Ideal numbers

[jgdavis]

I''ve been looking through the pricescope info but can''t seem to find what i''m looking for. What sort of range should I be looking for in an ideal cut (H&A etc.) diamond?
Depth
Table
Flouresence
Polish
Symmetry
Girdle

If there is an easy link to read about it on the site, if anyone would just like to post it that would be a big help too.

Thanks!

 

[belle]

https://www.pricescope.com/community/threads/ags-and-gia-cut-comparison-charts.41793/
here you can see how each of the two major labs would grade based on angles. if you want a well cut stone, look for combos in the range of an ags ideal (red) or an overlap of ags and gia ex (blue).

as far as polish/symmetry, well cut stones will at least be graded 'very good' most will be either 'excellent' or 'ideal'.
fluorescence will be indectable to the naked eye until you get to at least medium blue (make sure any fluorecscence is blue) and even then, it is usually not a problem.

girdles vary. i tend to prefer thin for better spread but you will often find them to be at least 'medium'. thick, very thick and especially extremely thick girdles will take up precious carat weight at the expense of size.

you can read more about all of these things in the 'knowledge' drop down menu at the very top of this page.

 

[Bluehammer]

My experience has been in looking for ideal cut stones. I leaned towards 60-62 depth, 55-57 table, 34.5-34.9 crown, and 40.5-40.9 pav.

These seemed to work for me and I found some nice stones. I got wrapped up in the numbers a bit and found that there are many good combos. My opinion from reading other posts is that you need to keep the crown and pav. numbers in mind as averages. Try to keep the stone in the range by looking at a Sarin report. I also found the HCA tool on the board to be a helpful guide, but not decision maker.

The biggest thing I can tell you is that everyone here is willing to give good advice based upon their opinion. I would trust your eyes and see if you like a stone cut for pinfire or broadfire. I have seen debates over certain awesome shallow cut stones and great deep stones. I would use this site to steer you on the path, but do not take anyones opinion as to the perfect numbers for the absolute fact.

If someone had the one magic formula then we would not have personal choice/opinion. Branded ideal cut stones stay within certain tolerances. They are designed to take a lot of guesswork out of the diamond search. For the convience, you pay a premium. You can find good looking stones that are not branded H&A, you just have to develop your own taste for a certain look and be willing to research. I did a lot of research and I have settled to do a final pick between 2 branded stones. I have seen both and the branded stone just was my flavor.

If you research a lot like me then you will probably get frustrated at some point. It was described to me like this. You have 3 identical Ferrari''s. Same color, options etc. Now choose one. Which has a better sounding exhaust? A more glossy finish? Tough to tell, but once you get past the frustration and pick one you will feel good. I still have not picked one yet, but I am now excited because I am down to 2. Neither of them are what I picked out on paper.

 

[jgdavis]

Thanks a ton belle and blue!

Blue- you''re 100% right. I think in trying to become knowledgable I''ve actually gotten too much information, to the point where I can''t see the forest from the trees. I''ll use those numbers to guide me along, and then i''ll just have to choose the diamond that I feel is best.

Thanks again for the help!

 

[MichaelLC]

Date: 8/11/2006 9:19:00 AM
Author: jgdavis
Thanks a ton belle and blue!

Blue- you''re 100% right. I think in trying to become knowledgable I''ve actually gotten too much information, to the point where I can''t see the forest from the trees. I''ll use those numbers to guide me along, and then i''ll just have to choose the diamond that I feel is best.

Thanks again for the help!

Or the scintilation for the diamond, as it were!

Agreed on the info-overload. There''s a lot of very experienced people here.

 

[Regular Guy]

5 sets of ideal stats (with order of presentation an inside out sandwich, oui...?)

The Book of Threes

HCA (entry and discussion)

Dave superceded list

Nice Ice stats (similar to Storm?)

