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 Post subject: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Tue Mar 01, 2016 5:38 pm 
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In conjunction with the Accredited Gemologist Association Task Force on Lighting and Color-Grading, I recently took our message on lighting standards for diamond D-Z color grading directly to the consumer through the influential pricescope.com consumer talk forum called rockytalky. ( http://www.pricescope.com/forum/rockyta ... 19341.html ) We are ultimately all about consumer protection, and the consumer should be made aware of this important issue. See

[pdfview]http://acagemlab.com/wordpress/wp-content/uploads/2016/01/probproofsolu11.pdf[/pdfview]

This retrospective article revisits the over grading problem and its solutions recommended by the AGA Task Force on Lighting and Color-Grading, which, were they implemented, would remove the stigma and resultant discounting of blue fluorescing diamonds.

Antoinette Matlins with President Stuart Robertson and the AGA board are reconvening the AGA Task Force on Lighting and Color-Grading with the goal of addressing lighting standards for grading colored diamonds and other colored gemstones.

Because research findings and solutions for white diamonds provide a knowledge base and framework for springboarding to grading colored gemstones, we encourage questions and discussion of this article. To get the word out, especially to consumers, we encourage interest and invite participation in this effort.

Michael D. Cowing, MSc, FGA


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Tue Mar 01, 2016 7:28 pm 
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Frankly I *prefer* diamonds that fluoresce. If I remember right, only 1 in 7 do, that makes them a bit more rare (not that diamonds are all that rare.)


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 12:45 am 
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I hear 40% of diamonds fluoresce. Michael can you shine any light on this? UV preferably.


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 7:13 am 
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I have been looking for months for an overblue diamond, fluorescing strongly and visibly in daylight, and so far never been able to find one. This seems to be a rarer bird than expected.
By the way, if any of you were informed of such a thing for sale...


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 11:24 am 
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I recently had a client who was looking for diamonds on BlueNile.
The ones which appeared to be huge bargains were the ones with Strong Blue Fluorescence. 30-39% back
No short supply.
He was looking for D-E-F color so I advised him to get a stone which which had negligible fluorescence. Not surprisingly these diamonds were not bargains. :wink:


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 12:53 pm 
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Coming back to my quest, I have been proposed several times stones with strong blue fluorescence ; these ones are actually plentiful ; but this fluorescence is still not strong enough that it can be seen in sunlight as a visible milky/hazy effect. Generally the fluorescence is strong mainly under UV light.


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 1:28 pm 
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The co-worker that I am helping with his purchase is looking at the Blue Nile data -base for a G color. The strong blues are much less money than the none-faint. I don't know all that much about diamonds but I hear that the strong blues make the better colors appear oily and the tinted stones whiter in some cases. Not something I would order online, these stones need to be seen side by side. My original recommendation is best - take a neon pink Mehenge spinel, drop it into a platinum mount with high quality diamond accents, and for half the price of that worthless white solitaire you will have the look of a million dollar pink diamond.

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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 2:11 pm 
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Isi wrote:
I have been looking for months for an overblue diamond, fluorescing strongly and visibly in daylight, and so far never been able to find one. This seems to be a rarer bird than expected.
By the way, if any of you were informed of such a thing for sale...


love them too.

I have two pink diamond with strong blue fluor. and two gray with blue fluor. and weak
and short phosphorescence.

Many with others with blue, yellow, orange and greenish yellow fluor - sold as untreated
( :^o ) on fleabay...

Esp. these lime greenish yellow stones with strong fluor are awesome ( Venezuela).

Will show you a tiny Marquise in St. Marie - yellow in incandescent light but vivid green-yellow in daylight.

Like these HPHT treated Ib diamond - artifical color but nice...

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gemstones, precision cuts and more...


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 4:49 pm 
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Quote:
Will show you a tiny Marquise in St. Marie - yellow in incandescent light but vivid green-yellow in daylight.


Yes please ! Wanna see.


