HCA, AGS and GIA

[2023]

Just a little observation for the record that many observers and commentators perhaps miss.
HCA is the only system that gives a positive score for spread. This is based on a simple observation that many consumers prefer a larger diameter.
So since my system adds up penalty's and gives a total score, where as the other mentioned systems do not, it is an obvious side effect that HCA will give a preference to stones with larger diameters for their weight and this means that there will be a slight preference directed to shallower stones. However per se my personal preferences are not that far from Tolkowsky - adjusted slightly shallower because it is what ladies want: i.e.

Size does count.
Bigger is better!

I have since adjusted the spread factor, but since this site is an original paper - I do not like to edit it. I do not have the current mimimum with me on vacation, but it is more like 40.5 and 32.5.

Christina, I never said I liked 'steep deeps' and, I repeat this for the last time (I will copy it next time so I don't have to write it again), I looked at what AGSideal and GIAex consider in their optimum cut stones.

I do not twist data, I am merely showing what three independent labs that have no invested interest whatsoever, in what they consider an ideal cut stone. GIA, AGS and AGA.

41.2/33.5 is not a steep deep and was an example I used.

Paul (a jellewer), John (a jeweller), Gary H (a jeweller) - all experts in their own right, understand exactly what I am saying...if I were twisting things as you suggest, don’t you think one of these professionals would have pulled me up on that by now instead of understanding what I am saying?

 

[2023]

2023 I agree there can be stones in the 2-3 range worth considering. If they are top symmetry, if there is no painting or digging.
When I first began working on the HCA data there were way fewer stones with really good optical symmetry, so given the choice of slightly deeper or slightly shallower in my experience shallower works better if there are sym deviations.

GIA now grades Symmetry and also takes into account painting or digging into their cut grade.

 

[Christina...]

Just a little observation for the record that many observers and commentators perhaps miss.
HCA is the only system that gives a positive score for spread. This is based on a simple observation that many consumers prefer a larger diameter.
So since my system adds up penalty's and gives a total score, where as the other mentioned systems do not, it is an obvious side effect that HCA will give a preference to stones with larger diameters for their weight and this means that there will be a slight preference directed to shallower stones. However per se my personal preferences are not that far from Tolkowsky - adjusted slightly shallower because it is what ladies want: i.e.

Size does count.
Bigger is better!

I have since adjusted the spread factor, but since this site is an original paper - I do not like to edit it. I do not have the current mimimum with me on vacation, but it is more like 40.5 and 32.5.

Christina, I never said I liked 'steep deeps' and, I repeat this for the last time (I will copy it next time so I don't have to write it again), I looked at what AGSideal and GIAex consider in their optimum cut stones.

I do not twist data, I am merely showing what three independent labs that have no invested interest whatsoever, in what they consider an ideal cut stone. GIA, AGS and AGA.

41.2/33.5 is not a steep deep and was an example I used.

Paul (a jellewer), John (a jeweller), Gary H (a jeweller) - all experts in their own right, understand exactly what I am saying...if I were twisting things as you suggest, don’t you think one of these professionals would have pulled me up on that by now instead of understanding what I am saying?

2023 I think that we all understand what your saying, however you continue to fail to understand the limitations of the HCA, and that's where the frustrations comes. It's not a secret that the HCA is tougher on steeper PAs. You were asked to make a suggestion to improve it. You suggested that people not automatically disregard stones that scored over 2 on the HCA. Most PSer suggest that the consumer acquire more information if the stone scores between 2-3, the HCA states that a stone is worth purchasing if the price is right at this level, so what you are suggesting isn't anything new or that hasn't been done or isn't recommended daily on these boards. I don't believe I have seen a thread where an OP posted a diamond with the only additional information being a low HCA score and someone telling the OP to pass. HCA is only the first step. Much more information is needed before purchasing, report #, who graded it, age of report, inclusions, magnified images, IS images. You can purchase a diamond without using the HCA at all, but since, like I've said many many times, most people on these boards are trying to weed through an enormous inventory, with very little actual experience, the HCA is a very helpful tool. So they may miss a beauty, well, they are also eliminating many many dogs too, and by the time they are ready to lay down their CC they will have learned to use and interpret other useful tools as well. The HCA is a starting point, the purchasers own eyes are the end point. So again, I would ask you what your suggestion is, what would you recommend that isn't already recommended everyday on these boards?

 

[Christina...]

