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OEC Ideal Cut?

prs

Brilliant_Rock
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I used automation to try and narrow it down as I wasn't getting anything that great by hand.
At least with a 50 table the 37.5ca range is a bust.
The pdf file shows the ASET files.
Darn it, I think I jinxed it by saying my luck was due to run out!!! :eek-2:

Although in retrospect our very small sample size of shallow stones is pointing us towards the left hand side of the chart.

Your pdf file blows my mind, talk about automation! Are you going to take a shot at the CA 40.0? Nothing ventured nothing gained! =)2
 

prs

Brilliant_Rock
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I think you guys are just having some fun! I think you're doing this the hard way, though!

I am going to have to say that Yoram cut my AVR and I think it is one of the best newly cut OECs. I would guess Karl will agree that Yoram is a master cutter. So I may be totally wasting my time, but I am going to show you my facet pattern, an ASET image, and the numbers from the grading report. Mine does have an advantage of facing up with a nice diameter since it was not cut too deep.

Obviously, there are many others with a different cut, but it seems to me that looking at a variety of newly cut OECs that were cut to have great light performance and have actual images of the stones would be a good way to approach this.

IMG_0838 b.jpg

IMG_0787.JPG

n IMG_0826.jpg
ASET name edited.jpg AVR.AGSreport 2.jpg
@diamondseeker2006 Yes, your AVR is extraordinarily beautiful, thank you for showing it to me. I was told about AVRs and CERs on the first page of this thread, and could have saved myself a lot of trouble if I'd just decided back then to go that route! :lol-2:

DW is holding out for one of these hundred year old beauties, created by a master cutter without all the benefit of modern technology. In our preferred size and color this is a bit like looking for a needle in a haystack, and Covid is definitely not helping. We've hardly stepped out of the house since March.

An AVR or CER is certainly a fallback option for us if all else fails. I haven't seen any 4.5ct L, VS stones on either site, but I'm sure I could get one cut if I asked.

I know Yoram is an exceptional cutter, and I've read every one of the informative articles on his blog. What really interests me about your diamond is why he chose a 35.7, 41.4 combination. He obviously could have cut what is supposedly the ideal 34.5, 40.8 combo, but he didn't. I would love to know why, maybe because the shorter lowers informed his decision?
 

Karl_K

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I know Yoram is an exceptional cutter, and I've read every one of the informative articles on his blog. What really interests me about your diamond is why he chose a 35.7, 41.4 combination. He obviously could have cut what is supposedly the ideal 34.5, 40.8 combo, but he didn't. I would love to know why, maybe because the shorter lowers informed his decision?
It was cut under contract, not designed by Yoram and its optimized to get ags0 which is mainly a brightness metric.
Yoram no longer cuts them.
 
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diamondseeker2006

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It was cut under contract, not designed by Yoram and its optimized to get ags0 which is mainly a brightness metric.
Yoram no longer cuts them.
Yoram cut very few AVRs, is my understanding. Jon has a whole range of measurements and mine is different than almost all others I have seen. Many are deeper and do not have the diameter of mine. But none of that matters since he is looking for an antique anyway!


@diamondseeker2006 Yes, your AVR is extraordinarily beautiful, thank you for showing it to me. I was told about AVRs and CERs on the first page of this thread, and could have saved myself a lot of trouble if I'd just decided back then to go that route! :lol-2:

DW is holding out for one of these hundred year old beauties, created by a master cutter without all the benefit of modern technology. In our preferred size and color this is a bit like looking for a needle in a haystack, and Covid is definitely not helping. We've hardly stepped out of the house since March.

An AVR or CER is certainly a fallback option for us if all else fails. I haven't seen any 4.5ct L, VS stones on either site, but I'm sure I could get one cut if I asked.

I know Yoram is an exceptional cutter, and I've read every one of the informative articles on his blog. What really interests me about your diamond is why he chose a 35.7, 41.4 combination. He obviously could have cut what is supposedly the ideal 34.5, 40.8 combo, but he didn't. I would love to know why, maybe because the shorter lowers informed his decision?
Thank you for your comment on my diamond! Okay, so you are looking for an antique diamond! Sorry about that! I haven't read all the posts between the beginning of the thread until now, so when I saw you and Karl discussing all the angles and making models, I thought maybe you were considering having one cut!!! So now I am not sure at all why y'all are doing that, because the one and only way to buy an antique diamond is to order it (after seeing photos), hold it in your hand and look at it in various lighting and environments, and see if you fall in love with it (return if not sure, because sometimes it takes seeing several or many to be sure!). I do also have an antique diamond that I love, and it was beautifully cut 100 or more years ago! There were some great cutters back then, and some not so great ones, as well! It's good you are particular, but to be very honest, I think looking at numbers is a waste of time if you are looking for an antique diamond. There are many beautiful variations of OECs and you must see them in person.

