Fancy Light Yellow--- Fancy or Cape???

[oldminer]

I have been involved with developing machinery to grade the color of diamonds and colored gems for the past 12 years. The unusual way which the GIA has created the grading system where diamonds of colorless to lightly tinted are graded from the side, more deeply colored diamonds are graded face-up and fancy shapes are graded at certain angles from the side and face-up definitely is a confusing and uncoordinated mess. It works in spite of the mess it creates, people still buy what they want to a great extent, and there are laws of supply and demand.

What is left in the midst of this confusion is a system which is very difficult, not impossible, to automate via technology. It just takes time and money. There could be a more elegant system already in use, but the trade has forced labs to make the best of each diamond. Colorless graded from the side and "fancies' graded face-up. Whichever is worth more money is the choice. It is very understandable and in this financial sense, logical, too.

I predict that someday we will grade colors of diamonds with universally accepted coordinates of color space that apply to all other industries. For the present, the working system keeps us all our our respective toes.

 

[strmrdr]

clearly in today''s market there is a demand difference between a Z yellow and a Z brown and a Z pink and a Z blue so I don''t have a problem with them separating them.
Switching to face up grading is another issue and im not sure how I feel about it.
Are radiant cuts discounted because they show more color?
ie: would a fancy light yellow RB sell for more per ct than a fancy yellow radiant?

 

[diagem]

Date: 8/10/2007 10:11:21 AM
Author: strmrdr
clearly in today''s market there is a demand difference between a Z yellow and a Z brown and a Z pink and a Z blue so I don''t have a problem with them separating them.
Switching to face up grading is another issue and im not sure how I feel about it.
Are radiant cuts discounted because they show more color?
ie: would a fancy light yellow RB sell for more per ct than a fancy yellow radiant? Yes Strmrdr..., but fancy''s are discounted compared to RB''s in the colorless range too!!!

The main issue is selling Cape Diamonds that are relatively less valuable than "Fancy" Colored Diamonds at "fancy" colored prices!!!

Like Garry mentioned in the previous page: "GIA''s fancy yellow G&G article gave examples of about M.N. O stones being cut into fancy colors with expert cutting. If some people will pay more for them then that is a market, and markets rule" .

I don''t know when this article was published..., but one thing is for sure...., No need for "expert" cutting or cutters anymore....

 

[Garry H (Cut Nut)]

DiaGem i have the article at work - will get it later and quote some parts. It is about 1 or 2 years old now.

Date: 8/10/2007 9:26:17 AM
Author: oldminer
I have been involved with developing machinery to grade the color of diamonds and colored gems for the past 12 years. The unusual way which the GIA has created the grading system where diamonds of colorless to lightly tinted are graded from the side, more deeply colored diamonds are graded face-up and fancy shapes are graded at certain angles from the side and face-up definitely is a confusing and uncoordinated mess. It works in spite of the mess it creates, people still buy what they want to a great extent, and there are laws of supply and demand.

What is left in the midst of this confusion is a system which is very difficult, not impossible, to automate via technology. It just takes time and money. There could be a more elegant system already in use, but the trade has forced labs to make the best of each diamond. Colorless graded from the side and ''fancies'' graded face-up. Whichever is worth more money is the choice. It is very understandable and in this financial sense, logical, too.

I predict that someday we will grade colors of diamonds with universally accepted coordinates of color space that apply to all other industries. For the present, the working system keeps us all our our respective toes.

You probably saw Tom Tashi (EGL LA SI3 inventor) had a presentation at the GIA Symposium last year on Face Up Diamond Grading for Colorless diamonds. (He has also previuosly proposed a Blue White grade for genuine blue whites - D-E med to very strong fluoro I think).

I think color grading colorless diamonds thru the side is really stupid DG.
The face up colour of a I <1/2ct is round is better than the face up color of a H 3ct round and a 3ct G radiant. It does not make sense!

I fully support face up color grading. You might remeber me supporting IGI''s approach to using face up for border line calls.

 

[Garry H (Cut Nut)]

Date: 8/10/2007 12:07:43 PM
Author: DiaGem

Date: 8/10/2007 10:11:21 AM
Author: strmrdr
clearly in today''s market there is a demand difference between a Z yellow and a Z brown and a Z pink and a Z blue so I don''t have a problem with them separating them.
Switching to face up grading is another issue and im not sure how I feel about it.
Are radiant cuts discounted because they show more color?
ie: would a fancy light yellow RB sell for more per ct than a fancy yellow radiant? Yes Strmrdr..., but fancy''s are discounted compared to RB''s in the colorless range too!!!

