Radiant Diamond Cut Evaluation Education

[Karl_K]

But when the customer got it, they were not happy with the diamond. They did like that the brightness of the facets when they were on. But the table facets, in particular that star pattern under the table, would flash on and off TOGETHER as a whole. So when they were "on" the table was very bright. But when they were off, the facets were uniformly dark in that pattern.

This is very simplified:
It is not that uncommon that the angle combinations that form virtual facets are in sync with each other in their on off cycle as described. Combine that with a long dwell time and narrow beam pattern and covering a larger area of the diamond and you get a black hole effect. The most common place for that to happen is under the table and in square, rectangular or oval shaped stones. I wont say it cant happen in rounds but I have never seen it.
A face up rotating video vs laying on its side would have likely shown it.

Stan mentioned something earlier about a larger red in ASET VF in otherwise crushed ice radiant that made the diamond dark and it is likely from the same cause. Long dwell times, narrow beam pattern.

 

[Gypsy]

A few general comments:
VERY cool stone from a standpoint of unique-ness. For better or worse, it's a very unusual combination of step cut top and some sort of modified brilliant pavilion. It would not be classified as a "Radiant Cut"
I am not comfortable making specific comments as it's possible the stone is available online.
If you could post limited specifics - like the GIA plot, depth and table- but omit specific weight color and clarity- so the stone is anonymous then we can try to give ideas on how the stone and ASET relate.

ETA- thanks Gypsy- let's see what they say

The stone is not available for sale any longer. The poster kept the stone.

 

[Texas Leaguer]

But when the customer got it, they were not happy with the diamond. They did like that the brightness of the facets when they were on. But the table facets, in particular that star pattern under the table, would flash on and off TOGETHER as a whole. So when they were "on" the table was very bright. But when they were off, the facets were uniformly dark in that pattern.

This is very simplified:
It is not that uncommon that the angle combinations that form virtual facets are in sync with each other in their on off cycle as described. Combine that with a long dwell time and narrow beam pattern and covering a larger area of the diamond and you get a black hole effect. The most common place for that to happen is under the table and in square, rectangular or oval shaped stones. I wont say it cant happen in rounds but I have never seen it.
A face up rotating video vs laying on its side would have likely shown it.

Stan mentioned something earlier about a larger red in ASET VF in otherwise crushed ice radiant that made the diamond dark and it is likely from the same cause. Long dwell times, narrow beam pattern.

Another interesting aspect of the stone Gypsy posted is something I have been wondering about and asking for clarifiction on from the experts. Notice that the lab report describes this stone as a "cut cornered rectangular mixed cut". Maybe this is why David remarked that this stone is not really a radiant - don't know, wouldn't want to speak for him. Are there other designations that the labs use to describe cut cornered shapes that might indicate that they would not be of expected radiant flavors?

I also noted as Karl did that Stan in the original original thread mentioned that ASET might have revealed the problem with the OP's stone with the black hole by showing red in the center. Maybe this is an example of that??

 

[Rockdiamond]

Cool!
I would have been immediately interested because it was so unique.
I believe that a photo showing the facets of the diamond shows that it is a very pleasing cut, in terms of the facet structure.
In spite of this, if we could see it spin, I think the darkness in the center would be evident.
I believe it would in my photos as well.
BUT- there was obviously something attractive about the diamond to the buyer.
They had considerations, and the opportunity to return, but the diamond won them over.
Which says something.

I have been looking at different examples, and thinking about this a lot.
A stone I was looking at for the "bad" category- it has a 78% table.
Top of the diamond is flat as a pancake.
In spite of this, the stone faces up really nicely. Even under tilt.
It's going to be difficult making rules.

 

[Rockdiamond]

Bryan, I believe GIA called it a "mixed" cut due to the step cut top and modified brilliant faceted pavilion.
Generally speaking Radiant cuts are either square modified brilliant, or rectangular modified Brilliant.
I believe that the red in the center is indicative of a dark area on this type of aset.
BUT- sometimes if the red is distributed differently the darkness is not static, and not unpleasant- it might add contrast and perceived brightness.

 

[Karl_K]

Bryan, I believe GIA called it a "mixed" cut due to the step cut top and modified brilliant faceted pavilion.
Generally speaking Radiant cuts are either square modified brilliant, or rectangular modified Brilliant.
I believe that the red in the center is indicative of a dark area on this type of aset.
BUT- sometimes if the red is distributed differently the darkness is not static, and not unpleasant- it might add contrast and perceived brightness.