So your goal is 4.5 L VS? Listen, trust me on one other thing, you need a wider range than that! My goodness, you want an outstanding cut OEC, so you need to have a range that will make it possible to find a stone. I think 3.5-5 cts is a reasonable range, for example. I think J-L or K-M is reasonable. I think if you are limiting this to one set of measurements and a single color, clarity, and a size near 4.5 cts, you very well may never find a diamond. Of course, budget is one parameter that needs to be set. It is possible to find a well cut modern round with a narrow set of requirements, but your parameters are just too restrictive to be realistic. I maybe shouldn't comment again without reading all the other posts, but this is just my impression from what you are saying now.

Oh, and I ordered several stones to look at before I bought this stone. So it is possible to do from home. Adam at Old World Diamonds likely has the largest selection of any antique diamond dealers, so that's a good place to start.
 

Karl_K

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We are looking into varies combos because we can and it is interesting.
I dont see why anyone would have a problem with that.
40ca is next.
 

prs

Brilliant_Rock
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When I first started this thread the advice I received was to forget about the numbers and concentrate on the beauty. I would know a beautiful OEC when I saw one. Actually I found it takes quite a lot of research to figure out what it is that makes certain OECs more beautiful than others. What it is in the facet patterns that distinguishes a traditional OEC from a transitional OEC. What particular flavor of facet pattern does DW like the best? And having figured out all that, how to look for and identify that facet pattern in a blurry photo or video? :)

I made a career of figuring out how processes worked, and then in many cases, having figured out how they work, making them work better. So I couldn't help myself, it just came natural for me to look at the numbers as I went thru the OEC learning curve. I've been at this since March and I'm now at the point where I know I can recognize a beautiful OEC when I see one. However I'm still learning, and looking at the numbers is helping widen my horizons in the search for a beautiful diamond.

I've admired @dreamer_dachsie's magnificent OEC since the day I first saw it, and decided to take a closer look at it to make sure I could recognize its sibling when I saw it. I first measured the table, and to my amazement it came out at 56%, so I tried on another image of her stone and it too came out at 56-57%.

dreamer_dachsie George T56-57 B.jpg dreamer_dachsie George, T56-57% A.jpg

Earlier in the thread @evergreen showed us her gorgeous OEC with a 57% table

evergreen T57%.png

Then I remembered a thread by @arkieb1 on "Charlie", her gorgeous OEC with a 60% table, or as she so eloquently put it "a table you could drive a bus through" :lol-2: Here's a LINK to her thread, and a photo

arkieb1 Charlie T60%.jpg

I had always thought a beautiful OEC needed to have a table no bigger than 53%, but I was wrong! Great looking transitional OECs come in all flavors...there are no rules!!! The fact you can have a beautiful OEC with a table of 57% or even 60% comes to me as a major surprise. It needs thinking about, but it does have the potential to open a lot of doors, stay tuned!! :mrgreen2:
 

Karl_K

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I had played with 40ca in the past and there were some interesting results in the .96 range on DiamCalc stereo brightness which is just a bit back from today's ideal cuts but good for the period.
I'm still working on other table sizes etc to see if there are "better" in the range.
 
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dreamer_dachsie

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That's very interesting about the table size. To my eye, it looks smaller than a similar table on an MRB, but maybe its an optical illusion bc of the slightly steeper crown.
 

prs

Brilliant_Rock
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That's very interesting about the table size. To my eye, it looks smaller than a similar table on an MRB, but maybe its an optical illusion bc of the slightly steeper crown.
The genius who cut your beautiful diamond certainly knew what he was doing. All the facets are in perfect proportion to the table, a master craftsman for sure!
 

prs

Brilliant_Rock
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Earlier in the thread I posted a drawing showing my preferred facet patterns for OECs with tables of 45%, 50%, and 53%. Now I know beautiful OECs can come with tables up to 60% I decided to do another drawing adding tables of 56% and 59%. I found I can get a better perspective on the drawings by adjusting my screen zoom to 50%

