Emerald Cut ideal Specs: Please advise & educate

[chl]

Hi all,

Am wondering if any of you EC lovers/pros can give me some feedbacks based on the specs as shown on the GIA.
I've read on this forum from Chrono (please contribute, I would be so grateful!) that the 'ideal specs' has a depth of 66 with a 15% crown with ratio of 1:14, no cutlet, medium girdle

1) how does one find the ratio and the cutlet, girdle or table, depth, crown on the GIA . Clearly I'm not well versed in the GIA.
2) Without having seen the stone in person, how do I guarantee no light leakage? Im worried as ECs can easily look like 'glass' or 'flat' and clear under normal lighting.

Im currently basing my research from a GIA, the specs are as shown:

Shape: Cut-cornered rectangular step cut (confused, why doesn't it just state EC?)
Measurement: 12.14 x 9.31 x 6.22mm
Carat weight: 6.36
Color: E
Clarity: VS1
Polish: VG
Symmetry: Good
Fluorescence: None

Proportions



Clarity Characteristics


Thank you all!!

 

[Matthews1127]

Hi all,

Am wondering if any of you EC lovers/pros can give me some feedbacks based on the specs as shown on the GIA.
I've read on this forum from Chrono (please contribute, I would be so grateful!) that the 'ideal specs' has a depth of 66 with a 15% crown with ratio of 1:14, no cutlet, medium girdle

1) how does one find the ratio and the cutlet, girdle or table, depth, crown on the GIA . Clearly I'm not well versed in the GIA.
2) Without having seen the stone in person, how do I guarantee no light leakage? Im worried as ECs can easily look like 'glass' or 'flat' and clear under normal lighting.

Im currently basing my research from a GIA, the specs are as shown:

Shape: Cut-cornered rectangular step cut (confused, why doesn't it just state EC?)
Measurement: 12.14 x 9.31 x 6.22mm
Carat weight: 6.36
Color: E
Clarity: VS1
Polish: VG
Symmetry: Good
Fluorescence: None

Proportions



Clarity Characteristics


Thank you all!!

Fancy cuts, like EC’s are tricky, and vastly varied. Personal preference plays a huge role in the selection of an “ideal” EC.
Symmetry, Polish, Clarity and color are very important, when determining the quality of EC’s. All of these characteristics pertain to how well (or not) the EC performs, and appears.
L x W ratio is a personal preference; some prefer more squatty, or square EC’s,while others prefer more rectangular, elongated EC’s. My sweet spot is between 1.40-1.55:1.
One important thing to understand, up front: you cannot judge a stone based solely upon its certificate & specs. EC’s require multiple methods of examination, and ultimately, if humanly possible, face to face observation, and examination.
GIA is very strict when it comes to what they call certain stones. Asschers are typically termed “Square Emerald Cut” as opposed to “Asscher Cut”. Essentially, an EC is a rectangular step cut diamond.
If there are other reasons behind this, I’m not aware of them.
FYI, the only IDEAL cut EC’s on the market are Brian Gavin’s Signature/Blue EC’s.
If you’re searching for “optimum” specs, there are some, but others are subjective.

 

[rockysalamander]

With ECs and most diamonds, you can't judge performance only from the GIA certification. You need to judge with videos and ASET. Still photos to some extent. From the cert, you can look at the size, location and type of inclusions. If you are open to buying online, its often easier for us to post examples for you to look at within your specs (size, color, clarity) and budget.

You can also spend some time looking at Brian Gavin ECs. He has the only ideally cut emerald that I'm aware of on the market. You can tune your eyes using BGs, although we just found a stunner for another poster just a few days ago on BGD.