David,
I thought I would not need to elaborate but I guess I do.
If a diamond has many slow flashing virtual facets not in sync like an oec they look great because they alternatively flash.
It is what gives them their charm slow bold flashes where a not to large portion of the stone is dark at one time and they fit together.
Now you take the same large slow virtual facet behavior and surround it by many small quick flashing virtual facets and it stands out like a sore thumb.
It is not indicative of a dark area it is indicative of a possible slower flashing area that when dark can make the stone look darkish at that time and angle because it does not fit with the rest of the stone. It may be the brightest part of the stone face up.
So just saying it makes it dark is not correct because it could also be what makes it bright.

edit: to be fair I will take the blame for this one for not elaborating earlier.

 

[Gypsy]

Interesting observations. I really liked the stone, but Karl, I think from what I remember of the Video (which if I could post it I would) it did not show up. Unless I missed it (entirely possible).

And the slow alternating facet flash of OECs (and other stones) is something I'd like to learn more about (maybe in another thread, or if you have written about it before). That's what I love about them. And about some cushions as well.

It is interesting that the slow large facet flash of that stone is the reason why it had that 'personality'. I do wish I had spotted that.


David, here's the interesting things about the customer. They previously had a traditional "crushed ice" radiant.

I do wish we could ask them which facet pattern they prefer and why. It would have been interesting.

As to why the customer kept this stone... I am always afraid that in cases like this they keep the stone because they trust my comments about it when I was evaluating it (pre-purchase) over their own observations. I try VERY hard to make sure that doesn't happen. But I am always worried when people keep stones that they don't immediately fall head over heels for.

I don't know if in this posters place I would have kept it. I have a higher tolerance for "personality" in my stones. So I might have. But it would really depend on how I felt about it over at least a week of playing with it. And that's ultimately what I recommended to this poster. The vendor has a fantastic return policy. And I just advised them that if they didn't love it, they should return it.

 

[Karl_K]

Interesting observations. I really liked the stone, but Karl, I think from what I remember of the Video (which if I could post it I would) it did not show up. Unless I missed it (entirely possible).

It may not show up with the stone laying on its side and the angle of the lighting.

 

[Gypsy]

Interesting observations. I really liked the stone, but Karl, I think from what I remember of the Video (which if I could post it I would) it did not show up. Unless I missed it (entirely possible).

It may not show up with the stone laying on its side and the angle of the lighting.

I'm going to look at the video again. See if I can spot it. I would be good to know and learn from it.

 

[Gypsy]

Yup. Karl is right. Does not show up in the video on its side.

Aww well. Something new to worry about.

 

[Gypsy]

Here's a similar stone (also sold). Also called a "mixed cut" with the step cut crown. I have a couple questions.

The GIA facet plots are very similar but slightly different-- are these stones really different, or was the GIA just getting jiggy with it, and really they should have used the same plot for both?


Would this stone also have the same problem (this was not purchased by anyone who reported on it's performance in person), potentially?

In other words, is it problem with this actually faceting in particular? Or is it a stone by stone issue?

 

[Gypsy]

Here's my question for you RD:

These both popped up as "radiants" on the vendor search. So... I also echo TL's question. What is the nomenclature we should be using?

What GIA facet plots (and corresponding images) would you call "true" radiants.

And what are others you consider "modified" radiants?

And what do call the ones I posted above? A rectangular mixed cut???

Something similar to this from Charmy's cushion thread, would be most helpful.
Thread:
[URL='https://www.pricescope.com/community/threads/cushion-101-my-experience-in-making-a-harry-winston-halo.183473/']https://www.pricescope.com/community/threads/cushion-101-my-experience-in-making-a-harry-winston-halo.183473/[/URL]

What I would like you to post for us on radiants:


http://www.pricescope.com/files/images/hwg-pic4.PNG[img]
[ATTACH=full]563620[/ATTACH]
[ATTACH=full]563621[/ATTACH]
[ATTACH=full]563622[/ATTACH]
[ATTACH=full]563623[/ATTACH]


This type of thing is what *I* as a consumer poster need from you.

Can you provide that?

And also, if you can provide that AND include typical ASETS of each style that would be OUTSTANDING.

 

[Texas Leaguer]

Regarding:
1) Why is it that we can not more specifically identify the type of stones you are referring to? I think this is central to the problem. There are cut cornered square/rectangular modified brilliants like the orc and others that have the "smaller more numerous reflections" and give an appearance of an "bottomless bucket of ice" and which have ASET signatures like what you are showing. There are other Radiants available in the market that are also cut cornered modified brilliants which are optimized for light performance and have what is understood to be classic ASET signature without the leakage. Without first making a clear distinction between these two distinct "flavors" and identifying them when disccussing them, I think it is a natural tendency to apply a better understood standard for ASET signature to both. As a result, there will be a tendency to think these stones are better or worse than others because of their ASET signatures rather than being different flavors.

