Question about AGS 0 stone

[Xtreemski1]

Hi I have purchased a stone that I absolutly love, but I have a question about it. I have the AGS document for it and it is graded as an AGS 000, but when I plug the numbers into the HCA cut advisor it falls well outside the AGS outline. I was wondering why this is. I know that the HCA is a very good tool for helping narrow down stones, but what measurments are making this stone fall where it does on the plot yet recieve the grade it did. Thnaks for any insite on this that you can provide.

Measurments:
Table % 54.7
Depth %61.2
Crown 34.2 or 15.4%
PAV 40.6 or 42.8%

 

[belle]

is this a new ags000 with a grade for light performance?

 

[Xtreemski1]

Yes I think it is. The date on the cert is FEB. 07, 2006, and it says Diamond Quality Document and Performanced Based in the upper right hand corner.

Some more measurments
Cut grade AGS Ideal 0.
Light Performance 0
Proportion Factors 0
Finish 0
Polish Ideal
Symmetry Ideal

 

[belle]

it is a new report if it has the grade for light performance. fortunately, ags evaluates each stone based on it''s own merits and even though the numbers may fall ''on the edge'' they will evaluate the diamond and assess it based on performance. hca narrows down and identifies potential ideal candidates based on numbers alone. hca is a fantastic tool but it can only be used as a preliminary assessment. anytime you make assumptions based on numbers alone versus live comparison, their is potential for conflict.

enjoy your diamond!

 

[Regular Guy]

Maybe try again? It''s outside by my run on angles (best to use these), but only just. Variability in the many details of how the actual stone is ray traced is generally accountable for this sort of thing...such that the "real" score is definitely regarded as the more "true" than the guideline mapped in the HCA chart...

 

[Xtreemski1]

Try again at what? Here is a cropped copy of the document.
Thanks!

 

[Regular Guy]

Date: 5/4/2007 9:31:39 AM
Author:Xtreemski1
when I plug the numbers into the HCA cut advisor it falls well outside the AGS outline....

...for me, it''s pretty close...

 

[Xtreemski1]

Ahh thanks for the clarification I thought you were suggesting getting another stone. It came out the same, I guess I just thought that since nome of the X was even touching the outline of the AGS box that it was pretty far out side the range. It does however fall in the other box, whis is the GIA EX box correct?

 

[JohnQuixote]

It does.

Remember the HCA is a prediction. The grading report is reality. When the diamond was actually scanned & measured for light performance at AGS it wound up being a 0.

Date: 5/4/2007 10:21:23 AM
Author: belle

it is a new report if it has the grade for light performance. fortunately, ags evaluates each stone based on it's own merits and even though the numbers may fall 'on the edge' they will evaluate the diamond and assess it based on performance. hca narrows down and identifies potential ideal candidates based on numbers alone. hca is a fantastic tool but it can only be used as a preliminary assessment. anytime you make assumptions based on numbers alone versus live comparison, their is potential for conflict.

enjoy your diamond!

In the cutting guidelines for manufacturers AGS predicts that those measurements will be on the borderline of 0-1. The HCA accurately reflected this, staying on the conservative side.

 

[Regular Guy]

Date: 5/4/2007 11:12:35 AM
Author: JohnQuixote
It does.

Remember the HCA is a prediction.

Well, in fairness, AGS certification for 0 is only relatively less predictive...

 

[strmrdr]

Read the .pdf document linked in this thread...
https://www.pricescope.com/community/threads/peter-yantzer-et-al-why-a-two-dimensional-cut-grading-system-is-pass%C3%A9.61708/

It will help explain why no chart can be accurate to the AGS grade.

 

[Regular Guy]

The article nicely describes why only holding stable a small set of characteristics, to include crown & pavilion angles, table & culet, will provide variability in predicted performance.

What is less completely clear to me is the variability in performance that is possible, given all theoretical proportion attributes remaining the same.

Perhaps in other words...I can believe that all we can do is provide the shape...(thus yielding the profession of diamond cutting) and in doing so, we do a lot. But, for shoppers of performance, to what extent is that the end of the story? Pretty high, I''m guessing. How substantive or trivial is it to guess?