Let's Play Detective ... your vote/input appreciated

[Christina...]

I guess, I don't feel so bad for not being able to solve the mystery now!

Why does AGS include 40 degree angular spectrum in their assessment if it isn't easily detected in human observation? How many stones, would you guess, are downgraded to AGS1 based on this degree of assessment?

 

[eric9547]

It teaches me AGS is more strict in their designation of Ideal than GIA. Would there be a scenario where an AGS 0 would not make GIA excellent cut?

 

[Rhino]

To answer the questions...

Maybe it teaches us, that we are paying for something we can't see like vvs2, D, and 1.00carat as opposed to 0.99, but this
is the Cut version of it.

Perhaps but that would depend on whether one was an individual wherein the 40 degree obstruction zone affects.

Given a 30 degree and 40 degree obstruction analysis, it would ultimately depend on the person's normal viewing distance or focal length when observing diamonds. For me personally it's half an arms length and the 30 degree zone works just fine. I help consumers all the time however who do not share my focal length and generally observe their diamonds at a closer focal length. This is what the 40 degree angular spectrum is taking into account.

So the AGS ideal cut is elusive unless you are buying one as it has a secret that only a diamond dealer like Rhino would know of,
given that people looking for education are going quite happily along with the Asset scope picture not knowing there is a higher
level which should be thought about OR has the AGS discovered something more desirable for better light performance.

No no... AGS is not being elusive nor is this information that is exclusive to myself. If a diamond is AGS graded in their current system, no need to worry as it covers both 30 and 40 degrees. I'll share with you where/when it would concern me.

Is it a cheat, and not important?

No cheat and yes very important. Pyramid, would you pay top dollar for an AGS 1? Truth be told the diamond looks fine to me and doesn't suffer from ill contrast effects, however I am one of those for whom the 30 degree obscuration zone works just fine. For someone else who has a different focal length, according to AGS not so and they are the grade setters.

I guess, I don't feel so bad for not being able to solve the mystery now!

Why does AGS include 40 degree angular spectrum in their assessment if it isn't easily detected in human observation? How many stones, would you guess, are downgraded to AGS1 based on this degree of assessment?

You shouldn't feel bad Christina. This was a tough one but a good example to learn from. The reason they include a 40 degree angular spectrum in their ray trace analysis is for those people who draw the diamond closer to their eyes than others upon regular observation. How many are downgraded to AGS 1 based on this? Good question. IMO these types of AGS 1's would make for a great buy as long as ...

a. The consumer doesn't mind the AGS 1 designation on the lab Report.
b. Has a focal length that will not impact the optics *to them*.

It teaches me AGS is more strict in their designation of Ideal than GIA. Would there be a scenario where an AGS 0 would not make GIA excellent cut?

True Eric. AGS' 11 grade system is more strict than GIA's 5 grade system however there are aspects of GIA's system that are more strict than AGS's. Both systems have their pros and cons. In answer to your question, absolutely there are AGS Ideal's that will not make GIA Ex.

Kind regards,
Rhino

 

[Rhino]

And before I cut out for the weekend, the GIA results.

In the poll (which now stands at 33 votes) 9 voted "Safely GIA Ex but not AGS Ideal" and 9 voted "Safe bet in both labs" with a total of 18 votes of confidence it would be GIA Ex.

Hate to break it but NEITHER IS IT A GIA EX!

Below are the Facetware results based on a Sarin HD scan and the diamond was also sent to GIA with confirms the results below as well.

Primary reason it didn't make Ex? The star facet length reached 60% (an actual average of 59.2% which GIA rounded to 60%). If it would have rounded to 55% it would have made Ex. Results below.

This, IMO is ridiculous. Generally when you do alter star facet length it can, at the same time alter upper half angles which can and do have a visual impact on the diamond (ala painting and digging) however this diamond is only dug out .33 degrees on the upper halves and painted -.9 degrees on the lower halves. Hardly enough to ding it. As ridiculous as it is a GIA VG will not fetch the same demand as an Ex.

Hope this helps and have a great weekend all.

