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Proportions, images and selecting round diamonds......

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FB.

FB.

Brilliant_Rock
Joined
Jun 29, 2009
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764
It is normal for PS members to ask for images - IS/ASET/photo of all prospective purchases.

But when we''re dealing with stones that are GIA Ex cut, Ex polish and Ex symmetry, plus scoring below 2 on HCA, plus scoring 1A or 1B on AGA''s charts, plus falling within AGS-0 cut range......just how many of those stones with great "on paper" stats actually get rejected by PS members for poor light performance?
I can''t recall seeing any rejects within those criteria.

All I can recall is a couple of (maybe?) AGS 0 that may have been borderline steep/deep - but the possibility of an unusual light performance was already "red flagged" by the proportions being a little out of normal.

Therefore, is it such a big deal if images are not available, as long as the seller is known to be reliable and has a good returns policy? After all, the final proof of a good stone is when you get to examine it yourself.

If anyone can recall stones that scored well on HCA/GIA/AGA/AGS but had unexpectedly bad IS/ASET/other images, please share.

Thanks,
 
Date: 11/29/2009 6:12:05 PM
Author:FB.
It is normal for PS members to ask for images - IS/ASET/photo of all prospective purchases.


But when we''re dealing with stones that are GIA Ex cut, Ex polish and Ex symmetry, plus scoring below 2 on HCA, plus scoring 1A or 1B on AGA''s charts, plus falling within AGS-0 cut range......just how many of those stones with great ''on paper'' stats actually get rejected by PS members for poor light performance?

I can''t recall seeing any rejects within those criteria.


All I can recall is a couple of (maybe?) AGS 0 that may have been borderline steep/deep - but the possibility of an unusual light performance was already ''red flagged'' by the proportions being a little out of normal.


Therefore, is it such a big deal if images are not available, as long as the seller is known to be reliable and has a good returns policy? After all, the final proof of a good stone is when you get to examine it yourself.


If anyone can recall stones that scored well on HCA/GIA/AGA/AGS but had unexpectedly bad IS/ASET/other images, please share.


Thanks,
Click to expand...
I''m a strong believer of looking at the stone and a return policy. Paper, images, etc can help you eliminate obvious problems, but numbers and analysis will never tell the whole story. You have to see it in person to really get a feeling of the stone, photos just do not capture the whole dimension. Naturally this is my opinioooooon.;-)

In my experience stones with good cuts, EX EX EX and good proportions with an HCA <2 are beautiful, ASET or not.

--Joshua
 
FB, hopefully you'll get some bounce.

I'll threads that provide grist for the mill.

I'll be interested to hear more.

 
Date: 11/29/2009 8:24:14 PM
Author: yssie
Date: 11/29/2009 8:13:40 PM

Author: Stone-cold11

There you go.


http://www.goodoldgold.com/diamond/6450/


http://www2.gia.edu/reportcheck/index.cfm?fuseaction=home.showReportVerification&reportno=16914471&weight=1.31


Perfect illustration of why GIA symm grading has nothing to do with optical symm. The helium scan shows how much variation there is for the facets and it still gets a GIA Ex in symm and cut.
Click to expand...

This is an eye opener!
Click to expand...
Yes, except is it visible to the naked eye?

--Joshua
 
I am just showing that it is possible to have leakage in the stone even with all the numbers going for it. Visible or not will depend on the viewer and lighting conditions. Even if it is not visible, because of stereo vision, light return will be reduce in.
 
Date: 11/29/2009 9:17:06 PM
Author: Stone-cold11
I am just showing that it is possible to have leakage in the stone even with all the numbers going for it. Visible or not will depend on the viewer and lighting conditions. Even if it is not visible, because of stereo vision, light return will be reduce in.
Click to expand...
Thanks, Stone.

But I don't see a GIA-certificated "Excellent" cut grade attached to that stone.
From the image, I wonder whether it has some painting and digging (highlighted pink in attached image) that has spoiled the precision of the angles.
But GIA would probably penalise such a stone into the Very Good (or lower) cut grade as a result of excessive painting and/or digging. I have a GIA "steep/deep" triple-Ex candiate myself, but it was penalised to VG as a result of painting/digging, but it actually looks much better than a normal steep/deep as a result.

Do you have any examples of GIA-certified Excellent cut (triple excellent if possible) that have all the optimum numbers but fail the image tests?

0 0 0 0 0 10b.jpg
 
Images provide that extra 20% security that your getting the performance your paying for without the hassle of returns.
It also backs up or refutes the claims made about the diamond.
More than anything else it helps keep people honest and makes customers feel good.
If the images don't match the words then you know to move on.

