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»  » Diamond Prices and Grading »
 » RockyTalky
»  » Misrepresentation of AGA Cut Chart
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Misrepresentation of AGA Cut Chart |
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| P: 8/24/2004 3:30:36 AM | |
kevinng Cut Rock Total Posts: 398 Last Post: 3/1/2008 Member Since: 6/10/2004 |
I have just come across this at Original Diamonds: AGA Cut Chart? The 1a grade for BR diamonds is narrower that the one at David's site. Plus, they have this H&A Ideal Cut (wonder who came up with that). I seriously doubt that David would come up with a H&A Ideal Cut chart. Maybe David should have a word with them?
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| Posted: 8/24/2004 3:30:36 AM | |
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There are 15 replies to this message. There are 15 replies on this page. |
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| P: 8/24/2004 7:52:03 AM | |
oldminer Ideal Rock Total Posts: 4,966 Last Post: 11/24/2009 Member Since: 9/4/2000 |
Here is what was sent to the website today: xxxxxxxxxxxxxxxxxxxxxxxxxxx I see you have the AGA Cut Charts on your site. It is wonderful to see this exposure. Since your site was last updated there are several changes in these charts. Please visit the www.gemappraisers.com site and feel free to copy the charts to make the changes. I have eliminated the weight break on rounds, changed the crown height on princess, changed girdle ranges, etc.... There are several changes, mostly minor, but of importance. THANK YOU for seeing to it that your clients are well served. Dave Atlas xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx We will see how it goes. Thanks for the advisory. I hope they make an update. David S. Atlas |
| Posted: 8/24/2004 7:52:03 AM | |
| P: 8/24/2004 11:00:33 AM | |
Sasori Cut Rock Total Posts: 100 Last Post: 10/24/2007 Member Since: 7/21/2004 |
Hi David, I'm confused, 1) I'm not able to find the cut chart on your website, so is there a H&A cut? 2) you mentioned that the charts at Originals was not updated. So its not a mispresentation of AGA cut chart but rather not updated only? ie an ideal base on old chart is no longer an ideal now. Or as Kevinng's title, the charts were misrepresented, and thus makes them eroneous to use? ie a diamond i bought last time which falls under Originals' ideal was never an ideal?? But I noted that it was mentioned that the 1a grade is narrower. Does it mean that the "old" chart is "stricter" while the updates allow for more leeway in judgement? *confuse confused*
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| Posted: 8/24/2004 11:00:33 AM | |
| P: 8/24/2004 12:40:16 PM | |
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oldminer Ideal Rock Total Posts: 4,966 Last Post: 11/24/2009 Member Since: 9/4/2000 |
Sasori;
NO ONE could say you are not confused. The AGA charts are readily found on the gemappraisers.com website. Use the left side of the screen and select accordingly. You can have DIY, do it yourself, grading or you can view the charts and rules. The website referred to that is using my chart has renamed the 1A stones, but parameters are just that, numbers.
Take a look at the current version before you get disturbed about any changes. A great diamond is great , no matter what the numbers, to a large extent.
David S. Atlas |
| Posted: 8/24/2004 12:40:16 PM | |
| P: 8/25/2004 1:23:32 AM | |
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Sasori Cut Rock Total Posts: 100 Last Post: 10/24/2007 Member Since: 7/21/2004 |
Thanks David, Found the chart, was hunting high and low, didnt realise I just need to click on the DIY the chart will appear. Great! stone is still an 1a. I realise there is no H&A cut under AGA cut chart. So there was never a H&A cut specification? And thus falling into the specification under Originals H&A does not guarantee a H&A? Thanks for taking the time to answer my queries. 
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| Posted: 8/25/2004 1:23:32 AM | |
| P: 8/25/2004 7:47:53 AM | |
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kevinng Cut Rock Total Posts: 398 Last Post: 3/1/2008 Member Since: 6/10/2004 |
Yes, H&A is a test of super symmetry. It does not gaurantee good proportions not light return. |
| Posted: 8/25/2004 7:47:53 AM | |
| P: 8/25/2004 8:46:24 AM | |
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oldminer Ideal Rock Total Posts: 4,966 Last Post: 11/24/2009 Member Since: 9/4/2000 |
If anyone has an example of a low light performance H&A cut round diamond, I sure would love to see it. I know that parameters alone do not dictate totally the light behavior, but to think that there is no relationship between well cut and H&A is nonsense also. There is a distinct correlation between excellent craftmanship and very good to superb light performance. There is also a very distinct relationship between poorly crafted and miserable light perfomance.
Part of the reason that parameters do not totally answer the need is the inherent inaccuracy and relative simplicity of the Sarin and Ogi devices. They do not measure perfectly and they do not begin to measure all the pertinent features of a diamond. For those reasons, predictions based on what is measured just don't go all the way to a full answer.
