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Examples of AGS000 with bad HCA scores...

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Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
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31,003
ONT face="Papyrus">We always discuss on here about how AGS 000 is not the end-all-to-be-all when you are searching for stones. When I was learning..I didn't really understand how the AGS000 grade didn't mean a great stone. Wasn't it supposed to be easy for you to find a great stone if you didn't know anything? Didn't the AGS000 grade mean that hands-down, that stone would be 'ideal'? Kind of like 'Diamonds for Dummies' (which I now think SuperbCert and ACA stones are...but I'd probably buy one cuz they sure do look pretty!). Like the Macintosh of diamonds?
I'm a PC girl myself.

Anyway--I was checking out a website online today that was recommended to me as local and I found out they use the virtcert engine that alot of other vendors do. For fun I was researching 1.50c+ stones and clicking on the ones that had Sarin results and punching them into the HCA (yes its Friday afternoon and I am very bored).

I was surprised to find that many of the 'ideal' AGS000 stones scored very badly on the HCA. Well not BADLY in all cases..more like..not quite 'excellent'. Well not *surprised* that there are AGS000 stones that score badly on HCA--but rather that so many of the stones that actually HAD Sarins for them on this site, had non-desirable results. Then I thought...what a great education tool!


So for those people who want to know about AGS000 or want to see a mediocre cut, but expensive stone...view the following.


http://search.virtcert.com/cgi/u/1038/v.cgi?stock=115642&_s=1038&_p=pia&_c=&_fs=1&prestock=

64.4 depth AGS 000 ideal G VS2 (ha ha 64.4% depth!)

4.8 on HCA Good/Good/Good/Good scoring


http://search.virtcert.com/cgi/u/1038/v.cgi?stock=146831&_s=1038&_p=pia&_c=&_fs=1&prestock=

2.4 HCA scoring, all VG --- AGS 000 according to Sarin (not too bad!)


http://search.virtcert.com/cgi/u/1038/v.cgi?stock=1116402&_s=1038&_p=pia&_c=&_fs=1&prestock=

4.8 HCA scoring, 2 VG, 2 Fair--AGS 000 according to Sarin (yikes!)


http://search.virtcert.com/cgi/u/1038/v.cgi?stock=1104399&_s=1038&_p=pia&_c=&_fs=1&prestock=

2.2/2.7 HCA scoring (accounting for diff table sizes on Sarin vs report), AGS 1 according to Sarin (better HCA than AGS all of the AG000 above? interesting.)

For those interested..my stone is an AGS7 due to the large table and shallow depth...it scores a 2.3/2.8 on the HCA depending on what day you punch it in (that Garry...always making changes!!). When I bought it, it scored a 1.5 on the HCA, but since then the criteria have shifted. It's a gorgeous stone and looks better than all the diamonds I have compared it to since we got it. (of course I am a little biased) When Lugus comes into town someday, I am comparing it to his sweetie's SC stone.


Anyway--just goes to show that the AGS000 grade does not always make the stone. For those of you searching, be sure to use all the tools available BESIDES the certification, because that does not guarantee anything except color and clarity and ctw...and sometimes not even that!
 

rbjd

Shiny_Rock
Joined
Feb 4, 2003
Messages
154
Mara, there's obviously some incorrect information going on with that first stone on your list. A 64.4 depth CANNOT BE AGS 0 proportions, so either the 64.4 number is wrong or the AGS 000 is wrong. And since we ALREADY KNOW that a real AGS 000 can only be a D, IF stone, that AGS 000 is clearly wrong for the listed stone.

That looks like a broker database you were searching from, which means that same stone is available through many brokers. I suspect whoever entered the data into the system got some of it wrong. Well, obviously that's the case.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Many of us wrongly and commonly use AGS000 to describe ideal cut, ideal symm and ideal polish. the REAL AGS000 means ideal cut and D IF as you note. I use AGS000 in the former way in my post.

