10 replies to this topic

[jmdatcs]

I've noticed that AGI doesn't actually use the work "ideal", their highest cut grade is excellent. Some of the places I've been looking have additional ranges above ideal(bluenile.com and signature ideal, for example). What range of table and depth % should I be looking for?

I know cut is the most important factor, but what about symmetry and polish? Should I make sure they are also excellent, or should I go with VG and put the money into clarity instead, or save the money?

Right now I'm looking for Ideal, J, SI1, 2ct.

Edited by jmdatcs, 20 October 2009 - 04:52 PM.

[jmdatcs]

One other question. How bad is it if the girdle varies from thin to slightly thick?

Edited by jmdatcs, 20 October 2009 - 05:12 PM.

[denverappraiser]

There’s been quite a bit of discussion on this topic and you might find it helpful to search the forum. There’s a search box at the bottom left corner of the page.

Basically, not everyone uses the term ‘ideal’ in the same way and there’s LOTS of abuse of that term. This is part of the reason GIA doesn’t use it. The classic usage is from AGS but even that is fairly complicated because they changed the rules dramatically in 2005. Some pre-2005 AGS stones no longer qualify and some of the current ones wouldn’t have qualified back then. Table/depth percentages is not enough information to decide with either system (or with GIA’s for that matter).

BN uses ‘signature ideal’ to describe a stone that is lab graded as either GIA-excellent or AGS-ideal. They don’t seem to have any other specific requirements in terms of cutting but they provide some additional paperwork, a different girdle inscription and I think a different sort of warranty program. Ask ‘em. The same holds for others. If they use an in-house grading system to describe a stone as ‘better’, insist that they tell you in what way it's better.

The difference between VG and EX symmetry and polish is very subtle. For most people this is a non-issue. Unless the stone is being marketed as a 'hearts and arrows' (which is a symmetry issue), or you just like the idea of getting as many high marks as possible, I wouldn't worry too much about this.

Thin - Sl. Thick girdle is fine. Avoid the extremes of Extremely thin and Extremely thick.


Neil

Edited by denverappraiser, 21 October 2009 - 04:43 AM.

[davidelevi]

Couple of other points on girdles: also avoid "wonky" girdles (as in more than two steps between min and max), and be wary of non-GIA/AGS grading, even on girdles. I have just seen a 5% (on average) girdle being described as "slightly thick" in its thickest point.

[Happy79]

hi

i am new to the forum, can someone pls advise if GIA grades cut, symmetry and polish as excellent, does it mean i can be guaranteed a very nice diamond, though not ideal cut?

thanks in advance!

[davidelevi]

By and large, ignore symmetry and polish if graded good or above (unless you are a detail freak), and focus on cut.

The problem in answering your question is that while "GIA 'Excellent' cut grade " is a clearly defined concept, "nice" and "ideal" are not. I have seen a few GIA Excellent that I didn't like, and many I did, but your definition of nice may be stricter or looser than mine - or our tastes may simply be different.

GIA Excellent is not a bad place to start; if you want a tighter one, go for diamonds that are graded AGS 0 (Ideal - this time with capital I, since this one is clearly defined), although you will restrict your choices considerably (and there are many GIA Excellent that if sent to AGS would come back as AGS 0/Ideal on cut).

[Happy79]

davidelevi, on Thursday, Oct 22 2009, 02:27 AM, said:

By and large, ignore symmetry and polish if graded good or above (unless you are a detail freak), and focus on cut.

The problem in answering your question is that while "GIA 'Excellent' cut grade " is a clearly defined concept, "nice" and "ideal" are not. I have seen a few GIA Excellent that I didn't like, and many I did, but your definition of nice may be stricter or looser than mine - or our tastes may simply be different.

GIA Excellent is not a bad place to start; if you want a tighter one, go for diamonds that are graded AGS 0 (Ideal - this time with capital I, since this one is clearly defined), although you will restrict your choices considerably (and there are many GIA Excellent that if sent to AGS would come back as AGS 0/Ideal on cut).

thanks for the reply

need some expertise to tell me which diamond is better?

1. HCA 5.6 - good, GIA triple Ex, 0.70, E colour VS1, florencense none
2. HCA 2.6 - very good, GIA triple Ex, 0.78, D colour VS2, florescence faint

price diff between 1 & 2 SGD 500.

[davidelevi]

Based purely on the data you have, I'd be tempted by the D/VS2. It's appreciably larger, and it's possibly better cut for not much more money. The difference between VS2 and VS1 is frankly irrelevant and invisible with the naked eye (in 9999 cases out of 10000). However, no tool or opinion based on the measurement of two average angles and two average proportions is ever going to tell you which diamond - with its 57 facets and myriads of angles - looks nicer to you.

