Diamond cut grade grading for same diamond. EGL : good, Sarin report: AGS-1 very good

[nanousa]

My husband bought me a beautiful sparkling round brilliant 1.06 ct. diamond. The diamond came with an EGL-usa certificate and the cut was graded Good. The jewelery store give us a Sarin report of the diamond and the grading reported by Sarin is AGS-1 Very good.

Here are the diamond specs stated in the EGL-usa certificate :

Weight : 1.06 ct
Color : G
max.: 6.63mm
min.: 6.60mm
depth : 4.00mm
table: 58%
crown height: 13.8%
pavilion depth: 43.4%
girdle: thin to medium faceted
culet: none
cut grade : good
symmetry : good
polish : excellent

Using these values in Holloway Cut Adviser, its scores 1 - Excellent

Here is the Sarin report proportions :

Diameter 6.61 (6.59-6.64)
Crown angle 34.0 deg EX
Crown height 13.9%
Pavil angle 41.0 deg
Pavil depth 43.1% EX
Culet 0.9% EX
Table size 59.7% VG
Total depth 60.2% EX
Girdle thick 0.7-2.1 EX

Proportion cut grade : very good

Using these values in Holloway Cut Adviser, its scores 2 - Very good using the angles and 2.4 using the % for pavil and crown.

How could EGL grade the cut of this diamond Good while the Sarin report states Very Good? I contacted EGL-USA to know more about this issue and they answered back that I need to send back the stone to them for consultation. Nothing in the certificate seem to indicate any abnormalities that would downgrade the cut to only Good. Could it be that the symmetry graded to Good that downgrades the cut ? What other factors influences the cut grading then proportions, symmetry and polish ? Could EGL be wrong about the cut grade ? All their measurements seems to point to a very good cut diamond. Which proportion report is most accurate EGL or Sarin ?

Thanks in advance for your answers

 

[jet2ks]

The symmetry rating of Good is what EGL-USA is using to grade the cut as Good, as well. Do you have the full Sarin report with ranges, not just the summary? That would tell a lot more.

It might be that this is stone on the border of Good and Very Good and a difference in the scan is what is determining the cut grade. If the Sarin that the jewelry store used isn''t properly calibrated, the numbers can be off slightly. In this case, I would probably put more credence in the EGL symmetry grade than the store''s.

 

[Lorelei]

Hi Nanousa,

Basically the use of terms such as good, very good, excellent and so on depend on the source and subject to variance accordingly as different criteria is often used. EGL use percentages for crown and pavilion measurements, angles are preferred however as they are considered to be more accurate. A Sarin report will give detailed measurements of the stone but can vary also as the calibration of the machine can depend on various factors.

The diamond looks like a very well cut stone!

 

[nanousa]

Well i don''t have a full Sarin report. I have only the summary. I could ask for the full one. So if i get this right, EGL uses the symmetry to grade the cut so the proportions seems to indicate a very well cut diamond but because of the symmetry it was downgrade the a only Good cut? Does symmetry influences the cut?

 

[stone-cold11]

Date: 5/25/2009 11:19:59 AM
Author: nanousa
Does symmetry influences the cut?

It might, by resulting in larger angle variations than the average values given, or not. Not way to tell unless more detailed scan info is provided or you have an Idealscope image?

 

[Lorelei]

Date: 5/25/2009 11:19:59 AM
Author: nanousa
Well i don't have a full Sarin report. I have only the summary. I could ask for the full one. So if i get this right, EGL uses the symmetry to grade the cut so the proportions seems to indicate a very well cut diamond but because of the symmetry it was downgrade the a only Good cut? Does symmetry influences the cut?

I don't know what criteria use to grade cut, part of it might be dependant on physical symmetry or not. You do have a well proportioned diamond looking at the angles, hence it should be a lovely diamond. Are you happy with it?

This page explains on lab graded physical symmetry which basically studies and grades how well the facets of a diamond are aligned, girdle, positioning of the table and culet etc,

http://diamonds.pricescope.com/symm.asp

 

[nanousa]

Yes i am very happy with it. It received a lot of comments on it even by people i don''t even know. It always puzzled me how could it have been grade to only Good while some friends have Excellent graded cut diamond that are not sparkling and shining as much. I meant to ask that question on the forum by curiosity.

