over several decades in the business I have seen and bought and sold a fair number of fluoro diamonds. And for much of that time I have been operating under the presumption that blue fluoro provides color whitening in any lighting environment that has a UV component. And so, I have never questioned the notion common in the trade that fluoro is a benefit to diamonds lower on the color scale. In light of recent research I am quite skeptical of that proposition today.

While some of it may very well be suggestibility, clearly part of it is the fact that as diamond dealers we spend a great deal of time studying our goods very close to fluoro lights. So we DO see some positive effects. However, I have serious doubts that the consumer is getting much benefit in terms of improved appearance. Unless of course they are spending a good deal of time outdoors. They do presumably get the benefit of lower price, and fluoro stones can potentially represent a bargain because of the market stigma. But that also presumes the stone has not been overgraded and does not have transparency issues. And the same market stigma that may benefit them on the front end, causes a liquidity problem for them on the back end.

I know the last few remarks where not specifically what you asked, but they do relate to the issue at the center of the article being discussed here, in that there is a need to ensure that fluoro stones are being graded accurately. That protects both the consumer and at the same time keeps fluoro diamonds from being unfairly punished by the market.

Great post and the bolded parts puts this thread into perspective and explains why GIA will not be adding lexan filters to their color grading environment anytime soon.

There is at least some consumer lighting where the whitening effect of UV or VV is a factor and this uncertainty, combined with not wanting to change historical practices is more than enough to give GIA pause. The 2008 G&G King article shows the Radiance spectra for the Verilux tubes currently in use in the GIA DIamond Dock color grading environment. GIA-GTL is fully aware of the transmission peaks at 414nm and 365nm and has deliberately chosen not to filter them out.

The underlined part, the market still is discounting these due to the potential overgrading of fluoro stones especially those in the Colorless range and should discount them appropriately due to the real risk of overgrading demonstrated by Michael's paper and references therein.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I clearly see effects in sunlight, especially direct sunlight. I would say that diffuse sunlight (like bright overcast) has a more positive effect on appearance than direct sun--- color masking with nice overall brightness. In direct sun there is a definite blue hue which is very nice, but there is a darkness that accompanies it that is not so attractive. I think that can be said of non-fluoro diamonds to some extent as well, but it seems to not play well with the blue hue of the strong fluoro. Direct sun in general is not the optimal lighting environment for diamond beauty - however, with the right background you can see some awesome fire (if the diamond has good fire potential).

Over several decades in the business I have seen and bought and sold a fair number of fluoro diamonds. And for much of that time I have been operating under the presumption that blue fluoro provides color whitening in any lighting environment that has a UV component. And so, I have never questioned the notion common in the trade that fluoro is a benefit to diamonds lower on the color scale. In light of recent research I am quite skeptical of that proposition today.

While some of it may very well be suggestibility, clearly part of it is the fact that as diamond dealers we spend a great deal of time studying our goods very close to fluoro lights. So we DO see some positive effects. However, I have serious doubts that the consumer is getting much benefit in terms of improved appearance. Unless of course they are spending a good deal of time outdoors. They do presumably get the benefit of lower price, and fluoro stones can potentially represent a bargain because of the market stigma. But that also presumes the stone has not been overgraded and does not have transparency issues. And the same market stigma that may benefit them on the front end, causes a liquidity problem for them on the back end.

I know the last few remarks where not specifically what you asked, but they do relate to the issue at the center of the article being discussed here, in that there is a need to ensure that fluoro stones are being graded accurately. That protects both the consumer and at the same time keeps fluoro diamonds from being unfairly punished by the market.

Great post and the bolded parts puts this thread into perspective and explains why GIA will not be adding lexan filters to their color grading environment anytime soon.

There is at least some consumer lighting where the whitening effect of UV or VV is a factor and this uncertainty, combined with not wanting to change historical practices is more than enough to give GIA pause. The 2008 G&G King article shows the Radiance spectra for the Verilux tubes currently in use in the GIA DIamond Dock color grading environment. GIA-GTL is fully aware of the transmission peaks at 414nm and 365nm and has deliberately chosen not to filter them out.

The underlined part, the market still is discounting these due to the potential overgrading of fluoro stones especially those in the Colorless range and should discount them appropriately due to the real risk of overgrading demonstrated by Michael's paper and references therein.

