GIA vs AGS Graded Diamonds – Which Gemological Laboratory is the Best?

This is an excerpt from an email which I received from a client asking for me to help him select diamonds for a three stone ring: “Each stone to be round brilliant cut, at least F color, at least VS2, triple excellent for cut/polish/symmetry and fluorescence to not be stronger than medium, and preferably all certified with GIA. I haven’t really had much to do with AGS so not sure about that lab, but you seem to hold them in high esteem so may consider them too.” — Ken L.  Based on this comment, I thought it might be helpful to share some insight about the two gemological laboratories.

A Brief History of the GIA and AGS Laboratories:

The Gemological Institute of America (GIA) was started in 1931 by Robert M. Shipley, a successful retail jeweler who wanted to create a uniform standard of grading diamonds and colored gems, so that the public could have greater trust in the industry. Shortly thereafter, Shipley launched the American Gem Society (AGS) in 1934, to unite retail jewelers around a common sense of morals and ethics by which they would conduct themselves with the public.

The GIA Laboratory issued its first diamond grading report in 1955, and they quickly became the industry standard for diamond grading. Since the GIA was the only premier gemological laboratory for many, many years, it enjoys a level of market recognition which rivals that of industry giant Tiffany & Co., but both have their challenges trying to retain their hold on the market.

The heavy weight contender for the GIA is the American Gem Society Laboratory (AGSL) which was launched by the American Gem Society in 1996, after the sister organizations suffered a bit of a falling out over whether an overall cut grade, including crown and pavilion angle measurements, should be added to GIA diamond grading reports… At the time, I remember thinking how great it would be to have that information added to GIA diamond grading reports, because we were selling diamonds that would benefit from the documentation of that type of information.

But the majority of the diamond industry flipped out, I mean, they completely lost their minds, because  they did not specialize in “diamonds of exceptional make” as we called them at the time, and they realized that making this type of detailed information available to the public, was the equivalent of tearing the lid off of Pandora’s box, forever… and they were right!

How the AGSL Changed the Diamond Industry Forever:

So when all of this went down, Peter Yantzer, who is the current director of the American Gem Society Laboratory, was the lab director for the Gemological Institute of America. Peter, who I consider to be a personal friend, and thus who I will refer to as Peter in this article, had been trying to get the board of directors at the GIA, to approve the addition of an overall cut grade and the crown / pavilion angle measurements to their diamond grading reports.

As I recall, the proposal was initially met with enthusiasm, there were talks of an industry wide boycott by some very large diamond cutting firms who threatened to send all of their diamonds to other, lesser known laboratories such as the European Gemological Laboratory (EGL), the International Gemological Institute (IGI), etc., and so the proposal was rejected.

But even though the initial proposal was rejected by the talking heads at the GIA, it had caught the interest of the board members of the American Gem Society, and they offered to fund a laboratory for Peter, who promptly opened the American Gem Society Laboratory in 1996.

Those of us who specialized in diamonds of exceptional make, found it pretty easy to adapt to the new industry standard for diamond grading, which provided an overall cut grade for round brilliant cut diamonds, using a numerical scale ranging from 0 – 10 based on individual grades for polish, symmetry, and proportions, with the overall cut grade of the diamond being equivalent to the lowest score for any parameter of cut quality.

Creation of the Great Divide within the Diamond Industry:

While the select few of us who already specialized in Hearts and Arrows Diamonds and other diamonds of exceptional make loved the cut grade system introduced in 1996 by the American Gem Society Laboratory, the majority of the diamond industry was not so fond of it.

So while we and other online vendors, like [what is now] Brian Gavin Diamonds, High Performance Diamonds, and James Allen, who focused on diamond cut quality and visual performance were promoting it online to all of our customers, the majority of the retail trade was flying the colors of the GIA, and hoping to sink the S.S. AGSL, by either flat out denying the existence of the laboratory, or challenging the validity of their grading practices all together.

Believe me, nothing was more entertaining at the time, than one of our customers calling us up to tell us that they had just walked out of a jewelry store which promoted themselves as a Member of the American Gem Society, but who purported to only sell diamonds graded by the GIA “because they are more accurate” and who apparently wasn’t even aware that the “society” which they belonged to had even launched a gemological laboratory! Whoops, might be time to crack open a trade magazine, or read your mail!

The stories got even funnier when our clients would tell us that the “diamond experts” at the store, didn’t have a clue as to what the crown and pavilion angle measurements for the GIA graded diamonds that they were selling, and that the only response that they seemed to have for any questions pertaining to “Hearts and Arrows Diamonds” was that all of that is “smoke and mirrors” and yet they couldn’t provide any insight into how the magic trick was performed (because they’d never seen one).

Awakening the Sleeping Giant:

Now June of 2005 is a bit of a blur to me, because that is when my wife Robin committed suicide. Yea sorry, I didn’t see that one coming either, but if you want to know more about it, you can read my article “The Suicide Note” on my personal development coaching blog, I wrote it on the seven year anniversary of her death… but one of the things that I distinctly remember about that time in my life is being amused by the fact that just as the GIA proudly announced that they were adding an overall cut grade, based on the proportions, polish, and symmetry grades of the diamond, the AGSL announced that they were moving beyond proportions based cut grading to focus on a grading platform that revolves around the actual light performance of the diamonds.

I remember thinking that it took almost a decade for the GIA to acknowledge the importance of cut grade and the effect that the crown and pavilion angles have upon light return, and the AGSL rolls up alongside them and quite literally blows them out of the water by introducing their Angular Spectrum Evaluation Tool (ASET) and in doing so, moved the industry forward light years beyond the proportions based cut grade system which the GIA still employs almost a decade later… That’s right, from my perspective, the industry leader in diamond grading, is running about a decade behind those other guys…

But which gemological laboratory is more accurate?

I’ve had my fair share of experience sending diamonds to be graded by both the GIA and the AGS gemological laboratories, and I’ve heard all sorts of theories about how each laboratory grades diamonds differently, more accurately, less accurately, than the other, and I have to tell you, I find them to be comparable in the level of consistency for carat weight, color, clarity, polish, symmetry, proportions, and fluorescence.

I’ve sent diamonds to both laboratories for side-by-side comparison of the diamond grading reports and feel that they are comparable in their grading standards, which is not really surprising since both laboratories employ GIA Graduate Gemologists as diamond graders, thus the GIA is still setting the standards for diamond grading, since they are the ones teaching people how to grade diamonds.

Keep in mind that the proportions of a diamond are determined by measuring the diamond using computerized proportions analysis, both the GIA and AGS use Sarin machines to measure their diamonds, but each one uses proprietary software which has been designed by Sarin to suit their individual grading standards for proportions… so there is very little variance between the gemological laboratories with regard to how diamonds are measured.

But factors such as clarity, color, and fluorescence, are graded by human eyes, which are subject to variance due to a variety of conditions, including the personal vision of each diamond grader… but each laboratory has their own system in place for the accurate determination of clarity, color and fluorescence grading, like having more than one grader look at a stone.

I have yet to see a discernible difference between the GIA Excellent and AGS Ideal grades for polish and symmetry, to the extent that I consider GIA Excellent to be the equivalent to AGS Ideal for polish and symmetry…

Differences between GIA Excellent & AGS Ideal:

The biggest difference in my mind between the GIA Excellent or “GIA 3X” overall cut grade, and the overall cut grade of AGS Ideal-0 lies in the differences between the parameters for the GIA Excellent proportions and the AGS Ideal proportions grading platforms… It seems to me that the parameters for the AGS Ideal-0 proportions grade are a lot tighter than the guidelines for the GIA Excellent proportions grade.