2023 I agree there can be stones in the 2-3 range worth considering. If they are top symmetry, if there is no painting or digging.
When I first began working on the HCA data there were way fewer stones with really good optical symmetry, so given the choice of slightly deeper or slightly shallower in my experience shallower works better if there are sym deviations.

GIA now grades Symmetry and also takes into account painting or digging into their cut grade.

right....Garry probably didn't realize this.

 

[2023]

delete thread

 

[2023]

2023 I agree there can be stones in the 2-3 range worth considering. If they are top symmetry, if there is no painting or digging.
When I first began working on the HCA data there were way fewer stones with really good optical symmetry, so given the choice of slightly deeper or slightly shallower in my experience shallower works better if there are sym deviations.

GIA now grades Symmetry and also takes into account painting or digging into their cut grade.

right....Garry probably didn't realize this.

At least you've gone from the random comments from PPs to eye rolling. I never meant to say Gary doesn't know that of course not, I'm saying when he first began working on the HCA ten years ago, he said, there were fewer stones with good optical symmetry. These days cut standards have risen so much, that we now even have the option of HnA diamonds etc. I was pointing that out for the average consumer, as to why there may be a potential paradigm shift is that now diamonds with excellent symmetry exist where painting and digging is taken into account as well.

Rhino (Jonothan Weingarten) from GoG has HnA diamonds at 41 pavilions with excellent optical symmetry making them HnA stones, back then a few years ago, people were totally freaked out. A lady back then, with a 41/34 took four pages of convincing from multiple tools from half a dozen jewellers/scientist/researchers, all saying 'this is a perfect stone' look we'll show you light leakage, refractive rays, scientifc papers, modelling, etc etc because she was so fearful of going outside her PS methods of thinking. Luckily she bought the stone, now a 41/34 on another post, Gary has said, 'you can't get more perfect than that'.

I never ever said there wasn't a place for the HCA - never in any of my posts did I say that.

 

[2023]

Just a little observation for the record that many observers and commentators perhaps miss.
HCA is the only system that gives a positive score for spread. This is based on a simple observation that many consumers prefer a larger diameter.
So since my system adds up penalty's and gives a total score, where as the other mentioned systems do not, it is an obvious side effect that HCA will give a preference to stones with larger diameters for their weight and this means that there will be a slight preference directed to shallower stones. However per se my personal preferences are not that far from Tolkowsky - adjusted slightly shallower because it is what ladies want: i.e.

Size does count.
Bigger is better!

I have since adjusted the spread factor, but since this site is an original paper - I do not like to edit it. I do not have the current mimimum with me on vacation, but it is more like 40.5 and 32.5.

Christina, I never said I liked 'steep deeps' and, I repeat this for the last time (I will copy it next time so I don't have to write it again), I looked at what AGSideal and GIAex consider in their optimum cut stones.

I do not twist data, I am merely showing what three independent labs that have no invested interest whatsoever, in what they consider an ideal cut stone. GIA, AGS and AGA.

41.2/33.5 is not a steep deep and was an example I used.

Paul (a jellewer), John (a jeweller), Gary H (a jeweller) - all experts in their own right, understand exactly what I am saying...if I were twisting things as you suggest, don’t you think one of these professionals would have pulled me up on that by now instead of understanding what I am saying?

2023 I think that we all understand what your saying, however you continue to fail to understand the limitations of the HCA, and that's where the frustrations comes. It's not a secret that the HCA is tougher on steeper PAs. You were asked to make a suggestion to improve it. You suggested that people not automatically disregard stones that scored over 2 on the HCA. Most PSer suggest that the consumer acquire more information if the stone scores between 2-3, the HCA states that a stone is worth purchasing if the price is right at this level, so what you are suggesting isn't anything new or that hasn't been done or isn't recommended daily on these boards. I don't believe I have seen a thread where an OP posted a diamond with the only additional information being a low HCA score and someone telling the OP to pass. HCA is only the first step. Much more information is needed before purchasing, report #, who graded it, age of report, inclusions, magnified images, IS images. You can purchase a diamond without using the HCA at all, but since, like I've said many many times, most people on these boards are trying to weed through an enormous inventory, with very little actual experience, the HCA is a very helpful tool. So they may miss a beauty, well, they are also eliminating many many dogs too, and by the time they are ready to lay down their CC they will have learned to use and interpret other useful tools as well. The HCA is a starting point, the purchasers own eyes are the end point. So again, I would ask you what your suggestion is, what would you recommend that isn't already recommended everyday on these boards?

