GIA and EGL-USA/Canada Color Grading

[CharmyPoo]

As part of an on-going for fun exercise, I have yet another stone with GIA and EGL-USA (Toronto Branch) comparison.

I was very surprised at the results but will share shortly.

Which diamond do you think is lower on the color scale?

 

[Rockdiamond]

Cool experiment!
The unset stone certainly seems to have more tint- however we can't really see the stone which is set into a ring. It looks like it may have Fluorescence, but that could be due to the glare....
If it is fluorescent, it can really make color grading far trickier.

I had not heard of EGL Toronto.....

I'm extremely interested to hear the results.
Thanks for posting them

 

[CharmyPoo]

EGL Toronto is essentially EGL-USA but their branch in Toronto. I find this lab to be extremely well ran and consistent in their results. I believe they have one appraiser (at least I always get the same one). He is very knowledgeable and consistently strict and very much aligned to GIA.

I will reveal the results shortly later.

 

[Dreamer_D]

Rock diamond I would love to know more about how Fluor can make color grading hard. How do different colora of Fluor affect color grading?

 

[Rockdiamond]

Rock diamond I would love to know more about how Fluor can make color grading hard. How do different colora of Fluor affect color grading?

What happens is that the body color of the diamond, as seen through the pavilion shows a given tint- say H. In a Med or Strong Blue stone the face up can look like an F. Regular readers, or people familiar with diamonds will know to expect a whiter face up in this situation.
Once we get down to "cape" and lower into actual yellow diamonds it's much trickier.
Sometimes medium or strong blue will make a cape stone look a lot more yellow in the face, which is counter-intuitive as compared to higher color blue stones, which tend to face up whiter.
For this reason stones in the M,N, O-P, Q-R , S-T range are incredibly difficult to grade if they're fluorescent.

 

[Dreamer_D]

David I thought that color was only graded face down? How does face up color come into play then?

 

[Rockdiamond]

It's true that non fancy colored stones are graded through the pavilion.
Even though the pavilion, medium or strong blue can ( not always) impact the color in a way making exact grading very difficult.

I've often wondered if GIA graders ever look at the face- and if so, will it influence the grade.

 

[Rockdiamond]

PS- I'm still very interested in the results.
With the latest round of bad publicity, and lawsuits, I am anxiously awaiting to see if EGL USA takes any kind of action- or changes their behvoir

 

[Evert P Botha]

I was going through our research archive this afternoon, and found this little gem. We cut some rough diamonds for a "gem hunter"- sad story when someone who knows nothing about rough diamonds goes shopping in Sierra Leone and looses his shirt, car and house. But I digress...

We cut a spectacular Cushion Modified Brilliant which has since evolved into one of our proprietary patents. The stone was beautiful and upon his insistence, we agreed that we'd send it to the GIA for grading and the results were more-or-less in line with what we expected- he expected a fancy color. Needless to say, based on advice from a "friend", he sent it to EGL USA for grading. Well...not sure what happened to this diamond in the end.

 

[CharmyPoo]

Since it doesn't seem like many consumers want to play, I will reveal the results and very interested to see what David thinks.

The larger loose diamond is graded as a Transitional Round Brilliant and as a GIA (NYC branch) M and an EGL (Toronto branch) L. This is consistent with what I see from these two GIA labs. The GIA NYC lab is consistently one grade lower than EGL Toronto lab in color. Both labs graded no fluorescence and VVS2.

In my own comparisons of the set stone, it is far whiter than the loose stone from a top down, bottom up and side perspective with indoor non-uv lighting. I compared it to a GIA K / EGL J stone and it still appeared whiter but more yellow than GIA G and GIA H stones. In outdoor sunlight, the set stone will turn close to shade of the GIA K / EGL J stone.

I took the stone into EGL (Toronto Branch) to get it graded - they discovered that the diamond was inscribed with a GIA number. GIA graded the stone as O-P with medium yellow fluorescence. EGL then took the GIA specs and graded it exactly the same - O-P with medium yellow fluorescence.