Round Brilliant Ideal Cut Diamond from James Allen, GIA #16770376To the extent that I often find myself staring at “Cut Grade…….Excellent” line on some GIA diamond grading reports and the proportions outlined on the proportions diagram and wondering how that determination was made. Admittedly, I also disagree with some of the proportion combinations which can obtain an AGS Ideal-0 proportions grade on the outlying regions of the proportions charts used by the AGSL, but it is a bit less of a stretch, and I am known to be a bit of a diamond snob. For instance, take the measurements of this 1.67 carat, F-color, VS-2 clarity, GIA 3X diamond from James Allen, pictured to the left, it has a total depth of 61.4% with a table diameter of 56% and a crown angle of 35.5 degrees which is offset by a pavilion angle of 41.0 degrees with a thin to medium, faceted girdle. The overall cut grade is GIA Excellent (proportions, polish, symmetry).

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Now I can tell you from experience that the combination of the 43.5% pavilion depth is a problem, because that happens to be the critical tipping point where I find that light begins not to strike fully off of the pavilion facets; and the effect of the 85% lower girdle facets is going to be that the sparkle is extremely small in size, which will affect the ability of our human eyes (as opposed to a camera lens) to disperse the flashes of white light into colored sparkle / fire, and thus this diamond is likely to perform best in pin-fire type lighting conditions, e.g. candle light and halogen jewelry store lighting, but not so well under normal lighting.

AGSL Proportions Chart for 56% Table Diameter:

AGS Proportions Chart for Round Diamonds with a 56 percent table diameterThe picture to the left is a portion of the proportions grading chart published by the American Gem Society Laboratory in 2008 for round brilliant cut diamonds. To use it, simply go to the chart designed to be used for the table diameter of the diamond being considered, which is 56% in this case, then cross reference the measurements for crown and pavilion angle.

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In this particular instance, the crown angle of the diamond is 35.5 degrees and the pavilion angle is 41.0 degrees, I cropped down the image on the right and bottom sides, so that the cross section where the two measurements meet on the chart, is the red box that appears in the lower right corner of the graph as indicated by the red arrow.  On the AGSL proportions scale published in 2008, the color pink is used to indicate AGS Ideal-0 proportions; AGS-1 Excellent is represented by the color red; AGS-2 Very Good is indicated by the color gold; AGS-3 Good is indicated by the color yellow. So the proportions rating of this diamond would be AGS-1 Excellent, and thus in this particular bout of the GIA vs AGS, the overall cut grade of GIA Excellent is not equivalent to the AGS Ideal-0 cut rating, but keep in mind that this does not take the crown height or pavilion depth measurements into account, and thus it reveals only part of the picture!

How to Read an ASET image on an AGS DQD:

AGS DQD for Brian Gavin Blue Fluorescent Diamond, AGS #104064812027But the differences between the highest overall cut grades offered by the AGS and GIA gemological laboratories, do not end with the parameters of their proportions grade. The biggest difference between the GIA and AGSL is that the AGSL employs the use of their Angular Spectrum Evaluation Tool (ASET) on their Proprietary Light Performance grading platform. The diamond grading report for this 1.512 carat, F-color, VS-2 clarity, from the Brian Gavin Blue collection, pictured to the left, shows how the diamond looks as seen through the ASET, as seen here in red, green, and blue. All of that red that is visible in the image, represents the brightness of the diamond, and light green indicates areas that are less bright, with the blue arrows representing the areas of the diamond that are reflecting the camera lens back towards the viewer.

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Notice how symmetrical the patterns are… The symmetry of the patterns represented by each color, are an indication of the precision of optical symmetry that this diamond has been cut to, and this will have a direct affect upon the sparkle factor exhibited by this diamond. The higher the degree of optical symmetry, the more contrast that is going to be created within the diamond, thus the more vivid it is going to appear, especially since this Brian Gavin Signature diamond is cut with lower girdle facets in the range of 75 – 78% which is going to create larger sparkle, that is bolder, brighter, and more vivid!

Now before you get too caught up in all of those red and green sections portrayed on the ASET image, I should point out that there will be many times when the two colors will meet or blend in a particular section of the diamond, this is because the edge of the range for both red and green, are shared by both colors when the diamond is gathering light from within the room from the vantage point of 45° so don’t freak out if you see both red and green somewhere like the center of the table facet, which is facing up as all green in this particular image… it’s perfectly normal.

It’s No Secret that I prefer the AGSL for Diamond Grading:

All right, I have nothing but respect for the GIA and their Gem Trade Laboratory, their contribution to the diamond industry is undeniable, and I find their grading practices to be consistent, however I personally prefer the additional insight provided by the addition of the ASET results on the AGSL Proprietary Light Performance Diamond Quality Document.

The reality is that with all other factors being essentially equal, e.g. if I were considering two diamonds, one graded by the GIA and the other graded by the AGSL, and both have the same carat weight, clarity, color, fluorescence, polish rating, symmetry rating, table diameter, total depth, crown angle, pavilion angle, girdle thickness, etc., that additional information such as the ASET image and other reflector scope images, such as the Ideal Scope and Hearts & Arrows Scope images, enable me to take the optical symmetry of the diamond into account.

And a lot of vendors are not equipped to provide these images for their customers, so if it so happens that the ASET image is provided on the Diamond Quality Document issued by the AGS Laboratory, it just makes my job that much easier… But this does not mean that you should only consider diamonds graded by the AGSL, because there are a lot of exceptional options to be found which have been graded by the GIA with an overall cut grade of GIA Excellent, or what is commonly referred to as “GIA 3X” if you know what to look for, and what to ask for…

When looking for round brilliant cut diamonds, I recommend limiting your search to diamonds which have been graded with an overall cut grade of AGS Ideal-0 or GIA Excellent, within the following range of proportions:

Total depth between 59 – 61.8%
Table diameter between 53 – 57.5% (maybe 58%)
Crown angle between 34.3 – 34.9 degrees
Pavilion angle between 40.6 – 40.9 degrees
Girdle: 0.7% thin to medium, faceted or polished
Culet: AGS “pointed” or GIA “none” (same thing)

Now here’s the twist… the parameters that I outline above represent the middle of the spectrum, or “the sweet spot” within the range that the AGSL specified for their zero ideal cut proportions rating, but there are other combinations of crown and pavilion angle that will provide a comparable volume of light return. Rather than get into a really long dialogue about all of the possibilities, just feel free to consider me your Personal Diamond Shopper and send me the details of any diamonds that you’re considering, I’m happy to look over the details for you and make recommendations.

Todd Gray
Todd Gray is a professional diamond buyer with 30+ years of trade experience. He loves to teach people how to buy diamonds that exhibit incredible light performance! In addition to writing for Nice Ice, Todd "ghost writes" blogs and educational content for other diamond sites. When Todd isn't chained to a desk, or consulting for the trade, he enjoys Freediving! (that's like scuba diving, but without air tanks)
Todd Gray

@NiceIceDiamonds

Professional diamond buyer with 30+ years trade experience in the niche of super ideal cut diamonds. In my free time, I enjoy freediving & photography.
The incredible #story behind the Sirisha diamond necklace by @BrianGavin 71 #Diamonds cut to order #Amazinghttps://t.co/dHOo1T99xT - 3 months ago

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59 comments
farah says January 19, 2017

Thank you so much, Todd! I really appreciate how quick and thorough your responses are–wow, it is good to know about knots. I wasn’t even aware to look out for them. I will definitely make sure to see the diamonds in person. In terms of the AGS graded diamond, it is 2.018 carats.

