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How GIA grades color in colorless vs. fancy colored diamonds

kenny

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Based on what I've read here this is my understanding; Pros are welcome to correct me if my understanding is wrong.

Contrary to what many people would think, if you put two colorless GIA H round diamonds side by side, a 1 carat and a 10 carat, they will NOT look the same color.
You will see more color in the larger one, whether face-up looking into the top, or face down-looking into the side of the pavilion with a white background.

Here's my question.
Does GIA give the opposite consideration to weight when grading color intensity of fancy colored diamonds?

Here's why I suspect they do.
In the pic below are two green diamonds, both graded natural Fancy Intense Green by GIA with no color modifiers.
Both pics are from the same vendor, fancydiamonds.net. and have the same white background.
I have read here that this vendor has a good reputation for the honesty of their photography.

The cushion on the left is 2.36 ct and the round on the right is 0.26 ct, almost 10 times smaller.
Note the larger diamond on the left has much weaker color than the smaller one.
This is just the opposite of how GIA grades the color of colorless diamonds.

I realize fancy colors are graded face up and colorless are graded face down.
But that does not affect my question since I'm comparing a fancy color to a fancy color.
I also realize you can't judge color by pics but the difference here is so dramatic and in the opposite direction.

Apparently, larger colorless diamonds in the same color-intensity grade will have more color, but larger fancy colored diamonds in the same color-intensity grade will have less color.

Here are the stones:

The 2.36 ct cushion on the left: http://www.fancydiamonds.net/view_diamonds/3667.htm

The 0.26 ct round on the right: http://www.fancydiamonds.net/view_diamonds/4217.htm

two greens.png
 

ChunkyCushionLover

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Re: How GIA grades color in colorless vs. fancy colored diam

Here is my lowly consumer understanding of color grading.

Colorless and Near Colorless is graded facedown, looking at the body using the calibrated stones. Doesn't matter the size of the sample being graded.

Fancy Color is graded faceup. Doesn't matter the size either but the ranges are much broader which is what you are seeing.

Both of the evaluations are done based on a color scale indepedant of size, even though color and saturation do depend on this.
Also GIA grading lighting may be far from the lighting used to take those vendor photos.
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

kenny said:
Based on what I've read here this is my understanding; Pros are welcome to correct me if my understanding is wrong.

Contrary to what many people would think, if you put two colorless GIA H round diamonds side by side, a 1 carat and a 10 carat, they will NOT look the same color.
You will see more color in the larger one, whether face-up looking into the top, or face down-looking into the side of the pavilion with a white background.

Here's my question.
Does GIA give the opposite consideration to weight when grading color intensity of fancy colored diamonds?

Here's why I suspect they do.
In the pic below are two green diamonds, both graded natural Fancy Intense Green by GIA with no color modifiers.
Both pics are from the same vendor, fancydiamonds.net. and have the same white background.
I have read here that this vendor has a good reputation for the honesty of their photography.

The cushion on the left is 2.36 ct and the round on the right is 0.26 ct, almost 10 times smaller.
Note the larger diamond on the left has much weaker color than the smaller one.
This is just the opposite of how GIA grades the color of colorless diamonds.

I realize fancy colors are graded face up and colorless are graded face down.
But that does not affect my question since I'm comparing a fancy color to a fancy color.
I also realize you can't judge color by pics but the difference here is so dramatic and in the opposite direction.

Apparently, larger colorless diamonds in the same color-intensity grade will have more color, but larger fancy colored diamonds in the same color-intensity grade will have less color.

Here are the stones:

The 2.36 ct cushion on the left: http://www.fancydiamonds.net/view_diamonds/3667.htm

The 0.26 ct round on the right: http://www.fancydiamonds.net/view_diamonds/4217.htm


Kenny..., this is a clear example of two opposing cuts..., one needed tricky cuts (which still doesnt seem to help much based on the vendors picture) while the other..., well the other does not need any explanations :devil: .
 

clgwli

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Re: How GIA grades color in colorless vs. fancy colored diam

Someone can correct me if I am wrong on this as I don't know much about green colored stones. But I understand that with yellow there are ranges for each color group and that these ranges are rather large by comparison to the colorless ranges. So there is a larger range of what is accepted for a Fancy Yellow than there is for a D or even a G colored stone.

