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AGS and HCA Disparity?

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simplysplendid

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Hi,

My girlfriend is picking out her e-ring so I am offering some assistance. She is looking at a GVS2 1.34 carat AGS000 diamond. The specs of the diamond are:

Table: 56.4%
Depth: 62%
Crown Angle: 34.6
Pavilion Angle: 41
Culet: None

I plugged the numbers above into the HCA and it generates a 2, with only Excellent for Light Return and Very Good for everything else. It also falls outside of the AGS Ideal box, yet this is an AGS000 diamond.

Would the experts kindly provide some advice why there is a disparity here? Thank you very much!
 

kenny

Super_Ideal_Rock
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Why not just look for another one that is in that nice warm fuzzy middle of the AGS box on the HCA chart?
 

belle

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is it a new grading report? (indicated by the addition of the section for ''light performance'' grade)
 

Regular Guy

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Not sure how important Kenny''s point is (curious, though), and Belle''s point should be attended to for sure (as it could provide a simple explanation). But the HCA author has directed contemporary AGS0 should supersede HCA disparities, as it''s built on a lot of real "diamond in hand" data....not to mention that Garry has suggested in redoing HCA, he might lift the boundary to 2.5 anyway.
 

Finding_Neverland

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Date: 1/30/2007 9:51:38 AM
Author: belle
is it a new grading report? (indicated by the addition of the section for ''light performance'' grade)
Belle''s suggestion to check the Cert is a good place to start. Could be you have what the AGS used to consider an AGS0 as far as cut. Now with the added Light Performance info being added, this diamond might not be an AGS0 under the new system.

"Diamonds with AGS 0 or ideal cut reports that were issued before 1st of June 2005 might not be considered to be AGS 0 under the new system, which is more like the HCA inverse crown and pavilion system. It uses light performance factors including software like DiamCalc, and the ASET scope, which is like a multi colored Ideal-Scope. Proportions are now only to guide to manufacturers and not the basis of grading. Stones must not breach certain ''bad proportions'' and finish rules outlined below (this chart is indicative, but not the same as later AGS copyrighted versions)."


http://diamonds.pricescope.com/agsideal.asp
 

strmrdr

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If its a new AGS0 cert and its a h&a stone then AGS is right and the hca is wrong in my opinion.
The hca is overly harsh on these combos they can be excellent diamonds as good or better than the under 2 stones if they have good optical symmetry and they are fairly tight.
AGS takes both into account in there software when they assign the grade.

note: no AGS dont grade optical symmetry but the light performance score is based on ASET and aset shows optical symmetry and in some combos rewards it.

edit: the lgf% is important also in this combo but didn't want to open that can of worms again but it is important and something the ASET shows and the AGS software takes into account when it scores the contrast ratios.

The reason that they differ is that AGS takes all that into account and the HCA doesn't so the HCA/Garry error on the side of caution and give them a 2+ which with some of them is the score they deserve.
I'm one of the HCA's biggest fans but it has exceptions where more knowledge is needed to properly apply it other than just the score.
 

Rhino

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Date: 1/30/2007 9:47:25 AM
Author:simplysplendid
Hi,

My girlfriend is picking out her e-ring so I am offering some assistance. She is looking at a GVS2 1.34 carat AGS000 diamond. The specs of the diamond are:

Table: 56.4%
Depth: 62%
Crown Angle: 34.6
Pavilion Angle: 41
Culet: None

I plugged the numbers above into the HCA and it generates a 2, with only Excellent for Light Return and Very Good for everything else. It also falls outside of the AGS Ideal box, yet this is an AGS000 diamond.

Would the experts kindly provide some advice why there is a disparity here? Thank you very much!
There is absolutely nothing wrong with a 34.6/41 combo in both a practical and critical analysis. I work extensively with many technologies when it comes to diamond cut quality and light performance and I can tell you from experience, there is nothing wrong with that angle combo whatsoever. Go for it.
 

simplysplendid

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Hi All,

Thanks guys..The cert is dated 04 Jan 2007. It says:

"Cut Grade: AGS Ideal 0
Polish: Ideal
Symmetry: Ideal
Proportion: Ideal"

The lgf is not available though..
 

belle

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Date: 1/30/2007 4:29:30 PM
Author: simplysplendid
Hi All,

Thanks guys..The cert is dated 04 Jan 2007. It says:

''Cut Grade: AGS Ideal 0
Polish: Ideal
Symmetry: Ideal
Proportion: Ideal''

The lgf is not available though..
it is an ''old'' format report. it would not have received the ideal grade under the new system. there is your discrepancy!
 

strmrdr

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Date: 1/30/2007 4:29:30 PM
Author: simplysplendid
Hi All,

Thanks guys..The cert is dated 04 Jan 2007. It says:

''Cut Grade: AGS Ideal 0
Polish: Ideal
Symmetry: Ideal
Proportion: Ideal''

The lgf is not available though..
likely came out as a new ags1 so they had the old report used.
The angle combo can go either way depending on the minor facets and how tight it is.
 