Now, I for the life of me cannot see ANY WAY possible that this stone (without applying UV light) can be seen as more yellow than the wide range of stones I compared it to. This leads me to wonder if GIA uses UV lighting when grading color even though I think color should be the grade without the influence of fluorescence. I am also surprised that EGL would match the GIA specs but perhaps this is them being consistent.

On a side note, I have never seen yellow fluorescence in a white diamond ... so that was interesting.

 

[CharmyPoo]

Evert - I am unable to see the grades on the image. What does the GIA cert say?

 

[CharmyPoo]

Just a note - the photos I posted are more yellow than real life of both diamonds but they are equally more yellow.

 

[Evert P Botha]

Re: GIA and EGL-USA/Canada Color Gradi

GIA K VS2 vs EGL I VS2
EGL Canada...we'll...that's a road less-traveled...I'll-advised.

 

[luvdajules]

Charmy Poo, thanks for posting this cool thread, very educational and interesting. Love your warm colored stones, the facet patterns are very pleasing.

 

[WinkHPD]

Since it doesn't seem like many consumers want to play, I will reveal the results and very interested to see what David thinks.

The larger loose diamond is graded as a Transitional Round Brilliant and as a GIA (NYC branch) M and an EGL (Toronto branch) L. This is consistent with what I see from these two GIA labs. The GIA NYC lab is consistently one grade lower than EGL Toronto lab in color. Both labs graded no fluorescence and VVS2.

In my own comparisons of the set stone, it is far whiter than the loose stone from a top down, bottom up and side perspective with indoor non-uv lighting. I compared it to a GIA K / EGL J stone and it still appeared whiter but more yellow than GIA G and GIA H stones. In outdoor sunlight, the set stone will turn close to shade of the GIA K / EGL J stone.

I took the stone into EGL (Toronto Branch) to get it graded - they discovered that the diamond was inscribed with a GIA number. GIA graded the stone as O-P with medium yellow fluorescence. EGL then took the GIA specs and graded it exactly the same - O-P with medium yellow fluorescence.

Now, I for the life of me cannot see ANY WAY possible that this stone (without applying UV light) can be seen as more yellow than the wide range of stones I compared it to. This leads me to wonder if GIA uses UV lighting when grading color even though I think color should be the grade without the influence of fluorescence. I am also surprised that EGL would match the GIA specs but perhaps this is them being consistent.

On a side note, I have never seen yellow fluorescence in a white diamond ... so that was interesting.

Very interesting. Being consistently one grade looser than GIA means tens of thousands of dollars more are paid at the retail level over the course of a year by a store using EGL Canada as their laboratory of choice while they are actually paying less at the wholesale level for the EGL certed goods. Nice work if you can get it, and still sleep at night.

Copying the answers to the test has always seemed wrong to me. Since from your pictures, both labs appear to have gotten it wrong, I find it even more reprehensible. It would be fascinating to see how both diamonds were graded if submitted to the same grader at the same time and if neither had the grading report inscribed on the girdle.

I realize that it is not possible to make an accurate assumption from only two stones, especially when going from photos that you say add yellow (equally) to both stones. Still, it is an interesting example of the lack of perfection of any laboratory and the need to see a diamond with your own eyes to know if YOU like it.

Thank you for sharing it with us.

Wink

 

[CharmyPoo]

Wink - the consistency was only referring to the multiple times I sent stones to both GIA and EGL. In those cases, I never shared the report and there was no GIA inscription.

I was told EGL graded blind and does not take from GIA reports. I do not believe that to be in this case.

 

[Rockdiamond]

Thanks again for this thread Charmy.
We can't re-enforce enough times the problems associated with trusting non GIA grades.