AGS (also already here)

 

[strmrdr]

A fixed range of numbers is old tech within any range you will find some not so great combos and you will leave out some great combos.
For example a crown between 33.8 and 36 can be kicken with the right pavilion angle and
pavilion angle between 40.4 and 41.1 can be kicken with the right crown angle BUT:
34/40.4 isn't a great combo but 36/40.4 is or 36/41 is a very bad combo but 34/41 rocks.
Get the picture?

So what do you do? either use the hca or use the new AGS0 candidate chart or a combo of the AGS and GIA charts and select ones they both agree on for the best of both systems.

 

[Regular Guy]

Hey, Storm, to this question you not too long ago would quote a set of proportions you liked, while even still stating you''d probably be criticized as a dinosaur.

Have you updated your thinking? Become PC?

I''m not crazy (recalling this), am I?

 

[strmrdr]

Date: 8/11/2006 12:39:28 PM
Author: Regular Guy
Hey, Storm, to this question you not too long ago would quote a set of proportions you liked, while even still stating you''d probably be criticized as a dinosaur.

Have you updated your thinking? Become PC?

I''m not crazy (recalling this), am I?

Your right....
iv seen the light! lol
I like number ranges they make things easy which is why I held on to them also there wasn''t as much info available then as there was now on the new thinking.
I''m not alone in this a lot of people , experts even, have had to move on with it and some still cling to the old system because its what they learned and because its easy.
Every once in a while we will read here about a vendor that gives a consumer the old number ranges as whats best.
The technology has changed and will continue to change and it will get harder and harder to keep up but at the same time systems are coming out to make it easier for the consumer.
The new AGS0 grade is an example they pass a few angle combos im not that thrilled about but I cant really say they are bad combos just that there might be slightly better ones. But the fact remains that it hides a lot of the complexity that we talk about here very often and makes a good starting point.
Once you get past that point it gets even more complicated.. h&a or not? True h&a or not?, lgf%, star%, twist and yaw, bic fic and tic, and so on and so on.

 

[strmrdr]

Here is why number ranges don't work well...
Look at the shape of the AGS0 candidate box and the GIA Ex box.
There isn't a simple number range that can cover it.

Then you take in account there are some combos outside the AGS0 box that rock and some of them even get the AGS0 performance grade it gets to be a real mess.

 

[strmrdr]

Having fun yet? lets throw another brick thru the window...
Not only do we need to take into account eyesight but we also need to take into account preferences, fire or brightness?
Given that info whats the ideal number range? ... Its impossible to say because there isn''t one....
Even the old AGA charts are historical reference material.

 

[Regular Guy]

I dunno, Storm, sounding to me like you''ve actually just had a conversion expersion, and that, where you say...

Date: 8/11/2006 12:53:04 PM
Author: strmrdr

Your right....
iv seen the light! lol

...you have!

 

[WinkHPD]

Here is another reason why numbers don''t work. I do not have the numbers available for this yet, but I hope to soon. I did receive it from Jim Caudill at AGS as an example of an overpainted stone that has good numbers but because of the extreme painting poor light performance. Notice how the edge of the stone is picking up WAY too much low angle light (represented by green) which will have the stone looking smaller than it is while weighing more than it should for the same diameter diamond cut. I intend to do it a thread later when I have all the info, but it seems totally appropriate to share this dog here to reinforce earlier comments.

In the old days this probably would have been one of those mysteriously unatractive ideal cut diamonds. Now both AGS and GIA would ding this one for its lack of performance.

Wink

 

[strmrdr]

Date: 8/11/2006 1:26:37 PM
Author: Regular Guy
I dunno, Storm, sounding to me like you''ve actually just had a conversion expersion, and that, where you say...

Date: 8/11/2006 12:53:04 PM
Author: strmrdr


Your right....
iv seen the light! lol

...you have!

Its been a while since I switched over I dont remember the exact date but its been a while...

