Radiant Diamond Cut Evaluation Education

[kmystery]

I am not a diamond expert by any stretch of the imagination but I love radiants and am particularly partial to the crushed ice look. I was looking into buying one and then my lovely hubby surprised me with a gorgeous rectangular radiant diamond ring. the crushed iced facets are amazing with the bottomless sparkle that mesmerises me (especially just after cleaning it, which I have just done now).

I do notice some tilt windows at times, and at first that did bother me a bit but I am used to it now and prefer to think of it as a bit of character in my diamond.

this post might be in the wrong place as I don't have any evaluation advice or experience, I just wanted to add some radiant love!

 

[MelisendeDiamonds]

It also has extremely uniform brilliance and color distribution and doesn't have "lifeless" zones. It does as I've said before, window out a little bit when the diamond is tilted.

Well not close to as "extremely" uniform as this diamond. Garry Holloway posted these some time ago and a video is on his youtube channel.

 

[RADIANTMAN]

I am not a diamond expert by any stretch of the imagination but I love radiants and am particularly partial to the crushed ice look. I was looking into buying one and then my lovely hubby surprised me with a gorgeous rectangular radiant diamond ring. the crushed iced facets are amazing with the bottomless sparkle that mesmerises me (especially just after cleaning it, which I have just done now).

I do notice some tilt windows at times, and at first that did bother me a bit but I am used to it now and prefer to think of it as a bit of character in my diamond.

this post might be in the wrong place as I don't have any evaluation advice or experience, I just wanted to add some radiant love!

I think your comment is in exactly the right place and what you call your "lack of experience" is precisely why your input is so welcome. Can you post a picture of your diamond? Even one taken on your phone could be helpful.

 

[Texas Leaguer]

It also has extremely uniform brilliance and color distribution and doesn't have "lifeless" zones. It does as I've said before, window out a little bit when the diamond is tilted.

Well not close to as "extremely" uniform as this diamond. Garry Holloway posted these some time ago and a video is on his youtube channel.

This is the kind of ASET signature that I would expect to see in a crushed ice flavor with excellent light performance. There is a good distribution of ASET colors indicating light being drawn from above the girdle plane from a wide range of angles. And while there is quite a bit of white, it is widely dispersed without many large continuous areas of white. It is easier to understand how this kind of leakage could provide some positive contrast and therefore contribute to "on/off" scintillation.

Having said that, this is an example of a cushion cut. I suppose it does not necessarily mean a radiant should have a comparable ASET signature just because the stones are of similar flavor.

 

[Rockdiamond]

HI Melisende- wow
Thank you for keeping it interesting.
So Stan is just making up discussions with GIA?

Sorry for the tongue in cheek attitude- but come on.
It's not only my long and rich personal relationship that gives me pause- it's Stan's standing professionally.
Which as a member of the trade, ( or someone who can use Google) you can easily check.

I'll address your posts later this evening- but please- can we establish a bit of professional and human courtesy?
I'm sure your contributions will enrich the discussion, but not if they're mixed in with baseless insults.

About the photo of the cushion that you just posted:
The photo of the cushion is either a CG photo- or taken in such a way that it bears almost no resemblance to how such a diamond looks in real life

 

[Texas Leaguer]

HI Melisende- wow
Thank you for keeping it interesting.
So Stan is just making up discussions with GIA?

Sorry for the tongue in cheek attitude- but come on.
It's not only my long and rich personal relationship that gives me pause- it's Stan's standing professionally.
Which as a member of the trade, ( or someone who can use Google) you can easily check.

I'll address your posts later this evening- but please- can we establish a bit of professional and human courtesy?
I'm sure your contributions will enrich the discussion, but not if they're mixed in with baseless insults.

About the photo of the cushion that you just posted:
The photo of the cushion is either a CG photo- or taken in such a way that it bears almost no resemblance to how such a diamond looks in real life

I did not see any "baseless insults" in his post. What he said was "To my knowledge that sounds highly implausible". The reference was pretty clearly his opinion that GIA was unlikely to change their nomenclature. And he laid out his reasons.