Again someone can correct me if I am wrong on this. But size alone wouldn't be the only factor in this. It could be that each of these stones falls more at the edges of the range for the color. The larger on the lighter side and the smaller on the darker.

Again I don't know much about green, but if the grading ranges they use for yellow is the same as green it could easily explain the differences.

ETA: I see now that CCL said the same thing about the ranges. I just took way too long to type mine out lol
 

kenny

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Re: How GIA grades color in colorless vs. fancy colored diam

Yes, I know each grade is a range of hue, tone, saturation etc. and GIA is notorious for their broad ranges within a color grade Itzik @ fancydiamonds.net said they have 10 within a GIA grade, but still! . . . come on!
Look at the enormous difference between those two identically-graded greens.
Look at the fact that one is almost 10 times the weight of the other.

I think my question is a reasonable and logical one.
 

ChunkyCushionLover

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Re: How GIA grades color in colorless vs. fancy colored diam

kenny said:
Yes, I know each grade is a range of hue, tone, saturation etc. and GIA is notorious for their broad ranges within a color grade Itzik @ fancydiamonds.net said they have 10 within a GIA grade, but still! . . . come on!
Look at the enormous difference between those two identically-graded greens.
Look at the fact that one is almost 10 times the weight of the other.

I think my question is a reasonable and logical one.

It is for this reason the colored gem gurus prefer AGL, AGTA or a strict use of the Munsell scale for colored stones. These definitely have different hues and saturation. Judging by the difference in shadows also different brightness of lighting or corrections too.
 

clgwli

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Re: How GIA grades color in colorless vs. fancy colored diam

Kenny without seeing the stones side by side in person, I wouldn't be able to make a comment about the colors. Even a photo of the two size by side would help more than a separate photo of each. I think it isn't wise to compare two colors when they aren't together. Particularly when it looks like there is a brown reflection going on in the stone on the left.

I think you might be shocked with how wide the ranges for colors are. Granted again my research was for yellows (or even yellows with brown) so I am way more familiar with those colors, but it was amazing to me with the ranges I saw. I've seen Fancy Intense that really looked more like Fancy Yellow and Fancy Intense that would would swear up and down was a Fancy Vivid. I've seen stones side by side as well and it is shocking. And I saw a Fancy Light set that looks lighter than my Y-Z color.

It's not precise at all and I would wager this has more to do with the range allowable than a size or even cut issue. I say this only because the side by sides that I have seen were very close in size as well as cut. For example the FLY I saw was 1ct and mine is .93ct. Definitely not enough size difference to account for the difference especially since the 1ct was very deeply cut and faced up way smaller.
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

clgwli said:
Kenny without seeing the stones side by side in person, I wouldn't be able to make a comment about the colors. Even a photo of the two size by side would help more than a separate photo of each. I think it isn't wise to compare two colors when they aren't together. Particularly when it looks like there is a brown reflection going on in the stone on the left.

I think you might be shocked with how wide the ranges for colors are. Granted again my research was for yellows (or even yellows with brown) so I am way more familiar with those colors, but it was amazing to me with the ranges I saw. I've seen Fancy Intense that really looked more like Fancy Yellow and Fancy Intense that would would swear up and down was a Fancy Vivid. I've seen stones side by side as well and it is shocking. And I saw a Fancy Light set that looks lighter than my Y-Z color.

It's not precise at all and I would wager this has more to do with the range allowable than a size or even cut issue. I say this only because the side by sides that I have seen were very close in size as well as cut. For example the FLY I saw was 1ct and mine is .93ct. Definitely not enough size difference to account for the difference especially since the 1ct was very deeply cut and faced up way smaller.