Bryan - the difference in ASET signature is much more about the difference in angles than differences in facet design so it is not, in my opinion at least, useful to separate out the two looks based on facet diagrams.

Stan, I am beginning to see what you are saying. Is it also correct to say that even if the lab report describes the cut the same way e.g "cut cornered square or rectangular modified brilliant" AND the report shows the same basic facet diagram, one could have crushed ice flavor and the other the brilliant flavor?

As an example, the two diagrams below are essentially the same facet configuration (albiet different length to width ratios). Could the stone represented by the GIA diagram on bottom be of opposite flavor and therefore need to have its ASET signature judged diffently?

 

[Rockdiamond]

Regarding:
1) Why is it that we can not more specifically identify the type of stones you are referring to? I think this is central to the problem. There are cut cornered square/rectangular modified brilliants like the orc and others that have the "smaller more numerous reflections" and give an appearance of an "bottomless bucket of ice" and which have ASET signatures like what you are showing. There are other Radiants available in the market that are also cut cornered modified brilliants which are optimized for light performance and have what is understood to be classic ASET signature without the leakage. Without first making a clear distinction between these two distinct "flavors" and identifying them when disccussing them, I think it is a natural tendency to apply a better understood standard for ASET signature to both. As a result, there will be a tendency to think these stones are better or worse than others because of their ASET signatures rather than being different flavors.

Bryan - the difference in ASET signature is much more about the difference in angles than differences in facet design so it is not, in my opinion at least, useful to separate out the two looks based on facet diagrams.

Stan, I am beginning to see what you are saying. Is it also correct to say that even if the lab report describes the cut the same way e.g "cut cornered square or rectangular modified brilliant" AND the report shows the same basic facet diagram, one could have crushed ice flavor and the other the brilliant flavor?

As an example, the two diagrams below are essentially the same facet configuration (albiet different length to width ratios). Could the stone represented by the GIA diagram on bottom be of opposite flavor and therefore need to have its ASET signature judged diffently?

I'll remind Stan to take a look and give his thoughts Bryan.
In my experience your statement is correct. We can not tell if it is "crushed ice" from the facet diagram.
Furthermore, there's varying degrees of "crushed ice"
I pointed to stone #1 as an example of a super well cut "crushed ice" stone, because the effect s bright, with virtually no dark areas.
There's well cut rectangular diamonds that may have some areas of light return which contain larger facet reflecitons through the table than other parts of the stone.
Basically a combination of crushed ice and chunky , in PS speak.
I have an example I will post this evening.
People have asked that more information- I agree, that will help.
Thanks to everyone for their patience as both Stan and I are putting time and effort in- but thankfully we've both got businesses to run as well.

 

[Rockdiamond]

Here's my question for you RD:

These both popped up as "radiants" on the vendor search. So... I also echo TL's question. What is the nomenclature we should be using?

What GIA facet plots (and corresponding images) would you call "true" radiants.

And what are others you consider "modified" radiants?

And what do call the ones I posted above? A rectangular mixed cut???

Something similar to this from Charmy's cushion thread, would be most helpful.
Thread:
[URL='https://www.pricescope.com/community/threads/cushion-101-my-experience-in-making-a-harry-winston-halo.183473/']https://www.pricescope.com/community/threads/cushion-101-my-experience-in-making-a-harry-winston-halo.183473/[/URL]

What I would like you to post for us on radiants:


http://www.pricescope.com/files/images/hwg-pic4.PNG[img]
[ATTACH=full]563649[/ATTACH]
[ATTACH=full]563650[/ATTACH]
[ATTACH=full]563651[/ATTACH]
[ATTACH=full]563652[/ATTACH]




This type of thing is what *I* as a consumer poster need from you.

Can you provide that?

And also, if you can provide that AND include typical ASETS of each style that would be OUTSTANDING.[/quote]

Great questions Gypsy!
You have picked two really unique and different stones- mixed cuts are rare.
For the purposes of clarification- the name "Radiant Cut" is like the name "Princess Cut", or "Asscher Cut"
None of these names appears on a GIA report- and some diamonds are harder to hang a label on.
With rarely seen shapes, it makes no business sense to add a category for on a website ( which is generally a costly change). So they get lumped in together.
From here on you'll know that if someone is looking for a radiant the GIA report should say "Cut Cornered Rectangular Modified Brilliant" or "Cut Cornered Square Modified Brilliant", that is a Radiant.