@Matthews1127 @ac117 @valeria101 @diamondseeker2006 @OoohShiny @tyty333 @mrs-b

Haha! Hi @Matthews1127 . Cross-posted

 

[chl]

Fancy cuts, like EC’s are tricky, and vastly varied. Personal preference plays a huge role in the selection of an “ideal” EC.
Symmetry, Polish, Clarity and color are very important, when determining the quality of EC’s. All of these characteristics pertain to how well (or not) the EC performs, and appears.
L x W ratio is a personal preference; some prefer more squatty, or square EC’s,while others prefer more rectangular, elongated EC’s. My sweet spot is between 1.40-1.55:1.
One important thing to understand, up front: you cannot judge a stone based solely upon its certificate & specs. EC’s require multiple methods of examination, and ultimately, if humanly possible, face to face observation, and examination.
GIA is very strict when it comes to what they call certain stones. Asschers are typically termed “Square Emerald Cut” as opposed to “Asscher Cut”. Essentially, an EC is a rectangular step cut diamond.
If there are other reasons behind this, I’m not aware of them.
FYI, the only IDEAL cut EC’s on the market are Brian Gavin’s Signature/Blue EC’s.
If you’re searching for “optimum” specs, there are some, but others are subjective.

Thank you Matthews. May someone please explain to me the depth and crown? and if we're able to gage light leakage from online and certification specs?

 

[chl]

With ECs and most diamonds, you can't judge performance only from the GIA certification. You need to judge with videos and ASET. Still photos to some extent. From the cert, you can look at the size, location and type of inclusions. If you are open to buying online, its often easier for us to post examples for you to look at within your specs (size, color, clarity) and budget.

You can also spend some time looking at Brian Gavin ECs. He has the only ideally cut emerald that I'm aware of on the market. You can tune your eyes using BGs, although we just found a stunner for another poster just a few days ago on BGD.

@Matthews1127 @ac117 @valeria101 @diamondseeker2006 @OoohShiny @tyty333 @mrs-b

Haha! Hi @Matthews1127 . Cross-posted

Thank you Rockysalamander.
Based on the image I posted for clarity, it is a VS1 which is quite high. Since I've never been exposed to many GIA markings for clarity, the one that i.ve posted , the marks in the centre, will that be obtrusive to the naked eye? will it be eye clean since on the chart it's right smack in the centre.
Thank you

 

[rockysalamander]

This might be a helpful additional starting guide, but it needs human eyes to evaluate a given stone.
https://www.pricescope.com/wiki/diamonds/emerald-cut-diamond

In a VS1, it should not be visible but that mark could be black carbon inclusions or solid crystals (crystals) and they are labelled the same, so YMMV.The feather should be too hard to see. Cloud should be fine at VS1, but always worth checking. Sometimes, an inclusion can be mirrored internally, so an innocuous crystal looks like there are 16 of them and suddenly that VS1 looks worse than a SI stone.

High clarity has some safety, but with a good vendor, a number of PS members have eyeclean SI stones. So, don't eliminate those options if folks here suggest them.

I would guess that most PS member select ECs strictly by eye initially (video, in person), only then do they check the cert. I certainly do for most diamonds.

 

[Matthews1127]

Thank you Matthews. May someone please explain to me the depth and crown? and if we're able to gage light leakage from online and certification specs?

This is the EC you posted, according to ct wt & dimensions. It shows what it will look like on a size 5.5 finger, set in a setting with a 2.0mm shank.
https://www.diamdb.com/diamond/6.36ct-emerald-12.14x9.31x6.22/

As for the inclusions in the center of the stone, whether or not they will be obstructive all depends on what kind of inclusions they are: clear or dark, carbon. You need to ask this question to the gemologist, or see for yourself with more visual aids, such as ASET and video. Even a static of the actual diamond may give you a better idea as to whether or not this VS graded stone is truly eye clean. The larger the diamond, the more noticeable some inclusions can become. If any of the inclusions are against the table, you may want to pass on this stone, even if they’re clear. Again, it’s all in what you can live with, and what bothers you.

 

[Matthews1127]

This might be a helpful additional starting guide, but it needs human eyes to evaluate a given stone.
https://www.pricescope.com/wiki/diamonds/emerald-cut-diamond

In a VS1, it should not be visible but that mark could be black carbon inclusions or solid crystals (crystals) and they are labelled the same, so YMMV.The feather should be too hard to see. Cloud should be fine at VS1, but always worth checking. Sometimes, an inclusion can be mirrored internally, so an innocuous crystal looks like there are 16 of them and suddenly that VS1 looks worse than a SI stone.

