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2 cut grading questions

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perfectionist

Rough_Rock
Joined
Apr 19, 2002
Messages
4
Hello,

I have two questions regarding cut grading. I'd appreciate any help you could give me.

1. I've read many places the the GIA does *not* grade cut. However, I just got "How to Buy a Diamond" by Fred Cuellar which states the GIA rates cuts in 4 classes, similar to AGS, based on dimensions meeting tolerances. Can someone tell me the most current status of the GIA cut-grading situation?

2. I'm interested in using the HCA, but it doesn't account for girdle thickness or culet size. Something I read suggested it would work better if it did. Does anyone have an opinion as to whether this really matters? Does anyone know the average girdle size used in the data collection for the system (that way I can look for stones with similar girdles)?

Thanks for any help on one or both questions!

Bill
 

pricescope

Ideal_Rock
Joined
Dec 31, 1999
Messages
8,266
Hi Perfectionist :)

Re: 1.
I believe those are very old grades. GIA abandoned class grading after their research had shown many combinations of crown and pavilion angles can produce great results. Currently GIA is working on a new cut grading system.

Re: 2.
You can enter culet into online HCA. It is very important to know culet if you are using pavilion depth % instead of angle. If you know pavilion angle culet is less important unless it is large and look like an inclusion or window in the center of a diamond.

We have stand alone version of HCA that rates girdle as well. Basicaly, it penalizes very thin or thick girdle because of chipping risk (very thin) or extra weight (very thick). Otherwise, girdle thickness is not so crucial.
 
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