I have seen both online with images and in person GIA EX stones that were not worth the premium over less expensive diamonds.
Online with images I have seen AGS0 diamonds that were not worth the premium also.
 
Date: 11/30/2009 3:59:29 AM
Author: Karl_K

I have seen both online with images and in person GIA EX stones that were not worth the premium over less expensive diamonds.
Online with images I have seen AGS0 diamonds that were not worth the premium also.
Click to expand...
I have also seen GIA Ex or AGS 0 stones that were not (IMO) worth the premium. Most - if not all - were steep/deep variants. None of them had HCA scores below 2.

-

If anyone can remember a Pricescope thread where a GIA-triple-Excellent (cut/polish/symmetry, with HCA less than 2 and had AGA cut grade 1A or 1B) or AGS 0 cut (with HCA less than 2 and had AGA cut grade 1A or 1B) was subsequently rejected by IS/ASET images, I'd love to see a link.

Thanks,
 
Date: 11/30/2009 3:28:55 AM
Author: FB.
Date: 11/29/2009 9:17:06 PM

Author: Stone-cold11

I am just showing that it is possible to have leakage in the stone even with all the numbers going for it. Visible or not will depend on the viewer and lighting conditions. Even if it is not visible, because of stereo vision, light return will be reduce in.
Click to expand...

Thanks, Stone.


But I don''t see a GIA-certificated ''Excellent'' cut grade attached to that stone.

From the image, I wonder whether it has some painting and digging (highlighted pink in attached image) that has spoiled the precision of the angles.

But GIA would probably penalise such a stone into the Very Good (or lower) cut grade as a result of excessive painting and/or digging. I have a GIA ''steep/deep'' triple-Ex candiate myself, but it was penalised to VG as a result of painting/digging, but it actually looks much better than a normal steep/deep as a result.


Do you have any examples of GIA-certified Excellent cut (triple excellent if possible) that have all the optimum numbers but fail the image tests?
Click to expand...

What are you talking about? The report check link is for that stone and that state that the stone is GIA Ex in cut.
 
Date: 11/30/2009 4:16:59 AM
Author: Stone-cold11



Date: 11/30/2009 3:28:55 AM
Author: FB.



Date: 11/29/2009 9:17:06 PM

Author: Stone-cold11

I am just showing that it is possible to have leakage in the stone even with all the numbers going for it. Visible or not will depend on the viewer and lighting conditions. Even if it is not visible, because of stereo vision, light return will be reduce in.
Click to expand...

Thanks, Stone.


But I don't see a GIA-certificated 'Excellent' cut grade attached to that stone.

From the image, I wonder whether it has some painting and digging (highlighted pink in attached image) that has spoiled the precision of the angles.

But GIA would probably penalise such a stone into the Very Good (or lower) cut grade as a result of excessive painting and/or digging. I have a GIA 'steep/deep' triple-Ex candiate myself, but it was penalised to VG as a result of painting/digging, but it actually looks much better than a normal steep/deep as a result.


Do you have any examples of GIA-certified Excellent cut (triple excellent if possible) that have all the optimum numbers but fail the image tests?
Click to expand...

What are you talking about? The report check link is for that stone and that state that the stone is GIA Ex in cut.
Click to expand...

Link to GIA check doesn't work.
I don't see a GIA cert listed on GOG's website.
33.gif


edit: see next post!
 
Ah! Found the GIA cert number on GOG's site.

35.0/40.8 angles, 58 table, 61.5 depth.

Something is odd with that one. So what has caused the stone to have *apparent* leakage and still manage to get into GIA Ex? What clever trick has the cutter done? Or is there something strange about the way the images were taken?

In fairness to my original statement; the stone does not fall into AGS 0 potential zone, although I concede that it almost does.
 
Date: 11/30/2009 3:59:29 AM
Author: Karl_K
Images provide that extra 20% security that your getting the performance your paying for without the hassle of returns.
It also backs up or refutes the claims made about the diamond.
More than anything else it helps keep people honest and makes customers feel good.
If the images don''t match the words then you know to move on.

I have seen both online with images and in person GIA EX stones that were not worth the premium over less expensive diamonds.
Online with images I have seen AGS0 diamonds that were not worth the premium also.
Click to expand...
In a nutshell.
 
I was having trouble accessing certain internet pages earlier - hence my confused replies.
19.gif

Now I can see the problem; the diamond's girdle has a kink in it that gives the same effect as a bit of painting/digging, knocking the angles out of alignment in the process. I must admit that I'm surprised that such a stone didn't get penalised; I've rarely -if ever- seen something so blatant. But had the proportions been right in the sweet spot of GIA Ex and AGS 0 candidate, I suspect that the angles would not cause nearly as much leakage and the stone would be acceptable.
Could it simply be an example of sporadic human error or too much leniency on the part of the grader - just like making the judgement of colour or clarity? We're all human and can make mistakes.
If I had been grading that stone, I would have penalised it either for symmetry, or for inappropriate brillianteering.
 