-Farah

Reply
    Todd says January 19, 2017

    Hi Farah,

    So the 2.018 carat, G-color, VS-2 clarity, AGS Ideal-0 cut round diamond was graded on the standard proportions based grading platform. Which is why the diamond grading report issued on July 14, 2016 does not provide an ASET Scope image. The Light Performance grading platform has been available for many years now. Which is why it bothers me when diamond dealers choose the lower level grading platform. It makes me wonder what is it that they’re trying to hide? I was really hoping that this AGS Ideal-0 cut diamond was going to provide us with the ASET Scope image, because it would have enabled me to demonstrate the effects created by the 41.2 degree pavilion and 43.7 degree pavilion depth combination. Which is not likely to perform as well as a diamond with a pavilion angle between 40.6 – 40.9 degrees.

    Here again, the shallower crown angle of 33.4 degrees is likely to produce a higher volume of brilliance, but it will be at the expense of dispersion (colored light, fire). The benefit of buying this diamond over the GIA graded counterparts is that the measurements stated on the diamond grading report are at least the real averaged measurements. The GIA rounds those measurements off, which makes it a lot more difficult to predict light return.

    — Todd

    Reply
farah says January 19, 2017

Thank you for the quick reply, Todd. Sorry, I messed up with my inputs…switched numbers between depth and table. Here are the lab report numbers, GIA 7236191031, AGS 104046879034, GIA 1235046428. Your help is much appreciated.

Reply
    Todd says January 19, 2017

    Hi Farah,

    You know, I was actually wondering about that… Instinctually, I thought that the table and total depth measurements might have been reversed, but decided to just go with the information provided.

    The Enchanted Diamonds Cut Score gives GIA #7236191031 a ranking of 88.4% out of a possible 100%. The 2.30 carat, G-color, VS-2 clarity, GIA Excellent cut round diamond has a pavilion angle of 41.0 degrees, which is combined with a pavilion depth of 43.5% which as discussed yesterday happens to be the critical tipping point where light begins not to strike fully off the pavilion facets. It’s likely that the 32.5 degree crown angle is going to produce significantly more brilliance (white sparkle) rather than the virtual balance of brilliance and dispersion (colored sparkle / fire) that comes with a crown angle between 34.3 – 35.0 degrees.

    Beware of the “knot” which is listed as being one of the primary inclusions. A knot is an included diamond crystal that breaks through the surface of the diamond. They are similar in concept to a knot that can be in a piece of wood. They can be knocked loose and fall out with time, leaving a cavity in their place. The problem with surface cavities is that they can fill-up with dirt and grime, and look like a dark spot in the diamond. They are very difficult (if not impossible) to keep clean. I generally avoid diamonds with cavities, chips, etch channels, and knots.

    I need the carat weight of AGS 104046879034 to be able to look it up using AGS Report Check.

    The Enchanted Diamonds Cut Score tool gives GIA #1235046428 a rating of 87.8% out of 100%. This is because the 2.06 carat, H-color, VS-1 clarity, GIA Excellent cut round diamond has a 60% table diameter and a 41.0 degree pavilion angle that is combined with a 43.5% pavilion depth. Here again, this is the critical tipping point where light begins not to strike fully off of the pavilion facets. And the crown angle of 32.5 degrees is also pretty shallow. You know from my previous explanation that this is likely to create a lot more brilliance, however it will be at the cost of dispersion / colored sparkle / fire.

    Remember that all of this is really a matter of personal preference and taste. That is why the parameters for the GIA Excellent and AGS Ideal-0 proportions grades are so broad. What appeals to one person may not appeal to the taste of another person. If you’re able to see the diamonds in-person, then pick the one that appears to exhibit the highest volume of light return and sparkle factor. However I definitely would not consider buying these diamonds online without the additional insight provided by ASET Scope, Ideal Scope, and Hearts & Arrows scope photographs.

    — Todd

    Reply
farah says January 18, 2017

Hi! Thank you for the helpful article comparing GIA and AGS. Would you be able to give me your insight/pick of the 3 brilliant round diamonds below? Diamond #1 and #2 are G and VS2. Diamond #3 is H and VS1. Any help would be greatly appreciated. Thank You, Farah
Total depth between #1-58% #2-56.6% #3-60%
Table diameter between #1-60.5% #2-61.1% #3-60%
Crown angle between #1-32.5% #2-33.4% #3-32.5%
Pavilion angle between #1-41% #2-41.2% #3-41%
Girdle: #1-med to slightly thick, faceted, 3.5% #2-1.1% to 3.6%, faceted #3-med to slightly thick, faceted, 3.5%
Culet: #1-none #2-pointed #3-none

Reply
    Todd says January 18, 2017

    Hi Farah,

    Thank you for your inquiry. It would be best if I had the diamond grading report numbers, so that I can try to look the diamonds up and see whether any images and additional details might be available. You can send those to me via the Diamond Concierge Service form if you do not want to make that information public.

    The proportions for these round brilliant cut diamonds are outside my preferred range.

    The total depth measurements of #1 and #2 are extremely shallow! And there is usually a lot of light leakage created by having a table facet that is larger than the total depth, especially when the crown angles are shallow like this. It would be really interesting to see reflector scope images for these diamonds! Did you find them online, or at a local jewelry store?

    Things can go either way with a 41.0 degree pavilion angle. If the corresponding pavilion depth is around 43% it is likely to produce a high volume of light return. However, in my experience, things tend to go sideways right around 43.5% which seems to be the critical tipping point where light begins not to strike fully off of the pavilion facets (lower half of the diamond). I suspect that the diamond with the 41.2 degree pavilion angle has a 43.5% pavilion depth?

    — Todd

    Reply
Jon says January 18, 2017

Thanks Todd.

The below was very useful. I was then wondering if you had any thoughts on 6215565150.
Most of the dimensions fall within your figures except for the crown angle and a bit concerned that it’s not within the AGSL proportions “Ideal” cut section of the chart..
I also haven’t seen a clarity photograph or reflector scope images so any thoughts on this too would be very greatly appreciated.

Thanks so much.

Reply
    Todd says January 18, 2017

    Hi Jon,

    Thanks for taking the time to reach out to me for advice. GIA #6215565150 is a 1.50 carat, F-color, VS-2 clarity, GIA Excellent cut round diamond. It is still listed in the MLS that we use to trade diamonds globally, unfortunately there are not any images provided. It was worth a shot! I can find images for virtual diamonds about 60% of the time.

    As you’ve noted, the crown angle of 33 degrees is just outside the range specified for the zero ideal cut proportions rating by the AGS Laboratory for round diamonds with a 57% table diameter and a 40.8 degree pavilion angle. It is also important to remember that the measurements that appear on an AGS Diamond Quality Document (DQD) represent the average of eight individual measurements taken per section. While the GIA takes that average measurement and then further rounds it off to the nearest half a degree or half a percent! So there is more wiggle room to account for with diamonds graded by the GIA.