Kindest regards,
Rhino

 

[kenny]

I knew that ... but I didn't want to show off.



NOT!

 

[ame]

FASCINATING! Cool test. SO I was half right, I didn't think it would make GIA EX, but I thought for sure the angles would work in AGS Ideal.

 

[MissGotRocks]

I was half right too - thought it wouldn't make AGS0 but thought it would make GIAxxx. Just shows to go you. . .

 

[justginger]

Great thread, Jon - really interesting and informative.

 

[Rhino]

I knew that ... but I didn't want to show off.



NOT!

You card!

To be perfectly candid the diamond threw me for a loop too. We took it in on consignment and our Sarin was down when the client dropped it off but everything seemed kosher and we sent it to GIA. I looked just like this when we got the results and of course we got our Sarin back by then. It's an important diamond so we're going to have it recut so it safely falls in spec of both labs top grades and H&A. I learned from the experience and I thought you guys and gals would appreciate it too. Thanks everyone for the kind words and your participation.

Have an awesome weekend (what's left of it!).

Warm regards,
Rhino

 

[Rhino]

I was half right too - thought it wouldn't make AGS0 but thought it would make GIAxxx. Just shows to go you. . .

I wasn't going to comment on your earlier post because I wasn't ready to give it away but I was impressed by your educated guess MissGotRocks. Good job.

 

[Karl_K]

It's an important diamond so we're going to have it recut so it safely falls in spec of both labs top grades and H&A.

Rhino

That makes me sad that a broken contrast model at one lab and bogus rounding as well as one number fits all rational at another means a perfectly fine diamond is going to be recut.
Frankly I would be perfectly fine with this diamond the way it is right now.

 

[MissGotRocks]

I was half right too - thought it wouldn't make AGS0 but thought it would make GIAxxx. Just shows to go you. . .

I wasn't going to comment on your earlier post because I wasn't ready to give it away but I was impressed by your educated guess MissGotRocks. Good job.

Thank you sir and thanks for the learning experience!

 

[GamGam]

Rhino,
I hope you come back and re-read my earlier post, because I think that all 13 of us who voted that the stone would be rated GIA Excellent but not AGS 0 are correct based on your first post. I have a diamond with the EXACT numbers which you posted and it is, indeed, rated GIA EXCELLENT. I can post the GIA number if you're interested.

 

[Karl_K]

Primary reason it didn't make Ex? The star facet length reached 60% (an actual average of 59.2% which GIA rounded to 60%). If it would have rounded to 55% it would have made Ex. Results below.

Rhino

I actually like longer longer stars with a 34 crown.
The difference is subtle but it is there.
It makes the uppers girdles slightly steeper which aids off axis light return and scintillation with 34 crowns.
As long as they don't get so steep that they go light in IS they are fine.
Which is why GIA down grades for long stars, with some crown angles they can make the uppers too steep but this is not one of those combos.

 

[Christina...]

Rhino,
I hope you come back and re-read my earlier post, because I think that all 13 of us who voted that the stone would be rated GIA Excellent but not AGS 0 are correct based on your first post. I have a diamond with the EXACT numbers which you posted and it is, indeed, rated GIA EXCELLENT. I can post the GIA number if you're interested.

In this case it wasn't because of the stones table, depth, pavilion and crown proportions that caused the downgrade, but rather the length of the star facets. Your particular stone likely has star facets around 50-55, in this case GIA round 59.2 to 60 and downgraded the cut to VG.

 

[Rhino]

It's an important diamond so we're going to have it recut so it safely falls in spec of both labs top grades and H&A.

Rhino

That makes me sad that a broken contrast model at one lab and bogus rounding as well as one number fits all rational at another means a perfectly fine diamond is going to be recut.
Frankly I would be perfectly fine with this diamond the way it is right now.

No disagreement my friend. I understand to a degree the AGS hit as the 34/40.6 combo is pushing it but to my (and what I would think most others) focal length it looks ok. Our Sarin HD measured 40.66 average pavilion mains but you do have some dipping as low as 40.3 degrees which are clearly too shallow. I can post a facet by facet if you're interested Karl.