Date: 11/30/2009 4:28:09 AM
Author: FB.

In fairness to my original statement; the stone does not fall into AGS 0 potential zone, although I concede that it almost does.
Click to expand...
It would get ags0 for performance from AGS check the PGS results.
With EX/EX pol/sym from GIA there is a chance it would get id/id from AGS for a full AGS0 as well.
 
Date: 11/30/2009 5:51:04 AM
Author: FB.
I was having trouble accessing certain internet pages earlier - hence my confused replies.
19.gif


Now I can see the problem; the diamond''s girdle has a kink in it that gives the same effect as a bit of painting/digging, knocking the angles out of alignment in the process. I must admit that I''m surprised that such a stone didn''t get penalised; I''ve rarely -if ever- seen something so blatant. But had the proportions been right in the sweet spot of GIA Ex and AGS 0 candidate, I suspect that the angles would not cause nearly as much leakage and the stone would be acceptable.

Could it simply be an example of sporadic human error or too much leniency on the part of the grader - just like making the judgement of colour or clarity? We''re all human and can make mistakes.

If I had been grading that stone, I would have penalised it either for symmetry, or for inappropriate brillianteering.
Click to expand...

So what is wrong with asking for an image to verify all these?
 
Date: 11/30/2009 6:26:03 AM
Author: Stone-cold11




So what is wrong with asking for an image to verify all these?
Click to expand...
Because in the UK, only carat, colour and clarity matter; most jewellers never speak of cut and most consumers never ask because they just don't realise. They believe that 1ct D Flawless is all you need for the most attractive looking diamond. Notice the thread posted last night - by one of my fellow Brits - with the F-colour IF-clarity stones shortlisted. That's what it's like in the UK. I wish it was different.
I don't know of a single jeweller in the UK that provides images. We either have to trust the jeweller, or personally inspect the stone, or have it delivered for inspection. Most people would consider that if their stone came with GIA Ex cut grade, that there was nothing better.
 
And you are asking them to trust the grading report after seeing this example? If you are going to buy a stone unseen, buy one at least with images available, get it independently appraised or buy your own IS/ASET scope.
 
Date: 11/30/2009 6:45:06 AM
Author: Stone-cold11
And you are asking them to trust the grading report after seeing this example? If you are going to buy a stone unseen, buy one at least with images available, get it independently appraised or buy your own IS/ASET scope.
Click to expand...
If the proportions are GIA XXX and right in the heart of the super-ideal cut grade (34.5/40.8/56/61), I find it hard to believe that a cutter could do sufficient damage to spoil the appearance, except maybe the very occasional diamond that you would be able to return, if not happy.
I suspect that you''d be more likely to be unhappy about a diamond that hadn''t been set straight or poor finishing of the mounting, than being unhappy because you got one of the odd stones that slipped through a strict screening process.
The stone you showed, while very educational, would seem - to me - to be a rare exception. I''d love to see a defective GIA triple-ex 34.5/40.8/56/61.
Or would you say that the stone that you posted is a fair and accurate representation of the majority of "on paper" triple-excellent GIA or AGS ideal cuts?
 
Rare, but how rare? I have already show that a good proportioned stone, GIA 3 Ex with AGS0 grade can show leakage, not sure what area of science you are in, but in deterministic science that theory is now debunked. Are you willing to bet your money on just seeing the paper report? It is something the buyer will have to weigh for himself.
 
Date: 11/30/2009 7:23:32 AM
Author: Stone-cold11
Rare, but how rare? I have already show that a good proportioned stone, GIA 3 Ex with AGS0 grade can show leakage, not sure what area of science you are in, but in deterministic science that theory is now debunked. Are you willing to bet your money on just seeing the paper report? It is something the buyer will have to weigh for himself.
Click to expand...
Stone, I am glad that you showed that diamond as an example.
1.gif

It serves to caution us all that even ideal stones aren't always what you think. To me, it will ensure that I won't deviate from my strict shortlisting criteria (and retuns policy) if I'm dealing with a UK seller who is unable to provide images.

It's difficult to know what to suggest for UK buyers because they either have to try to find an obscure dealer that provides images (who may or may not be very reliable, may not be competitively priced and is unknown to the buyer), or buy from the USA (with the possible issues that might arise from overseas transactions).

The lack of images provided by UK sellers seems to offer a potential business opportunity........hmmm.....maybe I should consider it. If nothing else, it will persuade some other UK sellers to up their game.
 
Date: 11/30/2009 7:42:16 AM
Author: FB.

