GIA

[peterspixie]

Hi, I am wondering if anyone can help answer a question for me...When looking for a diamond that comes with a GIA cert. if the cut is excellent the color is decent and it is anywhere between a VVS1-VS2 what does the clarity characteristics mean? (Yes I am a newb) here is a link as an example HERE does that "Cloud" show up with the naked eye? or what?! any help would be appreciated.

 

[stone-cold11]

That is a diamond quality dossier report. A report without a clarity plot, so the report just states what are the inclusions present which is the clarity characteristic. Will in no way be visible, at VS1 level, to the naked eye unless you have superhuman eye-sight.

The other report is the diamond quality report, which has the clarity plot.

 

[peterspixie]

okay that helps alot i appreciate it.

 

[FB.]

VVS inclusions are impossible to see.
VS inclusions are usually invisible, but occasional VS clarity stones have one or two very tiny specks that can be seen at six inches in ideal conditions if you know where to look and spend a few minutes getting the stone and the light *just right* (but even these "bad" VS stones will have invisible inclusions in most conditions and at more than ten inches). But I should stress that VS2 is almost always eye clean when considering round diamonds.

It's only once you get to the SI or lower grades, you need to start to worry about the inclusions.

 

[Todd Gray]

Proportions from the GIA Dossier:

Depth: 62.9%
Table: 55%
Crown Angle: 34.5°
Crown Height: 15.5%
Pavilion Angle: 41.2°
Pavilion Depth: 43.5%
Star length: 50%
Lower Half: 80%
Girdle: Medium to Slightly Thick, Faceted (4.0%)
Culet: None

Did you run the measurements for this diamond through the Holloway Cut Adviser? Available from the Tools / Cut Adviser link at the top of this page.

 

[kenny]

This is not a well cut diamond.
It is too deep.
A well cut diamond will look better.

I would not consider any diamond that scores over 2.0 on the HCA.
This one scores 3.2.
See this link for the HCA tool.

HCA

Unfortunately GIA allows diamonds that are too deep into their top cut category.
I believe they do this so cutters can retain more of the precious rough material so they make more money.

AGS has a tighter top cut bullseye.

That's why I think of GIA as being pro industry and AGS as being pro consumer.

 

[BobR]

Date: 12/17/2009 1:06:22 PM
Author: kenny
This is not a well cut diamond.
It is too deep.
A well cut diamond will look better.

HCA = 3.2.
I would not consider any dimaond that score over 2.0.
See this link.

HCA

Unfortunately GIA allows diamonds that are too deep into their top cut category.
I believe they do this so cutters can retain more of the precious rough material so they make more money.

AGS has a tighter top cut bullseye.

That''s why I think of GIA as being pro industry and AGS as being pro consumer.

Kenny
I''m not arguing with the knowledge and experience of folk here (not in any position to!!) but I would raise 1 point.:-
Whenever I see comments regarding steep/deep or deep stones, if it''s GIA graded then the comment very often seems to also relate to an issue with GIA grading, but in a number of cases AGS agrees with GIA, and grades them as AGS(0).
In this particular case the AGS predicted grade is Ex for AGS Gold and (0) for AGS PGS.
My understanding from a reply to a question I posted on diff between Gold/PGS is that Gold is similar to GIA ( 2-d) whereas pgs is 3-d light tracing (performance) So can I assume PGS is superior / more reliable than Gold??
Following is where I got AGS info from.

http://www.octonus.com/oct/mss/gia-agspgs.phtml


I grant that I''ve seen people comment that an AGS graded stone is deep, but I''ve never seen the comment also making an association with an issue with AGS grading as I see all too often with GIA graded stones.

I don''t see that many comments on AGS stones either, but that''s maybe because cutters who are looking for AGS(0) will normally go for the centre of the spectrum, but that still doesn''t alter the fact that both GIA/AGS (potentially) award their highest grade to these problem stones.
This is only my impression, and would be happy to corrected??

 

[kenny]

I think I read here once that GIA allows a much larger range of poor proportions than AGS.

AGS has a smaller bullseye.

So if the extent of your "cut education" is selecting top cut grade you are more likely to get true top cut from the top cut grades of AGS than GIA.

 

[BobR]

Kenny
My point has nothing to do with ''cut education'' rather to do with seeking balance!
If a stone potentially gets GIA Ex and /AGS (0), and it''s a steep/dep or too deep then, if if its a problem with GIA grading, it''s also a problem with AGS grading - qed

Date: 12/17/2009 1:49:21 PM
Author: kenny
I think I read here once that GIA allows a much larger range of poor proportions than AGS.

