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Performance Difference between GIA Ideal and AGS0

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CaratMan

Rough_Rock
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Mar 10, 2009
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I am shopping for RB stones in the 0.9-1.0 carat range and I was wondering if someone could explain to me (or show me) the differences between a GIA Ideal Cut with EX polish and symmetry and an AGS 0 stone with ID polish and symmetry? I have looked at some WF ACA stones as well as a GIA Ideal EX/EX at a local B&M. The B&M ran the GIA stone through their Sarin machine and came back at AGS 0 quality. I know that AGS 0 is the more coveted grade, but I am interested in paying for qualities that I can actually see.
 

oldmancoyote

Brilliant_Rock
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Aug 22, 2008
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GIA will not grade cut as "Ideal". Their top grade is "Excellent". That aside, since both AGS 0 (Ideal) cut grade and GIA Excellent can be given to a range of stones, it''s impossible to give a precise answer to your question, especially since the two ranges overlap quite a bit (to be precise, most AGS 0 stones are likely to be GIA Excellent; not the reverse).

Since AGS 0 is a stricter grading criterion than GIA Excellent, some dealers will send to GIA stones that are less likely to get an AGS 0, but not everybody does that for umpteen reasons.

As to whether you can tell the difference - you probably would on some stones, but not on others. There is no simple way to tell which grade will come on top, except to use your eyes on a case by case basis. Buy the stone, not the paper.
 

Lorelei

Super_Ideal_Rock
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Date: 3/23/2009 4:59:45 PM
Author: oldmancoyote
GIA will not grade cut as ''Ideal''. Their top grade is ''Excellent''. That aside, since both AGS 0 (Ideal) cut grade and GIA Excellent can be given to a range of stones, it''s impossible to give a precise answer to your question, especially since the two ranges overlap quite a bit (to be precise, most AGS 0 stones are likely to be GIA Excellent; not the reverse).

Since AGS 0 is a stricter grading criterion than GIA Excellent, some dealers will send to GIA stones that are less likely to get an AGS 0, but not everybody does that for umpteen reasons.

As to whether you can tell the difference - you probably would on some stones, but not on others. There is no simple way to tell which grade will come on top, except to use your eyes on a case by case basis. Buy the stone, not the paper.
Ditto all of the above. Also GIA round the numbers, AGS are considered to be more accurate. Also there isn''t a way to determine the individual characteristics of each as it is best to compare each on a case by case basis. If shopping online then the best way to do that is with ASET and Idealscope images.
 

elle_chris

Ideal_Rock
Joined
Feb 19, 2004
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3,153
Date: 3/23/2009 4:30:24 PM
Author:CaratMan
I am shopping for RB stones in the 0.9-1.0 carat range and I was wondering if someone could explain to me (or show me) the differences between a GIA Ideal Cut with EX polish and symmetry and an AGS 0 stone with ID polish and symmetry? I have looked at some WF ACA stones as well as a GIA Ideal EX/EX at a local B&M. The B&M ran the GIA stone through their Sarin machine and came back at AGS 0 quality. I know that AGS 0 is the more coveted grade, but I am interested in paying for qualities that I can actually see.
The Sarin machine doesn''t grade light performance as far as I know, so I would never say a GIA excellent is also an AGS0 unless AGS says so. What your jeweler said is that the numbers fall into the AGS0 category but again, it is NOT an AGS0.

As far paying for quality you can''t see, you would really need to see the two side by side to compare. You may see some differences, or you may not. Did you like the stone the jeweler showed you? Were you able to take it outside and view it in natural light?

Also, to get an idea of what an H&A stone looks like, you might try locating a Hearts on Fire dealer in your area and taking a look.

It''s pretty much impossible to say which is better and what you''re going to see or not without being able to compare. What I will say is, I have WF''s H&A''s and they''re gorgeous. I also have a GIA excellent that''s gorgeous as well. If comparing them side by side, I can''t see a difference. BUT prior to purchasing the GIA one, I had an appraiser check it out with me to make sure it was a quality stone.

All of this is said assuming the stone your jeweler showed you had great numbers. You might aslo try asking for an Idealscope or ASET image. I''m thinking if he has a sarin, he might have the other tools.
 

CaratMan

Rough_Rock
Joined
Mar 10, 2009
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29
Thank you for the helpful feedback everyone! The Sarin machine that this particular B&M had additional Cut Grade Analyzing software which measured the Fire, Brilliance, and Scintillation of each diamond on a standard 100 point scale (for each). All 3 scores came in from 78-81. They also had a H&A viewer (the VS1 H color RB that I was looking at had excellent Hearts and Arrows).
 
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