    Assuming that the crown angle is actually 33 degrees, then it’s likely that this diamond will produce a high volume of light return (due to the 40.8 degree pavilion angle) but will exhibit more brilliance (white sparkle) due to the shallower crown angle / height. There might also be some light leakage created by the shallower crown section, but we have no way of determining that without an ASET Scope, Ideal Scope and Hearts & Arrows scope image. When I run the diamond grading report number for this diamond through the Enchanted Diamonds Cut Score Calculator, they give it a cut score of 94.4% out of a possible 100% for the reasons I’ve explained.

    This might be a good option if you happen to prefer diamonds that exhibit more brilliance, as opposed to the virtual balance of brilliance and dispersion created by a crown angle between 34.3 – 35.0 degrees. But I’d definitely want to see some photographs of the diamond before purchasing it if you’re shopping online. Feel free to email them to me if you get them via diamonds[insert at symbol here]niceice.com or send me a link. If you’re buying the diamond in-person, then look for consistency in the way light is reflecting throughout the diamond, especially under the table facet, and be sure to pay attention to the amount of obstruction that may or may not be present.

    — Todd

    Reply
Jon says January 10, 2017

Hi Todd,

Thanks for providing so much info. It really helps when making such a big decision. I was wondering if I could trouble you in getting your thoughts on the following.

AGS#: 1195669929
Round Brilliant 7.43-7.46-4.53mm
Cut grade: GIA Excellent
Table: 60.0%
Depth: 60.9%
Crown angle: 34.0
Crown depth: 13.5%
Pav angle: 41.2
Pav depth: 43.5%
Fluorescence: None
Polish and symmetry: Excellent
F VS2

I was just wondering if you had any thoughts of the stone, how the light would look, the inclusions etc? To me the inclusions seem to be clustered around the one area but I am hoping a setting (I was thinking North South East West setting) would “cover” most of it anyway.

Thank you for your help in advance!

Jon

Reply
    Todd says January 10, 2017

    Hi Jon,

    Thank you for your inquiry. I want to direct you to the listing for the 1.54 carat, F-color, VS-2 clarity, GIA Excellent cut round on Enchanted Diamonds, because the listing provides a clarity photograph which will help illustrate my points.

    The proportions of this diamond are beyond my preferred range which is outlined in 15 Seconds to Diamond Buying Success. The first thing I notice when I look at the diamond clarity photograph, is how the middle of the table facet appears to be pulling inward from the edges towards the middle. It’s kind of a black hole type of optical effect which is being created by the larger 60% table facet and the steep pavilion depth.

    I want to draw your attention to the medium density patches of brown light reflecting under the table facet in the relative four o’clock and eight o’clock positions. The fact that both sides of the table facet are darker in those opposing sections is an indication that the degree of optical precision is off in those areas. We know this because the optics of a diamond are such, that the light reflecting from each of those locations is actually coming from the opposite side of the diamond. There is a diagram provided within the article Creation of Hearts and Arrows patterns that demonstrates this concept.

    I’m certain that if we were able to obtain an image of the “hearts pattern” for this diamond, that there would be a significant amount of extra space around each of the hearts in the four o’clock and eight o’clock position and that the hearts would vary in size and shape. Because that is what creates the optical effect that we’re seeing here within this diamond. It is also a contributing factor to the moderate obstruction visible under the table facet at the base of the arrows pattern.

    Another factor which is contributing to both the dark areas and the degree of obstruction that is visible under the table facet, is the combination of the 41.2 degree pavilion angle and the 43.5% pavilion depth. In my 30+ years of experience buying diamonds for the trade, I’ve noticed that “the critical tipping point” where light begins not to strike fully off the pavilion facets is 43.5% and anything beyond that is definitely going to impact the volume of light return. For optimum light return, I recommend focusing on diamonds with a pavilion angle between 40.6 – 40.9 degrees. Obviously you want to keep the pavilion depth below 43.5% in conjunction with that.

    The slightly shallow crown height of 13.5% combined with the 34.0 degree crown angle is likely to produce a higher volume of brilliance (white sparkle) as opposed to the virtual balance of brilliance and dispersion (colored sparkle) that tends to be created by a crown angle between 34.3 – 35.0 degrees. This however does not impact the volume of light return, but rather simply tilts the balance of brilliance and dispersion in one direction or the other. For instance, if you prefer a diamond that exhibits more dispersion (colored sparkle / fire) then you might prefer a slightly steeper crown angle, such as 35.5 degrees combined with a crown height of 15.5% but no steeper! Because when you go beyond that, then it’s possible that the diamond will not perform well under the diffused light that we live and work under in this modern age… However that diamond with a 36 degree crown angle and 16% crown height is likely to look spectacular under the pin-fire lighting conditions relied upon by most retail jewelry stores. (Oh, I get it!)

    Now the thing to realize is that I’m not telling you not to buy this diamond. I’m simply breaking it down by the numbers and telling you what I see in terms of how light is reflecting throughout the diamond, due to a combination of proportions and optical precision. My goal in doing so is simply to provide you with the insight to make a more informed decision. This diamond might be perfectly fine for your needs, or you might prefer something with better proportions and a higher degree of optical precision. There is no right and wrong, there is simply better understanding. I’m happy to help you search for additional options if you want to take advantage of my free Diamond Concierge Service. Just drop me a note and let me know the range of carat weight, color, clarity and price that you are open to considering.

    — Todd

    Reply
David says January 4, 2017

Hi Todd,
Very good information and learning a lot more about what to look for in a diamond. Thinking about going forward on this diamond and what to know if this worth the price that it’s offered at $2450

AGS#: 104090205017
Round Brilliant 5.33-5.37×3.29mm
l/w ratio: 1.01
Cut grade AGS Ideal
.578 carat
Table: 56.5
Depth: 61.5
Crown angle: 34
Crown depth: 14.7%
Pav angle: 40.8
Pav depth: 43.1%
Lower Girdle Length: 77%….Think this is correct
Star Length: 49%….. Think this is correct
The above two numbers are on the AGS report located on the diamond assuming they mean lower girdle length and star length
Faceted 1.5%-4.4%
Culet: Pointed
Fluorescence Negligible……not sure what this means???
Polish and symmetry ideal
F VVS2
Holloway score 1.1

Is there any other concerns you have based on the limited information. I am looking at quality with a lot of “fire” vs. the size of the stone

Thanks for your time!!
Dave

Reply
    Todd says January 4, 2017

    Happy new year Dave! All right, so you’re looking at AGS#104090205017 which is a 0.578 carat, F-color, VVS-2 clarity, AGS Ideal-0 cut round diamond with a total depth of 61.5% and a table diameter of 56.5% and a pavilion angle of 40.8 degrees, which is offset by a 34.0 degree crown angle. I looked up the diamond grading report and unfortunately it is in the format which does not provide an ASET Scope image – so I don’t have a way to judge the degree of brightness, nor determine how evenly light is reflecting throughout the diamond. By chance, does the vendor have those images? Ideally, I’d like to see an ASET Scope, Ideal Scope, and Hearts & Arrows scope image.

