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OEC Ideal Cut?

prs

Brilliant_Rock
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DW is considering an ER upgrade and has fallen in love with OECs. We have been able to see a number of OECs in person over the last few weeks, and for every one that looks pretty good, there are three or four that are just blah. One of the problems is when you walk into an estate jeweler it's more than likely they don't have GIA certs for what they claim are their OECs. Unfortunately even if they do have a GIA stating a stone is an OEC, it's just as likely the stone will not be beautiful.

There is a huge difference between GIA certs for MRBs and OECs. An MRB cert will tell you just about everything you need to know about the cut of that diamond. The only cut data on an OEC cert is table and depth, and that is just about useless when it comes figuring out if the diamond is going to be beautiful.

I've learned a lot here on PS as to what makes some OECs so beautiful, but all the knowledge and shared wisdom seems to boil down to "you'll know one when you see one". Given we have so many cut experts here on PS I'm hoping we might be able to temporarily borrow some of that expertise to help put some numbers on the cut proportions that make some OECs so beautiful.

In order to classify the type of cut, GIA must measure all the proportions of OECs, so quite why they don't put them on the certs is a mystery. @PreRaphaelite kindly shared with me the criteria that GIA use to classify round diamonds

GIA Cut Criteria.png

So maybe these criteria point us in the right direction to determine what proportions might be important help identify a beautiful OEC.

1) Table size less than or equal to 53%.
2) Crown angle greater than or equal to 40°.
3) Star length less than or equal to 50%.
4) Lower half length less than or equal to 60%.
5) Cutlet size medium or larger.
 

prs

Brilliant_Rock
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I'll start things off by saying that chunky crown facets are something all beautiful OECs have in common. So a smaller table is a must, but I have my doubts about the 53% GIA uses. I'm thinking 50% or even smaller might be more appropriate.
 

MakingTheGrade

Super_Ideal_Rock
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I think part of the difficulty is there is no consensus for “ideal” oec since preferences really vary.

For example, Distinctive Gems cuts “ideal” oecs and make that claim based on light return.

But for me it’s not my ideal oec because I prefer a larger cutlet and facets that are a bit chunkier. Like this:
http://instagr.am/p/B9ZekAPFd5D/
Probably why people say you need to see oecs in person to judge since there are so many flavors of oec!
 

distracts

Ideal_Rock
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I'll add that last I heard, people still considered GIA's criteria for OECs to be overly-restrictive. Maybe someone more up to date can comment on that? I've seen a bunch of "circular brilliants" I'd classify as OECs, or transitionals that are much more OEC-like. I'd definitely expand your accepted labs to include EGL USA. And I've seen some that have some wonky proportions that look great. Which brings us back to essentially the "you'll know it when you see it." I certainly know it when I see it - and there ARE a lot I don't like, but all the ones I do like look pretty similar. A lot of people have OECs that are beautiful but aren't the "flavor" I like. Like I for instance apparently don't like a really super high crown - mine have more moderate crown angles.
 

missy

Super_Ideal_Rock
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OECs really need to be seen with your own eyes. Only by seeing it with your (and your wife's) eyes can you determine if 1. it is a beautiful stone (to you) and 2. if it is your preferred flavor so to speak.
 

prs

Brilliant_Rock
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I think part of the difficulty is there is no consensus for “ideal” oec since preferences really vary.

For example, Distinctive Gems cuts “ideal” oecs and make that claim based on light return.

But for me it’s not my ideal oec because I prefer a larger cutlet and facets that are a bit chunkier. Like this:
http://instagr.am/p/B9ZekAPFd5D/
Probably why people say you need to see oecs in person to judge since there are so many flavors of oec!
Yes, that 3.15ct from parkfinegroup is exactly the type of OEC we are looking for; chunky facets in a flower pattern, and what I believe is the kozibe effect. I could be wrong when I say kozibe effect because I think what I'm describing are reflections of pavilion facets in the table that somewhat match the chunky crown facets.
 

EC8

Shiny_Rock
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Yes, that 3.15ct from parkfinegroup is exactly the type of OEC we are looking for; chunky facets in a flower pattern, and what I believe is the kozibe effect. I could be wrong when I say kozibe effect because I think what I'm describing are reflections of pavilion facets in the table that somewhat match the chunky crown facets.


It’s a beautiful OEC, just an FYI, kozibe is the reflection of the culet; i.e. the hexagonal shape at 6:30.

