Input on Internal/External Graining in VVS1 (HELP!)

[DrD]

I am looking at engagement rings with the hope of popping the question in the next month or two. The range I have been looking in is just over 3/4 ct with decent color, good clarity, and something that really sparkles. My girlfriend has small hands and doesn't want anything too big. In my search, I've found a .80ct VVS1, G color in Blue Nile's Signature Ideal collection for $4,447 (specs below and certs attached).

Specs:

Carat: 0.80
Color: G
Clarity: VVS1
Cut: Excellent
Polish: Excellent
Symmetry: Excellent
Fluorescence: Medium Blue

Measurements: 5.92 - 5.95 x 3.67 mm
Table: 57%
Depth: 61.9%
Crown angle: 35
Pavillion angle: 40.6
Girdle: Slightly Thick (Faceted)
Culet: none

Inputting the specs in HCA results in a 1.0 grade.

However, detailed in the GIA report is internal and external graining. I've read conflicting things about graining in near-colorless diamonds. My concern is that the stone will appear hazy with a combination of the fluorescence as well as the graining. A gemologist at Blue Nile pulled the stone and made the statement that the graining did not detract from the brilliance.

Is my concern warranted or should I pull the trigger and if the stone looks hazy, use BN's 30 return policy? I appreciate your guidance for a diamond newbie. Thanks!

 

[diamondseeker2006]

I don't think clarity in a VVS stone is even remotely a concern. I would however have a little more concern about buying a diamond without pictures or idealscope images, although this one looks potentially good based on the info provided.

An alternative would be this one, which is actually a top cut quality, hearts and arrows stone ,and the diameter is just as big as the BN stone:

http://www.goodoldgold.com/diamond/10297/

 

[Christina...]

I agree with DS. Transparency, if an issue, will generally be found in stones with a clarity grade of SI2 and lower. I also think the stone she linked is beautiful and have the same reservations about purchasing stones sight unseen.

 

[diamond-enthusiast]

I think you can improve on your purchase. Slightly thick girdle hides a little weight in the body. Not a fan of the angles though considering you are paying a premium for a signature ideal.

 

[DrD]

Thanks for the input and assistance DS and Christina. One of the things that jumped out to me about this stone was the high clarity grade (graining concerns notwithstanding). Many comparably priced diamonds that I was finding were a couple steps down in clarity. I also appreciate the goodoldgold link. I had previously done some digging on their site and liked what I saw. My main goal is to get the best stone for my money. Buying sight unseen is certainly unnerving though.

Diamond Enthusiast, can you explain your angles comment? I understand the girdle issue making the diamond appear slightly smaller from the top but was not aware that a slightly thick girdle held that much more weight than a medium. Thin and beyond scare me because of durability issues I have read about.

 

[diamond-enthusiast]

A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combinations. Though most on this forum would say that there isn't much detectable differences which is entirely subjective.

A 0.80 carat diamond with exactly the same table size with a medium girdle would face up bigger than your Bluenile diamond with a slightly thick girdle. Thin to medium is no cause for concern for durability issues in a VVS1 round diamond.

The Bluenile diamond is still decent. I'm just being picky here. You mentioned you want the best value for money. And if I am paying a premium for a supposedly signature diamond, I expect the best and no less. Otherwise, why would I even need to pay this premium for. That's the train of thought.

 

[John P]

A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combinations. Though most on this forum would say that there isn't much detectable differences which is entirely subjective.

Actually DE, these angles work quite well together. To demonstrate, I modeled Ideal-Scope simulations at 57T 40.6PA 35.00CA and 57T 40.75PA 34.5CA - the latter being "Tolkowsky" angles which are, arguably, the 'optimum' central combo. As you can see, they both produce tremendous brightness. Neither has under-table leakage, and the contrast patterns are the same for all practical purposes.

A 0.80 carat diamond with exactly the same table size with a medium girdle would face up bigger than your Bluenile diamond with a slightly thick girdle. Thin to medium is no cause for concern for durability issues in a VVS1 round diamond.

In general the T-M versus STK can be true (although I personally recommend STK girdles for tension settings).

But the report gives limited details, and +/- spread depends on specifics... So I modeled the top diamond per its GIA report. The girdle is indeed called "slightly thick" but lands at the thin-side of STK; barely a tick above MED. In fact, if the girdle thickness were reduced by 0.1% the GIA description would become MED with no change in spread. Fascinating! (well, to me, but I am a nerd). Meanwhile, I created the second model with a "medium" girdle at the high-side of MED, and you can see it gains only 0.01 mm in average spread.

The numbers are always cool to me. I hope this information is interesting.

 

[ecf8503]

Actually DE, these angles work quite well together......