Going into attack mode anytime someone says something you disagree with does not help move your thread forward.

 

[Rockdiamond]

Hi Bryan,
Lets speak plainly.
NO ONE is attacking you.
I've been attacked in this thread repeatedly.
Melisendre has shown hostility towards me, Stan and radiant cuts in general.
So please excuse me that I read his statement as doubting the discussion Stan had with GIA, as opposed to the outcome.

ETA- IF I read the statement incorrectly, Melisendre is perfectly free ( actually welcome) to correct how I read it.

 

[MelisendeDiamonds]

Having said that, this is an example of a cushion cut. I suppose it does not necessarily mean a radiant should have a comparable ASET signature just because the stones are of similar flavor.

I have found the appearance of the crushed ice cushions is very similar to that of crushed ice radiants. They have very similar pavilion facet structures. The physics of light and the light paths in both are strikingly similar.

But really color uniformity or sparkle uniformity is usually not highly prized by most unless it is in colored stones.
Here is an example of a very uniform crushed ice radiant.

 

[Rockdiamond]

Having said that, this is an example of a cushion cut. I suppose it does not necessarily mean a radiant should have a comparable ASET signature just because the stones are of similar flavor.

I have found the appearance of the crushed ice cushions is very similar to that of crushed ice radiants. They have very similar pavilion facet structures. The physics of light and the light paths in both are strikingly similar.

But really color uniformity or sparkle uniformity is usually not highly prized by most unless it is in colored stones.
Here is an example of a very uniform crushed ice radiant.

Totally agree that there are many Cushion cuts that have similar light performance to some of the radiant cuts we're speaking of.

I also agree that even distribution is an asset ( no pun intendd) on a FCD.
There's a lot of similarities between FCD and colorless Radiant Cuts.
But there's also some differences- one difference is contrast.
The best cut colorless Radiant cuts are generally tuned for more contrast.
But it's definitely a sliding scale- the best cuts of both Fancy Colored, as well as colorless Radiant cuts balance these two factors well.

 

[Texas Leaguer]

Having said that, this is an example of a cushion cut. I suppose it does not necessarily mean a radiant should have a comparable ASET signature just because the stones are of similar flavor.

I have found the appearance of the crushed ice cushions is very similar to that of crushed ice radiants. They have very similar pavilion facet structures. The physics of light and the light paths in both are strikingly similar.

But really color uniformity or sparkle uniformity is usually not highly prized by most unless it is in colored stones.
Here is an example of a very uniform crushed ice radiant.

Totally agree that there are many Cushion cuts that have similar light performance to some of the radiant cuts we're speaking of.

I also agree that even distribution is an asset ( no pun intendd) on a FCD.
There's a lot of similarities between FCD and colorless Radiant Cuts.
But there's also some differences- one difference is contrast.
The best cut colorless Radiant cuts are generally tuned for more contrast.
But it's definitely a sliding scale- the best cuts of both Fancy Colored, as well as colorless Radiant cuts balance these two factors well.

What do you mean by the statement "the best cut colorless radiant cuts are generally tuned for more contrast"?

Also, I hope this thread does not get diverted to fancy colors. That is a whole different ball of wax.

 

[MelisendeDiamonds]

I am not a diamond expert by any stretch of the imagination but I love radiants and am particularly partial to the crushed ice look. I was looking into buying one and then my lovely hubby surprised me with a gorgeous rectangular radiant diamond ring. the crushed iced facets are amazing with the bottomless sparkle that mesmerises me (especially just after cleaning it, which I have just done now).

I do notice some tilt windows at times, and at first that did bother me a bit but I am used to it now and prefer to think of it as a bit of character in my diamond.

this post might be in the wrong place as I don't have any evaluation advice or experience, I just wanted to add some radiant love!

Well that is an issue with colorless Radiants and a weakness in the design that can't readily be detected by ASET. To get crushed ice you need steep lower girdle facets and shallow mains producing lots of bounces and long light paths which produces the crushed ice.

The shallow mains can also produce the tilt window. The critical angle for Diamond is 24.4 if those pavilion mains can be only 11 - 12 degrees higher, tilt your diamond more than 12 degrees and you will start to see through it.

