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HCA - Interpreting AGS ideal candidates range

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allinmustwin

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Hi,

I have a query about the AGS ideal candidates range outlined in the HCA. If I want to purchase a diamond that meets AGS0 cut grade, does it matter where in the AGS ideal candidates range zone the diamond falls?

Basically, I''d like to know if it is more preferable for the stone dimensions to be right in the middle of the range (side to side / top to bottom) rather than on the boundary of the AGS ideal candidates range?

Regards,


Paul
 

Stone-cold11

Super_Ideal_Rock
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It does not matter if the stone is already graded by AGS as AGS0. But some like to have the parameters falls into the overlap region of AGS and GIA.
 

Lorelei

Super_Ideal_Rock
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Date: 3/2/2009 10:16:09 AM
Author:allinmustwin
Hi,

I have a query about the AGS ideal candidates range outlined in the HCA. If I want to purchase a diamond that meets AGS0 cut grade, does it matter where in the AGS ideal candidates range zone the diamond falls?

Basically, I'd like to know if it is more preferable for the stone dimensions to be right in the middle of the range (side to side / top to bottom) rather than on the boundary of the AGS ideal candidates range?

Regards,


Paul
Hi Paul and welcome!

It doesn't really make much of a difference, however some consider the bullseye to be where GIA and AGS overlap. Also the HCA is a first round elimination tool and not used for selection so with an actual AGS0 cut grade diamond which preferably has images such as ASET provided, the HCA isn't needed strictly speaking. However it is best even with AGS0 to evaluate each diamond carefully on its own desirable visual and physical properties, so if you would like to post the proportions of the diamond if you have a particular one in mind, and any images you have, we can check it over for you.
 

Allison D.

Ideal_Rock
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The best way to know for sure if a diamond meets the AGS0 cut criteria is to select a diamond that has earned the AGS0 report.

There are, of course, diamonds that would qualify for the AGS0 cut grade that are submitted to other labs, and if you want to consider one of those, predictors can be useful in letting you know if the stone would *likely* earn the AGS0 label.

Once you're 'within' the range of AGS0, it doesn't matter where in the range you fall.
 

Paul-Antwerp

Ideal_Rock
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Hi Paul,

I really like your name, by the way.

When comparing the HCA with the AGS-metric, you are really comparing two predictions, one very broad and easy, the other very detailed and complicated. Stone-cold and Lorelei basically already explained this in a very good way.

Since AGS-0 is still a range, there are bound to be peak-performing areas within that range. As such, not all AGS-0''s are equal, and I have often argued that the AGS-0-range is too broad for my liking, especially so in princess-cuts.

There is an interesting dichotomy in how to look at the AGS-grades. As a mass-manufacturer aiming for the grade, it is often most interesting to aim for the center of the range. With some error, you are bound to remain within the grade. It is also what AGS basically advises to cutters.

As a cutter aiming for the peak, regardless of the grading-system, I have found that that peak is most often at the edge of the 0-range. This is in some way counter-intuitive, and it is also more risky for the cutter, since there is less room for error.

Live long
 

Allison D.

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Date: 3/2/2009 12:01:28 PM
Author: Paul-Antwerp

Since AGS-0 is still a range, there are bound to be peak-performing areas within that range.
I agree with this to a point, Paul. I have no doubt there might be miniscule measurable differences, but I''m not sure I believe those measurable difference would even be discernable to most eyes.

If I place a single drop of lemon juice into a gallon container of water and compare that to a gallon of water that has no drop of lemon juice, there is definitely a measurable chemical difference between them. A chemistry lab will be able to discern which gallon was treated with the lemon juice, but no one would likely be able to actually taste the difference between the two.
 

strmrdr

Super_Ideal_Rock
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23,295
Paul is right there is a wide range of visual difference within the ags0 grade.
Some of it is good for example there are 60/60 AGS0s TICs BICs and near FICs.
Then you have quality differences, h&a vs near h&a to lesser optical symmetry as well as different levels of angle combinations.
Cutters are slowly figuring out how to game the system.
They cut for the worst edge and if they miss 0 on the AGS software it goes to gia for an EX.
While I doubt there is a truly bad combo that will make ags0 there are some questionable ones.
 