The numbers are always cool to me. I hope this information is interesting.

It is interesting to me! Thanks for the information and examples, John.

 

[DrD]

John, this is fascinating. Thank you very much for your input and assistance!

 

[bunnycat]

I love reading your posts John! Always informative!

 

[yssie]

A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combinations. Though most on this forum would say that there isn't much detectable differences which is entirely subjective.

A 0.80 carat diamond with exactly the same table size with a medium girdle would face up bigger than your Bluenile diamond with a slightly thick girdle. Thin to medium is no cause for concern for durability issues in a VVS1 round diamond.

The Bluenile diamond is still decent. I'm just being picky here. You mentioned you want the best value for money. And if I am paying a premium for a supposedly signature diamond, I expect the best and no less. Otherwise, why would I even need to pay this premium for. That's the train of thought.

Based on WHAT???

diamond-enthusiast, I very, very rarely encounter posters whose posts routinely make me want to just bang. my. head. against. a. wall. I most definitely feel that way about the vast majority of your posts.

Opinions stated as facts, facts stated without any reasoning, explanation, background... Insubstantiated facts in general are unhelpful because the OP has no way of knowing whether or not they're actually correct or why they may or may not apply, and other responders with more knowledge/background have no way of understanding why you've come to those conclusions and perhaps either sharing that knowledge/background with you or being led to think in different ways themselves.

This thread. The H&A thread.
THIS thread, in which you completely missed the point: [URL='https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939']https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939[/URL]
And THIS thread, wherein it passed you by yet again: [URL='https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/']https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/[/URL]

If you're going to try and help other people please actually put in the effort to TRY - preferably minus the grandiose assertions of simply knowing better, researching more, and observing more closely. Otherwise you're just doing everyone a disservice. And driving me bananas.

 

[Dreamer_D]

The diamond you selected looks fine and there are no concerns about clarity at the VVS level. John P has also graciously demonstrated that cut is not an issue.

I would like to suggest you are going very high on clarity without *need*. You can easily drop to VSI and probably VS2 and still have a totally eye clean diamond. I don't think you will save enough that way to jump the .90ct mark, but you will save! So that is something to consider if you have not already.

 

[DrD]

I would like to suggest you are going very high on clarity without *need*. You can easily drop to VSI and probably VS2 and still have a totally eye clean diamond. I don't think you will save enough that way to jump the .90ct mark, but you will save! So that is something to consider if you have not already.

Thank you for the suggestion. My search parameters included VS1 and VS2. This stone seems to be priced in line with stones in the VS range. However, I certainly have my eyes open though before I pull the trigger on this stone. There seems to be a drought of excellent (AGS 4O) stones in the .82-.90 range. I assume that is because most consumers are willing to make the jump to 1 carat and sacrifice some cut quality.

 

[Christina...]

I would like to suggest you are going very high on clarity without *need*. You can easily drop to VSI and probably VS2 and still have a totally eye clean diamond. I don't think you will save enough that way to jump the .90ct mark, but you will save! So that is something to consider if you have not already.

Thank you for the suggestion. My search parameters included VS1 and VS2. This stone seems to be priced in line with stones in the VS range. However, I certainly have my eyes open though before I pull the trigger on this stone. There seems to be a drought of excellent (AGS 4O) stones in the .82-.90 range. I assume that is because most consumers are willing to make the jump to 1 carat and sacrifice some cut quality.

Possibly, or perhaps it's because many shoppers search for stones that weigh just under 1ct to avoid the large premium that occurs at the 1ct mark. I'm happy that John was able to model the stone for you, making buying sight unseen much less risky and anxiety producing! I purchased a VVS1 in the past because it checked all my other criteria and my options were limited. There is something very very cool about viewing the stone with a loupe and knowing that it's essentially flawless. I never was able to locate the grade making pinpoint and I never got tired of telling people that my stone was virtually flawless!

 

[diamond-enthusiast]

Hi John,

Thank you for taking time to post and run results through DIamCalc and I appreciate your technical answers. For the open poster, I'm sorry if the following confuses things for you. I had very much wanted to keep this as non technical as possible.

First off all, there are limitations to Diamcalc. Very much like the HCA tool, your simulation is based on an averaged number.
Based on GIA's chart proportions, the range for excellent for pavilion angles lies between 40.6 degrees to 41.6 degrees.

The limiting factor here is really the 40.6 degrees pavilion in the diamond and GIA uses an average of 8 readings to get this. When you run Diamcalc, you are assuming that all angles are 40.6 degrees. It's a rare possibility that the angles are cut so precisely by the cutter that all 8 are exactly 40.6. I know this isn't probably isn't true in real life. Perhaps you might want to shed light on this and correct me if I'm wrong.