I think it has more to do with the cut than the color range itself.
These days the (majority of today's) cut(s) controls when the color intensity of polished Diamond crystal reaches the magic Fancy word.
That is not the case with Kenny's green!
 

clgwli

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Re: How GIA grades color in colorless vs. fancy colored diam

DiaGem said:
clgwli said:
Kenny without seeing the stones side by side in person, I wouldn't be able to make a comment about the colors. Even a photo of the two size by side would help more than a separate photo of each. I think it isn't wise to compare two colors when they aren't together. Particularly when it looks like there is a brown reflection going on in the stone on the left.

I think you might be shocked with how wide the ranges for colors are. Granted again my research was for yellows (or even yellows with brown) so I am way more familiar with those colors, but it was amazing to me with the ranges I saw. I've seen Fancy Intense that really looked more like Fancy Yellow and Fancy Intense that would would swear up and down was a Fancy Vivid. I've seen stones side by side as well and it is shocking. And I saw a Fancy Light set that looks lighter than my Y-Z color.

It's not precise at all and I would wager this has more to do with the range allowable than a size or even cut issue. I say this only because the side by sides that I have seen were very close in size as well as cut. For example the FLY I saw was 1ct and mine is .93ct. Definitely not enough size difference to account for the difference especially since the 1ct was very deeply cut and faced up way smaller.


I think it has more to do with the cut than the color range itself.
These days the (majority of today's) cut(s) controls when the color intensity of polished Diamond crystal reaches the magic Fancy word.
That is not the case with Kenny's green!
You may be right. But part of my point is also that without seeing them side by side you cannot tell.

My examples were given to say that even side by side similar cuts and sizes can vary that much as well though. I didn't say it to imply that I was right because honestly I have no idea. I could be very wrong. I only wanted to state that I was shocked with how different the same grades could look with similar cuts and sizes.

Probably in the end it's a little of this and a little of that. But without seeing them side by side no one can say for sure. We can only guess. ETA: I just wouldn't be so quick to say it has to do all with size and nothing else. So I am not sure that Kenny's thoughts about size are the cause for this. That was mostly my point. Again I could be wrong on it, but I just wouldn't be so quick to say it's a size issue more than another cause.
 

kenny

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Re: How GIA grades color in colorless vs. fancy colored diam

I certainly acknowledge that I'm no expert on how wide the range is within a GIA fancy color grade.
I hear again and again that the ranges are very wide.
I just ordered GIA's chart of Fancy Colored Diamonds http://store.gia.edu/ProductDetails.asp?ProductCode=colordiambooklet
Still I have a little bit of learning under my belt and the two diamond above have me puzzled.

Yes one diamond is almost 10 times the weight of the other so the camera had to be closer to the small round, but I think that has no effect.
If anything, wouldn't blowing up the small round make its color MORE diluted, rather than more intense?
Honestly, I believe very strongly that changing the size of an image (especially when done before the pic is even taken) does nothing to the color saturation.

I have no argument the GIA color intensity ranges are wide.
I have no argument that whites are graded face down and coloreds face up.
I have no argument that cut can greatly affect color intensity.
I have no argument that the only way to fairly compare these two would be live, side by side and one pic with both side by side is vastly superior to two separate pics.
I have no argument that lighting differences can affect how a diamond looks live and in a pic.
I have no argument that the lighting used by GIA is probably not identical to that used for these pics.

Even after agreeing with everything above that people have brought up . . . still . . . my question remains unanswered.
How is weight taken into account in GIA color grades?
Nothing brought up has answered my question and nothing brought up makes my question invalid.
It is a legit question.

I do not agree that throwing your hands up in the air and saying "Things vary" is a legit answer.
Yes, it is true that things vary, but there is an answer.
GIA graders know the answer.

Everyone understands and agrees in colorless diamonds a much larger stone of the same GIA color grade will show more color.
Is this also true for Fancy Colored diamonds, or is just the opposite as I suspect?
Or, does weight carry no weight whatsoever as has also been mentioned in this thread?
 

kenny

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Re: How GIA grades color in colorless vs. fancy colored diam

Getting back to the question, here are 3 possible answers.

