American Ideal chart questions

[MrsT]

I need help understanding the AGA Cut Grading System/American Ideal Chart for round brilliant cuts.

I have found some stones I'm considering and I'm puzzled about the measurements and where they fall in the American Ideal Chart.

Am I approaching this in the right way?
I check the measurements and see where they fall in the chart.
I have found stones that fall in the 1A,1B and even 2A column.
How do you determine then what this stone actually is when the measurements are in three different classes parameters?

How does a stone get an AGS0 cut grade when the crown angle is in the 2A class?
How does this same stone score VH,VH,VH on a brilliance report when all the measurements do not fall into the 1A paramaters?

Here is an example:
Table% 53.1 (1a)
Depth% 62.3 (1a)
CrownAng 33.1 (1b)
PavDepth% 43.7 (2a) (pav.angle 41.0
Plo.Sym: x/x (1a)
Girdle (1a)

This stone scores 1.0 HCA.

Hope someone can help.
Mrs T

 

[Garry H (Cut Nut)]

What is an American Ideal Chart?

 

[Regular Guy]

Garry, Dave''s AGA cut charts also refer to the American ideal...

 

[denverappraiser]

AGS does not use that chart as part of their procedure for determining their cut grades. If you''re interested in the AGS grading on a stone, get it graded by AGS.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[dimonbob]

How does a stone get an AGS0 cut grade when the crown angle is in the 2A class?
How does this same stone score VH,VH,VH on a brilliance report when all the measurements do not fall into the 1A paramaters?
Here is an example:
Table% 53.1 (1a)
Depth% 62.3 (1a)
CrownAng 33.1 (1b)
PavDepth% 43.7 (2a) (pav.angle 41.0
Plo.Sym: x/x (1a)
Girdle (1a)
This stone scores 1.0 HCA.




Using the above numbers the diamond would not be an AGS Ideal nor an AGS 0. According to AGS the grade of the diamond is the lowest of the numbers 2a which is a couple of grades lower than an AGS 0. A diamond with a Sarin report that says it is an AGS 0 means that it has the proportions of an AGS Ideal but it is still not an AGS Ideal unless it has an AGS certificate that says it is Ideal. There is more to being an AGS Ideal than having the right proportion numbers. It may be beautiful and it may have a HCA of 1 but it is still not AGS Ideal. Being a GIA EX EX with the AGS 0 proportion grade still does not make it an AGS Ideal.

GIA does not get it when it comes to grading the Ideal cut. AGS has now gone past the proportion grading system. All of those proportions still count but the final grade has to do with performance grading. So AGS has taken a step above where they once were and where GIA still playing catch up when it comes to cut grade.

This is not to say that the GIA certiified diamond is less beautiful than the AGS Ideal. Beauty is a different subject.

Both the Ford and the BMW will get you to your destination and at speeds over the speed limit dnd for the same MPG but which would you buy given a choice?

 

[MrsT]

Thanks for the replies.

If a stone I''m looking at has an AGS0 cert., and one or two of the measurements on the Sarin does not fit the "Ideal" parameters, then how is this stone graded as an AGS0?

Mrs T

 

[denverappraiser]

Date: 9/4/2006 5:12:03 PM
Author: dimonbob

A diamond with a Sarin report that says it is an AGS 0 means that it has the proportions of an AGS Ideal

Bob,

Not even that any more. The algorithm used by Sarin to decide if a stone has AGS0 proprotions is based on the pre-2005 parameters used by AGS as a part of their cut grading system. It was never the complete story but AGS no longer uses it at all. The scale used on Sarin reports that they call AGS is not the same scale as the one used by the American Gem Society Laboratory. As you point out, the way to get an AGS Ideal is to buy a stone graded by AGS.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[JulieN]

old system vs new.