This diamond is sitting directly at the border of Excellent and Very Good proportions based on GIA's chart.

To get a 40.6 average, here's what I think angles would look like in real life.

It definitely cannot be something like 40.6, 40.6, 40.7, 40.8, 40.6, 40.7,40.8 etc... The average of this will make it higher than 40.6.
More likely, it would look like the following. 40.4, 40.7, 40.5, 40.8, 40.7, 40.6,40.8 etc...

Issues in leakage will surface with angles less than 40.6 degrees. I'm just being picky as I mentioned earlier. If I want to get the best for a signature cut based on the premium paid, there are tons of other diamonds to consider over this particular stone.

I'm a geek.

 

[John P]

It is interesting to me! Thanks for the information and examples, John.

John, this is fascinating. Thank you very much for your input and assistance!

I love reading your posts John! Always informative!

Thanks for the thanks And you're all very welcome. I enjoy the opportunity to dialogue about this stuff.

 

[John P]

Hi John, Thank you for taking time to post and run results through DIamCalc and I appreciate your technical answers. For the open poster, I'm sorry if the following confuses things for you. I had very much wanted to keep this as non technical as possible.

DE, you're welcome. Thanks for thanking! In your prior post you said simply: "A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combination."

I understand you're making that statement more conditional now. Comments follow:

First off all, there are limitations to Diamcalc. Very much like the HCA tool, your simulation is based on an averaged number. Based on GIA's chart proportions, the range for excellent for pavilion angles lies between 40.6 degrees to 41.6 degrees.

RE Simulations based on averages: You’re absolutely right. The quick DC models are “perfect” wire-frames showing how basic 57 40.6 35.0 is a robust combination.

RE GIA’s excellent range: It’s too broad for me (personal opinion). Going deeper...

* In the GIA proportion charts 57T 35CA can get EX with pavilion anywhere between 40.6-41.6 PA - (wow! Up to 41.6)
* In the AGS cut charts 57T 35CA is an AGS0 candidate only with pavilion between 40.6-40.8 PA - (far tighter)
* And for fun… The AGA charts (old school PS) show 57T 35CA getting Class 1 with pavilion between 40.4-41.0

Summary: The most researched systems all reward 57T 35CA 40.6. Further, while the “target area” for GIA EX is extremely broad, the “target area” for AGS0 is extremely small. Yet this combination strikes both. I think that’s a strong endorsement.

Sidebar: Isn’t it interesting that Dave Atlas - years before AGS and GIA published their systems - elegantly straddled what would become the eventual two leading systems on this forum? Nice straddling, Dave.

RE Your comment about averaging: In spirit I am so with you, as this is an area I have long banged-the-drum about (!)

The limiting factor here is really the 40.6 degrees pavilion in the diamond and GIA uses an average of 8 readings to get this. When you run Diamcalc, you are assuming that all angles are 40.6 degrees. It's a rare possibility that the angles are cut so precisely by the cutter that all 8 are exactly 40.6. I know this isn't probably isn't true in real life. Perhaps you might want to shed light on this and correct me if I'm wrong.

You're not wrong. But all researched systems include a nominal deviation in the averages. So it's accounted-for.

To get a 40.6 average, here's what I think angles would look like in real life.

It definitely cannot be something like 40.6, 40.6, 40.7, 40.8, 40.6, 40.7,40.8 etc... The average of this will make it higher than 40.6.
More likely, it would look like the following. 40.4, 40.7, 40.5, 40.8, 40.7, 40.6,40.8 etc...

For what it’s worth, your second example is really not an issue. As mentioned, some deviation is accounted-for.
Here are two examples I scanned last night:

NOTE: There is no way to say the original diamond in the thread conforms or does not conform to either DE’s hypothetical data sets – or the sets I’m scanning and providing. I only include them for educational purposes.

Example A: This diamond has a 40.6 PA which runs from 40.4 - 40.8, like you gave in your example above. The eight individual measurements are 40.4, 40.6, 40.8, 40.7, 40.6, 40.5, 40.4. Also close to your hypothetical PA spread (were you channeling this diamond?) And not only is it a screaming AGS0, it’s at the extreme high end of AGS0 – and is also GIA EX, logically.



Example B: Just for fun, check this out. This beauty has a 40.8 PA, with the eight measurements being 40.8, 40.8, 40.8, 40.8, 40.8, 40.9, 40.8 (woot). But I must confess that this example is just to show what is possible sometimes, even with the hardest natural substance known to man. Rare but there. We are all witnesses.



