No Crown Height % on GIA Report?

[diamondlove4]

I was looking at a GIA report of a fancy shape diamond and it didn''t have the crown height % information listed at all. Is there a way to calculate this somehow from the other numbers available? Why isn''t it listed if it''s one of the important criteria to look at when evaluation a diamond. Thanks.

 

[stone-cold11]

When is the report dated?

Can you post the report number and the stone weight as listed?

 

[Lorelei]

Date: 11/15/2009 10:01:24 PM
Author:diamondlove4
I was looking at a GIA report of a fancy shape diamond and it didn't have the crown height % information listed at all. Is there a way to calculate this somehow from the other numbers available? Why isn't it listed if it's one of the important criteria to look at when evaluation a diamond. Thanks.

Crown height normally isn't included on a fancy shape report - this is usual, a Sarin scan is needed to get that info.

 

[stone-cold11]

Oops. didn''t notice the the fancy shape. Ya, GIA do not list the crown height for these so no way to tell unless you get the vendor to do a sarin scan on the stone.

 

[diamondlove4]

Is that because there isn''t an easy way to measure this? Seems so surprising that they wouldn''t have this measurement.

 

[Lorelei]

Date: 11/16/2009 11:12:58 AM
Author: diamondlove4
Is that because there isn''t an easy way to measure this? Seems so surprising that they wouldn''t have this measurement.

GIA only offer cut grades on round diamonds and that has only been since 2006, so far no cut grading for fancy shapes.

 

[denverappraiser]

GIA doesn’t claim to list all important criteria used in evaluating a diamond. It’s relatively recent that they list anything at all about the cutting and that’s limited to a general range on the cut of modern round brilliants. They could provide more dimensions if they wanted to, like the one you’ve asked about, but they feel that it would be more misleading than helpful to do so.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[FB.]

The GIA profile images are actually drawn quite close to true scaled proportions across the shortest axis of the stone, even though they say otherwise (probably so that you don't sue them because fancies are harder to measure accurately).
If you can measure the grading report, you can get a rough idea that might be enough to help you in deciding whether to shortlist the stone for more analysis (images etc).
Have a look at these two GIA profiles of pears and you'll see that they are different; GIA have shown a good likeness of their profile proportions.
Use the above ideas at your own risk. Bear in mind that crown and pavilion % is measured as a % of the stone's width and not it's depth!