Thanks queradas2 for reminding me about the 2008 article.
It make it very clear why GIA use the lighting they do.
Please understand that I have no affiliation with GIA - infact I believe they consider me something of an enemy, and if you look at theirs and my HCA patent you would conclude they stole it from me. So with that backdrop I fully support their decision.

Bryan never commented on indoor and his experiance with consumer opinion - just in grading rooms - and I have never used those lamps that are common. For color grading I use the very old fashioned warmer white tubes - and on that Michael has agreed they work better for various reasons.

I have re read the 2008 King article and I like it - I originally read it with more interest in the machine color grading than the fluoro topic because i agreed and was glad they had "come out" and were more transparent.

There is still 365 nm present, but less of it than earlier, and much more of the overall mid and warmer range emissions.
There is no 415 nm. See figure 8 with my comments in purple and blue.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There is no 415 nm. See figure 8 with my comments in purple and blue.

Yeah the radiance peak is at 408nm not 414nm as I had posted above, higher energy and I think still capable of exciting the blue fluorescence, potentially causing whitening and color overgrading.

Commercial fluorescent lighting is mercury vapor whose peaks stimulate the blue fluorescence from the N3 centers. The peaks are at wavelengths of 365nm in the Ultra Violet and 405nm in the deep Visible Violet. Daylight fluorescent tubes are lined with powdered phosphors that are excited by the long and short wave mercury vaper peaks to in turn fluoresce additional colors such as yellow and red that combine to give a particular color temperature light such as 3200K cool white or 6500K daylight. The following from page 2 is important to go over again:

The generally accepted data on gem quality white diamonds is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence. So the graph of response curves of a type 1A diamond due to different excitation wavelengths contains the answers for perhaps 99 plus percent of white diamonds.

The curve shapes show that fluorescence color due to N3 centers in Type 1A blue fluorescing diamonds is similar for different wavelengths, since each curve varies mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, mostly varying in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color, which varies in intensity depending on the excitation wavelength.

These similar blue fluorescent colors of varying intensities are seen in the representative responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which add fluorescence of other colors when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate, in that the blue fluorescence of type 1A white diamonds, which are the large majority, is well understood and can be taken into consideration in grading.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There is no 415 nm. See figure 8 with my comments in purple and blue.

Yeah the radiance peak is at 408nm not 414nm as I had posted above, higher energy and I think still capable of exciting the blue fluorescence, potentially causing whitening and color overgrading.

Commercial fluorescent lighting is mercury vapor whose peaks stimulate the blue fluorescence from the N3 centers. The peaks are at wavelengths of 365nm in the Ultra Violet and 405nm in the deep Visible Violet. Daylight fluorescent tubes are lined with powdered phosphors that are excited by the long and short wave mercury vaper peaks to in turn fluoresce additional colors such as yellow and red that combine to give a particular color temperature light such as 3200K cool white or 6500K daylight. The following from page 2 is important to go over again:

The generally accepted data on gem quality white diamonds is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence. So the graph of response curves of a type 1A diamond due to different excitation wavelengths contains the answers for perhaps 99 plus percent of white diamonds.

The curve shapes show that fluorescence color due to N3 centers in Type 1A blue fluorescing diamonds is similar for different wavelengths, since each curve varies mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, mostly varying in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color, which varies in intensity depending on the excitation wavelength.

These similar blue fluorescent colors of varying intensities are seen in the representative responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which add fluorescence of other colors when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate, in that the blue fluorescence of type 1A white diamonds, which are the large majority, is well understood and can be taken into consideration in grading.

So what Michael?
The participants, even David, have read your article and some of us read others also.
What are you saying?
That is not adding anything to discussions here.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There is no 415 nm. See figure 8 with my comments in purple and blue.

Yeah the radiance peak is at 408nm not 414nm as I had posted above, higher energy and I think still capable of exciting the blue fluorescence, potentially causing whitening and color overgrading.