The main issue is selling Cape Diamonds that are relatively less valuable than ''Fancy'' Colored Diamonds at ''fancy'' colored prices!!!

Like Garry mentioned in the previous page: ''GIA''s fancy yellow G&G article gave examples of about M.N. O stones being cut into fancy colors with expert cutting. If some people will pay more for them then that is a market, and markets rule'' .

I don''t know when this article was published..., but one thing is for sure...., No need for ''expert'' cutting or cutters anymore....

I have it in front of me now.
Gems & Gemology, Summer 2005

It is an excellent artcile of around 20 pages and excellent photos. It builds on an earlier (? 1994? article by King et al) G&G on fancy color.

They show an actual example figure 20 of 2 diamonds in the S-Z from side color - one gets Fancy Light and one gets a D-Z in face up.

Fancy color is a factor of tone and saturation - so body color can be a certain grade on D-Z but look very different to another diamond with the same D-Z grade. We all see this as we grade greyish, brownish and cape stones and can give them the same grade. We would probably place a slightly lower value on the brownish than the cape with the same grade?

 

[Garry H (Cut Nut)]

An example of one of the photo''s

 

[diagem]

Date: 8/10/2007 8:04:25 PM
Author: Garry H (Cut Nut)
DiaGem i have the article at work - will get it later and quote some parts. It is about 1 or 2 years old now.

Date: 8/10/2007 9:26:17 AM
Author: oldminer
I have been involved with developing machinery to grade the color of diamonds and colored gems for the past 12 years. The unusual way which the GIA has created the grading system where diamonds of colorless to lightly tinted are graded from the side, more deeply colored diamonds are graded face-up and fancy shapes are graded at certain angles from the side and face-up definitely is a confusing and uncoordinated mess. It works in spite of the mess it creates, people still buy what they want to a great extent, and there are laws of supply and demand.

What is left in the midst of this confusion is a system which is very difficult, not impossible, to automate via technology. It just takes time and money. There could be a more elegant system already in use, but the trade has forced labs to make the best of each diamond. Colorless graded from the side and ''fancies'' graded face-up. Whichever is worth more money is the choice. It is very understandable and in this financial sense, logical, too.

I predict that someday we will grade colors of diamonds with universally accepted coordinates of color space that apply to all other industries. For the present, the working system keeps us all our our respective toes.

You probably saw Tom Tashi (EGL LA SI3 inventor) had a presentation at the GIA Symposium last year on Face Up Diamond Grading for Colorless diamonds. (He has also previuosly proposed a Blue White grade for genuine blue whites - D-E med to very strong fluoro I think).

I think color grading colorless diamonds thru the side is really stupid DG. You might say primitive..., but stupid?

The face up colour of a I <1/2ct is round is better than the face up color of a H 3ct round and a 3ct G radiant. It does not make sense!
But if you add some Med. Blue Fluo. to the 3 ct. H you might get a F color grade? And a little Orange Fluo. to the 3 ct. G radiant you might get a Fancy Pink grade?? Yes..., that makes pure sense....

I fully support face up color grading. You might remeber me supporting IGI''s approach to using face up for border line calls.

I remember your support on the IGI''s approach..., and I agreed with you on that one (i think)...., BUT!!! The face-up appearance "has" to be taking into consideration (not only for border line calls) for ALL Diamonds..., face-up appearance is an important stage in grading but not the only stage!!!

Garry, how would you grade a briolette or a rough Diamond with no face/table? Ahhh!!! with technology!!! I hear ya...

 

[WorkingHardforSmallRewards]

Dont you guys generally say that H color rounds face up like D^F color diamonds in ideal cuts?

I can tell you, if I were to buy a G color diamond and it looked like a K-L from the side, I would simply forget about diamonds due to what I consider to be unreliable grading and buy a different gem, despite cultural expectations. so I in opionion I would be very opposed to grading from the top (I feel the same about fancy colors though, so after reading this thread I will be very cautious with any future fancy color purchases I might make down the line)

also, woudlnt it mean that you could take a very poorly cut diamond that graded as a H, recut it to ideal proportions at the loss of ct weight and end up with a D graded diamond that was worth more?