 

[Rockdiamond]

Hi Bryan,
I have not introduced Fancy Colored Radiant cuts for the reason you mention- but we can gain a better understanding of the technicalities of cutting by comparing the FCD mechanics to colorless.
I've done my homework in that I've had extremely in depth discussions on this aspect with some amazing cutters.
On a Fancy Colored Diamond, the facets are painted on the pavilion. This means they are not cut as deeply.
Put very simply so everyone can grasp this- imagine you're folding a piece of paper. The creases are the facet junctions. In a fancy color, the creases are far more subtle than on a colorless Radiant ( or cushion)
The sharper those creases, the higher the contrast. Higher contrast gives you brighter brights and darker darks.
Fancy Colors benefit from a bit less contrast.


This thread is amazing for so many reasons- but for me, it's that the discussion is leading to important concepts I never really considered before.


I showed this photo to Stan and we had different thoughts about it- but I think it will allow me to explain what I am seeing.

And he will likely correct some of my thoughts....

I can't speak about the fine points of the cut of each, from a cutter's standpoint- only visually.
With regards to light performance- the stone on the left is cut a little bit more like a fancy color.
The stone on the right has facets that are "crisper" than the stone on the left.
The aspect that makes assigning a grade to these properties so difficult, is that both stones are very well cut.


Interesting thought... what if cut grading was more like color grading.
Smaller increments to allow for more variations.
Maybe the stone on the right has a cut grade equivalent to an E color, and stone on the left is an F.
Even if we were to agree that the stone on the left is slightly brighter, not all observers will in real life.
Sometimes a Colorless stone that behaves somewhat like a fancy Colored, in terms of light performance, can be extremely attractive to observers.

 

[Rockdiamond]

As requested, a cleared picture of ASET on stone #5
Is this better?
It's the same picture, but I had to re-size it for the composite.

 

[distracts]

Also, I hope this thread does not get diverted to fancy colors. That is a whole different ball of wax.

I agree. As a consumer who knows little about radiants, this thread is challenging enough to follow as it is. Throwing colored diamonds in is not going to help it, especially since they have their own special considerations.

 

[RADIANTMAN]

Hi Bryan,
I have not introduced Fancy Colored Radiant cuts for the reason you mention- but we can gain a better understanding of the technicalities of cutting by comparing the FCD mechanics to colorless.
I've done my homework in that I've had extremely in depth discussions on this aspect with some amazing cutters.
On a Fancy Colored Diamond, the facets are painted on the pavilion. This means they are not cut as deeply.
Put very simply so everyone can grasp this- imagine you're folding a piece of paper. The creases are the facet junctions. In a fancy color, the creases are far more subtle than on a colorless Radiant ( or cushion)
The sharper those creases, the higher the contrast. Higher contrast gives you brighter brights and darker darks.
Fancy Colors benefit from a bit less contrast.


This thread is amazing for so many reasons- but for me, it's that the discussion is leading to important concepts I never really considered before.


I showed this photo to Stan and we had different thoughts about it- but I think it will allow me to explain what I am seeing.

And he will likely correct some of my thoughts....

I can't speak about the fine points of the cut of each, from a cutter's standpoint- only visually.
With regards to light performance- the stone on the left is cut a little bit more like a fancy color.
The stone on the right has facets that are "crisper" than the stone on the left.
The aspect that makes assigning a grade to these properties so difficult, is that both stones are very well cut.


Interesting thought... what if cut grading was more like color grading.
Smaller increments to allow for more variations.
Maybe the stone on the right has a cut grade equivalent to an E color, and stone on the left is an F.
Even if we were to agree that the stone on the left is slightly brighter, not all observers will in real life.
Sometimes a Colorless stone that behaves somewhat like a fancy Colored, in terms of light performance, can be extremely attractive to observers.

David- from a cutting standpoint the main difference in how one would cut a fancy yellow radiant vs. a colorless radiant is the angle of the pavilion mains which should be at 3-5 degrees flatter in a fancy color. In both cases its important to "paint" or expressed another way, not to "dig" the halefkas (bottom halves) because digging will bring black reflections into the stone.

