Girdle Thickness Affect on GIA Cut Grade

[Crash22]

Hello all,

I am looking at purchasing a round diamond that is GIA certified as a very good cut. I am wondering if the only reason it received a very good cut instead of an excellent cut grade is because the girdle thickness is listed as very thin to medium. The proportions seem to be the same as many excellent cut grade stones and are as follows:

Symmetry - excellent
polish - excellent
Table - 55%
Depth - 62.1%
Crown angle - 35.5
Crown height - 16
pavilion depth - 43.5
pavilion angle - 41
Star length - 55%
Lower half length - 80%

The choice I have is purchasing a diamond that is certified by the GIA as an excellent cut and SI2 clarity (that is eye clean) or this diamond that is also certified by the GIA as a very good cut and VS1 clarity. They are the same size and color, but the VS1 is a little more expensive. Thanks

 

[stone-cold11]

Yap, V-thin will result in a downgrade.

Post the GIA report number and the carat weight on the report.

 

[Crash22]

Thanks. Is having a very thin to medium girdle a big deal at all? Will it have any affect on the brilliance, fire, etc?

GIA report 2131836386, 0.84 carat.

 

[stone-cold11]

V thin girdle and lower is considered a chipping risk so the downgrade.

Anyway, the proportions, although will get Ex cut grade on GIA, will probably have some light leakage issue under the table, will not be the brightest in PSers' eyes.

Use the Cut Adviser to weed out not so good performer if you cannot see it yourself.
https://www.pricescope.com/tools/hca

 

[Crash22]

Thank you very much for your help. The cut adviser is cool. The VS1 stone in question came back with a 3.8 score while the eye clean SI2 came back with a score of 0.9 and excellent across the board. Guess that answers that.

 

[CedarRapids]

Another screening tool you can use:

https://www.pricescope.com/tools/AGA_NAJA_Cut_Class_Grader

Specs:

* Length:6.04
* Width:6.07
* Depth:3.76
* Total Depth:62.1%
* Table percent:55
* Crown height:16
* Girdle (from):Very thin
* Girdle (to):Medium
* Polish:Excellent / Very Good
* Symmetry:Excellent / Very Good
* Crown angle:35.5
* Pavilion depth:43.5

Results:

* Tab Percent: 1A
* Crown Angle: 2A
* Crown Height: 1A
* Pavilion Depth: 1B
* Girdle: 1B
* Depth: 1A
* Polish: 1A
* Symmetry: 1A
* TotalGrade: 1B

 

[Unknown]

Hi, similar question here, For one diamond with VG cut, <1 HCA score, another EX cut, >2 HCA score, which one could be better ?

 

[stone-cold11]

Case by case. Depends on what makes the stone a GIA VG in cut grade.

Post the report up.