Much larger colored diamonds of same GIA color intensity grade will have . . .

1. more color
2. less color
3. the same

. . . than much smaller ones.

I'm sure GIA knows the answer.
Does anyone here?
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

kenny said:
I certainly acknowledge that I'm no expert on how wide the range is within a GIA fancy color grade.
I hear again and again that the ranges are very wide.
I just ordered GIA's chart of Fancy Colored Diamonds http://store.gia.edu/ProductDetails.asp?ProductCode=colordiambooklet
Still I have a little bit of learning under my belt and the two diamond above have me puzzled.

Yes one diamond is almost 10 times the weight of the other so the camera had to be closer to the small round, but I think that has no effect.
If anything, wouldn't blowing up the small round make its color MORE diluted, rather than more intense?
Honestly, I believe very strongly that changing the size of an image (especially when done before the pic is even taken) does nothing to the color saturation.

I have no argument the GIA color intensity ranges are wide.
I have no argument that whites are graded face down and coloreds face up.
I have no argument that cut can greatly affect color intensity.
I have no argument that the only way to fairly compare these two would be live, side by side and one pic with both side by side is vastly superior to two separate pics.
I have no argument that lighting differences can affect how a diamond looks live and in a pic.
I have no argument that the lighting used by GIA is probably not identical to that used for these pics.

Even after agreeing with everything above that people have brought up . . . still . . . my question remains unanswered.
How is weight taken into account in GIA color grades?
Nothing brought up has answered my question and nothing brought up makes my question invalid.
It is a legit question.

I do not agree that throwing your hands up in the air and saying "Things vary" is a legit answer.
Yes, it is true that things vary, but there is an answer.
GIA graders know the answer.

Everyone understands and agrees in colorless diamonds a much larger stone of the same GIA color grade will show more color.
Is this also true for Fancy Colored diamonds
, or is just the opposite as I suspect?
Or, does weight carry no weight whatsoever as has also been mentioned in this thread?

Kenny its not an Axiom...,
Yes, when you look at a 1ct there will be a difference in the area size so naturally you will see more colored area in a 10ct.

But if the hue is a bit darker in a 10ct H than a 1 ct H the grading was inconsistent. The 10cts should have been an I or the 1ct should have been a G.

Subjectivity and optical illusion especialy in the Fancy colored arena..., and samples ofcourse 8-)
 

Rockdiamond

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Re: How GIA grades color in colorless vs. fancy colored diam

kenny said:
snip....Everyone understands and agrees in colorless diamonds a much larger stone of the same GIA color grade will show more color.
Is this also true for Fancy Colored diamonds, or is just the opposite as I suspect?
Or, does weight carry no weight whatsoever as has also been mentioned in this thread?

Thank you so much for the great laugh Ken.
Everyone agrees??? That is soooo funny. I love it.

Kenny, what if GIA told you that stones vary - even stones of the same color can look slightly different - and for many reasons.
It is NOT true, as a rule, that a larger stone will show more color than a smaller on of the same color. Or than the opposite holds true for Fancy Colors.
Some stones might ,when compared to others, but not all.
That's not throwing up one's hands and saying "things vary" it's just a fact.

I personally do not believe size ( or weight) comes into play on GIA grading.

If we're talking about fancy colors- again, they vary.
I'll give you an example you can well understand Ken.
What color is your skin?
Even easier- what color is your wall- or your car, or your piano?
Do any of these things have exactly the same shade, no matter what angle you're looking at them- or in what light- or in different surroundings?
Of course not, color- or how we perceive it, is affected by environmental, and other factors.
Irradiated stones, for example, have a more "consistent" color than natural fancy color stones, in general.
The treated ones have such strong color- it's almost like they are painted.
Natural Fancy Color Diamonds have a chameleon like personality based on so many factors.
The darker the stone, the less it changes due to environmental factors. Darker brown is a good example- they don;t change all that much.
The two greens you posted will change- a lot- based on how where and when we are looking at them.