    As far as predicting light return “by the numbers” we can assume that the 40.8 degree pavilion angle is going to provide a high volume of light return. The 34.0 degree crown angle is a bit shallower than my preferred range which is between 34.3 – 35.0 degrees, and this is likely to produce a hint more brilliance (white sparkle) as opposed to producing the virtual balance of brilliance and dispersion (colored sparkle / fire) that tends to be provided by that 34.3 – 35.0 degree range. The 75% lower girdle facet length should ensure that the sparkle is larger in size and bolder in appearance.

    “Negligible fluorescence” on the AGS grading scale is comparable to “none” on the GIA grading scale. The AGSL prefers the word “negligible” which means “not enough to measure” as opposed to “none” because the reality is that there always seems to be “some fluorescence” even when there appears to be none. Don’t get too caught up in it, fluorescence almost always helps a diamond look better.

    You are correct that the 49% measurement referenced on the plotting diagram is the star facet length, and the 75% is the lower girdle facet length; both measurements are well within my preferred range. Feel free to email me directly at diamonds[insert at symbol here]niceice.com if you have additional questions or want to forward those reflector scope images to me.

    — Todd

    Reply
Bob says November 30, 2016

Hi Todd!

Great read. Was just wondering what you thought of the below.

1.7 carat
Table: 60
Depth: 60.3
Crown angle: 33.5%
Crown depth: 13.5%
Pav angle: 41.2%
Pav depth: 44.0%

F VS2

Thank you so much for your help!

B

Reply
    Todd says November 30, 2016

    Hello Bob,

    I searched the multiple listing service (MLS) that we use to trade diamonds globally and located a 1.70 carat, F-color, VS-2 clarity, GIA Excellent cut round diamond with those measurements. Assuming that the diamond you are looking at is GIA #7223246706 then we’re going to be talking about the same diamond. The first thing that I want to point out is that the proportions of this diamond do not fall within my preferred range as outlined in the article 15 Seconds to Diamond Buying Success and thus it would not be a diamond that I recommend buying.

    However let’s break the diamond down “by the numbers” in order to better understand why I generally would not recommend a diamond with these proportions:

    My preferred range for the pavilion angle is between 40.6 – 40.9 degrees, because in my experience this is going to produce a high volume of light return. While it might seem that the pavilion angle of 41.2 degrees (in this instance) isn’t really that far from my preferred range, it is actually quite surprising how much of a difference that slight difference can make in terms of light performance.

    Another thing that I want to point out is the pavilion depth of this diamond, which is 44% and this is important because based upon all the diamonds I’ve viewed over the years, it seems that the pavilion depth of 43.5% is “the critical tipping point” where light begins NOT to strike fully off of the pavilion facets. This means that the facets on the lower half of the diamond tend to be a little bit off of where they need to be to reflect back the maximum amount of light. Keep in mind that the GIA rounds off this measurement to the nearest half a percent. Thus a pavilion depth of 43.3% is going to be rounded up to 43.5% on the diamond grading report. However by the same premise, a pavilion depth of 43.7% is going to be rounded down to 43.5% and thus there is a lot of wiggle room to work with. But here we have a pavilion depth of 44% which is definitely well beyond the critical tipping point of 43.5% and thus the diamond is definitely not likely to provide us with the best light return.

    Now there is an old adage in the diamond industry that if one half of the diamond is deep, then the other half of the diamond should be shallower in order to produce the best light performance. There’s another one that implies that diamonds with a 60% table and a 60% total depth will somehow automatically also produce the best light performance. Unfortunately neither one of those premises are true, simply because the proportions of a diamond are only one piece of the puzzle.

    But let’s assume for a moment that both of these premises were true… We already know that the pavilion depth of 44% is well beyond the critical tipping point of 43.5% where light begins not to strike fully off the pavilion facets… And based upon experience, I can tell you that the shallower crown height of 13.5% is likely to create more brilliance (white sparkle) as opposed to a virtual balance of brilliance and dispersion (colored sparkle) but that can be fine if that happens to be the look that you prefer in a diamond. After all, the reality is that all of this comes down to your personal preference – but I’m assuming that we’re talking about mine for the moment, since you asked for my opinion about this diamond (if I may be so bold…)

    Fortunately we don’t have to rely solely upon the numbers, nor my personal preferences and tastes as to how a diamond should look, because I was able to locate a clarity photograph and reflector scope images of GIA #7223246706 (once again assuming that we’re talking about the same diamond):
    GIA 7223246706 Excellent cut diamond reviews via Nice Ice, clarity, crown, and pavilion view, ring of death, optical precision issues, light leakage
    All right, so what do we have here? Lots of green and pink arrows that probably don’t mean a thing at first glance…

    (1) Focus in on the grey outline located along the edge of the table facet in the clarity image where the green arrows are pointing.
    (2) Notice that the green arrows are pointing to the same region which is colored red in the image of the arrows pattern.

    What we’re looking at here is the beginning of what is commonly referred to as “the ring of death” where light begins to leak around the edge of the table facet. Now it’s not full blown in this diamond, it’s literally right on the edge, which kind of confirms what I was referring to earlier about the pavilion depth of 43.5% being “the critical tipping point” where light begins not to fully strike off of the pavilion facets. This is what it looks like when that happens.

    Now the pink arrows are pointing at larger areas of obstruction and light leakage which are occurring under the table facet. In the clarity image, these larger black colored triangles tend to overpower and fill-up the larger triangular sections located between the arrows pattern. This type of obstruction tends to make the middle portion of the diamond appear to be darker and less bright.

    In the red colored arrows photograph (middle image) the black section located along the six o’clock region of the table facet is light leakage. It is actually being created by the extra space that appears around the edge of the heart pictured in the 12 o’clock region of the pavilion view that shows the hearts pattern. It can be interesting to discover how seemingly minor differences in the proportions and degrees of optical precision of a round diamond can create such dramatic differences in light performance.

    Since all of this is based upon the sum of my experience, I thought it might be a good idea to provide the results of the Holloway Cut Adviser for a diamond with these proportions. It is intended to be a diamond elimination tool, as opposed to being a diamond selection tool. This is because the HCA does not take the minor facets of a diamond into account, and they also can have a dramatic effect upon light performance. Thus the HCA is intended to help you weed out diamonds that are not likely to perform well, so that you can then obtain clarity photographs and reflector scope images for the remaining options and further fine tune your list:
    Holloway Cut Adviser Score of 4.8 for GIA 7223246706 only buy if price is your main criteria

    All right, so obviously this is not a diamond that I would personally recommend. However I have a feeling that it seems to be offered at an attractive price, because the cut quality of a diamond can affect the market price by as much as 60%. I’ll be happy to conduct a search and see what else might be out there if you decide not to purchase this one. Just send me details of your quest via the Diamond Concierge Service form. There is no charge to consumers for this service, my time is paid for by the various vendors who support this web site under the terms of my material connection disclosure.

    Reply
Joe says November 29, 2016

Hi, Todd! I am looking at three stones that are ideal or close to it, and would love your opinion.

Diamond #1:
Table 56
Depth 62.5
CA 35.5 (15.5%)
PA 40.6 (43.0%)
1.26 carat
E SI1
Holloway score 1.4

Diamond #2
Table 56
Depth 62.1
CA 35.0 (15.5%)
PA 40.8 (43.0%)
1.34 carat
G SI1
Holloway score 1.6

Diamond #3
Table 57
Depth 60
CA 33.0 (14.0%)
PA 41.0 (43.5%)
1.22 carat
F VS2
Holloway score 0.6

Thank you kindly. I will be viewing these stones in person and have access to Ideal Scope images.