Incredibly cool and unique to find a stone the color of yours with yellow florescence.
Fluorescence is just so durn weird.
Here's why I say it's weird.
I have an extremely sensitive eye when it comes to fluorescent diamonds.
In say.....60% of the cases when I look at a diamond under a grading lamp, I can tell without a UV light if the stone is medium or strong.
To me that's weird because a fair amount of the time stones that appear equally fluorescent in darkness, under UV, show different degrees of florescence, and color change properties in normal room lighting.
It's why fluorescence is such an enigma.
Sometimes it's amazing. Sometimes yucky. That is of course subjective, but in small percentage of cases, the stone has an oily dull look. What I'm calling yucky.
Many times when I can spot fluorescence in warmer stones, it's a very attractive aspect.
Point is
1) you can't remove all UV light from the spectrum- even for color grading purposes.
2) even if you could, the color and fluorescence combine to make the body color of the diamond seem a different color than it is.
If that makes any sense.
Bottom line and rel life experience:
Even GIA is far less consistent in the color grades between N down to Y-Z than they are in grades from D-M, or FLY to Fancy Vivid Yellow.


As far as EGL using GIA grading....well I guess everybody trusts GIA

A shame they would not admit that if pressed.....by maybe, just maybe it's one of those weird coincidences.

 

[oldminer]

One can spend hours on lab results which differ from one another. Reliable grading which inherently fits in with current market pricing is GIA based n the USA. Labs which happen to also grade accurately exist, but play less of a role in the market and prices tend to be discounted. Labs which are notorious for bad grading trade at far larger discounts within the trade. At the consumer level, there is no fixed situation. The price paid is dependent upon the sophistication of the consumer and can greatly vary in differing situations

It is possible to have UV free lighting and easily done, however, such a regimen does not assure no fluorescence. It does assure no UV fluorescence. Diamonds can fluoresce from wavelengths of light other than UV which are in the visible spectrum, too. Lots of lighting being sold as UV lighting is in the lower end of the visible spectrum and not UV but still some diamonds may react quite strongly to these visible light wavelengths. The impossible trick would be to grade a diamond without any chance of any fluorescence occurring whether it is from UV light or some wavelength of visible light. Fluorescence can be as little as a subtle color shift up to a very strong glow. Even a rather weak amount may have an adverse effect on consistent color grading of diamonds because the trade does not really have a "standard" lighting product which is "required' to be in use for every diamond grading house or lab. It could be a very simple LED lighting tool, not thousands of dollars, but there is nothing forcing this on the industry and the GIA is best served by being on top of the mountain looking down on the rest rather than putting us all on a somewhat more even footing. If all labs were the same, there would be no lab on top any more.

 

[Rockdiamond]

One can spend hours on lab results which differ from one another. Reliable grading which inherently fits in with current market pricing is GIA based n the USA. Labs which happen to also grade accurately exist, but play less of a role in the market and prices tend to be discounted. Labs which are notorious for bad grading trade at far larger discounts within the trade. At the consumer level, there is no fixed situation. The price paid is dependent upon the sophistication of the consumer and can greatly vary in differing situations

It is possible to have UV free lighting and easily done, however, such a regimen does not assure no fluorescence. It does assure no UV fluorescence. Diamonds can fluoresce from wavelengths of light other than UV which are in the visible spectrum, too. Lots of lighting being sold as UV lighting is in the lower end of the visible spectrum and not UV but still some diamonds may react quite strongly to these visible light wavelengths. The impossible trick would be to grade a diamond without any chance of any fluorescence occurring whether it is from UV light or some wavelength of visible light. Fluorescence can be as little as a subtle color shift up to a very strong glow. Even a rather weak amount may have an adverse effect on consistent color grading of diamonds because the trade does not really have a "standard" lighting product which is "required' to be in use for every diamond grading house or lab. It could be a very simple LED lighting tool, not thousands of dollars, but there is nothing forcing this on the industry and the GIA is best served by being on top of the mountain looking down on the rest rather than putting us all on a somewhat more even footing. If all labs were the same, there would be no lab on top any more.

Amazing stuff David.
The italicized part makes a lot of things clearer to me about what we see in diamonds reacting to UV, or other wavelengths.
I was only considering UV- as opposed to the full spectrum of light. Makes perfect sense.

As far as the part about standardized lighting helping....maybe, but my experience is that the range of different reactions to these wavelengths is very diverse- so no one solution would fit all stones.