Commercial fluorescent lighting is mercury vapor whose peaks stimulate the blue fluorescence from the N3 centers. The peaks are at wavelengths of 365nm in the Ultra Violet and 405nm in the deep Visible Violet. Daylight fluorescent tubes are lined with powdered phosphors that are excited by the long and short wave mercury vaper peaks to in turn fluoresce additional colors such as yellow and red that combine to give a particular color temperature light such as 3200K cool white or 6500K daylight. The following from page 2 is important to go over again:

The generally accepted data on gem quality white diamonds is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence. So the graph of response curves of a type 1A diamond due to different excitation wavelengths contains the answers for perhaps 99 plus percent of white diamonds.

The curve shapes show that fluorescence color due to N3 centers in Type 1A blue fluorescing diamonds is similar for different wavelengths, since each curve varies mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, mostly varying in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color, which varies in intensity depending on the excitation wavelength.

These similar blue fluorescent colors of varying intensities are seen in the representative responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which add fluorescence of other colors when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate, in that the blue fluorescence of type 1A white diamonds, which are the large majority, is well understood and can be taken into consideration in grading.

So what Michael?
The participants, even David, have read your article and some of us read others also.
What are you saying?
That is not adding anything to discussions here.

Garry,

Though the active participants like yourself demonstrate understanding of all that has been said over these many posts, the typical consumer may be very confused and put off by it all. This post was to let them know that the fundamental issue of blue fluorescence over grading in fluorescent lighting is well understood scientifically and so can be resolved in practice to benefit everyone.

This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet.

I'm concerned that many still do not see this as a solved problem or even a problem needing solution, and many others remain skeptical or think it is beyond their understanding. These efforts are to convince them this is an understandable issue that can be solved for the large majority of white gem quality diamonds.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There is no 415 nm. See figure 8 with my comments in purple and blue.

Yeah the radiance peak is at 408nm not 414nm as I had posted above, higher energy and I think still capable of exciting the blue fluorescence, potentially causing whitening and color overgrading.

Commercial fluorescent lighting is mercury vapor whose peaks stimulate the blue fluorescence from the N3 centers. The peaks are at wavelengths of 365nm in the Ultra Violet and 405nm in the deep Visible Violet. Daylight fluorescent tubes are lined with powdered phosphors that are excited by the long and short wave mercury vaper peaks to in turn fluoresce additional colors such as yellow and red that combine to give a particular color temperature light such as 3200K cool white or 6500K daylight. The following from page 2 is important to go over again:

The generally accepted data on gem quality white diamonds is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence. So the graph of response curves of a type 1A diamond due to different excitation wavelengths contains the answers for perhaps 99 plus percent of white diamonds.

The curve shapes show that fluorescence color due to N3 centers in Type 1A blue fluorescing diamonds is similar for different wavelengths, since each curve varies mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, mostly varying in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color, which varies in intensity depending on the excitation wavelength.

These similar blue fluorescent colors of varying intensities are seen in the representative responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which add fluorescence of other colors when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate, in that the blue fluorescence of type 1A white diamonds, which are the large majority, is well understood and can be taken into consideration in grading.

So what Michael?
The participants, even David, have read your article and some of us read others also.
What are you saying?
That is not adding anything to discussions here.

Garry,

Though the active participants like yourself demonstrate understanding of all that has been said over these many posts, the typical consumer may be very confused and put off by it all. Michael if I "understand you, and disagree, where does that leave us?
This post was to let them know that the fundamental issue of blue fluorescence over grading in fluorescent lighting is well understood scientifically and so can be resolved in practice to benefit everyone.

This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet.

I'm concerned that many still do not see this as a solved problem or even a problem needing solution, and many others remain skeptical or think it is beyond their understanding. These efforts are to convince them this is an understandable issue that can be solved for the large majority of white gem quality diamonds.

I fail to comprehend any part of that Michael.
It is because you say it is?

How can
"This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet. "
Daylight minus some of the readily and always available violet and blue light be subtracted from balance daylight?

And the very term "daylight" includes infra red and ultra violet radiance. So why on earth would you even use the term daylight in that sentence?

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To me, the important take away for consumers is to ignore this study. There's nothing whatsoever in it that relates to a consumers purchase of a diamond. Furthermore by continuing to refer to it Bryan is exasperating the issue here on PS.
I deal with GIA on a daily basis- there is no consistent issue with overgrading. No conspiracy.