 

[Lorelei]

Date: 5/25/2009 11:36:57 AM
Author: nanousa
Yes i am very happy with it. It received a lot of comments on it even by people i don't even know. It always puzzled me how could it have been grade to only Good while some friends have Excellent graded cut diamond that are not sparkling and shining as much. I meant to ask that question on the forum by curiosity.

This does come up a lot as really the criteria for what is good, very good, excellent and so on can be so diverse. Your diamond has good proportions which are really the bricks and mortar of a diamond's light return, sparkle and beauty. So although your diamond got a ' Good' cut grade, it actually has great ' engines' especially with the critical crown and pavilion angles which will make it a great looking diamond! Also out of interest the naked untrained eye will not notice any difference between good and above for polish and symmetry.

 

[jet2ks]

Date: 5/25/2009 11:36:57 AM
Author: nanousa
Yes i am very happy with it. It received a lot of comments on it even by people i don''t even know. It always puzzled me how could it have been grade to only Good while some friends have Excellent graded cut diamond that are not sparkling and shining as much. I meant to ask that question on the forum by curiosity.

If you are happy with it, that is all that really matters. Sounds like you have an excellent performing diamond to enjoy.

 

[Richard Sherwood]

Not quite sure why this diamond got a "Good" cut ranking. All the information points to a "Very Good" cut, by GIA standards.

In the GIA system, a diamond with a "good" symmetry can still achieve a "very good" cut ranking if all the other factors are kosher.

I''d be surprised if EGL was different in that respect.

 

[denverappraiser]

I’ve never really figured out the EGL-USA cut grading system but the Sarin is using the old AGS approach from back in the 90’s where each of a few parameters must fall within a certain range. It’s downgrading you because of the table size. Interestingly the two lists disagree on the table size by several percent. This is probably just a matter of calibration between the Sarin machines used (EGL uses Sarin equipment as well). Under GIA rules a 'good' symmetry can still be eligible for a 'very good' cut but EGL doesn't use the GIA cut grading system so under their rules it may be different. Ask 'em.


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

 

[Rockdiamond]

Congratulations on the diamond!
Personally I would not waste much effort on trying to figure out why EGL did what it did.
For one thing, no one in the trade accepts EGL color and clarity grading, so why even begin to put any faith into their cut grade system.
I''m not saying that this need to in any way lessen your enjoyment of the diamond- but the lab report you got is not highly thought of anyway.

The great news is you don''t wear the report.

 

[WinkHPD]

One thing that I do not believe has been mentioned yet, and that is the fact that with the AGS system the final grade can only be established after grading by a human eye to take the deductions for polish and symmetry.

A symmetry grade of good is a limiting grade and thus the highest grade possible would be good from the AGS. (Assuming that the AGS grader graded the symmetry as good.)

This is not seen in the sarin report and thus the listing of the POTENTIAL excellent grade is not a valid comparison until the human grading factor has been added in.

Wink

 

[nanousa]

Well i asked EGL if the symmetry downgrades the cut but i got no clear answer. Their only answer was : Send back the diamond for consultation. I am not ready to do that of course... Are they admitting that there might have been a mistake ?

 

[Rockdiamond]

They are not likely to admit any fault, or mistake.
ON the back of the report is a lot of tiny print boilerplate stuff- they have no responsibility for the grade yada yada.

Gem labs are generally slow to admit mistakes.
GIA does have a method for re-submitting a stone if you disagree with their color or clarity.
I don''t know if they are doing the same thing for cut grades....
But clearly, if you were going to send the diamond anywhere to get an accurate report, it should be to AGS or GIA.....

 

[nanousa]

Well i don''t think it is worth it to resubmit the diamond to any other lab GIA or AGS because it is just a piece of paper. All the proportions seem to indicate a very well cut diamond and that all it matters. Visually it is very nice.

 

[Rockdiamond]

Date: 5/25/2009 5:20:21 PM
Author: nanousa
Well i don''t think it is worth it to resubmit the diamond to any other lab GIA or AGS because it is just a piece of paper. All the proportions seem to indicate a very well cut diamond and that all it matters. Visually it is very nice.

AMEN!

It sounds like a lovely diamond- enjoy it!