Confused about AGS and/or AGA

[zhuzhu]

I found the grading chart for AGA on princess cut stone here http://www.gemappraisers.com/oldcutgraderules.asp. I also found several posting using AGS grading charts but can not locate that chart upon searching for it. Please help me understand the major differences between the two systems as well as the location of the AGS chart for princess cut. Thanks much

!!!

From the AGA chart, does this stone fit in class 2B?

Depth 76.5%
Table 80%
Girdle thick polished
Pavilion depth 40.1%
Pavilion angle 40.3
crown height 6.4%
crown angle 36

Much Thanks!

 

[JulieN]

I got AGA 2B, too. To find out what it would be under AGS, you''d have to submit it to someone who has PGS software (I think.)

 

[zhuzhu]

I am not sure what PGS software is. Would someone who has it please help? Thanks in advance!!!

 

[JulieN]

It would require direct assessment of the stone.

PGS, quoted from RockDoc https://www.pricescope.com/community/threads/risk-of-not-getting-a-brightest-diamond.45350/:

It does analyze and reports a numerical rating for the following
Brightness
Dispersion
Leakage
Contrast
Durability
Tilt
Weight Ratio
Girdle
Culet
Symmetry (examination in person required and entered in to the software)
Polish (examination in person required and entered in to the software)

It also issues a grade for

Light Performance Deduction
Proportion Deduction
Finish Deduction

and then Reports the AGS Cut Grading based on the NEW AGS system.
This would be very helpful for estimating the AGS cut grade for GIA graded stones, as well as reporting more indepth information about those with AGS reports. It does point to even the slightest variance within each grade.

 

[zhuzhu]

Thanks JulieN! I just saw your pic on the other forum, are you Indian? You and your bf look so adorable together! I used to date a graduate of IIT, Bambay, I simply LOVE the Indian culture and FOOD!!!!

 

[RockDoc]

PGS is the new AGS Proportion Grading Software.

I have the software that estimates what AGS would grade the stone if it were submitted to them.

To do this accurately it does require examining the symmetry and polish of the stone in person. It also requires a helium or sarin scan, not just the results.

The differences between the AGA / GIA and AGS is that the first two are proportion based in their result, the AGS PGS software considers proportions, but also calculates the light return using a very advanced ray tracing engine in its cut grade result.

Sarin reports, megascope reports that report an AGS grade is based on the proportion ONLY baisis of that grade, the AGS cut grade system is now different, so assuming a former AGS 0 cut grade, based on megascope or Sarin scans are not current now.

Rockdoc

 

[zhuzhu]

Thanks RocDoc, is there a idealscope scope software that can generate an estimated image of light return of this stone?

 

[JulieN]

Yes; you would need a Helium or Sarin scan and then import the data to generate an Ideal Scope estimate, but it''d be easier (and more accurate?) to get an Ideal Scope and check it out for yourself.

No, I''m not Indian, I just like to dress up once in a while. Thanks for the compliment.

 

[oldminer]

The old AGA Cut Class system for princess cut does not work well with the new style AGS 000 princess cut. However, we now utilize direct assessment of Light Behavior using ImaGem technology which does away with all parametric issues such as machine error, cloudiness and inclusions which might alter how light comes back from a particular diamond. We don''t work on theory based on measurements, but on actual pixel analysis of how each diamond works with light.

With just a short scan, we can give a result of how a princess cut does with light, just as one would put a diamond on a digital scale to know what it weighs. Right now, we have no way to provide consumers with a simplified system to know how the ImaGem results might turn out. You must have it placed on the device for its direct measure.