is gia cut grade purely quantitative?

[tellmemore]

hi all,
i''m considering a stone for which i have little information (so far) since the seller does not have the original cert on hand -- i have seen a copy though, provided by the original vendor of purchase, but it was too faint to see the inclusion map -- but will be receiving a reissued cert soon. the only #s i have are as follows:

table: 57%
depth: 60.8%
crown angle: 34.5%
pavillion angle: 40.2%

polish: ex
symmetry: ex

i have seen the stone in person though, and it agrees with me visually. the other missing piece of information is that the stone was certed before GIA began issuing cut grades. i am pretty certain i will go with the stone since i am getting a great price on it, and it looks great, but i''m curious whether it is worth getting it recerted to find out its cut grade. how sensitive is the GIA''s grading system to other unknown parameters like star length and such? and is it purely quantitative?

what do you think of this stone, in your opinion, based on the known measurements?

 

[Lorelei]

Date: 9/4/2009 8:31:46 AM
Author:tellmemore
hi all,
i'm considering a stone for which i have little information (so far) since the seller does not have the original cert on hand -- i have seen a copy though, provided by the original vendor of purchase, but it was too faint to see the inclusion map -- but will be receiving a reissued cert soon. the only #s i have are as follows:

table: 57%
depth: 60.8%
crown angle: 34.5%
pavillion angle: 40.2%

polish: ex
symmetry: ex

i have seen the stone in person though, and it agrees with me visually. the other missing piece of information is that the stone was certed before GIA began issuing cut grades. i am pretty certain i will go with the stone since i am getting a great price on it, and it looks great, but i'm curious whether it is worth getting it recerted to find out its cut grade. how sensitive is the GIA's grading system to other unknown parameters like star length and such? and is it purely quantitative?

what do you think of this stone, in your opinion, based on the known measurements?

Hi tmm,

I would be careful with the pavilion angle as there is a slight chance the diamond could show obstruction ( where the diamond darkens at close scrutiny due to the viewer's head or body blocking the light). To check for this view it up close to see if the diamond darkens in any way. GIA's cut grading are parametric based and the numbers are rounded too which can cloud the issue, this also includes the star and lower girdle facet percentages. I assume there is a Sarin report for this diamond which gives the proportions posted? Regarding getting this diamond regraded in order to get a cut grade, it is possible due to the pavilion angle that this diamond would get at best a Very Good cut grade from GIA anyway. What I would suggest is to see if you can view the diamond away from any store lights so you can see how it looks in plain daylight, jewellery store lights can be deceptive.

 

[tellmemore]

many thanks, lorelei! i will be sure to be on the lookout for that.

so, in your expert opinion, you would likely bet that this stone would be a VG cut at best?

 

[Lorelei]

Date: 9/4/2009 8:56:14 AM
Author: tellmemore
many thanks, lorelei! i will be sure to be on the lookout for that.

so, in your expert opinion, you would likely bet that this stone would be a VG cut at best?

Glad to help!

I take it there is a Sarin report available for this diamond which gives the measurements above?

From what I have learned yes with that pavilion angle the diamond wouldn't get better than VG for a cut grade. You might find this useful, GIA facetware. We don't have all the info to make it work but if you do it estimates the cut grade.

Here you go! http://www2.gia.edu/facetware/

Also just as a suggestion, to make sure this one really stands out to you see if you can compare it to some Hearts on Fire or Peerless from Jareds ( AGS0 cut grade) to see how this one compares to diamonds of known cut quality. If it does compare favourably then great but it will give you a base of comparison.

 

[Ellen]

Date: 9/4/2009 8:31:46 AM
Author:tellmemore
hi all,
i''m considering a stone for which i have little information (so far) since the seller does not have the original cert on hand -- i have seen a copy though, provided by the original vendor of purchase, but it was too faint to see the inclusion map -- but will be receiving a reissued cert soon. the only #s i have are as follows:

table: 57%
depth: 60.8%
crown angle: 34.5%
pavillion angle: 40.2%

polish: ex
symmetry: ex

i have seen the stone in person though, and it agrees with me visually. the other missing piece of information is that the stone was certed before GIA began issuing cut grades. i am pretty certain i will go with the stone since i am getting a great price on it, and it looks great, but i''m curious whether it is worth getting it recerted to find out its cut grade. how sensitive is the GIA''s grading system to other unknown parameters like star length and such? and is it purely quantitative?

what do you think of this stone, in your opinion, based on the known measurements?

Have you seen very well cut diamonds, to be able to truly compare?


In my opinion, you could do much better.

 

[tellmemore]

i have, and i can''t say that i notice a very big difference.

 

[Lorelei]

Date: 9/4/2009 9:20:49 AM
Author: tellmemore
i have, and i can't say that i notice a very big difference.

Ok thats fine, sounds like you have done some homework! I would say though to see if you can view it outside to see how it looks in everyday lighting conditions to make sure you will be happy with it.

 

[Ellen]

Date: 9/4/2009 9:20:49 AM
Author: tellmemore
i have, and i can''t say that i notice a very big difference.

Ok, good luck!