4D06E5B9-9EE0-471B-844A-05B18CAF4705.jpeg
 
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prs

Brilliant_Rock
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I'll add that last I heard, people still considered GIA's criteria for OECs to be overly-restrictive. Maybe someone more up to date can comment on that? I've seen a bunch of "circular brilliants" I'd classify as OECs, or transitionals that are much more OEC-like. I'd definitely expand your accepted labs to include EGL USA. And I've seen some that have some wonky proportions that look great. Which brings us back to essentially the "you'll know it when you see it." I certainly know it when I see it - and there ARE a lot I don't like, but all the ones I do like look pretty similar. A lot of people have OECs that are beautiful but aren't the "flavor" I like. Like I for instance apparently don't like a really super high crown - mine have more moderate crown angles.
I agree there are diamonds classed as "circular brilliants" that are just as beautiful as stones classed as OECs. In fact @Mrs_Strizzle has a thread on a circular brilliant that is more beautiful than many OECs. LINK

I've been hunting down GIA certs on diamonds that I consider beautiful. Actually these are almost always the same ones that PSers have fallen in love with and posted about. I'm not so sure there is too much difference in the "flavors" that PSers consider beautiful, they all have chunky facets in the flower pattern, and what I think is the kozibe effect.

In looking at the certs one thing stands out; there are beautiful OECs with table size varying from 41 to 52%, so table size is not a determining factor.

I'm also beginning to suspect there are beautiful OECs with crown angles less than 40°, in fact you @distracts have two of them!!! However yours is the only data point I have so far as GIA has chosen not to put the crown angle on its certs. :twisted:
 
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prs

Brilliant_Rock
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OECs really need to be seen with your own eyes. Only by seeing it with your (and your wife's) eyes can you determine if 1. it is a beautiful stone (to you) and 2. if it is your preferred flavor so to speak.
I agree, but I do want to know more about what it is in the cut proportions that make some OECs much more beautiful than others. Maybe a tweak or two could change an ugly duckling into a swan! =)2
 
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prs

Brilliant_Rock
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It’s a beautiful OEC, just an FYI, kozibe is the reflection of the culet; i.e. the hexagonal shape at 6:30.

4D06E5B9-9EE0-471B-844A-05B18CAF4705.jpeg
Thank you! Are the shapes radiating out from the central, little cutlet just multiple reflections of the cutlet or pavilion facet reflections?
 

distracts

Ideal_Rock
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I agree, but I do want to know more about what it is in the cut proportions that make some OECs much more beautiful than others. Maybe a tweak or two could change an ugly duckling into a swan! =)2
I'm wondering if one reason cut proportions seem less important with OECs is that there is a lot more variance within a single stone due to the cutting methods. They're in general a lot less symmetrical, and you may have different angles going on so if you're giving an average angle it may give significantly less of a picture of what's happening than with a modern stone. I've seen a lot that are ostensibly round but have either the culet or the table or both off-center to where it is quite noticeable at arm's length, so the angles on one half may be noticeably steeper than on the other, for instance. Some of these still looked pretty good despite the wonkiness.

Otherwise I'd think most of the angles that work together are more or less the same ones as for MRBs, though you might see a preference for FIC-type angles. BUT I'm not a numbers expert, so I don't know.
 

prs

Brilliant_Rock
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OECs really need to be seen with your own eyes. Only by seeing it with your (and your wife's) eyes can you determine if 1. it is a beautiful stone (to you) and 2. if it is your preferred flavor so to speak.
@missy I can go to Home Depot on my own, but wine is the only other thing I can buy without close wifely supervision. :mrgreen2: I can assure you the thought of buying a diamond that DW didn't love and approve never even crossed my mind. That's why, despite all my shortcomings, I've managed to keep this beautiful, sensitive, and mysterious creature by my side for almost 40 years!
 

dreamer_dachsie

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The shapes radiating out from the culet are the pavilion mains.
Thank you! Are the shapes radiating out from the central, little cutlet just multiple reflections of the cutlet or pavilion facet reflections?
Kozibe are reflections of the culet, they look like round bubbles:

1583718654300.png



The large facets under the table are the pavilion mains. They are part of what makes arrows in a modern RB. In old cuts, the lower girdle halves are shorter, so the mains are not split so far down, creating more of a flower pattern or pie pattern under the table.

All the facets are basically the same in an OEC and an MRB, but the relative size/proportions of each cut are different.