Thank you too for posting a link to Charmy's thread.
There's a lot of great info there about how a guide might be put together.
I do think that we would need to follow a slightly different course.
The specifics of Radiant cuts are different - things like matching GIA plot diagrams to physical appearance are different.
Indeed, modified brilliant cushion stones were mentioned only in passing in Charmy's guide- of course that was not the goal of that guide.

 

[Rockdiamond]

this is a great example of stone which both Stan and I consider to be a very well cut Radiant ( Cut cornered Rectangular Modified Brilliant)
This one is more tricky to analyze.

My impressions of the light performance: this stone has what I call a "non detrimental bowtie"
it's got remarkable scintillation at the ends- the middle portion of the stone is bouncing the light off larger facets back to your eye.
The cool thing is that it blends well and the larger facets are prone to white bright flashes in the "on" position and even when they darken, it's not very dark.
Compared to stone one, you have two truly well cut stones with different approaches in each case.


Part of what I would want to see in a cut grade for Radiant cuts, is one that would include both of these as top grades for Rectangular Diamonds.

 

[Karl_K]

David: stone 5 the aset picture is crap it is washed out and out of focus I cant tell a thing from it.
Retry and see if you can get a better picture please.

 

[RADIANTMAN]

Sorry to have been out of pocket for a few days. I'll try to catch up here.


1. Re: facet arrangements - by playing with the angles, most if not all of the facet arrangements I've seen for radiant-like diamonds can yield a broad continuum of different kinds of brilliance. There is simply no way to know what the diamond will look like by looking at the facet diagram. This is not only true for radiants. It is equally true for cushion modified brilliants and many other cuts.

2. Describing a black area around the culet when the diamond viewed straight on as "facets that flash on and off" - a neutral sounding characteristic - as opposed to "leakage" - a bad sounding characteristic - illustrates the point that both David and I have been trying to make about the the bias in the nomenclature. I recut diamonds all the time to eliminate darkness around the culet. If it is pronounced I (based on my years of experience with what bothers people and what doesn't in the real world) consider it, like a pronounced bowtie, to be a defect not a mere characteristic of facets flashing on and off.

3. Someone above referred to the idea that the best photo would be one that enables you to predict what the ASET will look like. It seems to me that the job of both the photo and the ASET is to help us understand what the diamond will look like.

4. Interestingly, the GIA is considering (with my consent which I've given) changing its nomenclature to use the word "radiant" in place of "cut cornered square/rectangular brilliant" in order to be less confusing to consumers.

5 On the diamond with the dark area posted above, it seems to me that the strong concentration of red around the culet area is what manifests itself as the concentration of black - in other words in this case the concentration of red is a warning sign. It is indicative of a dead area rather than a bright one. As for the photo, it would be interesting to know whether the dead area would show up more clearly in David's tweezer shot that it does in the photo provided, which hints at it but doesn't show it. I am far from an expert in photography but it doesn't seen to me that his photos are any more deceptive than the other photos shown. Every mode of photographing will highlight some characteristics more and others less. That's why videos are so much more instructive. I haven't seen the video of that diamond but I'd be surprised if the blackness did not show up if the video is stopped at the right spot, though by videotaping the diamond on its side rather than straight on its likely that the blackness appears less pronounced than it is when viewed straight on as it is in real life.

6. In David's diamond #5 - which I have seen live and believe everyone, except those who don't like radiants generally, would agree is a beautiful stone - you can see the slight red where the slight bowtie is. The trickiness is in gauging how much red in that area is too much. Its a continuum not a magic measurement. A little is ok for pretty much anyone, alot is not, and in between, well, you have to see the diamond or trust photos and/or the eyes of someone who has actually seen the diamond. If you're trusting someone else's eyes, its a good idea to give them an idea how "bowtie tolerant" you are so they can incorporate your personal taste into their judgment call.

 

[Texas Leaguer]

Sorry to have been out of pocket for a few days. I'll try to catch up here.


1. Re: facet arrangements - by playing with the angles, most if not all of the facet arrangements I've seen for radiant-like diamonds can yield a broad continuum of different kinds of brilliance. There is simply no way to know what the diamond will look like by looking at the facet diagram. This is not only true for radiants. It is equally true for cushion modified brilliants and many other cuts.