Interesting that 63% Lowers seems to work best for all table sizes of 53% and greater

OEC Fig 13 T45,50,53 S30,35,40 L70,65,63.jpg OEC Fig 14 T53,56,59 S40,45,50 L63,63,63.jpg
 

Karl_K

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Interesting that 63% Lowers seems to work best for all table sizes of 53% and greater
based on?
Its in the common range but im interested in your reasoning.
 

prs

Brilliant_Rock
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based on?
Its in the common range but im interested in your reasoning.
Karl, no reasoning involved, I'm not that smart. :) I got there by trial and error, just drew out different lower lengths and chose the one I liked most. It was a surprise to me that 63% worked the best for 53%, 56%, and 59%.

Looking at it more closely, as the table gets bigger more of the 63% lowers are exposed, and to me this seems to keep the facets under the table in better proportion. This is only my personal preference of course.
 

Karl_K

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Karl, no reasoning involved, I'm not that smart. :) I got there by trial and error, just drew out different lower lengths and chose the one I liked most. It was a surprise to me that 63% worked the best for 53%, 56%, and 59%.

Looking at it more closely, as the table gets bigger more of the 63% lowers are exposed, and to me this seems to keep the facets under the table in better proportion. This is only my personal preference of course.
I rather like high 60s or 70 with larger tables for a "transitional" favor also.
 

prs

Brilliant_Rock
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I rather like high 60s or 70 with larger tables for a "transitional" favor also.
Here are three different flavors with a 56% table. The first, at 47% is what I think a traditional OEC would look like...with very short lowers that don't reach the table. The second transitional is my preferred 63%. Although I have to admit the third, at 66%, gives a very bold look, and is more towards your preference.

I didn't want to go over 66% as, with rounding, that's as high as I would want to risk going, and still get into the GIA "Circular Brilliant" designation.

OEC Fig 15 T56,56,56 S45,45,45 L47,63,66.jpg
 

Karl_K

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just for fun......
1596785606137.jpeg
lp ratings are blah but it looks interesting with impossible to achieve optical alignment.
 

prs

Brilliant_Rock
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Wow, I keep hearing about 60/60 diamonds, but you just created a 40/40/40/40. @Rockdiamond has got to love this one! :lol-2:

What is causing the dark circle, is it a fish eye? Does that dark circle include reflections of the culet, ie the Kozibe effect?
 

Karl_K

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Wow, I keep hearing about 60/60 diamonds, but you just created a 40/40/40/40. @Rockdiamond has got to love this one! :lol-2:

What is causing the dark circle, is it a fish eye? Does that dark circle include reflections of the culet, ie the Kozibe effect?
Yes he would love it and so would Yoram. @diagem
Here is the ASET, yes Kozibe, min fish-eye
1596826588041.jpeg
 

prs

Brilliant_Rock
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During my research I've seen a number of threads asking if an MRB could be recut into an OEC. The answer has always been a resounding "No" because of the weight loss involved. Cutting the crown of an MRB to meet the small table, steep angle of a traditional OEC would indeed require an unacceptable loss in carat weight and spread. However I'm starting to think a recut might indeed be possible to a transitional OEC.

We know Henry Morse was cutting diamonds very close to the CA, PA of an MRB back in the 1880s, and @diamondseeker2006 in Post #240 showed us her gorgeous AVR, also cut very close to MRB proportions. This tells us the PA, CA of an MRB are very suitable for an OEC and will certainly provide great light return.

In Post #246 I showed there are some absolutely fabulous transitional OECs with tables up to 60%. So if we take a typical MRB with a table of 57% the only difference between it and a 57% transitional is the facet pattern. I know next to nothing about diamond cutting, but I believe the facet pattern could be easily changed by widening the pavilion mains in order to shorten the lower half facets. The carat loss from doing this would be next to nothing.

There is a PS thread on this very subject. Back in 2012 @twosanguinehearts actually went ahead and did it. Here is a LINK to her thread where she describes how her 2.4ct H&A was recut.

Her fabulous transitional diamond took quite a ride to its final Victor Canera setting, here's a LINK to that final thread. There are numerous videos in this thread showing how well it worked. If you would like to see more photos of her recut stone, and a couple of gorgeous settings, here are a links to the threads describing the stops the diamond made on its ride home. :love: :)

LINK1 JOTW
LINK2

It was very courageous of @twosanguinehearts to take this step, and I'm glad it worked out so well for her. I do hope she doesn't mind me sharing her experience. I think it might help inform a number of PSers who are considering this very thing.
 