But seriously: Most of the world’s finest diamonds will vary from the given average by several tenths. Many many other range to half a degree or more. Commercial diamonds will run even farther away from the given averages, making the “more likely” numbers you gave look conservative by comparison. This is a topic I am constantly pursuing as a consultant to certain labs and manufacturers.

Issues in leakage will surface with angles less than 40.6 degrees. I'm just being picky as I mentioned earlier. If I want to get the best for a signature cut based on the premium paid, there are tons of other diamonds to consider over this particular stone.

I disagree here. Especially if opposite facet pairs are cut to complement each other; leakage will not be an issue. Now if the center of the averages was lower 40.2 (etc) you might be right, but as I mentioned, the researched lab systems give center-averages with practical deviations in-mind. Esp in the case of AGS, where deviation will definitely influence the final performance scores.

I can point to Example A above for this; the deviation is 0.4 tenths of a degree, but the facets have been strategically paired with their opposites in perfect harmony to suit the average; and provide 3D optical symmetry in this case. It’s a screaming AGS0 with highest marks in all components and perfect H&A.

Without a manufacturer’s report on every diamond seen on PS we can speculate all day - as it relates to averaging and rounding and data sets.

I’m sure many of us agree that, in general, it would be useful to have more information than a grading report. A proper ideal-scope or ASET, for example, helps to show if enough deviation is present to create leakage zones. On that score I’m all-for having more info for diamonds posted online. But since we have only the basic data my conclusion for the original diamond – which is a GIA EX and AGS Ideal candidate – is that the data is promising.

[Edited to add: Admin - is there any way to increase the size of the attached JPGs? Thx.]

 

[me&myboys]

A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combinations. Though most on this forum would say that there isn't much detectable differences which is entirely subjective.

A 0.80 carat diamond with exactly the same table size with a medium girdle would face up bigger than your Bluenile diamond with a slightly thick girdle. Thin to medium is no cause for concern for durability issues in a VVS1 round diamond.

The Bluenile diamond is still decent. I'm just being picky here. You mentioned you want the best value for money. And if I am paying a premium for a supposedly signature diamond, I expect the best and no less. Otherwise, why would I even need to pay this premium for. That's the train of thought.

Based on WHAT???

diamond-enthusiast, I very, very rarely encounter posters whose posts routinely make me want to just bang. my. head. against. a. wall. I most definitely feel that way about the vast majority of your posts.

Opinions stated as facts, facts stated without any reasoning, explanation, background... Insubstantiated facts in general are unhelpful because the OP has no way of knowing whether or not they're actually correct or why they may or may not apply, and other responders with more knowledge/background have no way of understanding why you've come to those conclusions and perhaps either sharing that knowledge/background with you or being led to think in different ways themselves.

This thread. The H&A thread.
THIS thread, in which you completely missed the point: [URL='https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939']https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939[/URL]
And THIS thread, wherein it passed you by yet again: [URL='https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/']https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/[/URL]

If you're going to try and help other people please actually put in the effort to TRY - preferably minus the grandiose assertions of simply knowing better, researching more, and observing more closely. Otherwise you're just doing everyone a disservice. And driving me bananas.

Highly irrelevant and does not answer the question of the OP in any way.

This, ladies and gentlemen, is what cyber bullying looks like.

Yep. It's ugly.

 

[Christina...]

A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combinations. Though most on this forum would say that there isn't much detectable differences which is entirely subjective.

A 0.80 carat diamond with exactly the same table size with a medium girdle would face up bigger than your Bluenile diamond with a slightly thick girdle. Thin to medium is no cause for concern for durability issues in a VVS1 round diamond.

The Bluenile diamond is still decent. I'm just being picky here. You mentioned you want the best value for money. And if I am paying a premium for a supposedly signature diamond, I expect the best and no less. Otherwise, why would I even need to pay this premium for. That's the train of thought.

Based on WHAT???

diamond-enthusiast, I very, very rarely encounter posters whose posts routinely make me want to just bang. my. head. against. a. wall. I most definitely feel that way about the vast majority of your posts.

Opinions stated as facts, facts stated without any reasoning, explanation, background... Insubstantiated facts in general are unhelpful because the OP has no way of knowing whether or not they're actually correct or why they may or may not apply, and other responders with more knowledge/background have no way of understanding why you've come to those conclusions and perhaps either sharing that knowledge/background with you or being led to think in different ways themselves.