A consumer is going to purchase a single diamond. What difference do averages make to them?
It's not possible to draw meaningful broad conclusions about fluorescence that apply to any given diamond because the phenomena is to varied.
Studies about lighting and the pretty, colorful graphs may have significance in some regard- but there's nothing about them that adds anything to consumer education on diamonds. Just the opposite.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

There is no 415 nm. See figure 8 with my comments in purple and blue.

Yeah the radiance peak is at 408nm not 414nm as I had posted above, higher energy and I think still capable of exciting the blue fluorescence, potentially causing whitening and color overgrading.

Commercial fluorescent lighting is mercury vapor whose peaks stimulate the blue fluorescence from the N3 centers. The peaks are at wavelengths of 365nm in the Ultra Violet and 405nm in the deep Visible Violet. Daylight fluorescent tubes are lined with powdered phosphors that are excited by the long and short wave mercury vaper peaks to in turn fluoresce additional colors such as yellow and red that combine to give a particular color temperature light such as 3200K cool white or 6500K daylight. The following from page 2 is important to go over again:

The generally accepted data on gem quality white diamonds is that 98% are type 1A meaning they contain nitrogen aggregated in N3 centers in the crystal lattice, which results in the Cape Series tints of yellow and various degrees of blue fluorescence. The remaining 2% include type 2A, which lack readily detectable N3 nitrogen aggregation, and thus have no blue fluorescence. So the graph of response curves of a type 1A diamond due to different excitation wavelengths contains the answers for perhaps 99 plus percent of white diamonds.

The curve shapes show that fluorescence color due to N3 centers in Type 1A blue fluorescing diamonds is similar for different wavelengths, since each curve varies mainly in intensity. Notice that each of the curves has a similar shape with peaks in similar locations, mostly varying in the amplitude of the response. Each wavelength thus produces a similar blue fluorescent color, which varies in intensity depending on the excitation wavelength.

These similar blue fluorescent colors of varying intensities are seen in the representative responses of the 25 Type 1A diamonds in the study data base. These diamonds were illuminated with long wave mercury vapor tubes which contain ionized-mercury-vapor peaks of blue-fluorescence-stimulating monochromatic energy at wavelengths of 365nm in the Ultra Violet and 405nm in the Visible Violet.

Those same fluorescence-stimulating mercury vapor peaks are present in all fluorescent tube lighting where they excite similar blue colors of grade whitening fluorescence like you see in these Type 1A study diamonds.

In a percentage of white diamonds other color centers may be present which add fluorescence of other colors when stimulated with UV and VV, but that appears to be a low percentage. In that small percentage are white diamonds that fluoresce yellow, yellow-orange and rarely other colors such as green and red. All this is fortunate, in that the blue fluorescence of type 1A white diamonds, which are the large majority, is well understood and can be taken into consideration in grading.

So what Michael?
The participants, even David, have read your article and some of us read others also.
What are you saying?
That is not adding anything to discussions here.

Garry,

Though the active participants like yourself demonstrate understanding of all that has been said over these many posts, the typical consumer may be very confused and put off by it all. Michael if I "understand you, and disagree, where does that leave us?
This post was to let them know that the fundamental issue of blue fluorescence over grading in fluorescent lighting is well understood scientifically and so can be resolved in practice to benefit everyone.

This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet.

I'm concerned that many still do not see this as a solved problem or even a problem needing solution, and many others remain skeptical or think it is beyond their understanding. These efforts are to convince them this is an understandable issue that can be solved for the large majority of white gem quality diamonds.

I fail to comprehend any part of that Michael. It is because you say it is?
How can "This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet. "
Daylight minus some of the readily and always available violet and blue light be subtracted from balance daylight?

And the very term "daylight" includes infra red and ultra violet radiance. So why on earth would you even use the term daylight in that sentence?

Garry asks: How can "This is accomplished by grading the diamond's "true color" in daylight balanced illumination devoid of fluorescent stimulating levels of lighting energy from the Ultra Violet and Visible Violet. "
Daylight minus some of the readily and always available violet and blue light be subtracted from balance daylight?

And the very term "daylight" includes infra red and ultra violet radiance. So why on earth would you even use the term daylight in that sentence?