Lessics

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During my research I've seen a number of threads asking if an MRB could be recut into an OEC. The answer has always been a resounding "No" because of the weight loss involved. Cutting the crown of an MRB to meet the small table, steep angle of a traditional OEC would indeed require an unacceptable loss in carat weight and spread. However I'm starting to think a recut might indeed be possible to a transitional OEC.

We know Henry Morse was cutting diamonds very close to the CA, PA of an MRB back in the 1880s, and @diamondseeker2006 in Post #240 showed us her gorgeous AVR, also cut very close to MRB proportions. This tells us the PA, CA of an MRB are very suitable for an OEC and will certainly provide great light return.

In Post #246 I showed there are some absolutely fabulous transitional OECs with tables up to 60%. So if we take a typical MRB with a table of 57% the only difference between it and a 57% transitional is the facet pattern. I know next to nothing about diamond cutting, but I believe the facet pattern could be easily changed by widening the pavilion mains in order to shorten the lower half facets. The carat loss from doing this would be next to nothing.

There is a PS thread on this very subject. Back in 2012 @twosanguinehearts actually went ahead and did it. Here is a LINK to her thread where she describes how her 2.4ct H&A was recut.

Her fabulous transitional diamond took quite a ride to its final Victor Canera setting, here's a LINK to that final thread. There are numerous videos in this thread showing how well it worked. If you would like to see more photos of her recut stone, and a couple of gorgeous settings, here are a links to the threads describing the stops the diamond made on its ride home. :love: :)

LINK1 JOTW
LINK2

It was very courageous of @twosanguinehearts to take this step, and I'm glad it worked out so well for her. I do hope she doesn't mind me sharing her experience. I think it might help inform a number of PSers who are considering this very thing.
i loved that thread I just find it so hard to identify the pattern on the diamond and I can’t remember her posting various videos?

I’m not sure I posted this yet: another beautiful example of a flowery oec that has a “wide” table and isn’t very deep:
 

Karl_K

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Keep in mind that doing a recut even mrb to mrb is only a good idea a small percentage of the time.
Most of the time you have to not care about weight and value loss for it to make sense.
 

prs

Brilliant_Rock
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Keep in mind that doing a recut even mrb to mrb is only a good idea a small percentage of the time.
Most of the time you have to not care about weight and value loss for it to make sense.
Very true! I believe the recut of @twosanguinehearts' MRB didn't touch the CA, PA, or table. I think only the lowers were shortened, and I can't tell from the photos if a medium size culet was added or not. Weight was only reduced from 2.42 to 2.38ct, so pretty minimal loss.

There is definitely a value consideration in that you could have a super ideal MRB, and as soon as the lowers were shortened to 65%, the GIA cut grade would drop from EX to VG. At 60% lowers the cut grade would drop all the way to G. If its possible the diamond might be put up for sale at some point in the future, then a low cut grade would likely decrease its value. In my opinion anyone thinking of doing this might want to ensure the recut stone meets the GIA criteria for a "Circular Brilliant" designation, and not risk this potential value loss.
 

prs

Brilliant_Rock
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I've managed to find a small number of OEC data points, and have added them to the AGS chart. It does seem the chart is useful in helping us decide what CA PA combinations work well for OECs. We can see that beautiful OECs come in many different combinations, and it's interesting to note they are all in the high light return areas.

AGS Cut Guide 10mm MRB 50% Table Rev D.png

AGS Cut Guide 10mm MRB 50% Table Rev D2.png
 

prs

Brilliant_Rock
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Just wanted to recap what I've learned about OEC facet patterns.

I tend to focus on the table when deciding if I like the facet pattern in any particular OEC. However the table only accounts for about 25% of the face up area of an OEC, and in my opinion the pattern of the remaining crown facets is just as important. They do account for 75% of what I am looking at!

The crown facet pattern I like the best is when the star facets are aligned with the table. To do this the star length has to vary in proportion to the table, and the result is a perfect eight point star. I believe this is why these facets are called stars!

OEC Fig 10c T45,50,53 S30,35,40 L60,60,60.jpg

Fortunately many of the most beautiful OECs have this pattern, and it's not at all difficult to find. Our dreamer_d knows a beautiful facet pattern when she sees one.

dreamer_dachsie 8.1mm 7B.png

In some photos you can't make out the aligned star pattern over the entire face, but you only need to spot part of it to know it's there. Here are photos showing @Acinom and @joelly's beautiful star facet patterns.