High clarity has some safety, but with a good vendor, a number of PS members have eyeclean SI stones. So, don't eliminate those options if folks here suggest them.

I would guess that most PS member select ECs strictly by eye initially (video, in person), only then do they check the cert. I certainly do for most diamonds.

Ditto. If we based our purchase of my EC strictly on its certification & specs, I wouldn’t have my beautiful EC. My EC rivals any VS-VVS graded EC out there....magnified, side by side. It has an SI2 clarity grade. I laugh every time I type this...lol!!

 

[Matthews1127]

With ECs and most diamonds, you can't judge performance only from the GIA certification. You need to judge with videos and ASET. Still photos to some extent. From the cert, you can look at the size, location and type of inclusions. If you are open to buying online, its often easier for us to post examples for you to look at within your specs (size, color, clarity) and budget.

You can also spend some time looking at Brian Gavin ECs. He has the only ideally cut emerald that I'm aware of on the market. You can tune your eyes using BGs, although we just found a stunner for another poster just a few days ago on BGD.

@Matthews1127 @ac117 @valeria101 @diamondseeker2006 @OoohShiny @tyty333 @mrs-b

Haha! Hi @Matthews1127 . Cross-posted

Ha Ha!! Cross-post, we did!!! Hi, right back at ya, @rockysalamander!!

 

[chl]

This might be a helpful additional starting guide, but it needs human eyes to evaluate a given stone.
https://www.pricescope.com/wiki/diamonds/emerald-cut-diamond

In a VS1, it should not be visible but that mark could be black carbon inclusions or solid crystals (crystals) and they are labelled the same, so YMMV.The feather should be too hard to see. Cloud should be fine at VS1, but always worth checking. Sometimes, an inclusion can be mirrored internally, so an innocuous crystal looks like there are 16 of them and suddenly that VS1 looks worse than a SI stone.

High clarity has some safety, but with a good vendor, a number of PS members have eyeclean SI stones. So, don't eliminate those options if folks here suggest them.

I would guess that most PS member select ECs strictly by eye initially (video, in person), only then do they check the cert. I certainly do for most diamonds.

Thank you so much @rockysalamander , you are so kind to further explain to me that inclusions come in the following:
1) Black Carbon
2) Solid Crystals

May I kindly ask what is YMMV?
and o dear lord: "Sometimes, an inclusion can be mirrored internally, so an innocuous crystal looks like there are 16 of them and suddenly that VS1 looks worse than a SI stone."

That just almost gave me an anxiety attach

I will definitely ask for HD images and videos.

Thank you

 

[Matthews1127]

Thank you so much @rockysalamander , you are so kind to further explain to me that inclusions come in the following:
1) Black Carbon
2) Solid Crystals

May I kindly ask what is YMMV?
and o dear lord: "Sometimes, an inclusion can be mirrored internally, so an innocuous crystal looks like there are 16 of them and suddenly that VS1 looks worse than a SI stone."

That just almost gave me an anxiety attach

I will definitely ask for HD images and videos.

Thank you

Step cuts are extremely reflective, and that can play to the positive or the negative, depending on the position of the inclusions, and their nature. Another clever thing I noticed in some EC’s, including mine: the cert # can be reflected within the stone, depending on the angles. Not easily noticeable with the naked eye, but my jeweler & I both noticed it under magnification. I was relieved to learn that was what I was seeing with my naked eye, and not a cluster of inclusions, or a feather.
All step cuts are reflective, and pick up everything in their environment.
I’m still a bit concerned about the “Good” Symmetry grade your EC was given. You really need to see it move (horizontally) in different lighting environments to make sure it’s a top performer. A honker that size should dazzle the blind!!

 

[rockysalamander]

Ymmv = your mileage may vary

 

[chl]

PS :
Thank you @rockysalamander @Matthews1127 , you both are so kind to guide me.
May I ask you two a question, based off of the Proportion image I provided and reading the URL link RockySalamander suggested, I noticed that the spec image I provided states: 'extremely thin- thick' does this mean the diamond is more prone/susceptible to damage?