Reply
    Todd says November 29, 2016

    Hi Joe, thank you for your inquiry. Let’s run through the options one by one:

    The 1.26 carat, E-color, SI-1 clarity, GIA Excellent cut round diamond should exhibit a high volume of light return given the 40.6 degree pavilion angle. There is a little bit of extra total depth in the diamond due to the slightly steeper crown height, which is apt to create just a hint more dispersion (colored sparkle) as opposed to a virtual balance of brilliance (white sparkle) and dispersion. Not so much that the average person might notice… There is also a little bit of extra depth created by the slightly thick girdle edge.

    I actually like the proportions of the 1.34 carat, G-color, SI-1 clarity, GIA Excellent cut round diamond better. I’m guessing that you’re the person who has it on hold? Anyway, the 40.8 degree pavilion angle should produce a high volume of light return, while the 35.0 degree crown angle produces a virtual balance of brilliance and dispersion. This is more what I look for in a diamond…

    I realize that the HCA likes the 1.22 carat, F-color, VS-2 clarity, GIA Excellent cut round diamond, however it is pretty far off from my preferred selection criteria. In my experience, the pavilion depth of 43.5% happens to be the critical tipping point where light begins not to fully strike off of the pavilion facets… so the light return might not be what you’re hoping for.

    In addition, the shallower crown height tends to produce more brilliance, as opposed to a virtual balance of brilliance and dispersion… Now you might like this and this is why they say “there’s an ideal cut diamond for every preference” however mine tends to lean more towards a balance of brilliance and dispersion.

    The Ideal Scope images would be quite useful in helping you narrow down the possibilities. Would you like to send them to me?

    One thing to take note of is that amount of obstruction (black areas) that are visible at the base of the arrows, between the arrows… Notice that it tends to be less with the 1.34 carat and a little more prevalent in the other two diamonds that have proportions beyond my preferred range. Less obstruction under the table facet tends to make the diamonds look whiter and brighter as it creates more open white space.

    — Todd

    Reply
Todd Gray says June 28, 2016

Hello Karthik, thank you for your inquiry. Based upon the proportions of the diamond referenced, GIA #1223587440 should have a high volume of light return based upon the 40.6 degree pavilion angle. Note that the pavilion depth of 43% would be better suited for a pavilion angle of 40.8 / 40.9 degrees, but this may not have any effect at all… We’d need to see reflector scope images to make that call (ASET, Ideal Scope, H&A). The crown angle of 34.5 degrees should produce a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle) while the 80% lower girdle facet length is likely to produce pin-fire type sparkle.

So all of this is like 90% of the puzzle, the proportions are such that the diamond should exhibit really nice light return! But without reflector scope images, we can’t determine the degree of optical precision and see things such as light leakage. Unfortunately the listing in the MLS that we use to trade diamonds globally does not provide images for this particular diamond. Perhaps the vendor you are working with can provide the upon request. Feel free to email them to me if you are able to obtain them: diamonds[at]niceice.com obviously replace [at] with the “@” sign, or just send me a link to the stone online if the images are provided on the diamond details page.

All the best!
— Todd

Reply
Larry says June 14, 2016

Thanks for the insight Todd. I have another option AGS 0008941302 .756 CT. Would the pavilion depth and Crown angle combo perform closer to .758 CT AGS 0008442703 ?

Reply
    Aslan says June 14, 2016

    Hi Larry, so I looked up the specs on the 0.756 carat diamond using AGS report check:
    AGS#: 8941302
    Report Type: Diamond Quality™ Document
    Shape and Style: Round Brilliant
    Measurements: 5.83 – 5.88 x 3.63 mm
    Cut Grade: AGS Ideal 0
    Color Grade: AGS 0.5 (E)
    Clarity Grade: AGS 3 (VS1)
    Carat Weight: 0.756
    Fluorescence: Negligible
    Table: 55.0%
    Crown Angle: 34.5
    Crown Height: 15.5%
    Girdle: Faceted, 1.4% to 3.9%
    Pavilion Angle: 40.9
    Pavilion Depth: 43.1%
    Star Length: 52%
    Lower Girdle Length: 76%
    Total Depth: 61.9%
    Culet: Pointed

    The 40.9 degree pavilion angle should produce a high volume of light return, while the 34.5 degree crown angle produces a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle). The 76% lower girdle facet length should ensure that the sparkle is larger in size. Average outside diameter is 5.855 millimeters, so it should face-up a hint larger than your current diamond. The only concern that I have is the age of the diamond grading report. Be sure to have the characteristics of the diamond verified by an independent gemologist to ensure that the diamond is still in mint condition.

    — Todd

    Reply
Larry says June 9, 2016

Todd,
I wonder if you could give me your opinion? I have to replace a stone in a ring. The old stone was .758 CT AGS 0008442703. The stone they are proposing to replace it with is .76 CT GIA 6212931131. When I originally picked the AGS stone it was after looking at a number of GIA 3X because the AGS looked so much better. I’m worried that the GIA stone they are proposing isn’t going to look as good. Thanks

Reply
    Todd Gray says June 9, 2016

    Hello Larry,

    Thank you for your inquiry. All right, so I looked up the specifications for your original diamond using AGS Report Check. Thank you for providing me with the AGS diamond grading report number, and the diamond carat weight, as both of those are required to verify an AGS Diamond Quality Document (DQD). According to the AGSL, your current diamond AGS #0008442703 is a 0.758 carat, G-color, VS-1 clarity, round ideal cut diamond (AGS Ideal-0). The pavilion angle of 40.5 degrees should provide a high volume of light return. The crown angle of 35.1 degrees should produce a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle).

    Note that the GIA would round the 35.1 degree crown angle off to 35.0 degrees, because they round this measurement off to the nearest half a degree. If you’d like to know more about how the GIA rounds off the measurements provided on their diamond grading reports, read the article GIA vs AGS Graded Diamonds, which gemological laboratory is best. The 79% lower girdle facet length is likely to produce pin-fire type sparkle, I suspect that your diamond sparkles like a disco ball!

    According to the AGSL, your current diamond measures 5.87 – 5.90 x 3.60 mm. Add together the two measurements for outside diameter 5.87 + 5.90 = 11.77 divide that by 2 = 5.885 is the average outside diameter of your current diamond. According to the GIA Laboratory, the diamond which you are considering, GIA #6212931131 is a 0.76 carat, G-color, VVS-2 clarity, GIA Excellent cut round diamond which measures 5.83-5.85 x 3.63 mm. The average outside diameter of this diamond is 5.84 mm, so it’s actually going to face-up smaller than your current diamond.

    Both diamonds are G-color, the second diamond which you are considering is one clarity grade higher, but that is not something which you’re going to see with your eyes. More importantly, this diamond has a pavilion depth of 43.5% and that happens to be the critical tipping point where light begins NOT to strike fully off of the pavilion facets (lower half of the diamond). So it is quite likely that this diamond is not going to offer the same high volume of light return. The crown angle of 35.5 degrees is also too steep, this combination is likely to create less light return in volume and perhaps a bit more dispersion (colored sparkle) as opposed to a virtual balance of brilliance (white sparkle) and dispersion.