1583718475810.png

1583718555504.png

A lab report is only useful for color and clarity with old cuts. Everything else is judged visually. So you cant shop the paper.
 

dreamer_dachsie

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You also need to decide whether you care about the diamond being a true old cut or one that has been recut to look better. Lots of diamonds being sold as old cuts have been recut to improve their optics. I think most of these super round, optically very perfect OECs we see these days have been recut to some degree. The polish and symmetry grades on the GIA report can be suggestive, as old cuts usually are only "Good" . Typically they have bruted girdles and "flea bite" nicks on the girdle too. Vendors may not disclose this information, and it's hard to tell for sure *shrug*. Just my perception based on seeing many real old cuts in real life and many old cuts no PS in the last decade. I think the sameness of "PS flavours" comes in part from this practice.
 

CHRISTY-DANIELLE

Brilliant_Rock
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If you are really seeking "precision", I like the cut Victor Canera offers over the AV . But the bugger there might be finding the color, clarity and size I suspect you would be looking for.
20200308_211351.png

But it is definetly personal preference. I like a large culet, kozibe , high crown, and a flower petal center. I also found that I prefer a little wonkiness rather than perfection. Who knew?
You'll have to see a few to hone in on what speaks to you guys!
 

oldminer

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There really are no "Ideal Cut " OEC diamonds, but the modern version of these old cuts are certainly worthy of thier own category in terms of beauty and perfection of the older cut. GIA is mired in a semantics dispute with dealers over what is and what is not an OEC, but your eyes can do a very good job of telling you if you like the looks of a diamond regardless of the GIA name for the cut.

Attached is a chart of parameters I created years ago and revised a bit in 2009 which may be helpful in your screening of OEC round diamonds. I have seen middle of the road ones which looked just fine, so don't forget using your eyes as well as "parameters". If it helps you that's great and if it confuses you, buy only after you have shopped until you find the right diamond that makes you happy.
This is for screening out problematic stones, not for selecting a "best" one for you. Chart 5 revised 2009.jpg
 

AV_

Ideal_Rock
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I took years off this forum exactly when Jonathan @Rhino & Victor Canera were developing their OEC revivals ,( - so I do not know how these were thought out. I expect somewhat different patterns of brilliance from older round brilliants, if not necessarily better than these stones which were made, as far as I can guess, to look like modern RBC with large facets which is very, very rare among old stones - obviously, there is no other way to go to make a bright stone with those proportions, and some exquisite old brilliants were cut in the same vein, if still not quite [judging by patterns of reflections off the crown, so no .2º approximations, what can I show! www].

IMHO, the RBC has so many possibilities worth making. [I'd want a sampler! - not virtual, for once]
 

CaseyLouLou

Shiny_Rock
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There really are no "Ideal Cut " OEC diamonds, but the modern version of these old cuts are certainly worthy of thier own category in terms of beauty and perfection of the older cut. GIA is mired in a semantics dispute with dealers over what is and what is not an OEC, but your eyes can do a very good job of telling you if you like the looks of a diamond regardless of the GIA name for the cut.

Attached is a chart of parameters I created years ago and revised a bit in 2009 which may be helpful in your screening of OEC round diamonds. I have seen middle of the road ones which looked just fine, so don't forget using your eyes as well as "parameters". If it helps you that's great and if it confuses you, buy only after you have shopped until you find the right diamond that makes you happy.
This is for screening out problematic stones, not for selecting a "best" one for you. Chart 5 revised 2009.jpg
I like this table and have used it when looking at old cuts but when there is a GIA certificate, it does not usually provide the angles. So, I have 2 questions regarding this table:

1. In looking at just the first two columns, can you "mix and match" the percentages of table % and depth % between the two columns and still be ok, or does that completely negate the rating?

2. If the table % and depth % are within the first two columns, can one assume (at all) that the angles will be decent? Is there a way to guess if the angles aren't given?

Thanks!!
 

oldminer

Ideal_Rock
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You can't guess the angles without experience in making that judgement. You must expect to mix and match from the columns and not every data point is equal to any other data point. The importance of certain characteristics may have greater impact than others, but this will get you into a better position to "judge" or "screen" with some efficiency. When you have many points of data in the low quality zone then you screen out that one and look for another unless YOU love the look of that particular diamond. Every diamond has a home somewhere.
 

Victor Canera

Shiny_Rock
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I'm wondering if one reason cut proportions seem less important with OECs is that there is a lot more variance within a single stone due to the cutting methods. They're in general a lot less symmetrical, and you may have different angles going on so if you're giving an average angle it may give significantly less of a picture of what's happening than with a modern stone. I've seen a lot that are ostensibly round but have either the culet or the table or both off-center to where it is quite noticeable at arm's length, so the angles on one half may be noticeably steeper than on the other, for instance. Some of these still looked pretty good despite the wonkiness.