Also, may someone please tell me based on my chart what is my :
1) Table %
2) Total Depth %

How do I determine the Crown height based off of the Proportion and measurements from the GIA?
I feel so noob asking such questions, but I would just like to double check if I'm reading the chart right.

Last but not least, since I am looking at this diamond from a secondary vendor source, how do I ask about if they can determine if it is
1) Black Carbon
or
2) Solid Crystals

Would you say solid crystal is more dangerous as an innocuous crystal inclusion in a VS1 can run into the risk of internally mirroring 16 inclusions?

Thank you so so much!

 

[chl]

Step cuts are extremely reflective, and that can play to the positive or the negative, depending on the position of the inclusions, and their nature. Another clever thing I noticed in some EC’s, including mine: the cert # can be reflected within the stone, depending on the angles. Not easily noticeable with the naked eye, but my jeweler & I both noticed it under magnification. I was relieved to learn that was what I was seeing with my naked eye, and not a cluster of inclusions, or a feather.
All step cuts are reflective, and pick up everything in their environment.
I’m still a bit concerned about the “Good” Symmetry grade your EC was given. You really need to see it move (horizontally) in different lighting environments to make sure it’s a top performer. A honker that size should dazzle the blind!!

Thank you dear.
Mighty, it didn't even come across to me the "Good" Symmetry. by moving it horizontally how do I rate the symmetry other than checking the large flashes of sparkle and inclusions that may be shown due to the step cuts?

 

[Matthews1127]

Table: 66%
Depth: 66.8%

Your EC should flash along the steps from Top to center & from center to Top, without any pauses in reflection, or “dead” steps. They should all light up, in step-like fashion, not all on at once, and not all off at once, and stay consistently bright across the stone. No one wants a dark or dull center. Sparkle & scintillation should be along the N & S points of the EC, accordingly.
As for your crown angle, your report does not give that info.
Does anyone know how to calculate that from the info, provided?

Dark, carbon inclusions look like black specks inside a stone. Clear inclusions are difficult to see, and are non-obstructive, depending on their position inside the stone.

 

[chl]

Table: 66%
Depth: 66.8%

Your EC should flash along the steps from Top to center & from center to Top, without any pauses in reflection, or “dead” steps. They should all light up, in step-like fashion, not all on at once, and not all off at once, and stay consistently bright across the stone. No one wants a dark or dull center. Sparkle & scintillation should be along the N & S points of the EC, accordingly.
As for your crown angle, your report does not give that info.
Does anyone know how to calculate that from the info, provided?

Dark, carbon inclusions look like black specks inside a stone. Clear inclusions are difficult to see, and are non-obstructive, depending on their position inside the stone.

omg thank you! thank you! I will def refer to your explanation when I watch a video.

Yes pleas, should anyone know how to calculate crown angle, that would be greatly appreciate it.

Do GIA indicate dark black carbons (black specks) vs sold crystals (clear inclusions)

 

[Matthews1127]

omg thank you! thank you! I will def refer to your explanation when I watch a video.

Yes pleas, should anyone know how to calculate crown angle, that would be greatly appreciate it.

Do GIA indicate dark black carbons (black specks) vs sold crystals (clear inclusions)

I have never seen a GIA report that has describe bed the inclusions with the words “black carbon” or “solid crystals”. Trust me, you can’t miss black carbon inclusions, esp magnified. Solid crystals are not necessarily a bad thing. Placement is key, with an EC. Clear inclusions are what you’re hoping for. Once you get ASET & video, you’ll be able to see what we’re talking about.

 

[OoohShiny]

I have loads to do at work today so won't be any help until later, but I would just quickly say that an 'extremely thin' girdle should probably be avoided, as I understand it.

 

[Matthews1127]

I have loads to do at work today so won't be any help until later, but I would just quickly say that an 'extremely thin' girdle should probably be avoided, as I understand it.

Looking forward to hearing from you, later, my friend!! Was wondering when you’d join us!