Garry,

Don't get me wrong. It's not "daylight illumination" that was said. It is "daylight balanced illumination" like that in the DiamondDock prescribed by GIA in the basic technical specifications given by King et al. (200,

• An intensity of light in the range of 2000–4500 lux (186–418 fc) at the surface of the grading tray

• A colour spectrum close to CIE D55-D65

• A colour temperature between 5500 K and 6500 K

Grading the diamond's "true" or unenhanced color in this prescribed daylight balanced fluorescent illumination, can be accomplished in two ways, as it was accomplished in the 2010 study.

Method 1. Grading 3 or more feet from daylight balanced ceiling mounted fluorescent light.

The color of a diamond can be seen and graded against master diamonds at distances from daylight fluorescent overhead illumination of 3 to 4 ft. Such distances are typical of those at which diamonds are viewed in a variety of social occasions. At this distance there is negligible UV and the amount of visible violet is not strong enough to whiten the color grade.

Chosen for the 2010 study, the example of this lighting was the overhead daylight fluorescent light (Figure 11) containing four, 32 W Philips F32T8/DX tubes behind a clear plastic diffuser. Almost any artificial ceiling lighting could have been used, since at normal diamond viewing distances such illumination is essentially UV-free and has a visible light intensity which does not stimulate noticeable fluorescence. This lighting has a color temperature of 6500 K, and at a distance of 3 ft, an intensity of 200 fc with less than 1 µW/cm² of UV. The true body color was obtained comparing the 25 diamonds to the masters in this lighting.

Method 2. Use of a polycarbonate UV filter in front of fluorescent lighting as in this GIA microscope lighting test example.

Fluorescent lighting like that attached to GIA microscopes has provided a less expensive alternative to grading in a standard light box like the DiamondDock. These microscopes are fitted with a swing arm light attached to the front of the microscope stage, which contains twin Verilux, 6 in. fluorescent tubes, whose light is filtered and diffused with a white plastic cover. This was a daylight balanced grading light recommended to GIA students. It is used to this day by many gemologists and appraisers (the author included) as lighting for both diamond color grading and final judgments of clarity grade. The author’s microscope light with the addition of a Lexan polycarbonate UV filter is shown in Figure 10.

Unfiltered, at a distance of about an inch, this light has a strong UV component of 200 µW/cm² and a strong visible light intensity of 1000 fc. The standard white plastic diffuser reduces the UV to 10 µW/cm² and the light intensity to 800 fc. With the addition of a Lexan filter, the UV drops to a small 1 µW/cm² and the light intensity to 740 fc.

In the Verilux tubes in the DiamondLite and all commercial mercury vapor fluorescent lighting, at typical close grading distances the visible-violet wavelengths add to the stimulation of blue fluorescence formerly attributed only to UV. Even after filtering out UV, the visible violet present in light intensities at or above about 600 fc was found to whiten some ‘Strong’ and ‘Very Strong Blue’ fluorescent diamonds. To prevent the energy in the visible violet from noticeably affecting fluorescent diamond color, provisional testing indicated that the maximum fluorescent-tube light intensity should not exceed 400 fc. This compares with the lighting intensity range of 186–418 fc (2000–4500 lux) prescribed by King et al. (200.

So Method 2 obtains the unenhanced "true color" by filtering the UV in daylight balanced fluorescent lighting down to under 1 µW/cm² and the visible light to under 400 foot candles.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Michael,
Let's try it this way:
I'm not a scientist, nor are most consumers reading this.
I don't understand what the significance of the colorful graph is- and I don't believe a consumers needs to either.
Can you please describe in plain terms and specifically what you think the problem is?
Can you point to specific instances of this overgrading, and how it would affect a consumer?

I'll again admit upfront- I submit stones to GIA pretty much on a daily basis. I don't agree with every grade they issue, but that's the nature of grading.
I see no systematic issues here.

Also important to point out to consumers reading this- diamond grades are not written in stone. There's many times two graders will disagree on a given grade- especially if the color or clarity characteristics bring the stone close to the next higher or lower grade.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Philips,
If you're ready to go down into a mine and pull out your own diamond, then polish it, you'll have no need to "depend" on any diamond sellers.
Otherwise, you'll be in the same boat with the rest of us, who do have to employ, partner with, or buy from other people involved in the business. Given the open market created by the internet, it's fairly easy for consumers to price shop- as well as checking reputations of the seller they are considering.

Are there those who want to prey on unsuspecting consumers?
Yes of course.
Are any of the sellers involved in this discussion in that category?
No, not in my experience.

