Is there a difference between AGS light performance grade and HCA ratings

[Milo]

Hi
Is there a difference between light performance as graded by AGS as 0 or "ideal" and HCA TIC range ratings for light performance? Are they similar ways of grading light performance? Is one means of grading light more favorable over the other? If I am buying a AGS0 ideal with ideal "light performance", should I be statisfied that it will have TIC range light performance sight unseen? The diamond in question has an HCA rating is 0.4... I have read that low values can create dark spots in "certain circumstances". Would this diamond''s AGS ideal light performance grading ensure that this diamond this diamond would not be one of these "certain cercumstances" and should I have the confidence to buy online sight unseen with this information. I am waiting for idealscope image to post but I just needed an understanding of whether the HCA and AGS light performance are one in the same or if one is more desired over the other?

Thanks for your help- I''m a newbie and a little lost.

 

[stone-cold11]

HCA uses four variables to compute a score, AGS0 uses all the proportion of the stone to compute their cut grade. Idealscope will tell more.

What are the numbers you used for the HCA score?

EDT:
Ok, saw your other thread, should be fine, but Idealscope image will tell more.

 

[Allison D.]

Milo, there is a difference in that the HCA doens't grade, and it doesn't evlauate the actual diamond.

It's merely a screening tool; it predicts which diamonds are more likely to perform well and which are less likely based on a few key measurements. It helps you narrow down to the candidates that are most likely to perform strongly.

AGS' light performance grade is based on evaluating the actual stone in question.

If you're buying sight unseen, the AGS0 grade with light performance should give you reasonable assurance that the diamond performs well. From there, it's just a question of whether it's 'personality' appeals to you.

 

[Lorelei]

Date: 3/16/2010 2:32:19 PM
Author: Allison D.

Milo, there is a difference in that the HCA doens''t grade, and it doesn''t evlauate the actual diamond.

It''s merely a screening tool; it predicts which diamonds are more likely to perform well and which are less likely based on a few key measurements. It helps you narrow down to the candidates that are most likely to perform strongly.

AGS'' light performance grade is based on evaluating the actual stone in question.

If you''re buying sight unseen, the AGS0 grade with light performance should give you reasonable assurance that the diamond performs well. From there, it''s just a question of whether it''s ''personality'' appeals to you.

Ditto Alj.

 

[Milo]

Thanks a million.

 

[Paul-Antwerp]

I am not sure if I fully agree with Allison''s assessment.

The HCA for sure is a relatively blunt screening-tool, and it is often repeated that it should be used as a rejection-tool, not for selection.

Where the AGS grade defniitely uses more data to arrive at a grade, I still see it as a rejection-tool for two major reasons.

1. The minimum-level of the grade decides on a pass or not. Within that grade, one still has various levels of cut-quality for which there is no extra information.
2. The actual AGS-grade, like for most assessment-tools, is primarily based on the potential brightness of the diamond. Potential fire is a minor factor in the AGS-grade, while scintillation is not in the grade-assessment. In comparison with other screening-tools, this is not bad, they generally are based on less, but we need to understand that the AGS-grade is not (yet?) based on a full assessment of the stone''s cut-quality.

Therefore, my conclusion is that the AGS-grade is a rejection-tool, just like HCA, but with far more attention to detail and the actual stone.

Live long,