2. Describing a black area around the culet when the diamond viewed straight on as "facets that flash on and off" - a neutral sounding characteristic - as opposed to "leakage" - a bad sounding characteristic - illustrates the point that both David and I have been trying to make about the the bias in the nomenclature. I recut diamonds all the time to eliminate darkness around the culet. If it is pronounced I (based on my years of experience with what bothers people and what doesn't in the real world) consider it, like a pronounced bowtie, to be a defect not a mere characteristic of facets flashing on and off.

3. Someone above referred to the idea that the best photo would be one that enables you to predict what the ASET will look like. It seems to me that the job of both the photo and the ASET is to help us understand what the diamond will look like.

4. Interestingly, the GIA is considering (with my consent which I've given) changing its nomenclature to use the word "radiant" in place of "cut cornered square/rectangular brilliant" in order to be less confusing to consumers.

Interesting indeed! That would eliminate some of the uncertainty we are talking about in this thread. What parameters will GIA use to decide when to call it a radiant and when to call it say a "cut cornered mixed cut"? Would all stones that are now referred to "cut cornered square/rectangular modified brilliant" be called radiant?

5 On the diamond with the dark area posted above, it seems to me that the strong concentration of red around the culet area is what manifests itself as the concentration of black - in other words in this case the concentration of red is a warning sign. It is indicative of a dead area rather than a bright one. As for the photo, it would be interesting to know whether the dead area would show up more clearly in David's tweezer shot that it does in the photo provided, which hints at it but doesn't show it. I am far from an expert in photography but it doesn't seen to me that his photos are any more deceptive than the other photos shown. Every mode of photographing will highlight some characteristics more and others less. That's why videos are so much more instructive. I haven't seen the video of that diamond but I'd be surprised if the blackness did not show up if the video is stopped at the right spot, though by videotaping the diamond on its side rather than straight on its likely that the blackness appears less pronounced than it is when viewed straight on as it is in real life.

Not sure which diamond above you are referring to exactly ??

6. In David's diamond #5 - which I have seen live and believe everyone, except those who don't like radiants generally, would agree is a beautiful stone - you can see the slight red where the slight bowtie is. The trickiness is in gauging how much red in that area is too much. Its a continuum not a magic measurement. A little is ok for pretty much anyone, alot is not, and in between, well, you have to see the diamond or trust photos and/or the eyes of someone who has actually seen the diamond. If you're trusting someone else's eyes, its a good idea to give them an idea how "bowtie tolerant" you are so they can incorporate your personal taste into their judgment call.

I am very curious about this stone and its ASET signature. Perhaps my question has to do with quality of the ASET capture, which Karl remarked about earlier. But if it is accurate in terms of telling us where this diamond, which is reportedly beautiful, is drawing light from in the hemisphere above the girdle plane, how is it possible for the diamond to have sufficient "on/off" flashes in the face-up view with the extremely high amount of contiguous white? Would that mean the diamond requires side of back light in order to perform?

Stan, my comments/questions in blue above.

 

[RADIANTMAN]

Sorry to have been out of pocket for a few days. I'll try to catch up here.


1. Re: facet arrangements - by playing with the angles, most if not all of the facet arrangements I've seen for radiant-like diamonds can yield a broad continuum of different kinds of brilliance. There is simply no way to know what the diamond will look like by looking at the facet diagram. This is not only true for radiants. It is equally true for cushion modified brilliants and many other cuts.

2. Describing a black area around the culet when the diamond viewed straight on as "facets that flash on and off" - a neutral sounding characteristic - as opposed to "leakage" - a bad sounding characteristic - illustrates the point that both David and I have been trying to make about the the bias in the nomenclature. I recut diamonds all the time to eliminate darkness around the culet. If it is pronounced I (based on my years of experience with what bothers people and what doesn't in the real world) consider it, like a pronounced bowtie, to be a defect not a mere characteristic of facets flashing on and off.

3. Someone above referred to the idea that the best photo would be one that enables you to predict what the ASET will look like. It seems to me that the job of both the photo and the ASET is to help us understand what the diamond will look like.

4. Interestingly, the GIA is considering (with my consent which I've given) changing its nomenclature to use the word "radiant" in place of "cut cornered square/rectangular brilliant" in order to be less confusing to consumers.

Interesting indeed! That would eliminate some of the uncertainty we are talking about in this thread. What parameters will GIA use to decide when to call it a radiant and when to call it say a "cut cornered mixed cut"? Would all stones that are now referred to "cut cornered square/rectangular modified brilliant" be called radiant?