Date: 11/30/2009 7:23:32 AM
Author: Stone-cold11
Rare, but how rare? I have already show that a good proportioned stone, GIA 3 Ex with AGS0 grade can show leakage, not sure what area of science you are in, but in deterministic science that theory is now debunked. Are you willing to bet your money on just seeing the paper report? It is something the buyer will have to weigh for himself.
Click to expand...
Stone, I am glad that you showed that diamond as an example.
1.gif

It serves to caution us all that even ideal stones aren''t always what you think. To me, it will ensure that I won''t deviate from my strict shortlisting criteria (and retuns policy) if I''m dealing with a UK seller who is unable to provide images.
Click to expand...
If you''ve already reviewed this above, I don''t think your "shortlisting criteria" is all that...
 
Date: 11/30/2009 7:44:50 AM
Author: Regular Guy




Date: 11/30/2009 7:42:16 AM
Author: FB.





Date: 11/30/2009 7:23:32 AM
Author: Stone-cold11
Rare, but how rare? I have already show that a good proportioned stone, GIA 3 Ex with AGS0 grade can show leakage, not sure what area of science you are in, but in deterministic science that theory is now debunked. Are you willing to bet your money on just seeing the paper report? It is something the buyer will have to weigh for himself.
Click to expand...
Stone, I am glad that you showed that diamond as an example.
1.gif

It serves to caution us all that even ideal stones aren't always what you think. To me, it will ensure that I won't deviate from my strict shortlisting criteria (and retuns policy) if I'm dealing with a UK seller who is unable to provide images.
Click to expand...
If you've already reviewed this above, I don't think your 'shortlisting criteria' is all that...
Click to expand...
Not quite sure what you mean?
If you doubt my shortlisting criteria for dealing with a UK seller without images, here it is:

GIA triple Ex (AGS0 potential, HCA <2, AGA 1A)
34.5/40.8 (no tolerances allowed), with 56% table, 50-55 star, 75-80 LH, medium-sthk girdle and no greater than 61.8% depth.
A couple of % away from a 0.5/1.0 carat boundary.

I accept that an occasional bad stone is possible, but is extremely unlikely and I ensure a good return policy to fall back on. I'm probably more likely to buy a SI-clarity stone claimed to be eye clean that isn't, than to buy a stone that disappoints from my criteria.
 
Date: 11/30/2009 8:48:38 AM
Author: Regular Guy
I see this one's outside your tolerances...
Click to expand...
Frighteningly close, though (apart from not being GIA cert, which limits the amount of brillianteering, compared to AGS).
Isn't it easier to get cutters brillianteering tricks past AGS, but harder to get poor main proportions past them?

edit:
How did the cutter manage to get what appears to be leakage on one half of the stone, yet the H&A don't give much warning of it - unlike Stone's stone?
 
IS might be just due to tilt of the stone. Probably would do well to get the IS image retaken.
 
I''ve seen some AGS 0 diamonds with leaky IS images. They definitely exist.
 
Date: 11/30/2009 9:06:37 AM
Author: Laila619
I've seen some AGS 0 diamonds with leaky IS images. They definitely exist.
Click to expand...
Yes, I've seen a small number of not-so-good AGS stones.
But I exclude AGS stones from my criteria because firstly; they are not available in the UK and secondly; I am under the understanding that AGS are more tolerant of unconventional brillianteering.

But it would appear to be only a very small proportion - and probably no more risk than buying a stone that you've been told was eye clean, but upon inspection, you don't agree. Should we, therefore, demand some images of the inclusions, too?....or a calibrated re-check of the colour grade?
 
Date: 11/29/2009 6:12:05 PM
Author:FB.
It is normal for PS members to ask for images - IS/ASET/photo of all prospective purchases.

But when we''re dealing with stones that are GIA Ex cut, Ex polish and Ex symmetry, plus scoring below 2 on HCA, plus scoring 1A or 1B on AGA''s charts, plus falling within AGS-0 cut range......just how many of those stones with great ''on paper'' stats actually get rejected by PS members for poor light performance?
I can''t recall seeing any rejects within those criteria.

All I can recall is a couple of (maybe?) AGS 0 that may have been borderline steep/deep - but the possibility of an unusual light performance was already ''red flagged'' by the proportions being a little out of normal.

Therefore, is it such a big deal if images are not available, as long as the seller is known to be reliable and has a good returns policy? After all, the final proof of a good stone is when you get to examine it yourself.

If anyone can recall stones that scored well on HCA/GIA/AGA/AGS but had unexpectedly bad IS/ASET/other images, please share.

Thanks,
Click to expand...
What is the AGS-0 cut range? Is that their numerical evaluation as opposed to the performance based one?
 
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