In fact, buyers of diamonds that go overseas are faced with a unique situation: The differences in light make it very difficult to know what you are looking at.
For example- here in my office, where I'm well familiar with how each color looks, I can generally color grade without comparison samples.
When I purchase in Israel, I need to have stones I am familiar with to use as "benchmarks"
 

Karl_K

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Re: How GIA grades color in colorless vs. fancy colored diam

David can you give us a GIA colored diamond grading 101 lesson?
What factors are taken into consideration and which factors apply to what words?
How are they graded?
For example color would be under color: red/yellow/green
evenness of color is factored in where?
tone is factored in where?
color modifiers?

Pretend you are explaining it to a customer who is seated in front of you who wants a colored diamond but knows nothing about color grades.

Thanks in advance!
 

Andelain

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Re: How GIA grades color in colorless vs. fancy colored diam

<<<--- Takes a seat in front of David
 

yssie

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Re: How GIA grades color in colorless vs. fancy colored diam

Karl_K said:
David can you give us a GIA colored diamond grading 101 lesson?
What factors are taken into consideration and which factors apply to what words?
How are they graded?
For example color would be under color: red/yellow/green
evenness of color is factored in where?
tone is factored in where?
color modifiers?

Pretend you are explaining it to a customer who is seated in front of you who wants a colored diamond but knows nothing about color grades.

Thanks in advance!

ooh yes, I'd love to hear more about this too
 

Garry H (Cut Nut)

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Re: How GIA grades color in colorless vs. fancy colored diam

DiaGem said:
kenny said:
Based on what I've read here this is my understanding; Pros are welcome to correct me if my understanding is wrong.

Contrary to what many people would think, if you put two colorless GIA H round diamonds side by side, a 1 carat and a 10 carat, they will NOT look the same color.
You will see more color in the larger one, whether face-up looking into the top, or face down-looking into the side of the pavilion with a white background.

Here's my question.
Does GIA give the opposite consideration to weight when grading color intensity of fancy colored diamonds?

Here's why I suspect they do.
In the pic below are two green diamonds, both graded natural Fancy Intense Green by GIA with no color modifiers.
Both pics are from the same vendor, fancydiamonds.net. and have the same white background.
I have read here that this vendor has a good reputation for the honesty of their photography.

The cushion on the left is 2.36 ct and the round on the right is 0.26 ct, almost 10 times smaller.
Note the larger diamond on the left has much weaker color than the smaller one.
This is just the opposite of how GIA grades the color of colorless diamonds.

I realize fancy colors are graded face up and colorless are graded face down.
But that does not affect my question since I'm comparing a fancy color to a fancy color.
I also realize you can't judge color by pics but the difference here is so dramatic and in the opposite direction.

Apparently, larger colorless diamonds in the same color-intensity grade will have more color, but larger fancy colored diamonds in the same color-intensity grade will have less color.

Here are the stones:

The 2.36 ct cushion on the left: http://www.fancydiamonds.net/view_diamonds/3667.htm

The 0.26 ct round on the right: http://www.fancydiamonds.net/view_diamonds/4217.htm


Kenny..., this is a clear example of two opposing cuts..., one needed tricky cuts (which still doesnt seem to help much based on the vendors picture) while the other..., well the other does not need any explanations :devil: .

Regarding the cuts - if the smaler stone on the right was optimized for cut, it would go to Vivid, because it is probably right on the border already. Where as the larger stone, when cut to the same round as the smaller one would probably drop a grade - or may not even get fancy light.
So big ranges, and cut matters.
Size does not - it is purely face up colour.
But even ness of colour counts too - which is why a lot of rounds do better to have poor optical symmetry so they do not look like H&A's with heaps of contrast.
This entire section here will help you Kenny:
http://www.octonus.com/oct/projects/fancycolor-5.phtml
 

Garry H (Cut Nut)

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Re: How GIA grades color in colorless vs. fancy colored diam