5 On the diamond with the dark area posted above, it seems to me that the strong concentration of red around the culet area is what manifests itself as the concentration of black - in other words in this case the concentration of red is a warning sign. It is indicative of a dead area rather than a bright one. As for the photo, it would be interesting to know whether the dead area would show up more clearly in David's tweezer shot that it does in the photo provided, which hints at it but doesn't show it. I am far from an expert in photography but it doesn't seen to me that his photos are any more deceptive than the other photos shown. Every mode of photographing will highlight some characteristics more and others less. That's why videos are so much more instructive. I haven't seen the video of that diamond but I'd be surprised if the blackness did not show up if the video is stopped at the right spot, though by videotaping the diamond on its side rather than straight on its likely that the blackness appears less pronounced than it is when viewed straight on as it is in real life.

Not sure which diamond above you are referring to exactly ??

6. In David's diamond #5 - which I have seen live and believe everyone, except those who don't like radiants generally, would agree is a beautiful stone - you can see the slight red where the slight bowtie is. The trickiness is in gauging how much red in that area is too much. Its a continuum not a magic measurement. A little is ok for pretty much anyone, alot is not, and in between, well, you have to see the diamond or trust photos and/or the eyes of someone who has actually seen the diamond. If you're trusting someone else's eyes, its a good idea to give them an idea how "bowtie tolerant" you are so they can incorporate your personal taste into their judgment call.

I am very curious about this stone and its ASET signature. Perhaps my question has to do with quality of the ASET capture, which Karl remarked about earlier. But if it is accurate in terms of telling us where this diamond, which is reportedly beautiful, is drawing light from in the hemisphere above the girdle plane, how is it possible for the diamond to have sufficient "on/off" flashes in the face-up view with the extremely high amount of contiguous white? Would that mean the diamond requires side of back light in order to perform?

Stan, my comments/questions in blue above.

Hi Bryan,

When I was asked whether I was OK with the use of the word "radiant" I assumed they were considering describing all of the diamonds now called "cut cornered square/rectangular modified brilliants" as radiants but you know what happens when you assume...

The diamond with the dark area I was referring to is the one posted by Gypsy (I think) above that she recommended but the customer didn't like.

Your question about diamond #5 illustrates how hard it is to have this discussion about diamonds only David and I have actually seen. It's also, from my perspective, perhaps because I've seen the diamond and you have not, a bit backward. For me, the starting point is the diamond not the ASET and if my eyes and experience tell me that this is a beautiful diamond and my understanding of the ASET tells me it "shouldn't" be, then it my understanding of ASET that needs to change not my opinion of the diamond.

 

[Karl_K]

5 On the diamond with the dark area posted above, it seems to me that the strong concentration of red around the culet area is what manifests itself as the concentration of black - in other words in this case the concentration of red is a warning sign. It is indicative of a dead area rather than a bright one. As for the photo, it would be interesting to know whether the dead area would show up more clearly in David's tweezer shot that it does in the photo provided, which hints at it but doesn't show it. I am far from an expert in photography but it doesn't seen to me that his photos are any more deceptive than the other photos shown. Every mode of photographing will highlight some characteristics more and others less. That's why videos are so much more instructive. I haven't seen the video of that diamond but I'd be surprised if the blackness did not show up if the video is stopped at the right spot, though by videotaping the diamond on its side rather than straight on its likely that the blackness appears less pronounced than it is when viewed straight on as it is in real life.

I have seen the video and it does not show up at that angle and lighting as the diamond rotates, it is bright in the video.
It is also bright in ASET and the video therefore it does flash off and on.
Just because you do not understand my answer does not mean I am wrong.

 

[Karl_K]

Your question about diamond #5 illustrates how hard it is to have this discussion about diamonds only David and I have actually seen. It's also, from my perspective, perhaps because I've seen the diamond and you have not, a bit backward. For me, the starting point is the diamond not the ASET and if my eyes and experience tell me that this is a beautiful diamond and my understanding of the ASET tells me it "shouldn't" be, then it my understanding of ASET that needs to change not my opinion of the diamond.

How can we discuss the stone at all when the ASET picture is washed out and totally out of focus?

 

[RADIANTMAN]

Karl- where did I say you were wrong and what did I misunderstand?

I'm sure David will try to shoot a better ASET photo and will post it when he can.

 

[Karl_K]

Karl- where did I say you were wrong and what did I misunderstand?

I'm sure David will try to shoot a better ASET photo and will post it when he can.

point 2 and point 5 in your response taken together.

 

[RADIANTMAN]

Karl- where did I say you were wrong and what did I misunderstand?

I'm sure David will try to shoot a better ASET photo and will post it when he can.

point 2 and point 5 in your response taken together.

