Blue Fluorescent Diamonds - Facts and Fiction

[michaelgem]

Here is a recent Facebook discussion by Renee Newman, GIA graduate-gemologist, and acclaimed author of over a
dozen guides to gems and jewelry, about fluorescence in diamonds.



“Here are eight diamonds with strong to very strong blue fluorescence photographed by Michael Cowing
under typical daylight balanced fluorescent lighting & long-wave UV.
None of the diamonds has a hazy, milky, oily or cloudy appearance.

When I was working on the fluorescence chapter of the 3rd Edition of my “Diamond Handbook,” I
asked several retail jewelers if they sold strongly fluorescent diamonds and some told me they never
stock them because they are milky and oily looking. A few even advise against buying diamonds with
medium fluorescence even though, as this photo illustrates, highly fluorescent diamonds can have good
transparency. But non-fluorescent diamonds can be milky too.”

Renee Newman is pointing out that the consumer and trade belief that blue fluorescent diamonds
typically have a hazy, milky, or cloudy appearance is untrue. As this photo illustrates, highly
fluorescent diamonds can have good transparency, and conversely non-fluorescent diamonds can be
milky or cloudy. Blue fluorescence and transparency are properties evaluated separately in grading.

GIA has called into question “the trade’s lower ‘bid’ prices for moderate to highly fluorescent
diamonds in the better colors”. Their study “challenges the perception held by many in the trade that
UV fluorescence generally has a negative effect on the overall appearance of a diamond.”

However, there is a valid reason for discounting diamonds with medium
to very strong fluorescence. That is the over grading of color that is too often observed in the trade.
Over grading results from the whitening effect due to blue fluorescence that is stimulated in the
diamond due to use of UV-containing, fluorescent lighting in color grading.

Check out the new two page summary article on this controversial subject at:

Over Grading of Blue Fluorescent Diamonds Summary - ACA Gemological Laboratory

There is a valid reason for discounting diamonds with medium to very strong fluorescence. That is the overgrading of color that is too often observed in the trade. Overgrading results from the whitening effect due to blue fluorescence that is stimulated in the diamond due to use of...

acagemlab.com

or at adobe:

https://indd.adobe.com/view/3ec2cd0e-5f74-4a4b-96b8-4d819d0ecc90

Cheers,
Michael

 

[Garry H (Cut Nut)]

Hi Michael,
You never bothered to answer my comments on FaceBook?



Here is the link below that explains what we have been advising consumers to avoid clouds and internal graining in f;luorescent diamonds for years on this forum Michael.

And as for over grading color and the mistaken instruments etc used in your research - give me a call and I will explain point by point.

Effects of Blue Fluorescence on Diamond Appearance, Color Treatment and Brightening of “Edison” Pearls, and a Pioneering Gemstone Market in Pakistan | Gems & Gemology

An overview of the Summer 2021 <i>Gems & Gemology</i> content.

www.gia.edu

 

[Texas Leaguer]

To me the most interesting aspect of the new GIA study (2021) is the finding that contrast is diminished in highly fluorescent diamonds. This effect is similar to and could be mistaken for haziness, giving rise to the misperception that fluorescence alone causes haziness.

The finding that structural defects in the diamond are responsible for haziness (loss of transparency), and can be found in both fluorescent and non-fluorescent diamonds, is an observation that is consistent with my experience.

But I do not think the article fully accomplishes what it says it intends to accomplish; "help to reduce the confusion and biases in the industry and serve as a solid scientific foundation to ensure public trust with respect to diamond fluorescence". (Also, I have a bit of a problem with scientific experiments starting with a specific goal in mind). While demonstrating haziness per se is not a significant problem, they introduce loss of contrast, which is itself a pretty big deal!

When I look at diamonds, with or without fluorescence, and am trying to visually assess transparency, I am looking for what I refer to as "crispness". Diminished crispness of the scintillation patterns makes the diamond looks slightly flat, whether the result of haze or diminished contrast.

I have always advocated for a metric on a lab report that would give an indication of transparency. (again, independent of any association with fluorescence). Diminished transparency (from structural defects) hampers a significant percentage of diamonds, many in the most popular clarity ranges for consumers.

I am therefore heartened by the statement in the conclusion of the GIA article that such reporting is actively being considered.

The bulk contrast method presented here may also serve as a reliable way to quantitatively evaluate the effect of contrast loss on apparent transparency in future diamond grading processes. We are reviewing these quantitative and semi-quantitative results to see how they might be included in GIA grading reports.

 

[Garry H (Cut Nut)]

When I look at diamonds, with or without fluorescence, and am trying to visually assess transparency, I am looking for what I refer to as "crispness". Diminished crispness of the scintillation patterns makes the diamond looks slightly flat, whether the result of haze or diminished contrast.