Actually if you go to the url and click on the cert..it loads in a scanned copy of the REAL AGS certificate where it shows 64.4% as the depth. Also the Sarin, if you click on report, shows the same thing. I was shocked as well. But there it is!
 

rbjd

Shiny_Rock
Joined
Feb 4, 2003
Messages
154
You know Mara, that sure is interesting. I ran the numbers myself to determine depth:

7.50 + 7.57/2 = 7.535

4.83/7.535 =.6410

approx 64.1 depth

SO CAN SOMEBODY EXPLAIN HOW ON EARTH AGS GRADED THIS STONE AS AN IDEAL PROPORTION AGS 0 CUT WHEN IT OBVIOUSLY HAS A 64.1 DEPTH ACCORDING TO THE CERT? WHAT GIVES?
 

rbjd

Shiny_Rock
Joined
Feb 4, 2003
Messages
154
Somebody ought to capture the cert image on the 64 depth stone and post it here before the link gets clipped.
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
As requested...the report got a little clipped due to my sloppy screen shot..but here it is.

AGS644.jpg
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
And the Sarin report too.


Sarin644.jpg
 

Lugus

Shiny_Rock
Joined
Jan 17, 2003
Messages
213
This is precisely why each potential diamond buyer must spend 4 months of intense study before purchasing their stone! Oh wait, maybe that's just me.

Mara, I might be up that way to visit Nasa sometime soon. If you ever look out your window and think there are two suns, one just might be me driving by with the ring
 

rbjd

Shiny_Rock
Joined
Feb 4, 2003
Messages
154
OK, I figured it out. Per AGS grading standards, the PAVILION DEPTH can be up to 43.5 and still be AGS 0. Since this diamond has a 43.4 pavilion depth, it just made it in. In this diamond's case it makes for a 64.1 (or 64.4 per Sarin) TOTAL DEPTH AGS 0.

Thanks for pointing this out Mara. Just goes to show how wide of a range AGS 0 really is. I don't think I'd ever consider buying a 64 depth round brilliant diamond.
 

dimonbob

Brilliant_Rock
Trade
Joined
Dec 12, 2000
Messages
670
Ok, let me try to explain this.

In the first place AGS Ideal does not have a total depth measurement. It has a max and min pavilion depth, girdle thickness and table. It does have max and min crown angles. So it is possible if a diamond maxes out on the pavilion and girdle and has a small enough table, it will get into what we call high total depth numbers. So according to what I know, this is an Ideal cut.

What I have always found curious is the three different numbers numbers, pavilion depth, girdle thickness and crown height almost never equals what the total depth number is when using a Sarin machine.
 

mdx

Brilliant_Rock
Joined
Mar 1, 2002
Messages
570
Mara
The 16.5% Crown Height and 54.2 Table was the giveaway.
As you continue your looking with your obvious passion for beautiful diamonds I predict you are going to find a lot of absolutely stunning stones with HCA scores higher than 2.

Wayne
Melbourne Diamond Exchange Ltd.
 

Serg

Ideal_Rock
Trade
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Mar 21, 2002
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This is girdle trick.
See:

http://www.diamondtalk.com/forums/showthread.php?threadid=23315
Serg

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Post 1 - #214158 11-13-02 11:17 AM
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How much can the weight of two AGS0 diamonds differ if all the geometrical cut parameters are the same in the certificates.



Different parameters affects the weight difference, in particular the "squareness" of the girdle (deviation from the circle) does.

But I want to turn attention to the influence of the girdle thickness and problem of the correct measurement of this parameter according to AGS system.



Let's consider a symmetrically cut diamonds in the "classical" way (Unfortunately this is not defined exactly anywhere. Nevertheless for instance we can take pictures from the AGS certificate or models from the GIA site http://www.gia.edu/wd_1383ar_6367.htm#GirdleThickness or of from the DiamCalc software registered).



