Jump to content

So - Is This The Stone For Me?


Recommended Posts

Hello guys and gals.


Lookin' into a center stone. This one looks nice... my only concern is the depth percentage. It's a little high... but not terribly so. I am afraid it might affect brilliance and the perceived size of the stone as well.


I was shooting for a .70-.80ct stone... as big as possible for around $2,600 give or take a couple hundred.


My goals:


Eye Clean and colorless when set. Maximum brilliance and fire.


Diamond Information:



Certificate: GIA Shape: Round Cut: Ideal

Carat: 0.70 Color: H Clarity: VS2




Diamond Proportions: Measurements: 5.67-5.63-3.55 Depth Percentage: 62.8 % Table Percentage: 55 % Girdle: Slightly Thick

Culet: None (Pointed) Polish: Excellent Symmetry: Excellent Fluorescence: None

Link to comment
Share on other sites

GIA's highest 3 grades are Good, Very Good, and Excellent.... Ideal does not exist. Perhaps this is Very Good, perhaps Excellent. Perhaps the overall cut grade is not even assessed because it is a pre-2006 report. You'll need to get a copy of this report to know for sure.


I would ask the merchant why it states Ideal and who graded it accordingly.




Edited by Adylon
Link to comment
Share on other sites

Thank you. You have a good point. I would like to see the report. I'll ask.


So it isn't possible to simply look at the dimensions and see what category it would fall into?


You can see what cut grade the GIA gave (or would give) if you get the following additional info.


Crown Angle, Pavilion Angle, Star%, Lower Half%


Their top grade is EX.


Using the above measurements you could also see if it fits into the old AGS proportions-based 'Ideal' cut grade, but that metric changed in 2005: Now a diamond must be sent to AGSL to receive any official grade, since all 57/58 facets are taken into account using ray-tracing. It's possible to take the basic measurements and look them up in the cutting guidelines to predict whether it might earn that grade, but the only way it should be advertised as AGS Ideal is with lab documentation - unless the seller is clearly defining 'ideal' as his/her own local term.


For the record, the word ideal is much-abused.

Edited by JohnQuixote
Link to comment
Share on other sites

So essentially if it's AGSL then an "ideal" cut is their best... with excellent being more comparable to the GIA "very good" rating?


AGSL has 11 grades, 0-10 (0 is 'Ideal') and GIA has only 5 (the top is Excellent) so if they were in complete agreement AGS0, AGS1 and some of AGS2 would be equivalent to GIA EX. In some cases that is true but not always: The top GIA grade is much wider at the steep/deep end, where some GIA Ex combos are predicted to be as low as AGS3, but down on the shallow/shallow side AGSL has a few 'Ideal' combos that would get VG from GIA.


Although they have different approaches, there is a great deal of overlap in what the labs grant their highest marks. We can offer some understanding about the numbers if you have them (like why 123 received XYZ grade). Light performance indicators/photos are even more helpful.

Edited by JohnQuixote
Link to comment
Share on other sites

AGS "Ideal" Cut Grade is not necessarily the "best" or 'better' than GIA's Excellent or Very Good Cut Grade.


Different approaches but both roads lead to Rome.


There is visual variability in the top Cut Grades of both labs and you may be short-changing yourself by blindly following one of these top Cut Grades over the other.


Bottom line is for you to see and examine the diamond(s) before you make a buying decision.

Link to comment
Share on other sites

Personally, I rather like the AGS standards but ‘best’ is a word that doesn’t get used within AGS circles very often. As Barry points out, the labs aren’t measuring the same things. AGS-0 is sufficiently difficult for cutters to do that it doesn’t happen by accident. A decision was made early on in the process that this particular stone would be cut to AGS-0 proportions and that it would be submitted to AGS lab in the hopes of receiving the coveted AGS ‘ideal’ cut grade and consequently be sold for a premium price because of it. Other stones will take a different path. GIA is by far the most recognized lab in the world and it is often possible to cut the same piece of rough to GIA-excellent and get a slightly bigger stone.


For those who have been working through the shopping process, you will quickly observe that certain weight points, like 1.98 vs 2.01cts can make a tremendous difference in the prices and a cutter would be nuts to make a 1.95 AGS-0 in preference to a 2.00 GIA-excellent.


The result of this is an automatic divergence of stones. I see remarkably few stones that would get the top grade from both labs be accompanied by GIA paper. At the same time, I see some GIA-Very Good’s that are fabulous looking stones while AGS-5 (which might be quite lovely as well) is effectively non-existent because dealers with sense simply don’t submit those stones to AGSL in the first place.



Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...