    In my experience, diamonds cut with this combination of crown and pavilion angle is likely to only perform really well when viewed under jewelry store lighting, but they tend not to perform as well under real-world diffused lighting, which is what most of us live and work under these days. The steeper crown height tends to work well with candle light and fire light, but we really don’t spend much time in those lighting environments. If you want to trade-up, I’d pick another option and stick to the proportions outlined in the article 15 Seconds to Diamond Buying Success.

    Obviously I can’t tell you what to do, but it’s not an “upgrade” that I would do personally… I’m certain that your current diamond offers much better light performance. If you’d like assistance looking at other options, feel free to take advantage of my Diamond Concierge Service (it’s free to the public).

    — Todd

    Reply
max huang says June 8, 2016

I found this one GIA#2176512671, which met your rule. Is this one better?

Reply
    Aslan says June 8, 2016

    Hi Max,

    The proportions of the 1.31 carat, G-color, SI-2 clarity, GIA Excellent cut round diamond from Blue Nile are certainly an improvement. The 40.6 degree pavilion angle should produce a high volume of light return. The 34.0 degree crown angle is just a smidge less than my preferred range of 34.3 – 35.0 degrees; this is likely to produce just a bit more brilliance (white sparkle) as opposed to a virtual balance of brilliance and dispersion (colored sparkle). This effect (more brilliance) is likely to be increased by the 80% lower girdle facet length, which tends to produce pin-fire type sparkle, which is smaller in size (than what would be produced by LGF’s in the range of 75 – 78%).

    Due to the manner in which our human eyes “clip” the light, we’re likely to interpret the smaller sparkle as being more brilliant, because our eyes tend not to disperse the light into colored flashes of light (the process known as “dispersion”). Note that this does not make the diamond good or bad, this is merely a reflection of the proportions, and this certainly is a diamond that is worthy of consideration if you happen to prefer more brilliance, as opposed to a virtual balance of brilliance and dispersion. If you think that you prefer more of a balance of brilliance and dispersion, then we’ll want to keep the crown angle between 34.3 – 35.0 degrees, and the pavilion angle between 40.6 – 40.9 degrees for the highest volume of light return.

    If this diamond is of interest, we’re going to want to ask my friend in the diamond department to take a real good look at it, to determine whether the presence of the “clouds not shown” are creating any sort of an issue. The comment “clarity grade is based upon clouds which are not shown” can simply mean that there are quite a few tiny clusters of pinpoint size diamond crystals known as “clouds” that were too small to indicate on the plotting diagram with any degree of accuracy; or that the clouds are not a reliable tool to be used as a reference point for verifying this diamond in terms of clarity characteristics; or it can mean that they were so extensive that it covers too much of the diamond for it to be plotted.

    NOW sometimes small clusters of pinpoint size diamond crystals known as clouds are literally “nothing” to be concerned with. In fact, they are one of my favorite type of inclusions, because they tend to look like constellations of tiny sparkling stars! And other times, they can have a negative impact upon the diamond, causing it to look cloudy and dull. So what we’re going to want to do, is ask my friend in the diamond division at Blue Nile to get ahold of that diamond and take a real good look at it. This is not something that works so well if you call Blue Nile and ask, you’re likely to get the “oh yea, it looks great” scripted answer from the 1st level customer service front, but I’ve got direct access to the upper echelon of the diamond division – so go through me, we’ll get the answers you seek ASAP. They’re familiar enough with my expectations, that they’ll either tell us “Oh yea, you’re going to love it!” or “Hey Todd, this diamond is not for one of your clients…”

    Reply
Max says June 7, 2016

thank you so much! Please email me!

Reply
max lee says June 7, 2016

Todd,
Thank you so much!!! it is dft very very helpful!
1. In your option, comparing with GIA#5216723876 and GIA#6195735049, which one has the better a virtual balance of brilliance and dispersion under normal light?
2. GIA#5216723876 graded as excellent cut, but in AGS, it is below ideal and excellent and at VG cut. is this matter?
3. If my budget is 7K for loose diamond , do you have any recommendation?

Reply
    Aslan says June 7, 2016

    Hello Max,

    I really don’t recommend buying either diamond. All right, let’s take a look at GIA#5216723876 which is a 1.63 carat, G-color, I-1 clarity, GIA Excellent cut round from Enchanted Diamonds. Notice that Enchanted Diamonds is giving the diamond a cut score of 77.5% out of a possible 100. This is because of the 41.4 degree pavilion angle. Their listing also provides a clarity image, and an ASET Scope image. The arrows pattern exhibited by the diamond is completely lacking contrast brilliance, without seeing anything else, I can tell you that the diamond is going to lack contrast, which is what enables us to see depth within the diamond (this translates to a loss of perceived sparkle). But as if that was not bad enough, this ASET scope image shows the classic “ring of death” which is all the white space running around the edge of the table facet, that’s all light leakage!

    The second diamond, GIA #6195735049 is a 1.50 carat, G-color, I-1 clarity, GIA Excellent cut round from Enchanted Diamonds. They don’t provide images of the diamond, but notice that they give this one a lower cut score of 76.9% so we’re not off to a good start. Here again, the diamond has a 41.4 degree pavilion angle, so it’s likely to be leaking light. Would it be all right if I contacted you via email? I’ve got some questions to ask to fine tune your search.

    — Todd

    Reply
Max says June 1, 2016

Hi, Toddy, how are you? I found your article while i was looking up AGS vs GIA . Would you please give me some comment on GIA#6195735048? Thank you very much

Reply
    Todd Gray says June 2, 2016

    Hi there, I’m doing great! Thanks for asking… All right, I looked up GIA #6195735048 in the multiple listing service that we use to trade diamonds globally and the note provided by the cutter reads “almost eye clean!” which is pretty good for an I-1 clarity diamond. The reality being that I’d expect to be able to “readily and immediately” locate the inclusions within an I-1 clarity diamond with just my eyes, such is the nature of the I-1 clarity grade.

    The proportions of the diamond are beyond my preferred range, as outlined in the article 15 Seconds to Diamond Buying Success thus this is not a diamond that I would have recommended via my Diamond Concierge Service. The critical factor as I see it is the 44% pavilion depth. The critical tipping point where light begins NOT to strike fully off the pavilion facets (lower half of the diamond) is 43.5% and this is a full half a percent beyond that point. The crown angle of 33 degrees is pretty shallow, this is likely to produce a higher volume of brilliance (white sparkle) as opposed to a virtual balance of brilliance and dispersion (colored sparkle). Now this is completely a matter of personal preference… some people like to see a virtual balance of brilliance and dispersion, other people like to see more brilliance, and other people prefer more dispersion. I’m not saying that one is better than another, this is simply what this particular crown angle is most likely going to produce.

    Especially with the 80% lower girdle facet length, which tends to produce pin-fire type sparkle which is smaller in size. Due to the manner in which our eyes tend to clip light, the smaller sparkle is most likely to be interpreted as white light, and not fully be dispersed into colored light.

    So this is not really a diamond that I would buy sight unseen online, but if you’re able to see it in-person and evaluate it under different types of lighting environments (as opposed to just viewing under jewelry store lighting, which tends to create a Disneyland-type-lighting effect) then it might be a diamond that appeals to your personal sense of balance… but if you’re buying it sight-unseen online, then I’d try to find an option that has proportions within the preferred range recommended in the referenced article. Let me know if you’d like help.