This is a screen shot of the RapNet search page for fancy colored diamonds - you can see that while there are fewer graditions in colour - there are also tonal and shade differences. It is very complex, and human graders have a much tougher time than they do with D-Z!
DiamCalcColor is a scientific solution based on taking a spectrum of the rough diamond before polishing it, and incorporating this science into the planning and polishing.
(The same is being done for D-Z rough and allowing the cutter to know if say a 2ct cushion will be high I SI1 vs a 1.5ct round getting low G SI1. The 1.5ct round would fetch more $'s)

fancy color search.jpg
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

Garry H (Cut Nut) said:
Regarding the cuts - if the smaler stone on the right was optimized for cut[Color??], it would go to Vivid, because it is probably right on the border already.


You would recut such a stone to achieve the GIA "Vivid"?? (if it was a 1.50ct for example?)
 

Garry H (Cut Nut)

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Re: How GIA grades color in colorless vs. fancy colored diam

DiaGem said:
Garry H (Cut Nut) said:
Regarding the cuts - if the smaler stone on the right was optimized for cut[Color??], it would go to Vivid, because it is probably right on the border already.


You would recut such a stone to achieve the GIA "Vivid"?? (if it was a 1.50ct for example?)
Of course DG, but what I really meant was if it was planned that way the first time it was polished :)
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

Garry H (Cut Nut) said:
DiaGem said:
Garry H (Cut Nut) said:
Regarding the cuts - if the smaler stone on the right was optimized for cut[Color??], it would go to Vivid, because it is probably right on the border already.


You would recut such a stone to achieve the GIA "Vivid"?? (if it was a 1.50ct for example?)
Of course DG, but what I really meant was if it was planned that way the first time it was polished :)


You would..., wouldnt you :errrr: ... :twirl:

What about if they both could earn the GIA Vivid magic word..., which would you rather own?
 

ChunkyCushionLover

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Re: How GIA grades color in colorless vs. fancy colored diam

What about if they both could earn the GIA Vivid magic word..., which would you rather own?[/quote]

The one which says Deep ;-)
 

Rockdiamond

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Re: How GIA grades color in colorless vs. fancy colored diam

Karl_K said:
David can you give us a GIA colored diamond grading 101 lesson?
What factors are taken into consideration and which factors apply to what words?
How are they graded?
For example color would be under color: red/yellow/green
evenness of color is factored in where?
tone is factored in where?
color modifiers?

Pretend you are explaining it to a customer who is seated in front of you who wants a colored diamond but knows nothing about color grades.

Thanks in advance!
You're quite welcome Karl- that's a very comprehensive, well thought out question.
Basically, it is a bunch of questions, because the answers are different for different hues.
When you pose a question "how are they graded", you can either be asking about the methods used by GIA, or the grades themselves.
My answer is based more on the grades.
That is to say: I know what the results look like- I can ( and will) get some more info on the other aspect, GIA's methodology.... as much as GIA will discuss.

How are they graded?
Let's start with stones who's tint leans to the yellow family- which is one of the most common tints. In terms of goods coming to market, suspect brown might be on par, but I'm not sure of that. Let's start with yellow
D is totally colorless. J has a slight tint. M is increasingly tinted- in general much more noticeable in round brilliant cut when viewed through the pavilion- which is how GIA grades colorless.
As we go down the scale "N" is the last single color grade.
O-P, Q-R, S-T ranges might be called "Faint Yellow"
U-V, W-X, and Y-Z are light yellow.
GIA issues a number of products in diamond reports.
One of them is the Colored Diamond Identification and Origin- also known as a "Color Origin" report ,or "half report" lists shape, measurements, color omitting clarity. For some reason, GIA does not use the exact same name for the color grade on both the traditional "full report" and the Color origin.
U-V would be called simply, "U-V range" on the full report. On the half report GIA qualifies the name by calling it "Light Yellow"
Below Y-Z Range, is Fancy Light Yellow. Below that is Fancy Yellow, Fancy Intense Yellow, Fancy Vivid Yellow.
On a different track is Fancy Deep Yellow- which would generally be roughly equivalent to a stone intense, or even vivid, but the color is not the bright yellow we associate with a true "Canary" diamond. It's a darker yellow. Sometimes called a "poor man's vivid"

It seems to me that GIA is sensitive to certain market/rarity issues.
For example, an M color has a slight yellow tint- but it's called M
If it had that much pink tint it would probably be a Faint Pink- same for Blue.
If it has a brown tint, GIA retains the letter name, but qualifies it ( L, Light Brown)
Anyway, that's a start......