This thread. The H&A thread.
THIS thread, in which you completely missed the point: [URL='https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939']https://www.pricescope.com/community/threads/help-with-hca-tool-for-1ct-vs2-g-diamond.190157/#post-3463939?hilit=contrast#p3463939[/URL]
And THIS thread, wherein it passed you by yet again: [URL='https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/']https://www.pricescope.com/community/threads/1-77ct-e-si2-round-brilliant-worth-buying.190573/[/URL]

If you're going to try and help other people please actually put in the effort to TRY - preferably minus the grandiose assertions of simply knowing better, researching more, and observing more closely. Otherwise you're just doing everyone a disservice. And driving me bananas.

Highly irrelevant and does not answer the question of the OP in any way.

This, ladies and gentlemen, is what cyber bullying looks like.

Yep. It's ugly.

I shouldn't speak for Yssie, but I don't for a second believe that she was attempting to bully anyone. I believe that she was asking that he build upon his answers, since as it was originally written, it too did not answer the OPs question. In his second post he elaborated on his first, which offered clarity and was much more useful to the OP and anyone else following along. In the spirit of being helpful it's often necessary to support our thoughts and opinions with actual data to back it up, rather than simply inserting opinion stated as fact. THIS is the only way the OP has of understanding how a poster has come to their conclusion, OP can then take or leave said advice based on his OWN conclusions.


ETA: And if you are trying to make a point about bullying....your final comments don't fall far from the tree...

 

[yssie]

Christina, thank you. Your response to me&myboys summarizes exactly how I feel and why I feel that way, and I couldn't have stated it nearly as eloquently.

me&myboys, my intent was to cite clear, unarguable, and IMO inexcusable examples of responses that I feel are incorrect, misleading, and unhelpful to the OP, so that diamond-enthusiast understands exactly what it is about his posts I object to, since he did not return to either of those threads to respond, correct, explain, justify, or clarify. If you feel that my post was inappropriate then report it to the moderators and let them act as they see fit. Me, I'm just glad that for whatever reason diamond-enthusiast chose to actually come back and elaborate here as the exchange with Mr. Pollard that followed was both interesting and insightful.

 

[yssie]

Hi John, Thank you for taking time to post and run results through DIamCalc and I appreciate your technical answers. For the open poster, I'm sorry if the following confuses things for you. I had very much wanted to keep this as non technical as possible.

DE, you're welcome. Thanks for thanking! In your prior post you said simply: "A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combination."

I understand you're making that statement more conditional now. Comments follow:

First off all, there are limitations to Diamcalc. Very much like the HCA tool, your simulation is based on an averaged number. Based on GIA's chart proportions, the range for excellent for pavilion angles lies between 40.6 degrees to 41.6 degrees.

RE Simulations based on averages: You’re absolutely right. The quick DC models are “perfect” wire-frames showing how basic 57 40.6 35.0 is a robust combination.

RE GIA’s excellent range: It’s too broad for me (personal opinion). Going deeper...

* In the GIA proportion charts 57T 35CA can get EX with pavilion anywhere between 40.6-41.6 PA - (wow! Up to 41.6)
* In the AGS cut charts 57T 35CA is an AGS0 candidate only with pavilion between 40.6-40.8 PA - (far tighter)
* And for fun… The AGA charts (old school PS) show 57T 35CA getting Class 1 with pavilion between 40.4-41.0

Summary: The most researched systems all reward 57T 35CA 40.6. Further, while the “target area” for GIA EX is extremely broad, the “target area” for AGS0 is extremely small. Yet this combination strikes both. I think that’s a strong endorsement.

Sidebar: Isn’t it interesting that Dave Atlas - years before AGS and GIA published their systems - elegantly straddled what would become the eventual two leading systems on this forum? Nice straddling, Dave.

RE Your comment about averaging: In spirit I am so with you, as this is an area I have long banged-the-drum about (!)

The limiting factor here is really the 40.6 degrees pavilion in the diamond and GIA uses an average of 8 readings to get this. When you run Diamcalc, you are assuming that all angles are 40.6 degrees. It's a rare possibility that the angles are cut so precisely by the cutter that all 8 are exactly 40.6. I know this isn't probably isn't true in real life. Perhaps you might want to shed light on this and correct me if I'm wrong.

You're not wrong. But all researched systems include a nominal deviation in the averages. So it's accounted-for.

To get a 40.6 average, here's what I think angles would look like in real life.

It definitely cannot be something like 40.6, 40.6, 40.7, 40.8, 40.6, 40.7,40.8 etc... The average of this will make it higher than 40.6.
More likely, it would look like the following. 40.4, 40.7, 40.5, 40.8, 40.7, 40.6,40.8 etc...

For what it’s worth, your second example is really not an issue. As mentioned, some deviation is accounted-for.
Here are two examples I scanned last night:

NOTE: There is no way to say the original diamond in the thread conforms or does not conform to either DE’s hypothetical data sets – or the sets I’m scanning and providing. I only include them for educational purposes.