Bryan we are on the same page.
I have studied this matter but not yet published anything because we (Grant Pearson and me) discovered a strange feature (i.e. that N3 blue fluorescent diamonds in midday blue sky sunlight actually absorb 350 to 430nm spectrum rather than emit it).
We are actively involved in cracking that issue along with some leading minds.
But from my own research there are two really important factors. The luminosity and the increase in the blueness.
Both increase together with increasing exposure to visible and near visible violet light. So the idea that blue fluorescent diamonds loose contrast is actually not that simple. The get brighter and blue'er. The dark stars in a round diamond get much bluer and vastly brighter than the bright whiter parts. It's complex, but I am not seeing any negativity in that increase in blueness. And I kind of think that the blueness increases more in lower colored diamonds and less so in higher colored stones.

(An important fact pertaining to Michael Cowings research is he focused on shorter wave UV based on the 365nm used for hundreds of years for gem ID that was mistakenly applied as the grading methodology by labs. I firmly believe GIA is now using much higher wavelengths of perhaps 385nm (near visible) or even into the visible range. I believe Michael used a Dazor 5.7 UV A+B meter (made by Solarmeter) which was the wrong instrument. The company make a UVA 4.2 device but even that measures too low a wavelength - but I have that one and even some of that wave length do not pass through many window glass thyes. Most of the frequencies that create the most whitening impact pass through all windows and even a portion pass through Lexan.)

 

[michaelgem]

Here is a recent Facebook discussion by Renee Newman, GIA graduate-gemologist, and acclaimed author of over a
dozen guides to gems and jewelry, about fluorescence in diamonds.



“Here are eight diamonds with strong to very strong blue fluorescence photographed by Michael Cowing
under typical daylight balanced fluorescent lighting & long-wave UV.
None of the diamonds has a hazy, milky, oily or cloudy appearance.

When I was working on the fluorescence chapter of the 3rd Edition of my “Diamond Handbook,” I
asked several retail jewelers if they sold strongly fluorescent diamonds and some told me they never
stock them because they are milky and oily looking. A few even advise against buying diamonds with
medium fluorescence even though, as this photo illustrates, highly fluorescent diamonds can have good
transparency. But non-fluorescent diamonds can be milky too.”

Renee Newman is pointing out that the consumer and trade belief that blue fluorescent diamonds
typically have a hazy, milky, or cloudy appearance is untrue. As this photo illustrates, highly
fluorescent diamonds can have good transparency, and conversely non-fluorescent diamonds can be
milky or cloudy. Blue fluorescence and transparency are properties evaluated separately in grading.

GIA has called into question “the trade’s lower ‘bid’ prices for moderate to highly fluorescent
diamonds in the better colors”. Their study “challenges the perception held by many in the trade that
UV fluorescence generally has a negative effect on the overall appearance of a diamond.”

However, there is a valid reason for discounting diamonds with medium
to very strong fluorescence. That is the over grading of color that is too often observed in the trade.
Over grading results from the whitening effect due to blue fluorescence that is stimulated in the
diamond due to use of UV-containing, fluorescent lighting in color grading.

Check out the new two page summary article on this controversial subject at:

Over Grading of Blue Fluorescent Diamonds Summary - ACA Gemological Laboratory

There is a valid reason for discounting diamonds with medium to very strong fluorescence. That is the overgrading of color that is too often observed in the trade. Overgrading results from the whitening effect due to blue fluorescence that is stimulated in the diamond due to use of...

acagemlab.com

or at adobe:

https://indd.adobe.com/view/3ec2cd0e-5f74-4a4b-96b8-4d819d0ecc90

Cheers,
Michael

Furthering the discussion:

Kelly Smith: Fluorescence in a diamond actually makes the color look 1-2 grades better. I always recommend my clients consider this trait as a positive thing rather than a negative.

Dr Thomas Hainschwang: Kelly Smith, careful that's not the actual color of the stone though - the N3 fluorescence bands basically cancel out the N2 absorption bands - that's why a more yellowish diamond will look more colorless when blue fluorescence is distinct... it's only a fluorescence related phenomenon.

Michael Cowing: The actual color of the diamond, what the diamond trade historically called its “true color,” is the color seen at typical viewing distances (three feet or more) from artificial illumination, where grade whitening fluorescence is not stimulated. There the light at the diamond contains insufficient UV (less than one microwatt), and insufficient visible violet (VV) energy to stimulate grade whitening fluorescence.

The reason blue fluorescent diamonds often get a higher/better color grade than their true color from GIA and other labs is the 2008 GIA established standard grading light, which is unfiltered UV-containing fluorescent lighting that approximates northern daylight.

This new standard is the lighting that prior to 2000 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.” As a result, diamonds with strong to very strong blue fluorescence can receive a color grade that is higher than its true/inherent color unenhanced by fluorescence.

A diamond that was lab graded an I color with strong or very strong fluorescence may have an inherent color of J, K, or even L when viewed or graded under lighting which does not stimulate fluorescence.

This is why Martin Rapaport commented in the April 1998 issue of the ‘Rapaport Diamond Report’: ‘Unfortunately, the probability of a lab overgrading a fluorescent stone is much greater than a non-fluorescent stone and a large percentage of high color mistakes turn out to be fluorescent’. ‘Obviously from the market perspective there appears to be a reasonable basis for price discrimination.