Acinom 3A.png joelly 4.01ct L,VS2 2.png
 

yssie

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I'm now at the point where I know I can recognize a beautiful OEC when I see one.
@prs, I mean this with no disrespect intended, but have you or DW actually seen - in-person, with your own eyes - any of the stones you have such admiration for photos of? If not these specific specimens - comparisons with similar faceting?

There is an objectively correct way to approach to search with the science and technology that you appreciate:
1. See lots of stones in-person,
2. Identify, in-person, what those stones have in common - what trends, nuances, what particulars consistently draw your eye and your attention?
3. Correlate proportions and light reflector images to the trends and nuances and particulars that you identified in-person.

Only after taking these steps - in this order - can you have confidence that what you look for with technology is in fact what your eyes want to see IRL. No photographs or video can ever comprehensively depict a stone’s character and behaviour across a variety of lighting environments, and when we’re talking about non-standardized shapes and faceting like true antiques... It is VERY possible to fall in love with a patterning that photographs a certain way only to learn that it isn’t quite what you want in-person.

The very nature of PS, an internet medium, makes it easy to put far too much initial trust in photos, videos, design diagrams. PS zeitgeist demands X, therefore it must be best. DiamCalc identifies Y as elite, therefore it must be best. The more willing one is to dive into the technology backing a given recommendation, the easier it is to put faith in that recommendation... The easier it is to prioritize technology over in-person education. And yet, perversely, the more particular one is about what one is looking for - and based on this 9-page thread you, @prs, are a very particular person! - the more critical that in-person learning is.

As another person who has been buying diamonds for a very long time - I urge you to heed @diamondseeker2006's advice. There is no technology that can predict what flavour of OEC you will most enjoy looking at. The only way to find out is to look at stones yourself; to not do so, to disregard the downsides of a primarily-technological approach, is to do yourself and your search a huge disservice.
 

prs

Brilliant_Rock
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The under the table facet pattern is completely determined by the lower half facet length. However GIA requires this length to be equal or less than 60% in order for a diamond to qualify to be called an OEC. So for diamonds with 60% lowers the facet pattern looks completely different depending upon the table size.

OEC Fig 10A T45,50,53 S30,35,40 L60,60,60.jpg

I personally prefer a flower petal pattern and you can see it's not possible to get one with a 45% table, the lowers don't extend under the table. However with such a small table the absence of the petals is not that big a deal. @ForteKitty has a fabulously beautiful OEC with a 46% table.

ForteKitty OEC 3.87ct L,VS1 3.jpg

You can see from my facet diagram the OEC flower petal pattern is not very noticeable even with 50% and 53% tables. I have noticed that many of the OECs with strong flower petal patterns have GIA certs calling them "Circular Brilliants". This GIA designation allows the length of the lowers to be increased to 65%. Here's how the petals become more noticeable as the lower half length is increased.

OEC Fig 10B T45,50,53 S30,35,40 L65,65,63.jpg

I haven'y yet included a link to @joelly's recent acquisition so here it is LINK Her diamond is absolutely stunning, and I'm pretty sure GIA called it a Circular Brilliant because the lowers were grater than 60%.

joelly 4.01ct L,VS2 2.png joelly 4.01ct L,VS2 GIA.png

I prefer beauty over how GIA chooses to designate the facet pattern, but I can certainly understand why others might prefer the "Old European" designation. If I was in the trade I would lobby for "Circular Brilliant" to be changed to "Old Transitional", that name would be a whole lot sexier! =)2

That just about wraps this thread up for me, I can tell it's beginning to reach its sell by date! However if anybody wants to prolong the agony, I do have some hints on how to determine a well cut OEC from the GIA certs. :lol-2:
 

diamondseeker2006

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I am sorry, but you can never choose an OEC by looking at GIA reports or determine if they are well cut. I'll second what Yssie said, you order stones and look at them, or go to Old World Diamonds which has a large supply to look at. All the analysis may be enjoyable to you, but bottom line, your wife just needs to look at some stones in person to determine what she likes the most. Color and size can enter into the equation, too, and those are things you have to see to determine preferences in addition to facet pattern. I really hope you will go into this with no preconceived notions and just let her see several stones and choose the one she loves the most.
 
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