It wasn't directed to you. I was referring to Gypsy's experience with the customer who didn't like the diamond she recommended. I went back to the previous page and found a post of yours I hadn't seen before which I think is what you're referring to. You and I do not disagree. When I refer to a "dark area" I mean an area that appears dark to the eye which can certainly be the result of contrast with surrounding areas and which may not always appear dark. It might be quite bright when the orientation to the light is changed. As with pretty much every other characteristic of a diamond, whether its a "problem"depends on the size and location of the dark appearing area, the circumstances under which it appears dark, and how it interplays with the rest of the diamond.

It seems clear to me from the customer's photos that on the diamond Gypsy referred to it was a pretty obvious problem when the diamond was seen "live" despite the fact that the problem did not result from a shortage of light return as measured by the ASET.

 

[Rockdiamond]

Hi all
I will attempt another ASET
But it's not going to look all that different.
I'm using the same setup for each diamond so they all have the same considerations.
For what it's worth the aset image I posted matches what my eye sees I'm the aset I'm real life

 

[MelisendeDiamonds]

4. Interestingly, the GIA is considering (with my consent which I've given) changing its nomenclature to use the word "radiant" in place of "cut cornered square/rectangular brilliant" in order to be less confusing to consumers.

To my knowledge that sounds highly implausible. In recent years, probably over a decade, GIA describes the outline shape and facet pattern in their nomenclature and they will never use patented or formerly patented names or trade preferred terms on grading reports. I find it highly unlikely they will make an exception to this practice they use for all fancy shapes for the Radiant.

The nomenclature used by GIA for cut cornered squares or rectangles(all of them not just the Radiant) follows the same theme and similar rules as it does for cushions, for the fine details you could contact the lab and I'm sure they would answer your questions. But in general:

" facets which are similar to the facet arrangement of a round brilliant cut, but could have more or less, consisting of a table facet, girdle plain, bezel extending from the table to the girdle plain, and pavilion mains extending from the culet to the girdle plain"

"To be called modified the facets have to be systematically added deleted or modified usually on the pavilion altering the brilliant cutting style"

Since I have seen no cut cornered squares with pure brilliant pavilions, as in no examples where the pavilion mains extend from culet to girdle (not even in H&A type), I would be surprised to see any recent GIA grading reports with Cut Cornered Square or Rectangular Brilliants, there would be only Modified Cut Cornered Square Brilliant or Modified Cut Cornered Rectangular Brilliants on grading reports unless it is an error.

A mixed cut contains either a crown or pavilion that does not conform to the the brilliant style of cutting(like a step cut) usually combined with the other that does.

 

[Karl_K]

Karl- where did I say you were wrong and what did I misunderstand?

I'm sure David will try to shoot a better ASET photo and will post it when he can.

point 2 and point 5 in your response taken together.

It wasn't directed to you. I was referring to Gypsy's experience with the customer who didn't like the diamond she recommended. I went back to the previous page and found a post of yours I hadn't seen before which I think is what you're referring to. You and I do not disagree. When I refer to a "dark area" I mean an area that appears dark to the eye which can certainly be the result of contrast with surrounding areas and which may not always appear dark. It might be quite bright when the orientation to the light is changed. As with pretty much every other characteristic of a diamond, whether its a "problem"depends on the size and location of the dark appearing area, the circumstances under which it appears dark, and how it interplays with the rest of the diamond.

It seems clear to me from the customer's photos that on the diamond Gypsy referred to it was a pretty obvious problem when the diamond was seen "live" despite the fact that the problem did not result from a shortage of light return as measured by the ASET.

ok we do agree then.
I think if we sat down and discussed this in person we would agree on a lot of things.
A lot of things going on in one post and thread make things a bit confusing.

 

[MelisendeDiamonds]

This next stone will illustrate so many points I've been trying to make for a long time.
Please excuse the horrible ASET- I tried and tried to get it level, but it's a large stone.

Is this a well cut Radiant?
Yes.
Very much so.
It's spready diamond- so it's a five carat that looks like a 6 or even 7.
Remarkable sparkle and overall brightness.
The only apparent tradeoff for the size ( spready-ness) is that when you tilt the diamond, it requires less tilt to induce a window like effect.
Could it be better.
Yes.
Should it be??
That's a question that is part of this discussion- and many others here in the past.
Was there bad motivation to stop cutting at 5cts?
Let's say you are the diamond cutter.
You own this diamond, and cut it to it's maximum beauty at 5.00cts..
By working the pavilion a bit, you can bring a bit more contrast into the stone- basically make it a click brighter.
But you loose the 5ct mark.
When you do this, your cost on the diamond goes up, not down. You now have a 4.50ct that you invested additional and costly time and risk on the wheel. So you have a smaller diamond that has a greater overall cost.