 

[diagem]

Date: 8/10/2007 10:50:00 PM
Author: Garry H (Cut Nut)

Date: 8/10/2007 12:07:43 PM
Author: DiaGem

Date: 8/10/2007 10:11:21 AM
Author: strmrdr
clearly in today''s market there is a demand difference between a Z yellow and a Z brown and a Z pink and a Z blue so I don''t have a problem with them separating them.
Switching to face up grading is another issue and im not sure how I feel about it.
Are radiant cuts discounted because they show more color?
ie: would a fancy light yellow RB sell for more per ct than a fancy yellow radiant? Yes Strmrdr..., but fancy''s are discounted compared to RB''s in the colorless range too!!!

The main issue is selling Cape Diamonds that are relatively less valuable than ''Fancy'' Colored Diamonds at ''fancy'' colored prices!!!

Like Garry mentioned in the previous page: ''GIA''s fancy yellow G&G article gave examples of about M.N. O stones being cut into fancy colors with expert cutting. If some people will pay more for them then that is a market, and markets rule'' .

I don''t know when this article was published..., but one thing is for sure...., No need for ''expert'' cutting or cutters anymore....

I have it in front of me now.
Gems & Gemology, Summer 2005

It is an excellent artcile of around 20 pages and excellent photos. It builds on an earlier (? 1994? article by King et al) G&G on fancy color.

They show an actual example figure 20 of 2 diamonds in the S-Z from side color - one gets Fancy Light and one gets a D-Z in face up.

Fancy color is a factor of tone and saturation - so body color can be a certain grade on D-Z but look very different to another diamond with the same D-Z grade. We all see this as we grade greyish, brownish and cape stones and can give them the same grade. We would probably place a slightly lower value on the brownish than the cape with the same grade? I agree with you on this..., but it has nothing to do with Fancy colors!!!
D-Z colors are NOT fancy colored grades (in my opinion.) and don''t possess the tone and saturation that the fancy level requires.

BTW..., If I have to put a value on a RB of same size..., one is a TLB vs. another TLC..., I think the TLB will command a higher value.
Because of the reason stated above..., Its face-up appearance will be whiter than its counterpart (TLC). That''s where I fully agree that Face-up has a major influence on value!!!

But charging 2 x Y and more for a FLY when the value of S-Z is Y..., seems to me like a "Brilliant Marketing Tool" and not more!!!

 

[diagem]

This Diamond is still to my observation a 57 facet RB... It might have some alteration done to its proportions but it is still an RB.
And RB''s are not "a cut for intensifying color".
So most probably the Rough material was classified as a potentially VIVID type material, and not Cape''s cut by experts to achieve vivid grades.

Here is another example of a FIY regular RB cut.
The Fancy Intense Yellow material existed prior to the cutting.

 

[Garry H (Cut Nut)]

Date: 8/11/2007 2:07:27 AM
Author: WorkingHardforSmallRewards
Dont you guys generally say that H color rounds face up like D^F color diamonds in ideal cuts?

I can tell you, if I were to buy a G color diamond and it looked like a K-L from the side, I would simply forget about diamonds due to what I consider to be unreliable grading and buy a different gem, despite cultural expectations. so I in opionion I would be very opposed to grading from the top (I feel the same about fancy colors though, so after reading this thread I will be very cautious with any future fancy color purchases I might make down the line)

also, woudlnt it mean that you could take a very poorly cut diamond that graded as a H, recut it to ideal proportions at the loss of ct weight and end up with a D graded diamond that was worth more?

WH4SR i do not subscribe the the face up of ideal cuts being more than a slight improvement over another another round because it is human nature to not even attempt to assess color face up - too much sparkle.
A J might look like an I

 

[Garry H (Cut Nut)]

Date: 8/11/2007 2:49:24 AM
Author: DiaGem

This Diamond is still to my observation a 57 facet RB... It might have some alteration done to its proportions but it is still an RB.
And RB''s are not ''a cut for intensifying color''.
So most probably the Rough material was classified as a potentially VIVID type material, and not Cape''s cut by experts to achieve vivid grades.