 

[rockysalamander]

I not sure you can calculate the crown and such. The geometry of an EC varies too much stone to stone. But, this thread can be useful.
https://www.pricescope.com/communit...n-height-table-impact-on-overall-depth.41995/

 

[diamondseeker2006]

As others have said, we have to see images of the stone to give you an opinion. I don't think I have ever seen a VS1 that wasn't a safe buy as far as clarity goes. It actually is my favorite clarity because it generally means that inclusions are very hard to see with a 10x loupe and there's no great reason to need clarity higher than that.

Things on a report that make me think a fancy shape stone might be worth considering are very good or excellent for polish and symmetry, girdle between thin and slightly thick is preferable, decent crown height, and I happen to prefer tables that are smaller as in close to 60 but up to 65. I'd consider 66 if te stone was wonderful otherwise. This stone has a slightly large culet facet which is something desirable to me on an antique stone, but I am not sure whether it would be on this stone. Having excellent polish and symmetry and a proper sized girdle shows higher skill and care in cutting. I generally look for that in all diamonds, but there are exceptions.

We need to see this stone (and any emerald cut) to know if it is decent or not. Numbers from a report are just not adequate. It could be gorgeous or an absolute reject depending on how the facets are cut. Sites like James Allen show stone videos and that is where I recommend that you start searching. Many vendors have access to those stones, so you don't necessarily have to buy from them.

 

[chl]

Thank you so much for your replies.
In comparison, will this EC be a better/more safe bet?

Cut: EC
Measurements: 13.35 x 11.14 x 6.56mm
Carat: 8.13
Color Grade: I
Clarity Grade: VS2
Polish: VG
Symm: Excellent
FL: none

Proportion & Clarity Characteristics as shown below

 

[ac117]

IMO, there's no "safe bet" when we're talking fancy cuts. At a bare minimum, you should be provided with a video or even better, see the stone in person in various lighting conditions. You're dropping $$$ on a 6-8 ct emerald, I'm sure you want a beautiful stone. Emerald cuts are tricky and the facets of the stone are what you need to focus on, not just the table/crown/depth. This is why ASETs are also helpful although they don't tell the full story. You want the facets to light up sort of like individual steps - some contrast is actually good bc when you rock the stone back and forth, you want to see the facets dance and not be all on or all off at the same time.

 

[diamondseeker2006]

There are some positive things on the last report, but you are going about this backwards. I'd be looking VISUALLY (photos and videos) within the size and budget range you want, then look at the report. We can easiy eliminate stones that aren't worth looking at by seeing the picture and video. The ones that look pretty good, then we can look at all the specs.

 

[Matthews1127]

I can’t speak for anyone else, but I could never consider a stone that has a larger table than its depth. It just doesn’t seem geometrically reasonable, and throws all sorts of red flags!
We need photos of the actual diamond. Videos! ASET images! Otherwise, we’re not going to get anywhere!

 

[OoohShiny]

There are some positive things on the last report, but you are going about this backwards. I'd be looking VISUALLY (photos and videos) within the size and budget range you want, then look at the report. We can easiy eliminate stones that aren't worth looking at by seeing the picture and video. The ones that look pretty good, then we can look at all the specs.

+1 to this - although I am an inexperienced noob really, I only ever go by the pictures/videos for stepcuts rather than what the report says!

I think @Rockdiamond would be proud of me


Just to check, what is the budget we have to shop with here?

What are the desired clarity/colour/size (mm or carats) criteria?

If I'm spending other people's money, I need to know how crazy we can get lol

 

[chrono]

Pics and video is a must for ECs. There’s just no short cuts or buying by the numbers. The numbers are merely a general guideline to avoid an over deep EC, uneven girdle and such. I’ve seen duds with “perfect numbers”.

 

[oldminer]

The chart above gives you some parameters that help define the upper categories of emerald cut from less well cut emerald cuts. It is good for some rapid screening to speed up the selection process. Don't buy based on it. Screening is the goal for its use. Some may reject any parameters, some may use slightly differing parameters. There is no agreed set of numbers to provide you, but these seem to work reasonably well. A percent here or there is not the main issue. Screening out bad ones is the reason to use parameters, not to choose the final stone. I hope that is clearly understood.