The result of the flatter pavilion mains is that fancy colors are more "crushed icey" than well cut colorless radiants, prioritizing evenness of color over contrast and intensity and the "tilt issue is more pronounced. Mounting a fancy yellow is a highly polished 24 kt yellow basket will "enhance" the color of a fancy yellow radiant precisely because of the "leakage" created by the flatter angles.

The higher angle of the pavilion mains on a colorless radiant provide more contrast. When the angle gets too high the diamond develops a concentration of black around the culet that if it becomes prominent most of my customers and most of their customers, consider unattractive.

I agree that diamond # 2 has a pavilion angle on the flat side for colorless radiants but actually toward the high end of the range for fancy yellows - an angle that's actually OK (though not perfect) for either.

 

[Rockdiamond]

Also, I hope this thread does not get diverted to fancy colors. That is a whole different ball of wax.

I agree. As a consumer who knows little about radiants, this thread is challenging enough to follow as it is. Throwing colored diamonds in is not going to help it, especially since they have their own special considerations.

Point taken- to stay on course, and clarify: the aspect we are talking about- contrast- is a part of the recipe.
Sometimes a Radiant has a bit less contrast, and a more "even" sparkle. All smaller reflections. That would be like stone #1, or #2, which is on the left in my comparison shot.
Sometimes a stone has a bit more contrast- which results in some larger reflections- so that the sparkle is not consistent throughout the diamond. Some larger glitters, and a lot of smaller sparkles.
Stone #5- which is on the right in my photo is an example of good result in that type of stone.

Sometimes too much contrast in the center of a stone can look like a dark area.

Last word abut FCD's : since many people that buy radiant cuts buy FCD radiant cuts, and they may read this- much of what we discuss here applies to FCD "crushed ice" light performance diamonds as well.

 

[Karl_K]

As requested, a cleared picture of ASET on stone #5
Is this better?
It's the same picture, but I had to re-size it for the composite.

It is little better but still washed out and out of focus.
You can see some of the areas that look white in the smaller version are not but its not clear enough to see what is going on.

 

[Rockdiamond]

As requested, a cleared picture of ASET on stone #5
Is this better?
It's the same picture, but I had to re-size it for the composite.

It is little better but still washed out and out of focus.
You can see some of the areas that look white in the smaller version are not but its not clear enough to see what is going on.

Karl- I agree the photo is washed out- but I disagree about the focus.
To my eye, the focus is crisp- maybe the issue if dof- and exactly where that focus is placed.
I can see details on the crown, which is why I feel its in focus,
This is also an issue where photography will always fall short of stereoscopic vision in important ways.

Looking again, I do realize part of a discrepancy between what I see and the pictures.
Green.
it's a subtle color by nature- and even though the actual green of the aset is more of a neon green, it does not reflect that way in the picture.
When I look at the picture, i realize that the lack of green is a problem with the ASEt pictures
Another thing is that I can never get the exact same result twice in a stone like #5- because of the side and shape of the hole in the light.
And what I do notice is that although the general picture is similar, there's important differences occurring with a small amount of tilt.
Does diacalc do the CG ASET Karl?
Would that be a better solution?

 

[Karl_K]

Per Garry the ASET image is virtual based on a scan done in diamcalc the other image was done in Lbox the predecessor to dibox and is an actual photo.

 

[Karl_K]

Does diacalc do the CG ASET Karl?
Would that be a better solution?

beg borrow or buy a sarin hd machine and generate srn files to import into DC.
Beg borrow or buy a DiBox and take some better ASET images.

 

[Rockdiamond]

We have an Ogi.....

 

[Karl_K]

We have an Ogi.....

unfortunately it is useless for what would be needed to use DC to generate models.

 

[Karl_K]

There are several people with dibox in the diamond district you might want to ask around and see if you can use someones.

 

[kenny]

There are several people with dibox in the diamond district you might want to ask around and see if you can use someones.

I wondered what a "Dibox" was.