 

[Rhino]

Rhino,
I hope you come back and re-read my earlier post, because I think that all 13 of us who voted that the stone would be rated GIA Excellent but not AGS 0 are correct based on your first post. I have a diamond with the EXACT numbers which you posted and it is, indeed, rated GIA EXCELLENT. I can post the GIA number if you're interested.

I am curious to see GamGam. In the proportion graphic I posted it left out star facet length. I was waiting to see if anyone was going to ask about that.

 

[Rhino]

Primary reason it didn't make Ex? The star facet length reached 60% (an actual average of 59.2% which GIA rounded to 60%). If it would have rounded to 55% it would have made Ex. Results below.

Rhino

I actually like longer longer stars with a 34 crown.
The difference is subtle but it is there.
It makes the uppers girdles slightly steeper which aids off axis light return and scintillation with 34 crowns.
As long as they don't get so steep that they go light in IS they are fine.
Which is why GIA down grades for long stars, with some crown angles they can make the uppers too steep but this is not one of those combos.

I totally agree as well. If you recall a couple of years back I had H&A's with around a 60/40 star upper ratio and sometimes as much as 65/35. That coupled with the proportions they were typically being cut to (34-34.5/40.7-40.9/55-56) made for stupendous diamonds. In fact I think your wifey's has stars in this neighborhood if memory serves me right. But yes ... I agree totally.

Good star length coupled with proper lower half length on a modern round brilliant H&A contributes in fact to good pin fire scintillation as it amplifies high angle light return around the table reflections on the pavilion.

 

[yssie]

I missed the original poll but I just had to chime in and say thanks for posting this Rhino - it's a really interesting specimen! And I'm enjoying the explanations

 

[GamGam]

Rhino,
I'm so glad you saw my second post. Here's the GIA report Number:2115155783. Any addition info about my stone would be a + for me. And perhaps the key word in the poll was "safely".

GamGAm

 

[diamondseeker2006]

I would have never figured out the reason in a million years. But I don't need to worry since you always will always know these things, Jon!

 

[Ashleigh]

Jon, part of that explanation is over my head. So I wouldn't have gotten it right in a million years. Interesting to know nevertheless. Thanks.

 

[Resani_K]

I haven't a clue, but I enjoy reading everyone's posts and learning more. Modern diamonds are still a mystery to me.

and the final expressions is

 

[Rhino]

I haven't a clue, but I enjoy reading everyone's posts and learning more. Modern diamonds are still a mystery to me.

and the final expressions is

LOL If there is anything unclear that you'd like me to expound upon let me know and I'll be happy to explain.

GamGam ... just looked up your Report and yes ... the numbers are virtually identical EXCEPT yours has stars that are 55% as opposed to the 60% stars in this example.

 

[GamGam]

Rhino,
THanks for taking a look at the numbers on my stone.
Now a question for you, doesn't this mean that all of us who answered your poll about the numbers yielding Excellent cut are correct? Just bugging you a little.

 

[Rhino]

Rhino,
THanks for taking a look at the numbers on my stone.
Now a question for you, doesn't this mean that all of us who answered your poll about the numbers yielding Excellent cut are correct? Just bugging you a little.

Nope.

An Ex is an Ex and a VG is a VG even if it's for reasons we think are not good.

 

[TC1987]

What does this teach us? Um, that RockDiamond's adage that diamonds have to be seen is sometimes or (for the choosy consumer) always correct. (ducking and running ... )

I admit I was too lazy and too busy to study the scenario presented. The fact that the actual GOG ASET showed light blue arrow shafts where the computer sim bothered me and made me suspect lack of contrast, or that the diamond might be "bland" in some way, regardless of who or whether it was graded excellent. I purchased one GIA triple excellent that always seemed bland and boring to me. I later traded/upgraded for one that shows strong contrast patterns and am perfectly happy with it. I am nearsighted, and also farsighted now, so I get my best visual inspection at about the 12" range without glasses.