Regular Guy

Ideal_Rock
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Anyone want to guess what search parameters I used to find this vaguely related thread?
 

John P

Ideal_Rock
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Date: 3/2/2009 12:01:28 PM
Author: Paul-Antwerp

As a cutter aiming for the peak, regardless of the grading-system, I have found that that peak is most often at the edge of the 0-range. This is in some way counter-intuitive, and it is also more risky for the cutter, since there is less room for error.
Here is an example of what Paul is talking about. This is a screen shot of the cut-guides for 56T (one of the most forgiving table sizes in terms of candidates to earn the top LP grade).

Notice how often the falloff jumps to AGS2 (and sometims 3) instead of AGS1 if the AGS0 peak is not acquired. Indeed, this is risky for cutters dealing with tolerances of tenths of a degree.

ags-cut-guides-56t6mm.jpg
 

Garry H (Cut Nut)

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Date: 3/2/2009 12:01:28 PM
Author: Paul-Antwerp
Hi Paul,

I really like your name, by the way.

When comparing the HCA with the AGS-metric, you are really comparing two predictions, one very broad and easy, the other very detailed and complicated. Stone-cold and Lorelei basically already explained this in a very good way.

Since AGS-0 is still a range, there are bound to be peak-performing areas within that range. As such, not all AGS-0''s are equal, and I have often argued that the AGS-0-range is too broad for my liking, especially so in princess-cuts.

There is an interesting dichotomy in how to look at the AGS-grades. As a mass-manufacturer aiming for the grade, it is often most interesting to aim for the center of the range. With some error, you are bound to remain within the grade. It is also what AGS basically advises to cutters.

As a cutter aiming for the peak, regardless of the grading-system, I have found that that peak is most often at the edge of the 0-range. This is in some way counter-intuitive, and it is also more risky for the cutter, since there is less room for error.

Live long
Paul is right - and many people feel like Bruce Harding does that top edge on my charts is the best spot for the compromise between briliance / limited leakage and fire.
But there is no evidence.

UInfortunately AGS do not give out raw data ''below'' zero. they have several performance parametrs but they all go below zero - but they only record the amounts above that point - Perhaps Storm you can explain what i mean better as I am about to fly away.
 

strmrdr

Super_Ideal_Rock
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23,295
What I see going on is some cutters targeting this point.
If it gets the 0 on the AGS software off to AGS it goes if it gets the 4 or 2 off to GIA for an EX it goes.

S-ags-cut-guides-56t6mm.jpg
 

strmrdr

Super_Ideal_Rock
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Last time I checked reports Paul liked to play this zone...
With his cutting tolerance he can play the edges and get the grade while producing kicken diamonds.

S1-ags-cut-guides-56t6mm.jpg
 

strmrdr

Super_Ideal_Rock
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Messages
23,295
If I was doing a brand I would target these 2 points.
The left for TIC and the right for FIC and OEC

S-targets-ags-cut-guides-56t6mm.jpg
 

strmrdr

Super_Ideal_Rock
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The ACA target is here:

ACA-ags-cut-guides-56t6mm.jpg
 

strmrdr

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Date: 3/2/2009 4:13:09 PM
Author: Garry H (Cut Nut)
Date: 3/2/2009 12:01:28 PM

Unfortunately AGS do not give out raw data 'below' zero. they have several performance parameters but they all go below zero - but they only record the amounts above that point - Perhaps Storm you can explain what i mean better as I am about to fly away.
One the deduction flap on the report and on the AGS software for each category 0 is not a number it is a range.
If it falls into the 0 range whatever that might be it is set to 0.
Only when it is out of that range is the actual number displayed.
 