 

[strmrdr]

Date: 8/11/2006 1:50:27 PM
Author: Wink
Here is another reason why numbers don''t work. I do not have the numbers available for this yet, but I hope to soon. I did receive it from Jim Caudill at AGS as an example of an overpainted stone that has good numbers but because of the extreme painting poor light performance. Notice how the edge of the stone is picking up WAY too much low angle light (represented by green) which will have the stone looking smaller than it is while weighing more than it should for the same diameter diamond cut. I intend to do it a thread later when I have all the info, but it seems totally appropriate to share this dog here to reinforce earlier comments.

In the old days this probably would have been one of those mysteriously unatractive ideal cut diamonds. Now both AGS and GIA would ding this one for its lack of performance.

Wink

yikes Wink you mentioned the P word this thread is doomed!!!
lol
That is another area of change before it was 8* and new line ACA did painting and now its what degree of painting and what effect it has on appearance.

 

[WinkHPD]

Date: 8/11/2006 2:15:58 PM
Author: strmrdr

Date: 8/11/2006 1:50:27 PM
Author: Wink
Here is another reason why numbers don''t work. I do not have the numbers available for this yet, but I hope to soon. I did receive it from Jim Caudill at AGS as an example of an overpainted stone that has good numbers but because of the extreme painting poor light performance. Notice how the edge of the stone is picking up WAY too much low angle light (represented by green) which will have the stone looking smaller than it is while weighing more than it should for the same diameter diamond cut. I intend to do it a thread later when I have all the info, but it seems totally appropriate to share this dog here to reinforce earlier comments.

In the old days this probably would have been one of those mysteriously unatractive ideal cut diamonds. Now both AGS and GIA would ding this one for its lack of performance.

Wink

yikes Wink you mentioned the P word this thread is doomed!!!
lol
That is another area of change before it was 8* and new line ACA did painting and now its what degree of painting and what effect it has on appearance.

Alas, another thread gone bad.

DO NOT however, confuse this dog with either an EightStar or a New Line. This is a WAY overpainted thing, not pretty like one of the brands you mention.

Wink

Wink

 

[Regular Guy]

Storm, maybe everything''s context...like a week ago, where you said: "kinda unusual with a 53% table, I like the crown and pavilion angles"... here....

Do you still like those?

 

[Rhino]

LMAO ...

Wink ... are you sure you don't mean digging and not painting in that example?

 

[Rhino]

I had been meaning to write an article on this very subject and have the beginnings of it typed out ... "The Futility of Sarin Numbers" is the title. Lord willing I''ll finish this in some decade.

The reason why and which is pertinent to the topic of this thread is that you can have all the crown angles, all the pavilion angles, even the variances.

In the new schemes of cut grading however (both AGS and GIA), the most cherry set of angles can be tossed out of the window if you don''t have a knowledge of all the facet measurements and the ability to translate those numbers to optics.

Case in point.

I have a stone here. A Hearts and Arrows rock with precision patterning.

34.03 crown angles
40.91 pavilion angles
56.4% table
61.7% total depth
56% stars (not provided on most Sarin''s but on the newer AGS and GIA Reports)
77.8% lower girdle facet length (ditto)

Any anally retentive particpant on this forum will testify to a very cherry set of angles and measurements.

The stone does not make either GIA or AGS Ideal status.

 

[Rhino]

Here''s an IdealScope image of the stone.

Can anyone take a stab at *why* this stone would not make AGS or GIA Ideal grade in light performance? Is there any other data you''d like to see?

muahaha

 

[strmrdr]

Date: 8/11/2006 2:52:08 PM
Author: Regular Guy
Storm, maybe everything''s context...like a week ago, where you said: ''kinda unusual with a 53% table, I like the crown and pavilion angles''... here....

Do you still like those?

that combo is an ags0 candidate. If you went by a lot of the old school lists that combo would not be accepted.

The numbers are still important its what you do with them that has changed.

 

[WinkHPD]

Date: 8/11/2006 4:06:25 PM
Author: Rhino
Here''s an IdealScope image of the stone.

Can anyone take a stab at *why* this stone would not make AGS or GIA Ideal grade in light performance? Is there any other data you''d like to see?

muahaha

What can you tell us about the girdle?