You may use this automated tool right on Pricescope to assist you a bit more with some screening for emerald cut diamonds and many other shapes, as well. https://www.pricescope.com/tools/AGA_NAJA_Cut_Class_Grader

This automated tool is still NOT the way to make your selection of the final diamonds, but it will help you get past many stones which have some kind of proportion issue, relative size to weight problem, or possible durability issue.

An ASET tool is very useful for knowing more about light return and how the diamond will look in a piece of jewelry. It isn't a perfect way to choose, either, but it is helpful to search for a diamond which seems to do well with handing light. Very Good or Excellent symmetry and polish count just as length to width ratio count. You have to decide what suits your personal needs, budget and ideas best.

No document offered by Labs really covers all the details to properly select a fancy shapes without seeing it in person to be sure it works for you and your eyes. Those few emerald cut diamonds with "ideal" specs are guaranteed to be lovely, but are rather costly to produce. Diamonds not cut to those exacting specs may weigh more, take a less time to cut and therefore be a less pricey. It all makes sense when the financial side is looked at.

With round diamonds, pretty much everything is in the report or more readily seen with the images provided on line. Most fancy shape diamonds are individuals with personalities that are not fully described by reports and visual aides.

 

[Karl_K]

There is no number system that will guarantee a great EC. Period.
A stone might have all the right numbers and be a total blah and another may have all the "wrong" numbers and be stunning.
One of the most important criteria is crown height if its a flat top there is not much that can rescue it.
I have to laugh at any system that puts a upper number on a great crown height.
There is no such thing as too high a crown as long as it has a matching pavilion.

In step cuts I try and keep above a med girdle for durability reasons.

Depth does not equal spread, an EC with 60% depth can be smaller than a stone with a 65% depth and a stone with a 68% depth can be bigger than both.

I like to stay under 66% on the table unless I find one that is 66% or over that is exceptional. That happens occasionally but more often a large tabled EC is also a flat top. I saw a video the other day of a recently cut stone that had a 60% table but a under 10% crown height so a small table is not a sure sign of a good crown height.

 

[oldminer]

Karl K: "There is no such thing as too high a crown as long as it has a matching pavilion."

Karl, this statement is purely bogus. Sorry, but if the crown is high and the pavilion is deep, the overall depth of the stone will make the diamond look very small for a given weight. There is something wrong with such a combination even if it performs well. Asscher cuts are a wonderful example of a great looking diamond which looks small for its weight. The problem is simply that it looks way too small visually for the weight the customer will be asked to pay. I see this as a "problem" even when a diamond performs well with light.

With the depth-spread issue ,you are correct in a few cases, but most of my experience is in the real world, not in diamond design. Few deep depth diamonds look larger than more shallow cut diamonds of the same weight. The anomaly is due to the strange way GIA computes depth % based only on the width measurement which , of course, you fully understand. If they made depth % based on the average of length & width, it might be more sensible, but we don't have that freedom to change the GIA system. I see depth % as a screening tool, as it immediately warns folks away from diamonds which do not look visually as large as very well cut examples with the same weight. You can no doubt find an example of the exception to this blanket statement, but it is not helping people to find the diamond on-line they'd like to own. My suggestions might mistakenly screen out a few winners, but primarily they will will screen out the ones that are losers pretty fast. That's what screening does and I believe it is useful to shoppers who rely on experienced advice.

I know my advice is simple and somewhat controversial, so I have blanketed my posting with substantial warnings on the limitations of the advice. If I thought it was not useful, I would not post it. If Pricescope thought the AGA grading tool did not do some of the same things the HCA does in a different way and for many shapes, I am sure it would no longer be hosted. I don't make such decisions and make no money from it.

Sorry to be argumentative, but I after so many years, I understand there are differing opinions and we all have a place to make what each of us consider useful suggestions. Short of being able to see a diamond in person, the list of what is reliable to screen fancy shapes is very limited. Do you have a list of things to "avoid", things to "look for", or how to screen out the "bad ones"? That would be really helpful for shoppers.