Stone-cold11

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Hmm... Interesting. Did some rough calculation, 2D area only as a comparison.

Using the data provided by Karl, assuming 0 girdle for comparison.

Infinity
CA 34.5 PA 40.8
Crown Area = 589.7
Pavil Area = 1079.0
Total Area = 1668.7

WF ACA
CA 34.8 PA 40.8
Crown Area = 596.3
Pavil Area = 1079.0
Total Area = 1675.3

Gamers of the system
CA 35.3 PA 41.0
Crown Area = 607.5
Pavil Area = 1086.6
Total Area = 1694.1

Karl''s TIC
CA 34.1 PA 40.9
Crown Area = 580.9
Pavil Area = 1082.8
Total Area = 1663.7

Karl''s FIC
CA 36.3 PA 40.3
Crown Area = 630.3
Pavil Area = 1060.1
Total Area = 1690.3

So from the numbers, Inf cuts has the smallest weight for the same face-up, the gamer''s having the largest. But compared to Karl''s proposed numbers, his TIC will be smallest while his FIC numbers are almost on par with the gamers of the system. All things being equal, I would have thought FIC will account for a greater percentage among AGS graded stone?
 

strmrdr

Super_Ideal_Rock
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Date: 3/3/2009 5:14:29 AM
Author: Stone-cold11
Hmm... Interesting. Did some rough calculation, 2D area only as a comparison.
You have to measure what is cut away of the rough not what is left.
FICs have lower yield because of the high crown and shallow pavilion.
 

strmrdr

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RB left OEC right...The fic would be roughly the same as the OEC
Notice how much rough is lost on the pavilion of the oec compared to the RB.

modernRBvsModernOEC1.gif
 

strmrdr

Super_Ideal_Rock
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Messages
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What it boils down to is pavilion depth is free and crown material can be recovered in a second diamond.
So for max price out of the rough you go for the deepest pavilion you can and then balance the selling price of a higher crown main and a smaller 2nd stone against the selling price of a lower crown main and a larger second diamond.
Most of time the higher crown heavier main stone wins so it comes out steep/deep. The cut premiums put a check on it however.
The added selling price of a AGS0 helps some and has to be factored into it and brings the crown back down some.
Then you factor with the GIA EX addition which allows the crown to go back up some and pick the one that brings in the most money.
Or you cut to the steep/deep edge of AGS0 and if you miss you get the gia EX for max recover and profit from the rough on average over a large run.

The ACA, Infinity, GOG super-ideal and others like them only exist because there is a premium for very well cut diamonds.
Otherwise there wouldn't be enough profit in them to get rough.
 

allinmustwin

Rough_Rock
Joined
Dec 18, 2008
Messages
3

Hi all,


Thank you all for your prompt and informative replies... great to see the board is so active!


My initial logic was based on the assumption that if a diamond falls just outside the AGS0 range, then it automatically receives a lower cut grading; so if a diamond falls just within (or on) the boundary, although it might receive a AGS0 cut grade, it would not actually be in the peak-performing area within that range (which I had assumed would be right in the middle of the range). However, from the comments so far, it appears that the ''peak'' cut (for overall diamond performance) is most often at the edge of the 0-range.


Gary, when you say many people feel that the top edge on your charts is the best spot for the compromise between brilliance / limited leakage and fire, what do you define as the ''top edge''... the top of the chart or edge of the AGS0 range (and if so, which edge - left or right), etc?


Lorelei, when you mentioned that some consider the bullseye to be where GIA and AGS overlap... do you mean where the boundaries intersect or where both cut grades are within the same range?