Example A: This diamond has a 40.6 PA which runs from 40.4 - 40.8, like you gave in your example above. The eight individual measurements are 40.4, 40.6, 40.8, 40.7, 40.6, 40.5, 40.4. Also close to your hypothetical PA spread (were you channeling this diamond?) And not only is it a screaming AGS0, it’s at the extreme high end of AGS0 – and is also GIA EX, logically.



Example B: Just for fun, check this out. This beauty has a 40.8 PA, with the eight measurements being 40.8, 40.8, 40.8, 40.8, 40.8, 40.9, 40.8 (woot). But I must confess that this example is just to show what is possible sometimes, even with the hardest natural substance known to man. Rare but there. We are all witnesses.



But seriously: Most of the world’s finest diamonds will vary from the given average by several tenths. Many many other range to half a degree or more. Commercial diamonds will run even farther away from the given averages, making the “more likely” numbers you gave look conservative by comparison. This is a topic I am constantly pursuing as a consultant to certain labs and manufacturers.

Issues in leakage will surface with angles less than 40.6 degrees. I'm just being picky as I mentioned earlier. If I want to get the best for a signature cut based on the premium paid, there are tons of other diamonds to consider over this particular stone.

I disagree here. Especially if opposite facet pairs are cut to complement each other; leakage will not be an issue. Now if the center of the averages was lower 40.2 (etc) you might be right, but as I mentioned, the researched lab systems give center-averages with practical deviations in-mind. Esp in the case of AGS, where deviation will definitely influence the final performance scores.

I can point to Example A above for this; the deviation is 0.4 tenths of a degree, but the facets have been strategically paired with their opposites in perfect harmony to suit the average; and provide 3D optical symmetry in this case. It’s a screaming AGS0 with highest marks in all components and perfect H&A.

Without a manufacturer’s report on every diamond seen on PS we can speculate all day - as it relates to averaging and rounding and data sets.

I’m sure many of us agree that, in general, it would be useful to have more information than a grading report. A proper ideal-scope or ASET, for example, helps to show if enough deviation is present to create leakage zones. On that score I’m all-for having more info for diamonds posted online. But since we have only the basic data my conclusion for the original diamond – which is a GIA EX and AGS Ideal candidate – is that the data is promising.

[Edited to add: Admin - is there any way to increase the size of the attached JPGs? Thx.]

Thank you both for this discussion! I have a couple of questions:

1. W/ GIA rounding the average could be 40.5 - would that scenario change your opinion?
2. When you say that
but the facets have been strategically paired with their opposites in perfect harmony to suit the average; and provide 3D optical symmetry in this case,
At what point in the cutting process does this strategic planning happen? Would the cutter aim for 40.6s all around, get 'pretty close', and then adjust afterward? Or is the cutter actually planning those graduated strategically paired opposites from the beginning?

 

[DrD]

The discussion and opinions by all have been hugely beneficial to me. I appreciate everyone's input and assistance. This has been a very educational process. I have found another stone on B2C of which I will list the stats below. I do understand this doesn't fit the traditional AGS triple-0 standard and would not be a candidate for that "award."

Specs:

Carat: 0.84
Color: D
Clarity: VS2
Cut: Excellent
Polish: Excellent
Symmetry: Excellent
Fluorescence: Medium Blue

Measurements: 6.13 - 6.16 x 3.70 mm
Table: 56%
Depth: 60.2%
Crown angle: 33
Pavillion angle: 40.8
Girdle: Medium (Faceted)
Culet: none

HCA: 0.6 (!)

I have asked Ricky at B2C (who was extremely helpful over the phone) to have his supplier confirm first that this stone is eye-clean (an instant deal-breaker) and provide any additional information. He is going to try to provide an ideal-scope image and hopefully a ASET image as well. Pending the results of those reports, which would you recommend? I've listed some personal pros/cons below:

BN stone (.80carat, G, VVS1)
- Better cut
- Better clarity
- Lower final price (~$300 cheaper)

B2C stone (.84carat, D, VS2)
- Much better color
- Larger spread (0.21mm increase)
- Lower HCA

Finally, what do you think about purchasing both stones, evaluating them in person and taking them to a local expert, and returning one stone? Ultimately, I'm looking for the stone that is perfectly eye clean, sparkles like mad, and has the best specs possible.

Again, I very much value and appreciate your help and input. This process is fascinating!

 

[diamondseeker2006]

When you posted: ".06 (!)" HCA, do you understand that a lower HCA score is not better than say 1.0 or 1.5 or 1.9?

I do not care for low crown angles and do not look at any less than 34. I'd prefer the original stone over this one.