Diagem- I really love your cutting style and respect you tremendously.
But I do have to respond one one concept you introduce- I find your characterization of a given cutting style as "tricky" to be unfair.
If technology has advanced to the point that cutters can coax color out of rough that was formerly overlooked, I don't find it to be tricky at all.
Implying that it is a the decision the cutter is faced with to choose either 2.25 Fancy, or 1.50 vivid is misleading. It took a lot of choices- and apparently right ones- to get the rough, and polish it to the color that was achieved.
Garry- I'm sure that DiamCalcColor will be a great addition to the tools like that which are already in use.
 

Karl_K

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Re: How GIA grades color in colorless vs. fancy colored diam

Thanks David that is a good start.
out of what you covered so far at what point do they start grading face up?
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

Rockdiamond said:
I find your characterization of a given cutting style as "tricky" to be unfair.
If technology has advanced to the point that cutters can coax color out of rough that was formerly overlooked, I don't find it to be tricky at all.

David..., you are the one who combined my word 'tricky' with your word "unfair"!
But I do believe the pictures speak for themselves (and this is green not yellow ;)) )
 

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Rockdiamond

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Re: How GIA grades color in colorless vs. fancy colored diam

DiaGem said:
Kenny..., this is a clear example of two opposing cuts..., one needed tricky cuts (which still doesnt seem to help much based on the vendors picture) while the other..., well the other does not need any explanations :devil: .
Yoram- I know English may not be your first language ( although you speak it beautifully)- but the word "tricky" implies something.
Tricky has two meanings.
1) is related to "trickery"
2) Requiring caution or skill: a tricky recipe.
I believe you are using the first definition, in your meaning. Trickery: The practice or use of tricks; deception by stratagem.
It sounds like a negative comment. Of course we're all entitled to our own opinions- and yours carries a lot of weight due to your skill as a cutter.
Just for the purposes of discussion, I'd like to ask you to reconsider the motivation of the cutter here- or in a lot of cases of similar cutting techniques.
A natural ( rough)diamond does not look like what we know polished diamonds to look like. In essence the act of polishing brings out different textures which are not natural, per se.
This is generally known as a skill- yet it could also be termed a "trick"- after all, we've changed the appearance of a natural substance.
But I don't think any of us feel it's a trick to polish a diamond.

I love step cuts. In colorless it's really no big deal to find one.
If a dealer is looking for a stone from D /IF down to K/1- it's fairly easy to source such stones.
Try to find a 2 ct Fancy Intense Yellow Emerald Cut- it's far more difficult than finding a 2ct Intense Cushion or Radiant.
Part of the reason has to do with yield from the rough- monetarily.
Green, although exponentially more valuable than yellow, does follow some of the same rules.
If the stone was cut to step cut it might only be Fancy Light, or Fancy.
I, for one, love step cuts enough that if money was not a consideration, I'd prefer the step cut in a lighter shade to the modified brilliant in a darker shade.
But market forces prevail, and smart cutters need to make the right decisions to maximize profit where they can.
As you are all to aware, a $100,000 piece of rough can become worthless in the blink of an eye. Or unexpected occurrences of cutting make the finished diamond worth $5,000. These losses make the choices made even more important.
Another possibility is that you might make totally different choices with the same rough. It would be interesting if it were possible, to see the results.
 