AGS has a smaller bullseye.

So if the extent of your ''cut education'' is selecting top cut grade you are more likely to get true top cut from the top cut grades of AGS than GIA.

 

[Paul-Antwerp]

Date: 12/17/2009 1:35:11 PM
Author: BobR

Date: 12/17/2009 1:06:22 PM
Author: kenny
This is not a well cut diamond.
It is too deep.
A well cut diamond will look better.

HCA = 3.2.
I would not consider any dimaond that score over 2.0.
See this link.

HCA

Unfortunately GIA allows diamonds that are too deep into their top cut category.
I believe they do this so cutters can retain more of the precious rough material so they make more money.

AGS has a tighter top cut bullseye.

That''s why I think of GIA as being pro industry and AGS as being pro consumer.

Kenny
I''m not arguing with the knowledge and experience of folk here (not in any position to!!) but I would raise 1 point.:-
Whenever I see comments regarding steep/deep or deep stones, if it''s GIA graded then the comment very often seems to also relate to an issue with GIA grading, but in a number of cases AGS agrees with GIA, and grades them as AGS(0).
In this particular case the AGS predicted grade is Ex for AGS Gold and (0) for AGS PGS.
My understanding from a reply to a question I posted on diff between Gold/PGS is that Gold is similar to GIA ( 2-d) whereas pgs is 3-d light tracing (performance) So can I assume PGS is superior / more reliable than Gold??
Following is where I got AGS info from.

http://www.octonus.com/oct/mss/gia-agspgs.phtml


I grant that I''ve seen people comment that an AGS graded stone is deep, but I''ve never seen the comment also making an association with an issue with AGS grading as I see all too often with GIA graded stones.

I don''t see that many comments on AGS stones either, but that''s maybe because cutters who are looking for AGS(0) will normally go for the centre of the spectrum, but that still doesn''t alter the fact that both GIA/AGS (potentially) award their highest grade to these problem stones.
This is only my impression, and would be happy to corrected??

Your impression might be based on charts of third parties, who might have made mistakes in compiling the charts.

 

[Karl_K]

BobR

Here is where the confusion comes in: A particular combination in those GIA Rounded numbers might get AGS0 PGS barely but there are combos in those GIA rounded numbers that will get AGS2-4.
Where does this diamond fall?
No one knows..... But the odds are much better it is not AGS0.
Just because one combo with x/y angles gets ags0 pgs does not mean they all will.
In this case it is optical symmetry and the lgf% that will determine if it gets ags0 and neither one of those is available in this thread with the required accuracy.

 

[BobR]

Date: 12/17/2009 2:53:16 PM
Author: Karl_K
BobR

Here is where the confusion comes in: A particular combination in those GIA Rounded numbers might get AGS0 PGS barely but there are combos in those GIA rounded numbers that will get AGS2-4.
Where does this diamond fall?
No one knows..... But the odds are much better it is not AGS0.
Just because one combo with x/y angles gets ags0 pgs does not mean they all will.
In this case it is optical symmetry and the lgf% that will determine if it gets ags0 and neither one of those is available in this thread with the required accuracy.

Thanks Karl
Your comments help, but also leave me with a couple of questions :-

What I think may be the simplest first
- You refer to these borderline combos 'barely' achieving AGS(0). Can I deduce from this that not all GIA Ex/AGS Ideals are equal,, and if so is there a primus inter pares?? Tolkowsky??
and also
- The general concept of HCA suggests an inverse relationship between CA/PA.(as do AGS and perhaps to a slightly lesser extent GIA). Is it therefore valid to talk about issues with 'deep' stones in isolation (as earlier in this thread) or is that not meaningful? I have seen in other threads that there are concerns where a pa becomes 'too' deep, without taking the CA into consideration.
And here's where I play devil's advocate - both GIA and AGS allow certain combos with PA 41.8 to be graded as Ex/Id
What are the potential problems that cast doubt on these grades (presumably the ring of death, but any others??)

Forgive me if I'm asking questions that have been answered elsewhere, and feel free to point me to some document or thread. its just that this thread has enabled me to pull together some limked areas that I'm fuzzy on.
thanks
Bob

PS Just realised Ive wandered away from the original post - is it better if I star a new thread on this??