Wink

 

[strmrdr]

Date: 8/11/2006 4:06:25 PM
Author: Rhino
Here''s an IdealScope image of the stone.

Can anyone take a stab at *why* this stone would not make AGS or GIA Ideal grade in light performance? Is there any other data you''d like to see?

muahaha

gem file
full helium report

 

[JohnQuixote]

Date: 8/11/2006 4:06:25 PM
Author: Rhino
Here's an IdealScope image of the stone.

Can anyone take a stab at *why* this stone would not make AGS or GIA Ideal grade in light performance? Is there any other data you'd like to see?

muahaha

Ah. Friday brain teaser.

Since GIA doesn’t actually have an 'Ideal' grade or a light performance measurement I wonder if it’s a trick question Rhino?

Finish factors:

GIA: If polish/symmetry are ‘good’ it won’t qualify for GIA EX in cut.
AGS: If polish/symmetry are less than Ideal it won’t qualify AGS Ideal in cut. However, it could still qualify for Ideal in light performance.

Culet too large would be an issue but I don’t see associated leakage in the IS.
Wide ranging girdle thickness could be an issue.
Brillianteering could be an issue, but I’m not seeing evidence of this either.

Hypothetically, le-serious-buncho’nastydreck (also known as abundant clarity characteristics)

in a heavily included stone could interfere with performance…I think AGS considers this before awarding the light performance grade but I’m not sure how GIA is treating low clarities relative to cut grade since their system is proportions-based? In any event, the IS doesn’t appear so-included.

What are the variances?

Fun question.

 

[whatmeworry]

The edge leakage in the IS looks funky almost like the minor facets are skewed

 

[Rhino]

Date: 8/11/2006 5:46:56 PM
Author: JohnQuixote

Date: 8/11/2006 4:06:25 PM
Author: Rhino
Here''s an IdealScope image of the stone.

Can anyone take a stab at *why* this stone would not make AGS or GIA Ideal grade in light performance? Is there any other data you''d like to see?

muahaha

Ah. Friday brain teaser.

Since GIA doesn’t actually have an ''Ideal'' grade or a light performance measurement I wonder if it’s a trick question Rhino?

Finish factors:

GIA: If polish/symmetry are ‘good’ it won’t qualify for GIA EX in cut.
AGS: If polish/symmetry are less than Ideal it won’t qualify AGS Ideal in cut. However, it could still qualify for Ideal in light performance.

Culet too large would be an issue but I don’t see associated leakage in the IS.
Wide ranging girdle thickness could be an issue.
Brillianteering could be an issue, but I’m not seeing evidence of this either.

Hypothetically, le-serious-buncho’nastydreck (also known as abundant clarity characteristics)

in a heavily included stone could interfere with performance…I think AGS considers this before awarding the light performance grade but I’m not sure how GIA is treating low clarities relative to cut grade since their system is proportions-based? In any event, the IS doesn’t appear so-included.

What are the variances?

Fun question.

Hey John,

"le-serious-buncho’nastydreck"

LMAO Good educated guess, but its a VS.

Aight ... I''ll post more data tomorrow to help but before I turn in for the night I will share... this stone has been inspected by both GIA and AGS labs. Polish symm is GIA Ex/Ex and AGS Id/Id and is a VS2 clarity.

 

[Bluehammer]

I bet the key is something with depth and those little bits of whiteness that are too wide on the IS at the arrow points. The IS is telling with those white bits. Could be paint/dig, but I am thinking the facets are out of alignment. Course I am a novice.



Good times!

 

[JohnQuixote]

Update: The answer was disclosed in another thread. I don't think Rhino will mind my reposting it here for sake of closure.

Wink was johnny-on-the spot with his girdle info request: Digging is the culprit. It's difficult to see in that ideal-scope image above. It might be seen more easily in different single-color reflector setups. It's definitely more easily seen in the diamond's ASET model, below.

