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Oec To Gia Xxx - Shallow/flat, Economics, Color Upgrade?


ronk15a
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I recently acquired a 1.13CT L/VS2. The stone is an OEC with an atypical high crown, small pavilion depth, and shallow looking overall body. For some reason I thought it was good candidate for re-cutting to GIA triple X standards. Why? I have no idea; feel like an idiot.

The stone: It is a 1.13 L/VS2, small table, high crown, short pavilion depth, overall looks very shallow, open culet, extremely thin to medium girdle, some abrasions to the girdle. The diameter average is 6.73mm over a 4.09mm

Total depth shows: 60.8% (which from understanding is not shallow) and actually pretty ideal. It’s not 55% or 65% (it’s relatively optimum). For the modern round brilliant.

OK now for the questions:

 

Why does the stone look so shallow, when TD is relatively optimal? Its 60.8%

 

In regards to re-cutting shallow looking OEC like mentioned above, is it accurate to say that the chances are it is “almost never†economical to re-cut an OEC to GIA XXX (due to yield loss) hence dollar loss?

Additionally is accurate to say from an economical point of view that re-cutting stones to GIA triple X standards are only money-wise when the stone is pretty close to that already in proportion

 

i.e.: 57, 34.5, 41.6, 61.5, 50/80 medium to slightly thick.  

Lastly; I was discussing this re-cut with a good colleague of mine and he had mentioned to me that when re-cutting round stones from (OEC to IDEAL) K and lower, more yellow will come out, J and higher you can potentially see 1 grade higher in color? Is this accurate?

Your thoughts are much appreciated!

Regards R.K.
 

Edited by ronk15a
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Total depth = Crown Height (CH) + Girdle Thickness (GT) + Pavilion Height (PH). The fact that the sum of the 3 numbers adds to something "decent" for an RBC means nothing at all. Imagine the three extreme cases:

 

CH = ~60 --> you have a tall rose cut.

PH = ~60 --> you have a princess cut with a very small crown.

GT = ~60 --> you have a rough, thick macle.

 

They all have total depth of 60% or so. Getting any of those to look like an RBC with any kind of decent yield will be a task, just like recutting "something" that has 20/20/20 (whatever you want to call this monstrosity - hamburger cut?) would be. Plenty of other unsuitable combinations...

 

My guess - repeat guess - from your description is that you have a stone with a huge crown and therefore a very shallow pavilion. It ends up looking shallow (all you need is CH = 25%... and you and the stone are stuck with a ~35° pavilion angle).

 

Chances for recut are "almost always" not obvious. A lot of the most obvious candidates have already (unfortunately, in many cases) been recut. "Almost all" of these obvious chances included recuts from OMC/OEC to modern rounds (with a varying definition of modern over time) - and "almost all" of these recuts started from OMC/OEC with a TD well above 60.

 

Whether recutting is worth it financially depends on a lot of things, and generalising on "OEC to modern XXX RBC only works financially when proportions are already close" is demonstrably false  - you only need one counter-example, and any stone with a severe chip on a deep crown is likely to be one of those...

 

Last point on colour: I'm not sure what you mean when you say "more colour will come out" - yet you seem to intend this as K --> J, which means less colour. Or perhaps it's my perspective on colour where "more" means almost always better.

 

In any case, regardless of what you meant or typed, optical paths in a modern "ideal" round are shorter than in old stones, and generally modern stones look less yellow than old ones face up. From the side ("proper" grading), you are removing material, so whatever amount of colour was there in the body is going to be less - unless for whatever reason the core of the stone is more coloured than its skin. So I'd expect any recut to show less colour through the table and - though this may be minimal - through the side. This said, this is where logic and a little knowledge of optics leads me, not experience; if someone has done a lot of recuts and tells you otherwise, I'd be sceptical, but willing to understand why and change my opinion.

Edited by davidelevi
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First and foremost thank you for your prompt response. Ok got it. Lastly in regards to color, I agree with you. (Makes perfect sense) My colleague on the other hand has a vested “financial interest†in what he says; unfortunately his grain of salt has just gotten a great deal thicker…Thanks Davide!

Just curious: Neil B. what are your thoughts regarding color specifically related to re-cutting as mentioned above? Thanks!
 

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Recutting to modern sorts of parameters usually drives up apparent color in terms of the way it looks but it doesn't actually change the body color.  Remember, color grading is done from the side and back.  Maybe you'll see a J or K out of it, but if your L is accurate, it's likely to still be an L when your done.

 

I probably wouldn't touch a recut here.  A K-xxx is a tougher sell than an L-OEC unless it's damaged or really a dog.  Losing the 1.00 weight point just makes it worse and remember, you're PAYING to play here.  An option, by the way, is to 'tune up' the stone but keep it an OEC and keep it over a carat.  You've got 13% to play with and often you can help things a lot with a little bit of tweaking.  

 

I wouldn't say almost never on the OEC recut question but it is definitely tricky.  High color/clarity OEC's are pretty hard to move at good prices and that's exactly what people are looking for in modern stones.  This has as much to do with your marketing plans as it does gemology.  

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What do you mean by?
Usually drives up apparent color in terms of the way it looks

Does this coincide with Davide’s or my colleague’s theory? Or neither.
I always thought that re-cutting from an OEC to IDEAL RBC usually makes the stone look whiter regardless of its current grade. Be it E-N, etc…

 

especially face up, and sometimes if your lucky through the side.
 

Edited by ronk15a
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What do you mean by?

Usually drives up apparent color in terms of the way it looks

 

Does this coincide with Davide’s or my colleague’s theory? Or neither.

I always thought that re-cutting from an OEC to IDEAL RBC usually makes the stone look whiter regardless of its current grade. Be it E-N, etc…

 

especially face up, and sometimes if your lucky through the side.

 

I mean it makes the stone look whiter from the faceup position, but that doesn't always, or even usually, translate to a higher lab color grade.

Edited by denverappraiser
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