This is indeed an open discussion/ forum- so if there is a seller who is participating here, and screwing folks, they're not going to be able to get away with it for long.
In a similar manner, if there's an alarmist raising false red flags, that will also need to come under scrutiny. This is a case of that.

As I've described so many times in this discussion alone:
1) Color and clarity grades are interpretations, not scientific measurements. There's no "certainty" with any GIA grades.
2) The phenomenon of fluorescence is not a consistent one from stone to stone. Even two stones with identical characteristics under a UV lamp can and will look different in normal lighting.
3) GIA has developed a methodology that accommodates these physical realities. There's no "perfect" light under which to grade diamonds, any set of parameters we select won't be accurate in a fair percentage of instances compared to "real life" lighting"

And in my last post, I am asking for specifics- who is being damaged, and exactly how.
I should think anyone following the discussion would be interested in that aspect.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To me, the important take away for consumers is to ignore this study. There's nothing whatsoever in it that relates to a consumers purchase of a diamond. Furthermore by continuing to refer to it Bryan is exasperating the issue here on PS.
I deal with GIA on a daily basis- there is no consistent issue with overgrading. No conspiracy.

A consumer is going to purchase a single diamond. What difference do averages make to them?
It's not possible to draw meaningful broad conclusions about fluorescence that apply to any given diamond because the phenomena is to varied.
Studies about lighting and the pretty, colorful graphs may have significance in some regard- but there's nothing about them that adds anything to consumer education on diamonds. Just the opposite.

You are well within your rights to ignore this study or any other. But ignoring things does not lead to greater understanding - discussing them rationally sometimes does.

If you do not find any value in this particular discussion, why not just move on and let those of us who are interested discuss the topic on our own? Do you fancy yourself some sort of thought policeman?

If you are not willing or able to advance the discussion in any meaningful way, that's ok. Maybe just read for a while. Perhaps then you would not be asking questions of the author that are clearly addressed in his work.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Bryan, When someone is addressed as Philips addressed me, an answer is warranted IMO.

I'm not ignoring the study, and I'm also participating in the discussion by raising important points- these are crucial to consumers of diamonds, and which are NOT buried somewhere in the study.

If the author is not willing to address points being raised by me, and Garry, perhaps it should stop being touting it as some sort of scientific breakthrough. It might be in some sense, but not in regards to the purchase of a diamond by a consumer.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael I proposed some experiments to detect if VV is making diamonds face up whiter in light good enough to detect slight color differences.
Would you be prepared to participate?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael I proposed some experiments to detect if VV is making diamonds face up whiter in light good enough to detect slight color differences.
Would you be prepared to participate?

It seems to me this is the crux of the matter. There appears to be agreement that UV in normal indoor lighting is of insufficient intensity to stimulate grade whitening fluorescence. So if there is whitening being observed in normal lighting scenarios, then VV could be a possible cause.

I would think that using the same instruments used in the studies being discussed, you could get readings from a variety of everyday lighting scenarios that would detect the presence and measure the strength of the VV wavelengths (as GIA did in the 2013 study of an assortment of fluoro devices). You could then attempt to stimulate fluoro diamonds with those same wavelengths and strengths and see what is being emitted, if anything.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael I proposed some experiments to detect if VV is making diamonds face up whiter in light good enough to detect slight color differences.
Would you be prepared to participate?

It seems to me this is the crux of the matter. There appears to be agreement that UV in normal indoor lighting is of insufficient intensity to stimulate grade whitening fluorescence. So if there is whitening being observed in normal lighting scenarios, then VV could be a possible cause.

I would think that using the same instruments used in the studies being discussed, you could get readings from a variety of everyday lighting scenarios that would detect the presence and measure the strength of the VV wavelengths (as GIA did in the 2013 study of an assortment of fluoro devices). You could then attempt to stimulate fluoro diamonds with those same wavelengths and strengths and see what is being emitted, if anything.

Brian I mentioned before that the equipment used does not measure VV radiance energy. It cuts off just before the VV.
Both Thomas's multi colored chart and the on from GIA G&G Summer 2013 show that VV plays a role.

It appears to me that Michael Cowing is not interested to participate in any experiment that I have propsed, or to propose one himself?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael I proposed some experiments to detect if VV is making diamonds face up whiter in light good enough to detect slight color differences.
Would you be prepared to participate?