If you read the thread you wouldn't need to ask that

 

[Garry H (Cut Nut)]

The HCA is a predictor of LP not cut grade.

Thanks Christina.

Small refinement, HCA is a predictor of potential light performance

 

[Garry H (Cut Nut)]

Also HCA (and to a lessor extent ideal-scope and ASET) are rejection tools, not selection tools.

When I wrote the patent for HCA I included minor facets (lower and upper girdles) as an additional option, but at the time this information, and girdle thickness information were not easily available as they are now.
With all that additional info, and painting and digging info, it would be possible to generate a data base that is closer to a selection tool.

it is true that some stones that are worthy will be dinged by HCA, but the vendors who share full images etc rather than relying on a girdle inscription "H&A's" - they deserve to be able to sell most of those stones as premium stones. Rarely does this board stop that 2023.

 

[2023]

Hi Gary,

Thank you for responding again. Do you think there is ever a chance you would modify the HCA to allow in those candidates that do get 'dinged' so to speak at 2? I totally do understand it would take a bit of time and resources.

I do think the some of the longer term posters do not just reject at 2, but for some posters I do believe there is a psychological fear of that number, and the leakage argument goes spiralling out of control. I have also seen posts were literally even 1 vs 1.8 is disputed, or Fire vs Scintillation is discussed based on the numbers generated.

It was incredibly apparent in that thread I linked to on 41 pavilions how huge an impact you have on the average PSer. Its incredibly apparent in general. Literally with all the data and half a dozen jewellers commenting, they even said please ask Gary. Luckily the lady bought it and it was a happy ending.

 

[Garry H (Cut Nut)]

Hi Gary,

Thank you for responding again. Do you think there is ever a chance you would modify the HCA to allow in those candidates that do get 'dinged' so to speak at 2? I totally do understand it would take a bit of time and resources.

I do think the some of the longer term posters do not just reject at 2, but for some posters I do believe there is a psychological fear of that number, and the leakage argument goes spiralling out of control. I have also seen posts were literally even 1 vs 1.8 is disputed, or Fire vs Scintillation is discussed based on the numbers generated.

It was incredibly apparent in that thread I linked to on 41 pavilions how huge an impact you have on the average PSer. Its incredibly apparent in general. Literally with all the data and half a dozen jewellers commenting, they even said please ask Gary. Luckily the lady bought it and it was a happy ending.

If I am to modify HCA then it is not a 'bit of work' - its a huge undertaking and I would only do it if there was a strong business case. There are some things happening that make it unwise for me to do that just now. I hoped this would have been resolved 2 years ago, but it involves a very slow moving machine.
However there are other developments that I am involved in with 'the cut group' that may supersede HCA.

 

[2023]

That's unfortunate, but it does make sense. I can totally understand that it would need to be commercially viable, not to mention the numbers of online vendors who have huge amounts of inventory that fit your model - it would make it politically very difficult too I imagine.

Thank you so much for your honesty and response to this thread.

 

[Christina...]

The HCA is a predictor of LP not cut grade.

Thanks Christina.

Small refinement, HCA is a predictor of potential light performance

yes, thanks for correcting that Garry!

edit:

there are other developments that I am involved in with 'the cut group' that may supersede HCA.


I've seen you mention this before and THIS is really interesting!

 

[Garry H (Cut Nut)]

edit:

there are other developments that I am involved in with 'the cut group' that may supersede HCA.


I've seen you mention this before and THIS is really interesting!

It will be once devloped.
Devlopment takes 5 times more time and 10 times more money and resources than originally envisioned.

 

[Christina...]

edit:

there are other developments that I am involved in with 'the cut group' that may supersede HCA.


I've seen you mention this before and THIS is really interesting!

It will be once devloped.
Devlopment takes 5 times more time and 10 times more money and resources than originally envisioned.

I remember using words very similar when building our home!

Based on your past works, and the works of the 'cut group', I'm sure this is collaboration well worth the effort. And one that will be much appreciated by both PS members and the industry. I'm looking forward to when you are able to share more details. I have to ask.... can you make an approximation as to how long before the public may expect a peek?

 

[Garry H (Cut Nut)]

maybe 2 years. Not sure if you multiply that by 5 or if its already factored in Christina!