I might- just might- consider doing that, if it was my diamond- but I could not fault someone for choosing to leave it as it is.
And it leaks

ETA- just looked at it again- no way I'd put it back on the wheel

Rockdiamond,

We have different posting styles and a far different viewpoint on this topic but allow me summarize the qualities of this diamond from the objective information you have provided.

This diamond:

Pros:
Spread(stated by RD)
Higher Yield(stated by RD)
Cheaper/Ct than other cuts (implied from RD yield statement)
Fast Scintillation (bucket of glitter, small sparkles from small patches on ASET)
Limited Potential for Head Shadow (from ASET very little blue)

Cons
Lack of edge to edge brillance(large areas of white, from ASET)
Lack of sparkle uniformity or brightness and color uniformity (different size color zones from ASET)
Many Potentially Lifeless Zones (areas of crown where the light is gathered from pavilion rather than the crown from ASET)

----------------------------------------------------------------------------------------------------------------------------------------------------------------

Now the list above brings up some important points.

If something is "Well Cut" due to Yield, Spread and/or Price and the appearance criteria are important but not prioritized than surely you will not get a good correlation with ASET if this is called "Well Cut".

Even for this cutting style the ASET is telling us how uniform the sparkles and areas of the diamond that will be less brilliant. There are Radiants and cushions with Radiant cut pavilions with much better color and brightness uniformity and smaller more even sparkles. I will try to dig up some examples.

 

[RADIANTMAN]

This next stone will illustrate so many points I've been trying to make for a long time.
Please excuse the horrible ASET- I tried and tried to get it level, but it's a large stone.

Is this a well cut Radiant?
Yes.
Very much so.
It's spready diamond- so it's a five carat that looks like a 6 or even 7.
Remarkable sparkle and overall brightness.
The only apparent tradeoff for the size ( spready-ness) is that when you tilt the diamond, it requires less tilt to induce a window like effect.
Could it be better.
Yes.
Should it be??
That's a question that is part of this discussion- and many others here in the past.
Was there bad motivation to stop cutting at 5cts?
Let's say you are the diamond cutter.
You own this diamond, and cut it to it's maximum beauty at 5.00cts..
By working the pavilion a bit, you can bring a bit more contrast into the stone- basically make it a click brighter.
But you loose the 5ct mark.
When you do this, your cost on the diamond goes up, not down. You now have a 4.50ct that you invested additional and costly time and risk on the wheel. So you have a smaller diamond that has a greater overall cost.

I might- just might- consider doing that, if it was my diamond- but I could not fault someone for choosing to leave it as it is.
And it leaks

ETA- just looked at it again- no way I'd put it back on the wheel

Rockdiamond,

We have different posting styles and a far different viewpoint on this topic but allow me summarize the qualities of this diamond from the objective information you have provided.

This diamond:

Pros:
Spread(stated by RD)
Higher Yield(stated by RD)
Cheaper/Ct than other cuts (implied from RD yield statement)
Fast Scintillation (bucket of glitter, small sparkles from small patches on ASET)
Limited Potential for Head Shadow (from ASET very little blue)

Cons
Lack of edge to edge brillance(large areas of white, from ASET)
Lack of sparkle uniformity or brightness and color uniformity (different size color zones from ASET)
Many Potentially Lifeless Zones (areas of crown where the light is gathered from pavilion rather than the crown from ASET)

----------------------------------------------------------------------------------------------------------------------------------------------------------------

Now the list above brings up some important points.

If something is "Well Cut" due to Yield, Spread and/or Price and the appearance criteria are important but not prioritized than surely you will not get a good correlation with ASET if this is called "Well Cut".

Even for this cutting style the ASET is telling us how uniform the sparkles and areas of the diamond that will be less brilliant. There are Radiants and cushions with Radiant cut pavilions with much better color and brightness uniformity and smaller more even sparkles. I will try to dig up some examples.

David is not a diamond cutter and I think his comments on yield were for the purpose of making the point that cutters are not "greedy" or "honorable" based on the cut quality of their diamonds. They all make their cutting decisions based on profitabilitytaking into account their particular marketing niche and if they didn't, fine cuts or poor, they wouldn't be in business for very long.

I have no way of estimating the actual yield from the rough on diamond #2 since I have seen only the polished, but I can say that it does not appear to me to be a diamond that was cut in a manner that resulted in particularly exceptional yield from the rough. Quite the contrary actually. I don't think this diamond would have been cut any differently if there had been more "room" above 5 carats.

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.