[Happy79]

davidelevi, on Thursday, Oct 22 2009, 01:19 PM, said:

Based purely on the data you have, I'd be tempted by the D/VS2. It's appreciably larger, and it's possibly better cut for not much more money. The difference between VS2 and VS1 is frankly irrelevant and invisible with the naked eye (in 9999 cases out of 10000). However, no tool or opinion based on the measurement of two average angles and two average proportions is ever going to tell you which diamond - with its 57 facets and myriads of angles - looks nicer to you.

Thanks, I guess I would most probably buy the D VS2, given that the size is also bigger
specs of the diamond:

ROUND BRILLIANT (Diamond 1)
Measurements: 5.66 - 5.69 x 3.56 mm
Carat Weight: 0.70 carat
Color Grade: E
Clarity Grade: VS1
Cut Grade: Excellent

PROPORTIONS:
Depth: 62.7%
Table: 57%
Crown Angle: 36.0°
Crown Height: 15.5%
Pavilion Angle: 41.2°
Pavilion Depth: 43.5%
Star length: 55%
Lower Half: 75%
Girdle: Medium, Faceted (3.5%)
Culet: None

FINISH:
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
CLARITY CHARACTERISTICS:
Cloud

ROUND BRILLIANT (Diamond 2)
Measurements: 5.89 - 5.90 x 3.65 mm
Carat Weight: 0.78 carat
Color Grade: D
Clarity Grade: VS2
Cut Grade: Excellent

PROPORTIONS:
Depth: 61.9%
Table: 57%
Crown Angle: 35.5°
Crown Height: 15.5%
Pavilion Angle: 40.8°
Pavilion Depth: 43.0%
Star length: 50%
Lower Half: 80%
Girdle: Medium, Faceted (3.5%)
Culet: None

FINISH:
Polish: Excellent
Symmetry: Excellent
Fluorescence: Faint

CLARITY CHARACTERISTICS:
Crystal, Needle

I did a research, and seems like Diamond 2 cutting falls under ideal in AGS criteria...

[Happy79]

Happy79, on Thursday, Oct 22 2009, 08:07 PM, said:

davidelevi, on Thursday, Oct 22 2009, 01:19 PM, said:

Based purely on the data you have, I'd be tempted by the D/VS2. It's appreciably larger, and it's possibly better cut for not much more money. The difference between VS2 and VS1 is frankly irrelevant and invisible with the naked eye (in 9999 cases out of 10000). However, no tool or opinion based on the measurement of two average angles and two average proportions is ever going to tell you which diamond - with its 57 facets and myriads of angles - looks nicer to you.

Thanks, I guess I would most probably buy the D VS2, given that the size is also bigger
specs of the diamond:

ROUND BRILLIANT (Diamond 1)
Measurements: 5.66 - 5.69 x 3.56 mm
Carat Weight: 0.70 carat
Color Grade: E
Clarity Grade: VS1
Cut Grade: Excellent

PROPORTIONS:
Depth: 62.7%
Table: 57%
Crown Angle: 36.0°
Crown Height: 15.5%
Pavilion Angle: 41.2°
Pavilion Depth: 43.5%
Star length: 55%
Lower Half: 75%
Girdle: Medium, Faceted (3.5%)
Culet: None

FINISH:
Polish: Excellent
Symmetry: Excellent
Fluorescence: None
CLARITY CHARACTERISTICS:
Cloud

ROUND BRILLIANT (Diamond 2)
Measurements: 5.89 - 5.90 x 3.65 mm
Carat Weight: 0.78 carat
Color Grade: D
Clarity Grade: VS2
Cut Grade: Excellent

PROPORTIONS:
Depth: 61.9%
Table: 57%
Crown Angle: 35.5°
Crown Height: 15.5%
Pavilion Angle: 40.8°
Pavilion Depth: 43.0%
Star length: 50%
Lower Half: 80%
Girdle: Medium, Faceted (3.5%)
Culet: None

FINISH:
Polish: Excellent
Symmetry: Excellent
Fluorescence: Faint

CLARITY CHARACTERISTICS:
Crystal, Needle

I did a research, and seems like Diamond 2 cutting falls under ideal in AGS criteria...

one more question, is HCA rating more important to establish the brilliancy of the diamond or the GIA cert? I have one graded as very good for cut only but HCA grades 0.9 Excellent. While another is GIA graded excellent but HCA grades 2.6 very good only....

[davidelevi]

The HCA reflects (in a rather mechanical way) Garry Holloway's personal preferences and ideas about what makes a diamond nice - it works without seeing the stone and it comes up with an evaluation based on averages of four key parameters.

GIA's criteria are different, looking at many more angles and proportions, and include a visual examination of the stone. It is possible that for example GIA has awarded a grade of "Very Good" for things that the HCA does not take into account (e.g. the angling and shaping of the minor facets of the diamond to increase its weight - so called "brillianteering").

Some people blame GIA for being too lax on awarding "Excellent" cut grades, but in all, I'd rather trust a team of experts who have seen the diamond rather than a computer program that hasn't.

Incidentally - I haven't seen it, but your 0.78 seems very very very nice on paper.