And ditto to Christina on Yssie's motives and desire for accuracy when people are giving advice here. She is about as far from a bully as it gets.

 

[Christina...]

Hi John, Thank you for taking time to post and run results through DIamCalc and I appreciate your technical answers. For the open poster, I'm sorry if the following confuses things for you. I had very much wanted to keep this as non technical as possible.

DE, you're welcome. Thanks for thanking! In your prior post you said simply: "A 40.6 degrees angle would most likely result in slight leakage with under the table with that kind of angle combination."

I understand you're making that statement more conditional now. Comments follow:

First off all, there are limitations to Diamcalc. Very much like the HCA tool, your simulation is based on an averaged number. Based on GIA's chart proportions, the range for excellent for pavilion angles lies between 40.6 degrees to 41.6 degrees.

RE Simulations based on averages: You’re absolutely right. The quick DC models are “perfect” wire-frames showing how basic 57 40.6 35.0 is a robust combination.

RE GIA’s excellent range: It’s too broad for me (personal opinion). Going deeper...

* In the GIA proportion charts 57T 35CA can get EX with pavilion anywhere between 40.6-41.6 PA - (wow! Up to 41.6)
* In the AGS cut charts 57T 35CA is an AGS0 candidate only with pavilion between 40.6-40.8 PA - (far tighter)
* And for fun… The AGA charts (old school PS) show 57T 35CA getting Class 1 with pavilion between 40.4-41.0

Summary: The most researched systems all reward 57T 35CA 40.6. Further, while the “target area” for GIA EX is extremely broad, the “target area” for AGS0 is extremely small. Yet this combination strikes both. I think that’s a strong endorsement.

Sidebar: Isn’t it interesting that Dave Atlas - years before AGS and GIA published their systems - elegantly straddled what would become the eventual two leading systems on this forum? Nice straddling, Dave.

RE Your comment about averaging: In spirit I am so with you, as this is an area I have long banged-the-drum about (!)

The limiting factor here is really the 40.6 degrees pavilion in the diamond and GIA uses an average of 8 readings to get this. When you run Diamcalc, you are assuming that all angles are 40.6 degrees. It's a rare possibility that the angles are cut so precisely by the cutter that all 8 are exactly 40.6. I know this isn't probably isn't true in real life. Perhaps you might want to shed light on this and correct me if I'm wrong.

You're not wrong. But all researched systems include a nominal deviation in the averages. So it's accounted-for.

To get a 40.6 average, here's what I think angles would look like in real life.

It definitely cannot be something like 40.6, 40.6, 40.7, 40.8, 40.6, 40.7,40.8 etc... The average of this will make it higher than 40.6.
More likely, it would look like the following. 40.4, 40.7, 40.5, 40.8, 40.7, 40.6,40.8 etc...

For what it’s worth, your second example is really not an issue. As mentioned, some deviation is accounted-for.
Here are two examples I scanned last night:

NOTE: There is no way to say the original diamond in the thread conforms or does not conform to either DE’s hypothetical data sets – or the sets I’m scanning and providing. I only include them for educational purposes.

Example A: This diamond has a 40.6 PA which runs from 40.4 - 40.8, like you gave in your example above. The eight individual measurements are 40.4, 40.6, 40.8, 40.7, 40.6, 40.5, 40.4. Also close to your hypothetical PA spread (were you channeling this diamond?) And not only is it a screaming AGS0, it’s at the extreme high end of AGS0 – and is also GIA EX, logically.



Example B: Just for fun, check this out. This beauty has a 40.8 PA, with the eight measurements being 40.8, 40.8, 40.8, 40.8, 40.8, 40.9, 40.8 (woot). But I must confess that this example is just to show what is possible sometimes, even with the hardest natural substance known to man. Rare but there. We are all witnesses.



But seriously: Most of the world’s finest diamonds will vary from the given average by several tenths. Many many other range to half a degree or more. Commercial diamonds will run even farther away from the given averages, making the “more likely” numbers you gave look conservative by comparison. This is a topic I am constantly pursuing as a consultant to certain labs and manufacturers.

Issues in leakage will surface with angles less than 40.6 degrees. I'm just being picky as I mentioned earlier. If I want to get the best for a signature cut based on the premium paid, there are tons of other diamonds to consider over this particular stone.

I disagree here. Especially if opposite facet pairs are cut to complement each other; leakage will not be an issue. Now if the center of the averages was lower 40.2 (etc) you might be right, but as I mentioned, the researched lab systems give center-averages with practical deviations in-mind. Esp in the case of AGS, where deviation will definitely influence the final performance scores.