I''d be interested to get people''s initial opinions on a few stones that I have looked at so far, purely from a cut (and probable performance) perspective. Two of the stones are from one retailer whilst the other two are from a different vendor; however, given the identical crown and pavilion angles of three of the stones (2-3), is it a fair assumption that they are from the same cutter, or could it just be a high coincidence? FYI, all rate EX/EX/EX/VG on the HCA (I was trying to include the results as a picture, but I''m not quite sure how to embed an image into the post).


Diamond 1
Depth = 61.1%
Table = 56%
Crown Angle = 35
Pavilion Angle = 40.7
Culet % = 0
HCA = 1.1 (falls square in the middle of AGS0 range)
Diamond 2
Depth = 62.1%
Table = 55.5%
Crown Angle = 34
Pavilion Angle = 40.7
Culet % = 0
HCA = 0.9 (falls on left most edge of AGS0 range)
Diamond 3
Depth = 62.5%
Table = 54%
Crown Angle = 34
Pavilion Angle = 40.7
Culet % = 0
HCA = 1.0 (falls on left most edge of AGS0 range)
Diamond 4
Depth = 61.9%
Table = 55%
Crown Angle = 34
Pavilion Angle = 40.7
Culet % = 0
HCA = 0.9 (falls on left most edge of AGS0 range)

Obviously without additional information, it is hard to make a judgement call based on numbers alone... and I might be seen a splitting hairs giving the very similar cut angles. Having said that, I''d still be interested to hear people''s opinions on the cut of these diamonds.


Thanks in advance!


Regards,



Paul
 

strmrdr

Super_Ideal_Rock
Joined
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23,295
based on the numbers 2 3 4 would have similar personalities with 1 being the odd one however the basic numbers don't tell the whole story.
A diamond can have the exact same average angles as another and look totally different based on the lower girdles and the optical symmetry.

next step get pictures and IS/ASET images
 

allinmustwin

Rough_Rock
Joined
Dec 18, 2008
Messages
3
FYI... I''ve seen H&A photo of all the stones; they pretty much all appear to have identical optical symmetry (and are all F colour / VS1 clarity / IGI triple EX).

Diamond 1 and 3 were definitely cut at the same factory. I''m assuming given the matching Crown Angle = 34 / Pavilion Angle = 40.7, that the other stones also originated from the same cutting house (is that a fair assumption, or are those angle combinations fairly common?). I''m just curious, because the vendor for stones 1 and 3 claims to have ''exclusive'' distribution for this particular brand of diamond (and is selling the stones at a premium to the other vendor).

What I forgot to mention in my other post is that I now, thanks to everyone''s comments, understand that AGS0 is a range and that there are certain ''premium'' angle combinations that produce relatively better cut/performing stones (of course, I''m still at a lost as to those elusive ''magical numbers'' that I should be seeking out)! ;-)
 

Paul-Antwerp

Ideal_Rock
Trade
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2,859
First question, you are saying IGI-triple EX. Could you confirm that? IGI''s cut-grading is not often discussed here, nor is its accuracy in reporting and possible rounding. If indeed IGI, are the stones loose and is the report a grading-report, or are we talking about a finished jewelry report or a report/appraisal?

Your assumption that the same average angles as reported point to the same cutter is not correct. The angles reported are averages and probably rounded. You can have stones with the same combo, looking completely different and coming from the same cutter. You can also have the same combo, looking similar and coming from various cutters.

Anyway, all that is not really important, I think. I think it is important for you to find a stone that you like. In that case, your efforts to link the HCA-result to AGS-potentials in order to finally find peak performance are pointless. You should start by looking at the HCA as a rejection-tool. In this way, you have already selected four potentials.

Now, you obtain H&A-pics and idealscope (or ASET)-pics. And take it from there.

And if IGI-graded, you need to ask yourself what effect that has. Do let us know also in which country you are.

Live long,
 

strmrdr

Super_Ideal_Rock
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woops wrong thread...

yield and labor
Sometimes the cut bonus is bigger than the size bonus sometimes not.
There are sophisticated machines and computer software that calculate this down to the penny.
 
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