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 7:44 pm 
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The Research

The Gemological Institute of America (GIA), seeking to put the whole matter to rest, embarked on a massive comparison of diamonds with and without fluorescence. The results were exhaustively detailed in an article in Gem & Gemology’s Winter 1997 issue entitled “A Contribution to Understanding the Effect of Blue Fluorescence on the Appearance of Diamonds.”

The mammoth study involved a random sample of 26,010 grading reports for diamonds in the range of colorless to faint yellow. According to the article, “The data revealed that approximately 65 percent of these diamonds had no reported fluorescence to long-wave UV radiation.” Further, of the 35 percent of diamonds that showed fluorescence — 9,175 diamonds — 38 percent showed faint fluorescence and 62 percent had medium to very strong fluorescence. Of these 5,710 diamonds with medium to very strong fluorescence, nearly all fluoresced blue. Only 3 percent, or 162 stones, showed another color, such as yellow, white or orange.


so, if we omit those with "faint fluorescence", we are left with 24% with medium to strong fluoresence. that is higher than I remember, but they had a pretty big sample size. :-D


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Wed Mar 02, 2016 10:44 pm 
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dchallener wrote:
The Research

The Gemological Institute of America (GIA), seeking to put the whole matter to rest, embarked on a massive comparison of diamonds with and without fluorescence. The results were exhaustively detailed in an article in Gem & Gemology’s Winter 1997 issue entitled “A Contribution to Understanding the Effect of Blue Fluorescence on the Appearance of Diamonds.”

The mammoth study involved a random sample of 26,010 grading reports for diamonds in the range of colorless to faint yellow. According to the article, “The data revealed that approximately 65 percent of these diamonds had no reported fluorescence to long-wave UV radiation.” Further, of the 35 percent of diamonds that showed fluorescence — 9,175 diamonds — 38 percent showed faint fluorescence and 62 percent had medium to very strong fluorescence. Of these 5,710 diamonds with medium to very strong fluorescence, nearly all fluoresced blue. Only 3 percent, or 162 stones, showed another color, such as yellow, white or orange.


so, if we omit those with "faint fluorescence", we are left with 24% with medium to strong fluoresence. that is higher than I remember, but they had a pretty big sample size. :-D


With a sample size that great you are not going to find better data. We have 97% of the 62% of medium to very strong fluorescence diamonds being blue among the 35% of diamonds showing any fluorescence at all. Let's see, .97 x .62 x .35 = 21% of the population of 26,000 diamonds are candidates for over grading due to the labs and the trades use of UV-containing, grade-whitening fluorescent illumination.

How do you feel about paying E color prices discounted perhaps 10% that when viewed in your home or office lighting drop to I color worth 37% less than E in a one carater VS1? That was typical for very strong blue diamonds graded in the GIA diamondlite from the 60's through the 90's.

Check out the 6 I color study diamonds from the 1997 GIA article from which we are quoting these percentages. Look in particular at figure 6b which is the combined image of two diamond halves showing the body color absent stimulation of fluorescence of a None (whiter lower left half) and a Strong Blue fluorescent diamond (darker upper right half), both having been graded the same I color in the DiamondLite.


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Thu Mar 03, 2016 2:37 am 
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Have You ever heard about LUMISENSE ? - HRD Antwerp colorimeter ( not for sale) made just for their own purposes , "Lumisense is not affected by the serious limitations (diamond type, fluorescence) "

http://www.wtocd.be/en/Projects/lumisense_auto_color.html

I've heard from some clever people that HRD is the best Lab in diamond colour grading


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Thu Mar 03, 2016 11:29 am 
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You have posted an excellent article PolGem. Please, everyone, take the time to read this!


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 Post subject: Re: The Over Grading of Blue Fluorescent Diamonds Revisited
PostPosted: Thu Mar 03, 2016 3:27 pm 
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I've seen this instrument in operation and liked a lot! WTOCD guys are just amazing. My jaw dropped when they told about an orientation independent polishing method for diamonds :shock: The only "problem" is that many of their projects are funded so that the outcome will not be available for open market. This is the case even with Lumisense.

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