I can point to Example A above for this; the deviation is 0.4 tenths of a degree, but the facets have been strategically paired with their opposites in perfect harmony to suit the average; and provide 3D optical symmetry in this case. It’s a screaming AGS0 with highest marks in all components and perfect H&A.

Without a manufacturer’s report on every diamond seen on PS we can speculate all day - as it relates to averaging and rounding and data sets.

I’m sure many of us agree that, in general, it would be useful to have more information than a grading report. A proper ideal-scope or ASET, for example, helps to show if enough deviation is present to create leakage zones. On that score I’m all-for having more info for diamonds posted online. But since we have only the basic data my conclusion for the original diamond – which is a GIA EX and AGS Ideal candidate – is that the data is promising.

[Edited to add: Admin - is there any way to increase the size of the attached JPGs? Thx.]

Thank you both for this discussion! I have a couple of questions:

1. W/ GIA rounding the average could be 40.5 - would that scenario change your opinion?
2. When you say that
but the facets have been strategically paired with their opposites in perfect harmony to suit the average; and provide 3D optical symmetry in this case,
At what point in the cutting process does this strategic planning happen? Would the cutter aim for 40.6s all around, get 'pretty close', and then adjust afterward? Or is the cutter actually planning those graduated strategically paired opposites from the beginning?

I'm actually curious about this as well.

http://www.goodoldgold.com/diamond/7153/

Average pav angle 40.7, however according to the helium http://www.goodoldgold.com/items/7153/ILLUSTRATED%20REPORT.pdf
variances are 40.8, 40.78, 40.71, 40.6 40.54, 40.54, 40.58, 40.7

The stone has superior optical symmetry, were the variances planned or did the cutter, as Yssie asked, plan for all 40.7's and just adjusted as he went?

 

[diamondseeker2006]

Surely the cutter is aiming for the greatest consistency possible! I know in my first H&A stone, the variances in each area of measurement were tiny..one of the best cut stones I have ever seen. Obviously from the GOG stone, which shows ASET and idealscope images, the very small variation in pavilion facets does not affect the performance of that stone.

 

[yssie]

Surely the cutter is aiming for the greatest consistency possible! I know in my first H&A stone, the variances in each area of measurement were tiny..one of the best cut stones I have ever seen. Obviously from the GOG stone, which shows ASET and idealscope images, the very small variation in pavilion facets does not affect the performance of that stone.

I would think so too! But something about the way John phrased it as "strategically planned" makes me wonder?


ETA
CCL welcome back! Do us all a favour and stick around

 

[Christina...]

When you posted: ".06 (!)" HCA, do you understand that a lower HCA score is not better than say 1.0 or 1.5 or 1.9?

I do not care for low crown angles and do not look at any less than 34. I'd prefer the original stone over this one.

And ditto to Christina on Yssie's motives and desire for accuracy when people are giving advice here. She is about as far from a bully as it gets.

I completely agree, it's a beautiful stone. I was curious about Johns comment about leakage not being an issue if opposite facet pairs are complimentary and wondered if this stone was a good example of that being the case.

oops! Quoted the wrong post, but you know to which I was referring!

 

[Christina...]

Thank you CCL!! I've enjoyed reading you posts in many of the older threads and am looking forward to reading (and learning) much more from you! Welcome back!

 

[John P]

Thank you both for this discussion! I have a couple of questions:

1. W/ GIA rounding the average could be 40.5 - would that scenario change your opinion?

You're quite welcome Yssie. I appreciate the dialogue.

RE Rounding: This is something I fear I rant-about...so thank you. I was going to go into it above, but the post was already becoming a tome.

A 40.5 PA still works, in this case, because of room in the crown. As it relates to lab metrics, it's still EX (logically) and remains an AGS0 or AGS1 candidate in the different permutations. Taking this further (read that as OCD) I looked at the 'shallow-shallow' possibility of 57 40.5 34.8 where, despite positive laboratory-implications, I would personally flag it...but math eliminates it. Here's how: A diamond with those mm measurements and averages of 57 40.5 34.8 would weigh 0.81 cts unless the girdle was dug out; in which case it would become VG with the note "Cut grade affected by brillianteering." FWIW, the level of bezel paddling I see in the GCAL micrograph agrees with the math.

I'm pressed for time, but will definitely come back to your second question - and follow-ups by DS2006 and Christina - a bit later.

 

[DrD]

John (and all), thank you all for your continued input. I will continue watch this thread closely. I purchased the .80 stone in question today and am anxiously awaiting its arrival (as well as popping the question in a couple weeks ). I would absolutely love to see a Sarin report of this stone (although I doubt that's possible/cost effective) and would love learning as much more about it as possible.