Let all cut parameters of this diamond are AGS0 except the girdle thickness.

Let the girdle be 4.5% at bezels and 2.8% at valley. Therefore this diamond is AGS3.

But smart cutter doesn't want to loose money so he increases the slope of the "upper girdle facets" by 3-5 deg.* that leads to decrease of the girdle thickness at valley by 1% (so new value is 1.8%). The girdle thickness at bezels remains the same 4.5%, the weight almost remains as well but now the diamond is apprised as AGS0. The example of such diamond is AGS 0003479101.

*Of course the real process is more sophisticated and performed at the stage of crown cutting, here we just show you a demonstrative way.



The diamond with the "classic" cut with the girdle 1.8% at valley and 3.5% at bezel has weight that is less by 3-4%.



The questions:

How correct is that the "smart" diamond is granted with the same highest AGS mark as the "classic" one.



How correct is girdle appraising by measurements at the points of one type?



If the beauty of these diamonds is apprised, should these diamonds receive the same marks or different?



--------------------------------------------------------------------------------
MSUSerg
 

Richard Sherwood

Ideal_Rock
Joined
Sep 25, 2002
Messages
4,924
I thought you would get a kick out of the DiamCalc simulated IdealScope image for that stone, Mara. Look at all the leakage inside the table area, as well as the light pink showing up in the upper girdle bezel areas! No wonder it scores so low on the HCA.

--------------
What I have always found curious is the three different numbers numbers, pavilion depth, girdle
thickness and crown height almost never equals what the total depth number is when using a Sarin
machine.
--------------

That used to puzzle me as well DimonBob, until Garry clued me in that the pavilion depth and crown height are measured from the girdle "peaks", while the girdle thickness is measured at the "valleys". The difference is usually about 1.3 to 1.7%, which is the "missing link" in the total depth vs crown+girdle+pavilion measurements.

RBC- 1.718.jpg
 

Mara

Super_Ideal_Rock
Joined
Oct 30, 2002
Messages
31,003
Wow Rich that diamond is a mess! The leakage along the girdle facets...could that be because of what Serg was posting about? Modification of the upper girdle facets to push the stone into the AGS 0 range?
So it sounds as though there are two possible scenarios: a) thick girdle=modification of minor girdle facets to push girdle range into AGS0, even though it ends at slightly thick which is still not ideal or b) combination of table, pav and girdle to still be within the AGS 0 range?

Could both have happened? Or is it always one or the other?

What might cause the light leakage under the table in the stone in the DiamCalc image?

Thanks for the explanations on the AGS0 grade and how this particular stone may have fallen into that range. It's very interesting to see the research being done on minor facets and how that really does affect the beauty and marks of a stone.

I think this thread in general is a great educational read for anyone considering that AGS 0 stones are the way to go without additional research. Nothing against the AGS 0 grade but obviously there is much more to the puzzle than just the big pieces.

 

niceice

Brilliant_Rock
Joined
Jan 29, 2003
Messages
1,792
As with all things based upon a range, there is a high and low range for the zero ideal cut rating... No doubt this is an attempt by the AGSL to appease the political powers that be within our industry. The center of the range is probably what Peter Yantzer really had in mind when he created his zero ideal cut rating and you'll note by a study of such stones will produce very nice results on the HCA. This is where consumer awareness becomes important, the realization that "AGS Ideal-0" is not an absolute guarantee of performance, just a potential indicator. We suggest that people search for diamonds with a total depth between 59 - 61.8% because this range of total depth prevents them from buying diamonds that have too much depth and wasted carat weight that is not a visual benefit. There are also preferred ranges for the crown angle (34.3 - 34.8 degrees) and the pavilion angle (40.5 - 40.9 degrees) although other crown / pavilion angle combinations will produce similar visual results... The key to selecting a beautiful diamond is to do your research before you buy, thanks for starting an excellent thread Mara!
 
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