Rhino's comments from the other thread: If you note in the IS image below you can vaguely make out the existence of digging (slightly paler reds via the model's IS image). In actual IS imagery it can be difficult to ascertain. Thats when an ASET image brings out these features more obviously.

 

[denverappraiser]

Date: 8/10/2006 7:19:00 PM
Author:jgdavis
I've been looking through the pricescope info but can't seem to find what i'm looking for. What sort of range should I be looking for in an ideal cut (H&A etc.) diamond?
Depth
Table
Flouresence
Polish
Symmetry
Girdle

If there is an easy link to read about it on the site, if anyone would just like to post it that would be a big help too.

Thanks!

This is proceeding from a false premise. Allow me to rephrase the question. Is there a way to tell if a round stone is ideal cut or will show H&A symmetry based on the information contained in a standard GIA or AGS lab report?

Answer: Ideal - Sometimes. H&A – No.

AGS has several types of reports that include a cut grade, in particular their main style of reporting called a Diamond Quality Document. Ideal cut stones will say ‘ideal’ in this section. They have some reports that deliberately exclude this information. The other main AGS document is similar and is called an Diamond Quality Report. This does not have the cut grade and it’s primary reason for existing is if the lab client doesn’t want the cut grading mentioned on the report. You’re pretty safe to assume that this means that it’s non-ideal if it has one of these.

All GIA reports issued since Jan 2, 2006 on round brilliant cut diamonds have a cut grade listed. The top grade is listed as ‘excellent’. This is not exactly the same as ideal but lots of people use the terms interchangeably and there’s a decent amount of overlap. A GIA cut grade of excellent doesn’t mean it’s ideal, but it’s a pretty good place to start. Older GIA reports don’t contain enough information to make this decision,

H&A is not discussed on any of the reports issued by either lab.

I know, I didn’t give the answer you wanted, so I’m going to take the liberty of rephrasing your question again: How do you find out if a particular diamond is going to be awesome?

Answer: 1) Ask the dealer. 2) Look at the diamond. 3) Get it appraised.

Choosing a dealer that thinks the same way you do and that you are inclined to trust goes a long way towards ending up with the right stone. They don’t all use the same tools, they don’t all use the same language and they don’t even all agree about what constitutes the best. That’s why it’s important to get someone who thinks like you.

If you’re buying online, it’s hard to arrange to look at the stone. Actually, it’s pretty easy but it usually comes with a fee in the form of time, tied up credit availability and return shipping costs and looking at stones in a store is usually ‘free’. There are benefits to both approaches but either way, don’t finalize the deal until you’ve seen the stone and had the opportunity to show it to your mother, your astrologer, your appraiser and anyone else who’s opinion you respect.

An independent appraiser can provide you with a standardized viewing environment, an assortment of tools and equipment for testing various things and an experienced eye for looking at these things. Buying diamonds isn’t rocket science but a bit of practice really does help and hired assistance can make it a whole lot less stressful.

I know, that’s still not the right answer. Let’s try another rephrasing of the question. Is there a way to sort through a database populated with data gleaned from ‘certificates’ that will tell me which is the best diamond?

Answer: No

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

 

[JohnQuixote]

Neil - I assume you're replying to the original post from a while back? (edited: am I crazy, or was the OP not quoted in your post before?)

Date: 8/23/2006 2:55:05 PM
Author: denverappraiser


AGS has several types of reports that include a cut grade, in particular their main style of reporting called a Diamond Quality Document. Ideal cut stones will say ‘ideal’ in this section. They have some reports that deliberately exclude this information. The other main AGS document is similar and is called an Diamond Quality Report. This does not have the cut grade and it’s primary reason for existing is if the lab client doesn’t want the cut grading mentioned on the report. You’re pretty safe to assume that this means that it’s non-ideal if it has one of these.

While I agree it's important to check the numbers, we've had thousands of ideal diamonds graded using the DQR. It costs less than a DQD, and those savings can be reflected in the price offered to the customer.