How to grade cut for oval cut?

[AndyDiamond]

Hi everyone,

I think I got the gist of round brilliant cuts down now. I am wondering how to evaluate the cut quality for an oval cut. I see even on the GIA certs don't grade the cut. However, I do see online vendors make their own grading for cut. Is there certain criteria I should be looking for in terms of table and depth %?

 

[DiamondsDiamonds]

For ovals:

Depth: 59-63%
Table: 55-60%
L/W ratio: 1.33-1.66

 

[diamondseeker2006]

Regardless of the numbers, you cannot judge any fancy cut stone without seeing the image of the stone. You can pretty much safely buy an ideal cut round sight unseen, but you can't with any other shape.

 

[marcy]

Watch for big windows, the proportions of the stone and how the stone looks and performs. Oval stones are very pretty.

 

[AndyDiamond]

Watch for big windows, the proportions of the stone and how the stone looks and performs. Oval stones are very pretty.

What do you mean by big windows?

 

[tyty333]

Watch for big windows, the proportions of the stone and how the stone looks and performs. Oval stones are very pretty.

What do you mean by big windows?

Windows are places where you can sort of see threw the stone...on an oval this would be in the bow-tie area. An aset image
will also help determine the light return.

You need to look for minimal bow-ties (which can not be determined from the numbers).

http://www.diamondsourceva.com/Education/Cut/diamonds-bow-tie.asp

https://www.pricescope.com/wiki/diamonds/oval-cut-diamond

https://www.pricescope.com/tools/aga-diamond-shape-selector

 

[AndyDiamond]

Reading GIA reports, I see the stone described as "oval brilliant" and some say "oval modified brilliant". What's the difference if any?

 

[mjertl]

my e-ring is an oval. It does not conform to the tables of recommended proportions for an oval... But I looked at AT LEAST 20 ovals in person, and the one I chose was by far the most beautiful I saw - minimal/no bowtie, lovely fire, and I could go on and on... I can't emphasize enough the need to see an oval in person! Honestly, I don't even think seeing pictures would be adequate. Video's maybe, but nothing compares to lining up a few stones, turning them about, looking at them in different light...

 

[tyty333]

Reading GIA reports, I see the stone described as "oval brilliant" and some say "oval modified brilliant". What's the difference if any?

This is my *guess*...

An oval brilliant is cut similar to a round brilliant but stretched out near the points of the oval. You can sort of see arrows
in some of them. Example:
http://www.jamesallen.com/diamonds/H-VS1-Ideal-Cut-Oval-Diamond-1397998.asp

Oval modified brilliants are cut differently (not round brilliant like but not sure how).
Example:
http://www.jamesallen.com/diamonds/J-VS1-Fair-Cut-Oval-Diamond-1427474.asp
http://www.jamesallen.com/diamonds/I-SI1-Ideal-Cut-Oval-Diamond-1436948.asp

 

[oldminer]

As an expert I differ from others who also might consider themselves experts. It is my belief that you can do a lot to predict the cut quality of a fancy shaped diamond which you have not yet seen. There is no way you can judge such diamonds in the dark or at a long distance, but you can definitely weeed out many stones which could not possibly be well cut for performance, shape, or proportions.
Using the AGA/NAJA Cut Class grader found under "TOOLS" on Pricescope can assist you in going in the right direction. It would not surprise me to find a diamond grading 2A or 2B giving excellent light return, but there may be some minor issue with the cut of the diamond in some other, less noticeable way. You might find a rare diamond cut to 1A or 1B range which just didn't look so good to you. It would be a rare stone cut to those parameters that the cutter could not make beautiful, too. However, a poorly cut 1A or 1B is a distant, theoretical possibility. Nothing in parametric judgement of quality is 100% perfect. To be useful as a screening tool, 100 percent is not necessary.

 

[Amys Bling]

An ASET image will help you to determine how the stone performs- you can see if there is a bowtie or any "dead areas" in the stone that are the windows some speak of.