Otherwise I'd think most of the angles that work together are more or less the same ones as for MRBs, though you might see a preference for FIC-type angles. BUT I'm not a numbers expert, so I don't know.
Hi @prs

@distracts really nailed it on the head here. IMHO, for true antique OECs, the proportions are less important because within those average proportions there’s usually a good amount of variance due to the cutting limitations that people had back in the day. With a modern diamond for example a pavilion angle of 40.8° on a lab report gets you pavilion facets that are +- 0.1° or so (depending on cutting abilities) to that angle. In an antique stone, 40.8° could mean a 1° variance between the different facets. It’s probably more worthwhile to judge real antique stones based on their face up appearance. Take a look at a diamond and see if it speaks to you. One thing to check for is that it doesn’t have obstruction which darkens the middle of the diamond.

Good luck and have fun
 

prs

Brilliant_Rock
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The shapes radiating out from the culet are the pavilion mains.


Kozibe are reflections of the culet, they look like round bubbles:

1583718654300.png



The large facets under the table are the pavilion mains. They are part of what makes arrows in a modern RB. In old cuts, the lower girdle halves are shorter, so the mains are not split so far down, creating more of a flower pattern or pie pattern under the table.

All the facets are basically the same in an OEC and an MRB, but the relative size/proportions of each cut are different.

1583718475810.png

1583718555504.png

A lab report is only useful for color and clarity with old cuts. Everything else is judged visually. So you cant shop the paper.
Thank you so much for the Kozibe explanation, and that's the best facet nomenclature diagram I've ever seen. Now I'll be able to remember exactly where all those different facets are located. :)
 

prs

Brilliant_Rock
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Given that GIA include star length and lower half length as part of their criteria for OECs, and those lengths are significantly lower than those for MRBs, I have to conclude they are significant in the makings of beautiful OECs.

Is it the low star facet and lower half facet lengths that give us those chunky facets, and flower patterns we all love in the most beautiful OECs?
 
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Inked

Rough_Rock
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Oct 22, 2019
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OECs really need to be seen with your own eyes. Only by seeing it with your (and your wife's) eyes can you determine if 1. it is a beautiful stone (to you) and 2. if it is your preferred flavor so to speak.
I agree. I bought an OEC that might in fact completely stink based on proportions that people who know diamonds look for. I really dont even know. I never asked any of the professionals because I was afraid I'd love it less if they said it stunk.

That said, there was a diamond I kept going back to on LAD website, and since she had a one week return policy, i decided to go for it. Seemed like a no risk way to see if I liked it. I fell in love the moment I opened the package. All the stats aside, it's MY diamond. I love it. It's perfect to me.

So I will echo the others and say you need to see it, because they're all cut different.
 

Karl_K

Ideal_Rock
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A lot of old real oec cuts were cut with somewhat shallow pavilions compared to current design theories.
This leads to some darkness at close range under the table but view them form a distance and the story changes.
Someone mentioned seeing a bunch in person and a lot of them were blaw, I am willing to bet at earring and pendant distance they would rock someones world.
 
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Karl_K

Ideal_Rock
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What is funny is that Tolk and Morse/wade designs the ideal cuts on the oec era are not even considered oec cuts by GIA.

And a must read:
American Cut; The First 100 Years by Al Gilbertson
 

arkieb1

Ideal_Rock
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I've owned a perfectly cut August Vintage Cushion and I sold it, it was pretty but I liked the other diamonds I have more than it..... I now have a fat arrowed transitional that is a fireball that has a table you could drive a bus through, a 100+ year old slightly wonky 5.34 carat OEC and a really cool genuine Antique stone that is a cross between a French cut, a Peruzzi Cut, and an Old Mine cut.

Genuine Antique stones have been handcut often without the use of modern day cutting machines and techniques, they therefore should be judged with your eyes NOT with a number chart.

If you go for a new old cut that is another way to get perfection if you don't want to spend time searching for the right stone for you.
 

canuk-gal

Super_Ideal_Rock
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The shapes radiating out from the culet are the pavilion mains.


Kozibe are reflections of the culet, they look like round bubbles:

1583718654300.png



The large facets under the table are the pavilion mains. They are part of what makes arrows in a modern RB. In old cuts, the lower girdle halves are shorter, so the mains are not split so far down, creating more of a flower pattern or pie pattern under the table.

All the facets are basically the same in an OEC and an MRB, but the relative size/proportions of each cut are different.

1583718475810.png

1583718555504.png

A lab report is only useful for color and clarity with old cuts. Everything else is judged visually. So you cant shop the paper.

This picture is worth a thousand words!!!!!!!!!!!!!! Big thumbs up.
 
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