GIA ex/ ex/ ex

[ucbryan]

For any stone getting a GIA ex/ex/ex & HCA score under 2. Does anyone have a rough estimate how much difference in light performance you can truly detect in the naked eye?

 

[MissGotRocks]

A GIA ex/ex/ex stone scoring under a 2 on HCA is promising. We would need the specs on the stone to give you a better analysis - preferably along with an IS image.

The rest of your question is a bit vague - explaining light leakage that the eye would or would not see is impossible. Showing light leakage from an IS image would be possible and is probably the question you are trying to ask.

Do you have an image or can the vendor provide you with one?

 

[ucbryan]

no its just a question about how the grades from GIA/AGS , translates into light performance. Im wondering more about the general concept of whether you are probably safe buying any stone w/ GIA triple ex in terms of its light performance. I understand that there will be varying light performance within these ranges, but would you get a bad stone if the grades were all this high?

 

[MissGotRocks]

You cannot assume that all GIA excellent stones will be top performers. Stones must be evaluated on a case by case basis as GIA rounds numbers.

Do you have a particular stone in mind that you are trying to evaluate?

 

[MikeRato1]

http://www.goodoldgold.com/4Cs/NewCutGrading/GIAExAGSIdeal/

informative article if this is what you are asking about...

 

[Lorelei]

Date: 2/16/2009 10:27:58 PM
Author: MissGotRocks
You cannot assume that all GIA excellent stones will be top performers. Stones must be evaluated on a case by case basis as GIA rounds numbers.

Do you have a particular stone in mind that you are trying to evaluate?

Ditto