Radiant cut proportions

[nineta]

I am extremely confused about the proportions in a square radiant cut...

I am looking for a +/- 2ct stone for a solitaire and based on the AGA cut grade chart, the Radiants are in the same basket as the Emerald cuts (e.g.: table 61-63.5% and depth 60-65% for ideal cuts). However, wouldn''t a square Radiant be better placed in the Princess category (i.e.: Table 62-68% and depth 64-75%)?

What should be the correct proportions for a square (let''s say, up to 1.1 l/w ratio?

Many thanks in advance!

 

[valeria101]

What does "correct" mean to you ?


There is a good reason for the AGA clasiffication... Most radiant cuts are not made to resemble a princess cut with clipped corners (although some stones are cut this way, for better or for worse) but have a very different facet design. The cut of princess diamonds is prone to different faults than the radinat, or the Ec... While there could be arguments for either kind of clasiffication, I would most likely end up agreeing with the AGA, although it is hard to judge these choices from the pther side of the jeweler's counter

))

It is rather hard to find square radiants anywhere close to AGA's standard - as Nicrez recently discovered. She went for Henry Grossbard's branded radiant. If I understand correctly, this firm introduced the radiant cut under patent, you may want to inspect their site for another opinion on what A rad's propostions 'should' be.

A critical evaluation of both AGA's and Grossbrad's numbers, would probably as much as oe can do to get some THEORETICAL view on what these proportions could be. Judging stones would probably rely less on stats : these are ment as guidelines, not hard-line rules, I suspect.

Just my 0.2, of course

 

[nineta]

Thank you Valeria,

What I mean with 'correct' is the optimal proportions for light return and brilliance. It startles me that the optimal proportions for an ideal radant can go from 60% to 75% depth, depending which chart you use (emeralds vs princess). And from a pure geommetrical point of view, it's difficult to understand that a rectangular cut should have the same proportions as a square cut... Even Grossbard talks about different depth requirements for different proportions of radiants (rectangular vs more square). I've sent him an email and post his answer here...

 

[valeria101]

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On 2/29/2004 5:52:14 AM nineta wrote:

Thank you Valeria,

What I mean with 'correct' is the optimal proportions for light return and brilliance.
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No, no, no... those proportions (AGA's at least) are not meant to maximize light return !!! Actually, just knowing the pavilion and crwon % would not determine the shape or optical performance of a rad - you'd need a half more dozen angles to pluck into a mathematical model or something (such as the HCA does and DiamCalc) and, as far as I know, no study is yet available to say what proportions give top light return in a Radint.

SO ? what you want is a radint that passed some test for light return (Idela Scope Brilliance Scope or simmilar). I knwo Whiteflash has a couple of small radiants with Iscope images taken. maybe he can source one within your specifications light return tests and all ? No matter who the seller you will pick is, if light return is what you want, you would need to select the stone using such a device, not numbers, I am affraid...

 

[valeria101]

You may want to read the explanation of what the AGA standards stand for. Also, a discussion http://www.gemappraisers.com/chartFrameset.htm of how the AGA chart for rounds relate to light return. For the other shapes, such discussion is not feasible since no equivalent tool to the HCA ia available for non-rounds... as far as I know.

The "Four Cs" page on the radiantcut.com explains that their cut model and parameters aims to achiece superior brilliance, fire and proportions. Given that detailing in technical terms what these are (such as the use of Brilliance Scope, Isee2 and others requuire for rounds) is by no means a requirement (or a straighforward choice for a sensible sales strategy)... it is up to you to decide wether this page conveys as much guarantee of cut quality as whichever light return measuring device you prefer. Taugh call.

It is probably much easier to get a few of these stones, branded (Grossbard's) and not (say 1A-2B per AGA) and see for youself. No test may beat good taste, IMO.... Does this make sense?

 

[oldminer]

Valeria is one of the few who have given sufficient thought to what the AGA system both means and does not mean. With AGA numbers you can know about "good cutting". You don't know about light return from the AGA system. These details are also extremely important. Brilliancy, scintillation, and intendsity combined with a great shape, will give you the best sort of fancy cut diamond.

You will find some very biased information on fancy cut diamonds available in the Internet. The majority of this comes from cutters who want to sell you primarily overly deeply cut diamonds. While these stones may well give you wonderful light return, they won't look their size because they are too deeply cut. They will provde a lot of extra profit to the cutters when they sell, because if they were well cut, they'd weigh less weight and would not be such foolers of naive buyers who only see carat weight as a goal.

These are all generalities. Specific stones have specific details of cut and light return combination. You may choose a diamond with any combination that suits you. Many retail consumers own and love AGA 2B, 3A, and 3B fancy shaped diamonds. SOme of these stones may have very good light return. They fall down somewhere in cut quality, their shaping, but it may not be something important to that consumer. To a perfectionist, it is a matter of much importance.

The facts are what informed consumers are entitled to know and appreciate. How they use them, is not a major concern of mine. Having consumers kept in the dark is a far more dangerous situation than having what amounts to more information than one can easily handle.

At least thoise who participate here have an opportunity to sharpen their buying skills.

 

[Nicrez]

Many people will say that the AGA charts are actually a very good reference sheet for cuts on a radiant, and I have to say that I agree wholeheartedly! David Atlas, you are KING!!!!Those charts kept me sane!They ARE like emeralds, because they have the same crown cuts, except the pavilion is cut to belike a round brilliant (or should be)!

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I noticed that Square Radiants (aka Box Radiants) are rare in their well cut form.Most people think a Princess and a Box Radiant are similar and they is simply NOT true.I saw both types.I started with Princess and neded in Radiants.A Princess cut has a different crown facet arrangement, and the crown tends to be very low and very flat.That makes they table heavy in general, and their pavilion pattern is in a 4 pointed concentric star shape, which IS NOT like a BR!Some BR are cut with princess patterns on the pavilion, and so there is little formality of design in generic radiants, hence why we finally went to Grossbard’s radiants.We sought a high colorless and larger stone with fewer inclusions, so that made our search MUCH harder.Yours doesn’t have to be!

/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>/www.pricescope.com/idealbb/images/smilies/3.gif[/img]>

Stick to the rule of finding a radiant with under 70% depth and table, closer to 65% or so, and you will notice that they indeed sparkle more, have less bow-ties, and less fisheyes and generall do what they are supposed to do, and sparkle like a round brilliant but still be square!!!

Good luck and keep us posted!!!!