Here is another example of a FIY regular RB cut.
The Fancy Intense Yellow material existed prior to the cutting.

Looks like a beauty DG

The GIA example apparently had poor symmetry and proportions. Otherwise it would have had a dark star and too much contrast, as well as a very short ray path. It is easy to take a vivid material and make a Fancy Intense.

This chart shows how the software predicts the contrast of a range of proportions. The expert might have estimated the best results the "before" crown and pavilion combination, but the software suggests an area with less contrast (after) which is this case might also have a better yeild. (red is lower contrast as shown in the index on the right)

 

[Garry H (Cut Nut)]

And surprise surprise - in this example the color is also better in this proportion combination too.

 

[diagem]

Date: 8/11/2007 3:00:40 AM
Author: Garry H (Cut Nut)

Date: 8/11/2007 2:49:24 AM
Author: DiaGem

This Diamond is still to my observation a 57 facet RB... It might have some alteration done to its proportions but it is still an RB.
And RB''s are not ''a cut for intensifying color''.
So most probably the Rough material was classified as a potentially VIVID type material, and not Cape''s cut by experts to achieve vivid grades.

Here is another example of a FIY regular RB cut.
The Fancy Intense Yellow material existed prior to the cutting.

Looks like a beauty DG

Thanks,!!!!

The GIA example apparently had poor symmetry and proportions. Otherwise it would have had a dark star and too much contrast, as well as a very short ray path. It is easy to take a vivid material and make a Fancy Intense.

This chart shows how the software predicts the contrast of a range of proportions. The expert might have estimated the best results the ''before'' crown and pavilion combination, but the software suggests an area with less contrast (after) which is this case might also have a better yeild. (red is lower contrast as shown in the index on the right)

Garry, it looks very interesting and pretty!!!
But you are showing me here that a deeper (higher yield as you called it) Diamond consisting a CA of 48 degrees combining a PA of 47.5 degrees, with the combination of "low contrast pavilion brillianteering" will optimize the Diamond.
Or am I not reading something correctly? You know I am not a big Tech-DiaGem...

 

[diagem]

Date: 8/11/2007 3:07:08 AM
Author: Garry H (Cut Nut)
And surprise surprise - in this example the color is also better in this proportion combination too.

And again..., in the deep zone!!!

 

[Garry H (Cut Nut)]

silly me! I forgot to say it is an oval.
The software calculates the chroma, saturation and tone of each virtual facet and the lower right box shows where each part of the mozaic falls on the GIA''s color space. It is a bit like cheating. sort of insider trading

 

[diagem]

I figured its not a RB...
Still..., this oval is not the one described (the steep/deep) above..., right?

 

[Garry H (Cut Nut)]

Date: 8/11/2007 9:39:15 AM
Author: DiaGem
I figured its not a RB...
Still..., this oval is not the one described (the steep/deep) above..., right?

That would be the stone before making it steeper and deeper DiaGem.
Later today I might try to model the 2 for you if Drnea lets me have some play time

 

[diagem]

Date: 8/11/2007 10:19:27 PM
Author: Garry H (Cut Nut)

Date: 8/11/2007 9:39:15 AM
Author: DiaGem
I figured its not a RB...
Still..., this oval is not the one described (the steep/deep) above..., right?

That would be the stone before making it steeper and deeper DiaGem.
Later today I might try to model the 2 for you if Drnea lets me have some play time

What would it color grade at this stage?

 

[Garry H (Cut Nut)]

Date: 8/12/2007 12:16:15 AM
Author: DiaGem

Date: 8/11/2007 10:19:27 PM
Author: Garry H (Cut Nut)
That would be the stone before making it steeper and deeper DiaGem.
Later today I might try to model the 2 for you if Drnea lets me have some play time

What would it color grade at this stage?

It was not my project DG, but looking at the mosaic where it is about 1/3rd Deep and 1/3rd Fancy - It could be somewhere between the 2.

But here I have taken another (different) colored diamond spectrum and modelled my guess at the photo in the GIA Symp presentation (shown below, and then changed the crown and pavilion angles to those ''recomended'' in the slide from the presentation for saturation and contrast. (This is anything but scientific)

I think you would agree the stone above is more saturated and has more even color and less dark contrast then the one below?
So it might be enough to move the stone from fancy deep border into safely fancy and closer to fancy intense. Bbut dont shoot me because this might be al wrong for the only fancy uellow spectrum i could find easily.