Rhino

Ideal_Rock
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Date: 1/30/2007 5:08:27 PM
Author: strmrdr

Date: 1/30/2007 4:29:30 PM
Author: simplysplendid
Hi All,

Thanks guys..The cert is dated 04 Jan 2007. It says:

''Cut Grade: AGS Ideal 0
Polish: Ideal
Symmetry: Ideal
Proportion: Ideal''

The lgf is not available though..
likely came out as a new ags1 so they had the old report used.
The angle combo can go either way depending on the minor facets and how tight it is.
I don''t understand how ya''ll can be quick to arrive at the conclusion that it''d be an AGS 1 in the new system.
I''ve seen steeper combos than this in the new system that make ideal grade for light performance rather easily. I''ve also seen new ideals with pav angles down to 41.2. With those propotions, polish & symmetry there are 2 factors that might disqualify it in the new system and that would be either digging or excessive painting of the girdle facets and there''s not a whole lot of those around, although they do exist, so if this stone appeals to you you may want to request a new report or have an experienced appraiser who knows how to grade features of girdle cutting to look at it to appraise for you. 1.3xct G VS2 diamonds are not easy to come by and I wouldn''t pass this up so quickly even with the older report.

My .02c
 

strmrdr

Super_Ideal_Rock
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Messages
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The date is Jan 2007 so for some reason someone chose to use the old cert the most logical reason was it got an ags1 under the new system.
There are stones with those angles that get ags0 yes..but for whatever reason I bet this one didnt and thats why the old style cert was used.

Which pisses me off that AGS is still letting it be used.
 

Garry H (Cut Nut)

Super_Ideal_Rock
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You guys seem to know from the wording that it is an old stlyle report - not light performance. Good catch.

Rhino when a stone is right on the edge of steep deep the faceting must be very tight and symmetrical. Or in a case like this a little painting could save it, and any digging kills it. I would have no problem with it if it was slightly painted or regular and H&A''s grade.

I endorse this:
Date: 1/30/2007 10:23:09 AM
Author: Regular Guy
Not sure how important Kenny''s point is (curious, though), and Belle''s point should be attended to for sure (as it could provide a simple explanation). But the HCA author has directed contemporary AGS0 should supersede HCA disparities, as it''s built on a lot of real ''diamond in hand'' data....not to mention that Garry has suggested in redoing HCA, he might lift the boundary to 2.5 anyway.
 

Finding_Neverland

Shiny_Rock
Joined
Jan 10, 2007
Messages
412
Maybe they have rheems of old paper already printed that they didn''t want to trash??!!


There''s got to be some rhyme and reason to it. I saw 2 Certs from October ''06. The mid month one was printed old style. The newer one, printed just 2 weeks later, was printed new style.

Maybe someone from AGS or someone in the know could explain why one diamond gets the whole report while another get''s the old style report. Is this maybe like the "mini Certs" that used to be printed with some stones??
 

JohnQuixote

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Date: 1/31/2007 1:07:09 AM
Author: Finding_Neverland
Maybe they have rheems of old paper already printed that they didn't want to trash??!!


There's got to be some rhyme and reason to it. I saw 2 Certs from October '06. The mid month one was printed old style. The newer one, printed just 2 weeks later, was printed new style.

Maybe someone from AGS or someone in the know could explain why one diamond gets the whole report while another get's the old style report. Is this maybe like the 'mini Certs' that used to be printed with some stones??
The manufacturer or sender requests the report style, and can do so after the lab sends a pre-grading indication. So, if this diamond missed ideal in the new AGS light performance metric the sender may have requested the old report format (under which it still makes ideal).

The new range is more strict. AGS wanted to give upstream manufacturers time to adjust but will stop printing the old format in March. Many stopped using the old report as soon as the new one came out. Others have adapted more slowly.

What this may actually do is cause some manufacturers to send stones like this to the GIA instead of AGS in the future. It will still earn EX if not in the 2% of diamonds affected by painting or digging in GIA's metric.
 

Rhino

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To a degree I can understand AGS wanting to allow the industry to wait and catch up to the new system but to a degree I also don''t like it either. A supplier sends stones to them ... it doesn''t make it in the new system, then they have the option to give it the old better grade.
If GIA were doing this I can''t begin to imagine the howling that would go on here.

What John has suggested may be true however it may also not be either. The manufacturer or store submitting the stone may have been used to and liked the old system and will hold onto it for as long as humanly possible and the stone may be just fine. At best we can only speculate.

Garry, I understand your point and totally agree with yours and Ira''s comments but when I see diamonds with this kind of reflector image lambasted by unknowing consumers on the forum who don''t know any better because of its numbers, it''s really a shame. And this stone on the Sarin DiaMension is 34.8/41 (Helium is same with a difference of almost .1 in the crown) and scores over a 2.0 on the HCA. Something is wrong and it certainly isn''t the diamond. It passes with flying colors every exam you can throw at it. This may be the case with this persons stone as well is all I''m saying.

Kind regards,

br189diamxray2.jpg
 

Rhino

Ideal_Rock
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Date: 1/31/2007 1:06:05 AM
Author: JohnQuixote

Date: 1/31/2007 12:21:51 AM
Author: strmrdr

Which pisses me off that AGS is still letting it be used.
Cutoff date for old report format 03/07 last I heard.
They''ve had enough time to adjust.
This is good (the cut off date) and I totally agree. The industry has had plenty of time to adjust.

Peace,
 

strmrdr

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Date: 1/31/2007 9:14:43 PM
Author: :)
While we are on the subject...

Am I blind reading this report? It looks like an AGS 000 with 35.7 and 40.8 with 55.2 and 61.9? that would give a Holloway of 2.9? It doesn''t even fall in the AGS box??? Is the report smudged and I am looking at it wrong?
http://www.jamesallen.com/diamond.asp?cid=131&item=887957
nope your not reading it wrong....
everything came together on that stone and it got the score...
there are all kids of wierd combos that get the new ags0 but its a very narrow box to hit once you get outside the tic range.

The new AGS system is not proportion based in theary a ton of combos could get ags0 but some are far more likely too.
 
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