Rockdiamond

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Re: How GIA grades color in colorless vs. fancy colored diam

Karl_K said:
Thanks David that is a good start.
out of what you covered so far at what point do they start grading face up?
That is a very good question Karl.
Again- they may be sensitive to market forces. People are buying these colors for their yellow broadcast. It being Sunday, I can't check today, but I can ask a buddy over there tomorrow.
Based on my experience, the grades from N-O all the down to Y-Z are very difficult to accurately and consistently grade. Part of the reason is that it's a lot easier to grade the absence of something, versus how much is presence. In colorless, we're looking for how much color isn't there.
Also is the difference between Face up and through the pavillion view- which can be dramatic in these shades.

Generally, we don't contest GIA when we submit stones.
There's an option, if the person submitting the diamond disagrees with the result.
You can re-submit. If GIA changes the grade, they don't charge. If they do not change it, it's half the price of the report.
Generally we don;t do it.
One time I can remember was when we submitted three stones of very similar face up color- all radiant cut.
One got W-X, the other Y-Z, and the third got.....S-T!!
It really looked almost as dark as the Y-Z- really close.
In that instance we resubmitted the S-T along with the W-X to bolster our case. The stone did receive a U-V ( I still think it was W-X)
The point is, these are tough calls.
Forget about rounds- they are even more difficult to find consistency in the grades, how the stones faces, and how it looks from behind.
 

diagem

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Re: How GIA grades color in colorless vs. fancy colored diam

Rockdiamond said:
Yoram- I know English may not be your first language ( although you speak it beautifully)- but the word "tricky" implies something.
Tricky has two meanings.
1) is related to "trickery"
2) Requiring caution or skill: a tricky recipe.
I believe you are using the first definition, in your meaning. Trickery: The practice or use of tricks; deception by stratagem.


Actually the second one, no deception at all..., just not sufficient quantity of color overall to genuinely categorize them as "Fancy"..., I know GIA grade these light tints based on faceup appearance only, so my opinion is: to earn a "Fancy" colored grade level, a significant quantity shade/hue must be clearly noticed from all directions. Not only in the faceup appearance. Cutting cape (light tinted) material into a certain face-up appearance to satisfy GIA criteria by adapting certain tricks or formula's is what I meant.
 

John P

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Re: How GIA grades color in colorless vs. fancy colored diam

Boy, I wish I had more time for PS lately. Great discussion.

I originally planned to link to a fantastic relevant reference covering over 100 GIA articles over a span of more than 70 years. "Colored Diamonds" (ed John King) gives great historical perspective on this topic and lends itself to the complexity some of our experienced trade members are working to communicate in this thread. Apparently it was a limited run, as I can only find used copies (Amazon) that are quite expensive:
http://www.amazon.com/Gems-Gemology-Review-Colored-Diamonds/dp/0873110528

Nice that my copy has grown so valuable, I suppose, but sad that it's not still widely available - unless someone knows differently?

Meanwhile here's another resource. It's a nice jumping-off point with strong graphics, for anyone interested:
http://store.gia.edu/product_p/colordiambooklet.htm
 

kenny

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Re: How GIA grades color in colorless vs. fancy colored diam

John Pollard said:
Boy, I wish I had more time for PS lately. Great discussion.

I originally planned to link to a fantastic relevant reference covering over 100 GIA articles over a span of more than 70 years. "Colored Diamonds" (ed John King) gives great historical perspective on this topic and lends itself to the complexity some of our experienced trade members are working to communicate in this thread. Apparently it was a limited run, as I can only find used copies (Amazon) that are quite expensive:
http://www.amazon.com/Gems-Gemology-Review-Colored-Diamonds/dp/0873110528

Nice that my copy has grown so valuable, I suppose, but sad that it's not still widely available - unless someone knows differently?

Meanwhile here's another resource. It's a nice jumping-off point with strong graphics, for anyone interested:
http://store.gia.edu/product_p/colordiambooklet.htm

Thanks John, I just ordered that GIA chart and also their separate chart on pink diamonds.
Do you have any idea why GIA did not include the unmodified color green in the main chart? :((

I'd love to get a copy of that GIA book, now on Amazon for $700+ USED. :angryfire:
GIA charged only $60 when new.
 
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