It seems to me this is the crux of the matter. There appears to be agreement that UV in normal indoor lighting is of insufficient intensity to stimulate grade whitening fluorescence. So if there is whitening being observed in normal lighting scenarios, then VV could be a possible cause.

I would think that using the same instruments used in the studies being discussed, you could get readings from a variety of everyday lighting scenarios that would detect the presence and measure the strength of the VV wavelengths (as GIA did in the 2013 study of an assortment of fluoro devices). You could then attempt to stimulate fluoro diamonds with those same wavelengths and strengths and see what is being emitted, if anything.

Brian I mentioned before that the equipment used does not measure VV radiance energy. It cuts off just before the VV.
Both Thomas's multi colored chart and the on from GIA G&G Summer 2013 show that VV plays a role.

It appears to me that Michael Cowing is not interested to participate in any experiment that I have propsed, or to propose one himself?

Garry,
From my reading of both the 2010 Cowing study and the 2013 GIA study (although they were studying different things), the wavelengths capable of stimulating fluorescence in diamonds with N3 centers (the vast majority of all diamonds in the normal range), do not extend beyond 415 nm. In the Thomas Hainswhang tests ( 3D graph in Cowing study) the wavelengths that stimulate fluorescence, including the visible violet, are shown and discussed. It seems relevant to note that the strength of the fluoro stimulated by wavelengths between 400 and 415 as depicted in the graph is much lower than those in the ultraviolet.

Visible light is generally considered to be that with wavelengths greater than 400 nm although there is variability between people in their ability to see light in the range around 400. But there are no wavelengths past 415 that can stimulate fluorescence in N3 centers. Is that your understanding as well?

As you and I agreed earlier, the VV light intensity drops off with distance from the source in the same way the UV drops off. At 3-4 feet from a fluorescent light source the lighting is essentially UV free (less than 1 microwatt). The various gradings of the test stones in the Cowing study show that under 200 foot candles (which is ample to see by) there is no significant whitening taking place, indicating that neither UV nor VV stimulation is happening.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I don't want to interrupt the highly technical discussion you want to have with Garry- but I do think that we can add a lot of value to consumers reading this if we can identify in simply terms what the problem is for them, as you see it.
Putting aside all the data about UV/VV and what might theoretically active fluoro- please identify specifically where you think a consumer has liability or risk based on Fluorescence.

As I've stated all along, I believe the study is attempting to raise a red flag that does not exist.

 

[Karl_K]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Putting aside all the data about UV/VV and what might theoretically active fluoro- please identify specifically where you think a consumer has liability or risk based on Fluorescence.

The price of the diamond is based on the material color(non-fancy) anything that can affect the correct grading of the material color is important for consumers.

Whether it makes it look better or worse and when is a less important conversation.

Garry, the study that needs doing is a huge number of diamonds in a double blind study to see how badly it effects the grading of diamonds using current techniques that the labs are using.

Also keep in mind the range of the grades the effect that will not move a middle I or J up a grade could move another diamond from g to e and that is a huge amount of money.
That is one reason I am not as concerned about it in the hij range than in the def range.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Putting aside all the data about UV/VV and what might theoretically active fluoro- please identify specifically where you think a consumer has liability or risk based on Fluorescence.

The price of the diamond is based on the material color(non-fancy) anything that can affect the correct grading of the material color is important for consumers.

Whether it makes it look better or worse and when is a less important conversation.

Garry, the study that needs doing is a huge number of diamonds in a double blind study to see how badly it effects the grading of diamonds using current techniques that the labs are using.

Also keep in mind the range of the grades the effect that will not move a middle I or J up a grade could move another diamond from g to e and that is a huge amount of money.
That is one reason I am not as concerned about it in the hij range than in the def range.

