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Grading Reliability


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Hi there,


I've been researching Diamonds for all of about 2 hours and I'm already lost.. I've got my head around the 4 C's but my question is more around the organisations grading them..


I imagine some a more reliable than others and i've already come across quite a few.. Can anyone recommend ones that are trustworthy and ones to avoid?


Any assistance would be much appreciated..




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As a consumer (or even as a professional!), I would advise you to rely only on GIA, AGS and - though rare in the USA - HRD and Gübelin for colour and clarity grading (and treatment/enhancement information). Cut is a complicated topic and to some extent it depends on what you want to set as your criteria (e.g. HRD's overall cut grading system is in my opinion not very good, but they are the only one of the 4 that grade H&A symmetry, and they do that well).


This doesn't mean that a stone without a report from one of these labs is necessarily a bad stone; it is what it is, and the report doesn't change its objective qualities. However you do not have anything other than the vendor's word and your skills at grading to go on... and I would count it a point against the vendor if they do not stick their neck out and tell you what they think of the stone rather than asking you to rely on what they know is an unreliable report.


ETA - the "rest" may well include perfectly respectable organisations and individuals, but it rather boils down to whether you have any knowledge of them and thus reason to trust their judgement. I would consider Neil Beaty's (one of the key contributors to this forum) grading as highly reliable, but he doesn't (yet?) have a worldwide brand or reputation.

Edited by davidelevi
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Which brings up an interesting question (of no help to ice_noob):   What does "smoking hot" look like to different people?    How would you describe "smoking hot" and what makes it different from "really pretty"?

Edited by Mainer
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The first one is the question that GIA asked a few hundreds of people back in the early 2000s, and came up with its cut grading system - including a fairly wide "Excellent" grade that caters for several different looks.


What I would describe as "smoking hot" is two quite different types of look. This is one:




Modern superideal, smallish table and highish crown; hypersimmetrical and very very sparkly.


This is another one:




Old cut so asymmetrical, broad flashes, lots of fire and significantly less bright than the one above. Biggish culet, and a touch of Kozibe effect


But if you really really want to know what's smoking hot for me, it's not a round, and it's not white. Much more likely to be something like this:




6 carats of vivid yellow Asscher cut.


What makes them different from "really pretty"? The fact that I say so - and that's back to the issue with any scale that tries to turn what are continuous or near-continuous variables (amount of light reflected, amount of light refracted, size of the reflection/refraction window, etc.) into a small number of discrete grades: ultimately the choice of where to place the boundary is arbitrary.


In the case of the three stones above, the other thing that sets them (in my opinion) beyond "really pretty" is that they are all somehow rather exceptional:


The modern cut is cut to an exceptional level of precision, by one of the best cutters currently active in the industry.

The old cut is exceptional by having survived - and more so because it's over 4 carats, which means the temptation of recutting it into something more "fashionable" must have been considerable at some points in its life as a cut stone.

The Asscher is exceptional because of size, colour and quality of cut.

Edited by davidelevi
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Had to look up Kozibe effect.  It's lovely,  like looking deep down into the heart of a pool. However,   I'm assuming that AGS  and GIA  don't consider this desirable in better cuts and I'll never see one for real.  That's the problem of looking for a diamond in lab reports,  you see the standard "really pretty"  and are probably missing the  interesting stuff.    

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However, I'm assuming that AGS  and GIA  don't consider this desirable in better cuts and I'll never see one for real.

To some extent - it's a characteristic of older cuts, not least because to be visible it requires a culet of some size, and you are right that in modern cuts that is frowned upon. That doesn't make a modern cut "better" than an older one, even though it is objectively brighter.


As to "seeing one for real", they aren't that uncommon, and when (if?) you organise your dealer visit(s), then asking them to get a few old-style stones in is perfectly possible, just as it is possible to get one (or more) shipped to you at the risk of paying shipping charges and little else.


That's the problem of looking for a diamond in lab reports,  you see the standard "really pretty" and are probably missing the interesting stuff.

That's why you shouldn't stop at a lab report. There are plenty of people willing to provide more information than what's available in a lab report before they ship things to you (or you go to them to see the goods in person). Thinking that you'll know everything - or even most things worth knowing - about a diamond by getting lost in the minutiae of a lab report is the basic mistake...
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