 

[diagem]

Date: 8/12/2007 3:04:55 AM
Author: Garry H (Cut Nut)

Date: 8/12/2007 12:16:15 AM
Author: DiaGem

Date: 8/11/2007 10:19:27 PM
Author: Garry H (Cut Nut)
That would be the stone before making it steeper and deeper DiaGem.
Later today I might try to model the 2 for you if Drnea lets me have some play time

What would it color grade at this stage?

It was not my project DG, but looking at the mosaic where it is about 1/3rd Deep and 1/3rd Fancy - It could be somewhere between the 2.

But here I have taken another (different) colored diamond spectrum and modelled my guess at the photo in the GIA Symp presentation (shown below, and then changed the crown and pavilion angles to those 'recomended' in the slide from the presentation for saturation and contrast. (This is anything but scientific)

I think you would agree the stone above is more saturated and has more even color and less dark contrast then the one below?
I agree..., but it does not make sense..., the contrast on this deep stone should be more...
So it might be enough to move the stone from fancy deep border into safely fancy and closer to fancy intense. Bbut dont shoot me because this might be al wrong for the only fancy uellow spectrum i could find easily.

I have a problem with this image..., see my circles showing pavilion at culet through crown main...
Its leakage and should contrast differently..., I think..., what do you think?

 

[diagem]

One more try...

 

[diagem]

last Try:

 

[Garry H (Cut Nut)]

i cant see your image DG, but i imagine you mean the points where you see the culet in the crown mains?

I have just ran ray traces over that area and most of the light does multiple bounces and comes back out the crown. Hard to show onscreen. but here is a try

 

[Garry H (Cut Nut)]

OK- see it now -yes there is a triangle of leakage on each side. You can see it here because i made the area behind the stone black. Thru an ideal-scope it is of course white.

 

[diagem]

Date: 8/12/2007 3:53:53 AM
Author: DiaGem
last Try:

How would the stone face-up with a 30 degree CA and leaving the pavilion in-tact?

 

[diagem]

Date: 8/12/2007 4:16:27 AM
Author: DiaGem

Date: 8/12/2007 3:53:53 AM
Author: DiaGem
last Try:

How would the stone face-up with a 30 degree CA and leaving the pavilion in-tact?

And..., how would it face-up with a 48 deg CA + 35 deg. PA?
I hope you dont mind...

 

[Garry H (Cut Nut)]

Can I charge you by the hour DG?
30C top
35P middle
steep deep at the bottom

 

[diagem]

Date: 8/12/2007 4:41:57 AM
Author: Garry H (Cut Nut)
Can I charge you by the hour DG?
30C top
35P middle
steep deep at the bottom

Can "I" charge you?

J.Kidding..., don''t blow...

Garry..., I must admit I am impressed...

I am not certain if this virtuality can be translated to reality...
As I said before..., there are some factors "during" the whole process of taking a rough Diamond and transforming it to a polished Diamond
in which I am certain that the technical part does not take into account. (as of yet!!!) Especially in Fancy Colored Diamonds!!!
But maybe I am mistaking.

 

[Garry H (Cut Nut)]

Date: 8/12/2007 8:39:06 AM
Author: DiaGem

Date: 8/12/2007 4:41:57 AM
Author: Garry H (Cut Nut)
Can I charge you by the hour DG?
30C top
35P middle
steep deep at the bottom

Can ''I'' charge you?

J.Kidding..., don''t blow...

Garry..., I must admit I am impressed...

I am not certain if this virtuality can be translated to reality...
As I said before..., there are some factors ''during'' the whole process of taking a rough Diamond and transforming it to a polished Diamond
in which I am certain that the technical part does not take into account. (as of yet!!!) Especially in Fancy Colored Diamonds!!!
But maybe I am mistaking.

It is rather funny DG, that when Sergey said he could make a scanner that could plot and allocate inclusions, most people in the trade said the same things. It is worth remebering that behind this technology there are some brilliant minds.

This is not a virtuality, it is a reality that uses virtual imaging and ray tracing. Sergey has developed the most advanced devices for transforming rough diamonds into polished, and he has more huge advances coming down the highway.

so if there is some part you are not certain about, ask away, online or offline if someone will kill you