David S. Atlas |
| Posted: 8/25/2004 8:46:24 AM | |
| P: 8/25/2004 9:34:04 AM | |
Garry H (Cut Nut) Ideal Rock Total Posts: 11,587 Last Post: 11/25/2009 Member Since: 8/16/2000 |
Brad and Jan will like this one  Great HCA, great H&A's, AGS 0, laser inscribed H&A AGSL xxxxxx. Pretty good BS. But the Ideal-scope can not be fooled  Garry Holloway FGAA DipDT |
| Posted: 8/25/2004 9:34:04 AM | |
| P: 8/25/2004 9:40:31 AM | |
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kevinng Cut Rock Total Posts: 398 Last Post: 3/1/2008 Member Since: 6/10/2004 |
I have not seen very poor light performances in H&A diamonds. However, I have seen some that do not appear to be superior. H&A diamonds are sold with a premium and as a consumer, I would expect the light return to be high. This one I spotted in GOG's education stone: Mediocre H&A |
| Posted: 8/25/2004 9:40:31 AM | |
| P: 8/25/2004 10:12:16 AM | |
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oldminer Ideal Rock Total Posts: 4,966 Last Post: 11/24/2009 Member Since: 9/4/2000 |
I have always stated that I thought H&A was a fortunate accident and had little to do with performance or quality. This continues to be my opinion. If someone wants to spend money on an appearance that can't even been examined after the diamond is set in the ring, more pwoer to them, but it would not be my way of selecting a diamond. n If someone wants to spend a premium amliunt for the H&A effect, no problem, but it is marketing and not science at work.
H&A images have many levels of correctness. Not all H&A looks are the same and not every one is equal to every other one. I was given a long lesson by Mr. Gavin of Whtieflash on this subject. He can grade the quality of H&A appearances and infer from them the cut / symmetry of the diamond. So to him there is some added meaning, but he is a master of this and I am more an observer of it. (H&A).
I think this thread gives due warning to consumers that H&A has some meaning, but possibly not as much as one might think from listening to all the hype. You just can't believe everything that is said in advertising, can you?
David S. Atlas |
| Posted: 8/25/2004 10:12:16 AM | |
| P: 8/25/2004 4:16:42 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,587 Last Post: 11/25/2009 Member Since: 8/16/2000 |
---------------- You had posted a link to another stone Kev? One that was worse than 'mediocre'. Why did you take it down? Garry Holloway FGAA DipDT |
| Posted: 8/25/2004 4:16:42 PM | |
| P: 8/25/2004 5:18:45 PM | |
Rank Amateur Ideal Rock Total Posts: 1,547 Last Post: 5/5/2009 Member Since: 2/26/2003 |
The other one he posted had a bit better BS report but still had the ring of death. The only difference is that it didn't appear to be one of the educational stones.
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| Posted: 8/25/2004 5:18:45 PM | |
| P: 8/25/2004 5:20:20 PM | |
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Garry H (Cut Nut) Ideal Rock Total Posts: 11,587 Last Post: 11/25/2009 Member Since: 8/16/2000 |
Meaning?
Garry Holloway FGAA DipDT |
| Posted: 8/25/2004 5:20:20 PM | |
| P: 8/26/2004 7:25:44 AM | |
mdx Ideal Rock Total Posts: 570 Last Post: 11/29/2007 Member Since: 3/1/2002 |
Here is a simple demo we use in discussion with clients re Hearts and Arrows Hopefully it can be of some help For practical purposes when we grade loose diamonds we identify two types of H&A, One is where the diamond is cut within a range of angles and dimensions that displays a H&A pattern. We would suggest a grade of “displays Hearts and Arrows” This is a diamond that is within the range of dimensions but was not specifically cut as a Hearts & Arrows. The second is a diamond that was specifically cut to emphasis the hearts and arrows pattern. Usually identified by smaller lower girdle facets. This we would grade “Hearts and Arrows” The two images below represent two diamonds with exactly the same weight and basic dimensions you would enter into the HCA. For ref. Weight. 1.00 ct Diameter. 6.50mm Total Depth: 60.4% Crown Height: 14.8 Crown Angle: 34.5 Table Diameter: 57% Pavilion. Depth: 42.9 Pavilion Angle: 40.65 The diamonds on the left has lower girdle facets of 82% and the diamond on the right 74% Notice the difference, but both have the same dimensions save for the lower girdle facets Johan  Diamond Exchange Ltd. (Australia) |
| Posted: 8/26/2004 7:25:44 AM | |
| P: 8/26/2004 7:59:47 AM | |
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kevinng Cut Rock Total Posts: 398 Last Post: 3/1/2008 Member Since: 6/10/2004 |
---------------- Meaning... I was trying to be nice when I took it out.  |
| Posted: 8/26/2004 7:59:47 AM | |
| P: 8/27/2004 7:18:51 AM | |
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kevinng Cut Rock Total Posts: 398 Last Post: 3/1/2008 Member Since: 6/10/2004 |
OK... I am putting another educational stone back. This one is better: Mediocre H&A |
| Posted: 8/27/2004 7:18:51 AM | |
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