... https://www.youtube.com/watch?v=L_ift331-Uk

 

[Karl_K]

There are several people with dibox in the diamond district you might want to ask around and see if you can use someones.

I wondered what a "Dibox" was.

... https://www.youtube.com/watch?v=L_ift331-Uk

yep that is it....
For full disclosure Garry was involved in its development and I recommend it to vendors who ask me about photo systems but I do not get a commission for doing so.
If I was getting a commission I would not bring it up as an option here as that would be against the rules.

 

[Rockdiamond]

Very cool - that Dibox- we are checking to see if we can beg or borrow one

Kenny- I heard a story on NPR today that made me think of this discussion.
They were talking about the current political discourse.
One person says "Let's discuss the merits of fixing this bridge"
His political opponent answers- "I heard you were accused of having sex with a goat"
"Can we talk about this bridge??"
"How many goats have you slept with?"

Kenny- we both love to spend time here- and you have a tremendous amount to offer.
I am earnestly asking you to please ask questions, bring up points about ASET, leakage, and radiant cuts that you feel are relevant.
That will add value to the discussion for all the participants.

 

[Rockdiamond]

We have considered 3 stones which are rectangular, which as we have mentioned, present challenges for cutters.
This stone has a more prominent bow tie as compared to stone #5.
Neither Stan, nor I consider it to be "badly cut"- just less well cut than stone number #1 or stone #5

This stone points out some very interesting aspects to this discussion.

We are looking at the cut- and evaluating it.
Stan and I will likely diverge on a few points.
Since I buy a lot of FCD Radiant cuts, I necessarily consider stones that are less well cut.
And it gives me a different perspective.
I likely would not purchase this diamond for our inventory- because the photos show a pretty substantial bow tie.
But then again, if the price was right I might.
The bow tie as shown, looks worse in the picture than it does in person.

So- it's a Very good cut- if a buyer likes the way it looks it can be a bargain, if the price relates to the quality of cut- which it does in many market cases I've seen.

 

[Texas Leaguer]

We have considered 3 stones which are rectangular, which as we have mentioned, present challenges for cutters.
This stone has a more prominent bow tie as compared to stone #5.
Neither Stan, nor I consider it to be "badly cut"- just less well cut than stone number #1 or stone #5

This stone points out some very interesting aspects to this discussion.

We are looking at the cut- and evaluating it.
Stan and I will likely diverge on a few points.
Since I buy a lot of FCD Radiant cuts, I necessarily consider stones that are less well cut.
And it gives me a different perspective.
I likely would not purchase this diamond for our inventory- because the photos show a pretty substantial bow tie.
But then again, if the price was right I might.
The bow tie as shown, looks worse in the picture than it does in person.

So- it's a Very good cut- if a buyer likes the way it looks it can be a bargain, if the price relates to the quality of cut- which it does in many market cases I've seen.

I would like to see a photo of the diamond that is face up to the light. In the tweezer shots the light is coming from an angle that most likely illuminates the pavilion. If we want to correlate ASET signatures (which represent how the diamond handles light from the hemisphere above the girdle plane)), we need to compare it to a photo of the diamond with light coming from the same direction.

 

[Rockdiamond]

Hi Bryan,
The aset shows red in exactly dark the areas clearly indicated in my picture.
I'll gladly take another shot later as time permits- but this aset and my picture match.
There's no effort to light the pavilion in my photos- and quite frankly, this aset and picture should please put to rest the baseless criticism that my pictures won't show darkness where it exists in diamonds..

 

[Karl_K]

Hi Bryan,
The aset shows red in exactly dark the areas clearly indicated in my picture.
I'll gladly take another shot later as time permits- but this aset and my picture match.
There's no effort to light the pavilion in my photos- and quite frankly, this aset and picture should please put to rest the baseless criticism that my pictures won't show darkness where it exists in diamonds..

There is little to no light coming from the red zone in ASET in your tweezers shots which is what people have been complaining about. Its all green zone and overly bright and hitting the pavilion, show the light box photo like the rest of them.
These pictures rather than putting to rest the complaints about your photos prove them.