Checking CUT grades on older GIA reports.....Interesting

[Garry H (Cut Nut)]

First find the certificate # and Carat weight from any site that lists diamonds with report info

Enter the data here http://reportcheck.gia.edu/ and click retrieve

You will see a page that lists the new cut report data. (Rarely there will be no info - just a note to say something like "this stone must be sent back to the lab")

I looked up a few stones on GOG and then ran the data thru http://facetware.gia.edu/
In a few cases I got conflicting grades - the lab seems generally a bit tougher than Facetware - this could be a curse for manufacturers?

Some examples

http://www.goodoldgold.com/1_23ct_e_vs2.htm report 14780212 1.23ct C35.5 P41.2 T59% DEpth 62.2
VG by lab Ex by Facetware

http://www.goodoldgold.com/1_35ct_h_si1.htm Report 14276146 1.35ct C 34.5 P41.4 T55% Depth 62.6% Medium Girdle
This gets VG on both Facetware and the new Lab report - but if you drop the depth % by 0.1% it gets Excellent. So a diamond with a GIA medium girdle can have too poor a spread?

I invite other to play and post their results here

 

[strmrdr]

gia new cert:
http://www.goodoldgold.com/1_24ct_h_vs1_h%26a1.htm

 

[valeria101]

wrong post...

 

[Paul-Antwerp]

Indeed, very interesting, Garry.

 

[Serg]

re:http://www.goodoldgold.com/1_23ct_e_vs2.htm report 14780212 1.23ct C35.5 P41.2 T59% DEpth 62.2
VG by lab Ex by Facetware

Garry< What girdle did you use In Facetware?

try 5%

 

[Garry H (Cut Nut)]

Date: 1/22/2006 3:41:17 PM
Author: Serg
re:http://www.goodoldgold.com/1_23ct_e_vs2.htm report 14780212 1.23ct C35.5 P41.2 T59% DEpth 62.2
VG by lab Ex by Facetware

Garry< What girdle did you use In Facetware? medium and entered 62.2% which calculated 4% - but when I raise the stones depth % to 62.5% the girdle thickness goes to 4.5% and the stone drops down to VG. The next drop comes at 63.9% which is girdle 5.5%

try 5% Why?

 

[Serg]

Date: 1/22/2006 6:06:39 PM
Author: Garry H (Cut Nut)

Date: 1/22/2006 3:41:17 PM
Author: Serg
re:http://www.goodoldgold.com/1_23ct_e_vs2.htm report 14780212 1.23ct C35.5 P41.2 T59% DEpth 62.2
VG by lab Ex by Facetware

Garry< What girdle did you use In Facetware? medium and entered 62.2% which calculated 4% - but when I raise the stones depth % to 62.5% the girdle thickness goes to 4.5% and the stone drops down to VG. The next drop comes at 63.9% which is girdle 5.5%

try 5% Why?

61.9-14.3-42.8=4.8

 

[Garry H (Cut Nut)]

Date: 1/23/2006 3:02:59 AM
Author: Serg

Date: 1/22/2006 6:06:39 PM
Author: Garry H (Cut Nut)

Date: 1/22/2006 3:41:17 PM
Author: Serg
re:http://www.goodoldgold.com/1_23ct_e_vs2.htm report 14780212 1.23ct C35.5 P41.2 T59% DEpth 62.2
VG by lab Ex by Facetware

Garry< What girdle did you use In Facetware? medium and entered 62.2% which calculated 4% - but when I raise the stones depth % to 62.5% the girdle thickness goes to 4.5% and the stone drops down to VG. The next drop comes at 63.9% which is girdle 5.5%

try 5% Why?

61.9-14.3-42.8=4.8

1. GOG Ogi scanner is always 0.2 degree too shallow on pavilion.
2. If you use #''s from GIA report and dimensions and make weight correct - you get 3.6% girdle.

 

[Serg]

re:2. If you use #''s from GIA report and dimensions and make weight correct - you get 3.6% girdle.

It is incorrect operation for nonstandard girdle.

 

[oldminer]

Since 1986 I published parameters for use as screening tools for finding the general quality of the cut for various shaped diamonds. People from all around the world quietly adopted these parameters, but most were smart enough to take into account their inherent limitations. We''ve made tens of thousands of AGA-CERTs with these grades without ever having a problem with a consumer or a dealer.

Now the GIA is supporting their notion that you can purely determine the quality of cut by making more measurements. However, in rounding off measurements and additionally taking into account the degree of machine error, they now want to suggest their "grade" has the substance to make it more than a screening tool. Somehow, I doubt the validity of the end result will be more than "a useful screening tool".

Before you know it, people will be saying something like, "Well the grade is a very good one, but you must examine the stone with your own eyes, to be sure it is a great stone." If this happens, then we''ll all know that their system has problems and is misused except for screening. It seems as if the cutters and researchers here already think there are problems.

Maybe the GIA ought to look again at their methodolgy and perfect things before they make a larger problem for themselves and the trade, too. This may delay their grading program for a few months or a year, but we''ve waited so long, it ought to be "the best" when its finally offered. Then again, we do have alternatives, but I think everyone was hoping for a meticulous and useful job to be done by GIA.

 

[sylvesterii]

perhaps I am doing something wrong, or perhaps the diamond report is too old (2002), but I don''t get any more info than what was included on the original GIA diamond report...

 

[Rod]

I had the same issue, except my stone was graded by the GIA in September of 2005. I wonder why it would not provide the updated information for a stone so recently graded??

 

[Serg]

re:the lab seems generally a bit tougher than Facetware

See http://www.diamondcut.gia.edu/06_estimating_a_cut_grade.html

Factors Affecting Results

The GIA Facetware™ Cut Estimator is intended to provide an estimation of the cut grade that would be received from the GIA Laboratory for the same diamond. However, there are several reasons why the grade provided by GIA Facetware™ may be different from that received from the GIA Laboratory. Some of the reasons are:

The diamond''s actual proportions (such as the crown angle or star length) or visually assessed parameters (such as the girdle thickness or symmetry) as determined by the GIA Laboratory are different from the proportions or parameters assumed by the user.

The diamond has been manufactured using non-standard brillianteering such that it is significantly "painted" or "dug-out" (i.e., the diamond has its upper- and/or lower-half facets fashioned at tilt angles different from those traditionally used for standard round brilliant diamonds). Click here to learn more.

The accuracy and tolerances of different methodologies and optical devices used to measure a diamond''s proportions or parameters may differ from those used by GIA. Click here to learn more.
To learn about other important limitations of the software or limitations on use of the software for business purposes, please familiarize yourself with the Assumptions and Terms of Use, available through the software interface.