Really good points Karl- the price effect is more of an issue in totally colorless stones.
My perspective is that color grading is subjective-if you show a given stone to ten different competent color graders, all using identical lighting, you're going to have a percentage of borderline stones where 50% go one way and 50% go the other.
If you change GIA's lighting, this aspect will not change.
If you look at a large swath of colorless diamonds in person, and their pricing it bears this out to some degree.
Even looking online you have a huge variation in prices on ostensibly identical diamonds. An F which is very close to G may trade lower than one that just missed being an E

IN terms of prices- fluorescence has become more of a mind clean issue for many online buyers- particularly in the higher colors.
Consequently, prices of MB/SB DEF stones are discounted pretty heavily.
Therefore a consumer can get a bargain if they like MB/SB and can pick a nice one.
That's why I'm asking for specific instances where a consumer might get hurt due to current grading techniques.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Putting aside all the data about UV/VV and what might theoretically active fluoro- please identify specifically where you think a consumer has liability or risk based on Fluorescence.

The price of the diamond is based on the material color(non-fancy) anything that can affect the correct grading of the material color is important for consumers.

Whether it makes it look better or worse and when is a less important conversation.

Garry, the study that needs doing is a huge number of diamonds in a double blind study to see how badly it effects the grading of diamonds using current techniques that the labs are using.

Also keep in mind the range of the grades the effect that will not move a middle I or J up a grade could move another diamond from g to e and that is a huge amount of money.
That is one reason I am not as concerned about it in the hij range than in the def range.

Really good points Karl- the price effect is more of an issue in totally colorless stones.
My perspective is that color grading is subjective-if you show a given stone to ten different competent color graders, all using identical lighting, you're going to have a percentage of borderline stones where 50% go one way and 50% go the other.
If you change GIA's lighting, this aspect will not change.
If you look at a large swath of colorless diamonds in person, and their pricing it bears this out to some degree.
Even looking online you have a huge variation in prices on ostensibly identical diamonds. An F which is very close to G may trade lower than one that just missed being an E

IN terms of prices- fluorescence has become more of a mind clean issue for many online buyers- particularly in the higher colors.
Consequently, prices of MB/SB DEF stones are discounted pretty heavily.
Therefore a consumer can get a bargain if they like MB/SB and can pick a nice one.
That's why I'm asking for specific instances where a consumer might get hurt due to current grading techniques.

Here are two specific cases from the 2010 study:

Box B: Effect of fluorescence on diamond values in
the gem trade

Example of inadequate discounting of fluorescent diamonds

Stone 4, (which drops from an F in Diamondlite to a J) is a textbook example of a ‘false colour’ diamond warned about by
Wade in 1916. Based upon the possible over-grading of this type of fluorescent
diamond, it would be reasonable to conclude that typical trade discounting of
substantially sized ‘Very Strong Blues’ like 4 may be insufficient. For example, a
3 ct pear-shaped F VS2 ‘Very Strong Blue’, might be discounted between 10 and
20% from its asking price of $54,000 to around $45,900. At its unenhanced grade of J
its corresponding price would be $33,600, well below the typical
discounted price of $45,900. (Note: the significance of these high wholesale
asking prices from Rapaport (2009) lies in their comparative values rather than in
the absolute amounts.)

Example of over discounting of the rarer diamonds historically described
as ‘blue white’

Consider how unreasonable the current practice is of applying similar
discounts to all ‘Very Strong Blue’ fluorescent diamonds in a particular colour and
clarity range without knowledge of their unenhanced colour. Where diamond
4 is likely not to be discounted enough, it appears unfair to similarly discount
diamond 5, a 3.02 ct cushion shaped D VS1 ‘Very Strong Blue’ that holds its
colour within a grade when not excited. Diamond 5 is one of the rarer fluorescent
diamonds whose price today would be discounted the same percentage from
$73,000 to $62,000. Its price at its unenhanced grade of E would be $69,000,
$7000 above its discounted price.

This rare D with its blue-white appearance
in daylight, should command the premium it once did over the more common
diamonds that are graded D because of their fluorescence.
This data base indicates that these rare diamonds in the blue
fluorescence strengths of ‘Very Strong’, and ‘Strong’ that hold their
colour within a grade in the absence of fluorescence stimulation can be unfairly discounted.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi Michael- thank you for responding.
You're calling a stone which someone claimed "dropped an "F in Diamondlite to a J" as a "textbook example"
Have you seen this particular diamond Michael?
We all ( most) agree there's a whitening effect - however we are taking about a shade or two. I've never seen a stone that shows such a wide disparity. In over 40 years grading.
So there's no way that's any kind of "Textbook example"
If it even exists at all.

Over discounting is not a consumer problem. It is an opportunity.