    Reply
Edward says April 21, 2016

Hello,

I was hoping you could give me some advice on this loose diamond which I am considering buying.
I’m particularly after advice on how the proportions are on this diamond as well as any other useful informtion that you can possibly give me.

Here is the GIA certificate link

http://www.gia.edu/cs/Satellite?pagename=GST%2FDispatcher&childpagename=GIA%2FPage%2FReportCheck&c=Page&cid=1355954554547&reportno=2171440464

Any advice you can give me about this diamond I would greatly appreciate.

I am buying it from a private seller and I have inspected it and it appears to be very eye-clean and a very lovely diamond which I will put in an engagement ring setting for my partner.

I’m pretty set on this diamond, however I just wanted to ask for your thoughts before I proceed as I found your article very helpful and informative.

Many thanks,

Edward

Reply
    Todd says April 22, 2016

    Hello Edward,

    Thank you for your inquiry. I looked up the details for the 0.96 carat, F-color, SI-1 clarity, GIA Excellent cut round diamond which you are considering using GIA Report Check. According to the diamond grading report, the diamond has a total depth of 62.4% which is a bit beyond my preferred range of 59 – 61.8% as detailed in the online tutorial 15 Seconds to Diamond Buying Success. This alone is not really an issue, but it will cost you a bit in terms of the visible outside diameter of the diamond. There is a little bit of carat weight which is being buried in extra total depth, instead of being visible as outside diameter. Minor point… a technical point.

    The pavilion angle of 40.8 degrees is great, it should produce a high volume of light return! The crown angle of 35.5 degrees is just a hint steeper than my preferred range of 34.3 – 35.0 degrees. The GIA rounds this measurement off to the nearest half a degrees, and my suspicion is that the crown angle is actually a bit steeper than 35.5 degrees, since the crown height is 16.5% and this is likely to cause the diamond to display a bit more dispersion (colored sparkle / fire) as opposed to a virtual balance of brilliance (white sparkle) and dispersion. However this effect will be tempered a bit by the fact that the diamond has 75% lower girdle facets, which tend to create sparkle which is larger in size.

    This is not a diamond that I would have selected if I were searching for one, because I adhere strictly to the selection stated in the tutorial referenced above. I tend to focus on those diamonds which have proportions and an overall cut grade that put them in the range of the Top 1% to 0.001% of the annual production for rounds. However that is not to say that this diamond is bad, it’s easily within the Top 2% and it definitely has potential, but it’s the kind of diamond that I would only consider if I were able to judge the light performance in-person.

    In my experience, most diamonds cut like this look great under pin-fire type lighting conditions, such as jewelry store halogen / LED lighting, but don’t perform as well under diffused light due to the steeper crown height. This is not to say that the diamond will not be sparkly and all that, only that it would be even more so if cut to tighter proportions… At present, you’re looking at a diamond that is in the Top 2% range, it should look quite wonderful, it’s just a matter of what level of light performance you’re looking for, and there is a higher spectrum if you so desire.

    I’d walk it around and view it in different lighting conditions, and determine whether it exhibits good contrast brilliance especially under fluorescent lighting if you tend to spend a lot of time under that type of lighting.

    Reply
Tiffany says April 29, 2015

I am looking at purchasing smaller diamonds (0.3ct – 0.5ct) and have seen some that have larger than recommended tables so that the stone looks larger face up. Would all stones with larger tables (e.g. 59% – 61%) considered to be out of proportion then and therefore could not have AGS0 rating?

Reply
    Todd Gray says May 1, 2015

    It is possible for round brilliant cut diamonds with larger table facet diameters, such as those in the 59 – 60% diameter range to have an overall cut grade of AGS Ideal-0, and/or have proportions equivalent to the AGS Ideal zero proportions grade, as indicated on the AGS Proportions Chart from 2008, which includes a broader range of proportions. My preference however is for ideal cut diamonds which adhere to the original definition of an ideal cut diamond, and even then only those that are cut to the middle of the range designated for the zero ideal cut rating; however this is largely a matter of personal preference, which is why there is a broader range of options beyond the ones that I adhere to as a buyer.

    Reply
Olivia says March 24, 2015

Hello I am in the market for a diamond, Can you please tell me what you think? The Price was not bad compare to what I see, and with the score od 2.8 with HCA.

GIA 5183968768
1.5 ct E color VS2 Clarity 3Ex
Table:58%
Depth:61.9
Crown Angle: 35.5%
Crown Height: 15%
Girdle: Faceted, Medium to Slightly Thick
Pavilion Angle: 40.5%
Pavilion Depth: 43%
Star Length: 50%
Lower Girdle Length: 80%

Reply
    Todd Gray says March 25, 2015

    Thank you for your inquiry. The proportions of a diamond, and overall cut quality which consists of the degree of optical precision, polish, and symmetry, can affect it’s market price by as much as 60% and this is a factor in the price of this diamond. The first thing that caught my attention is that the pavilion angle is 40.5 degrees, but the pavilion depth is 43% and that is an indication to me that something is off about the facet structure of this diamond. A pavilion angle of 40.5 degrees should be combined with a pavilion depth more in the range of 42.4 – 42.5% while a pavilion depth of 43% would be more appropriate for a pavilion angle of 40.8 / 40.9 degrees. The same principle holds true for the crown angle of 35.5 degrees, it is too steep for the crown height of 15% and will likely cause this diamond to exhibit a higher amount of dispersion, as opposed to a virtual balance of brilliance (white sparkle) and dispersion / fire (colored sparkle) but some people like this, whereas I definitely prefer ideal cut diamonds that exhibit more of a balance of the sparkle factors. My expectation is that this diamond would perform extremely well, and look quite beautiful when viewed in a pin-fire type lighting environment, such as that provided by candlelight, due to the steep crown angle; but that it will not perform as well when viewed in diffused lighting conditions, such as what we tend to live and work under these days.

    If you’re looking for options that are likely to deliver a virtual balance of brilliance and dispersion, with a high volume of light return, then I’d focus on ideal cut diamonds, GIA 3X / GIA Triple Excellent / AGS Ideal-0, etc., that have a crown angle between 34.3 – 34.9 degrees which is offset by a pavilion angle between 40.6 – 40.9 degrees; possibly even a crown angle of 34.2 – 35.0 degrees, if combined with the right pavilion angle offset. I’ll be happy to look for options for you to consider, and/or look over additional options if you’d like to submit an inquiry via my free diamond concierge service, just provide me with an idea of what you’re looking for, along with the price range.

    Reply
      Olivia says March 25, 2015

      I am sorry I made a mistake on the pavilion angle, this diamond pavilion angle is 40.8% with the pavilion depth os 43%. Go by what you said that 43% pavilion depth should pair with 40.8% pavilion angle, I guess this diamond seems good? This diamond listed for $12,200 and the most comparable one I can find now it over 13K. My budget is around $12,500. Suggestion?

      Reply
        Todd Gray says March 25, 2015

        A pavilion angle of 40.8 degrees combined with a pavilion depth of 43% is great! The diamond should exhibit a high volume of light return, and is a perfect choice if you like things more fiery! The lower girdle length of 80% will help to offset that effect a bit by evening out the perception of brilliance, by creating smaller flashes of light / sparkle that are more like pin-fire. Good option for the price!

        Reply
          Olivia says March 25, 2015

          Thank you so much for your help! Your article is great and learned a lot from it.

          Reply
Vik says March 21, 2015

I am considering a diamond for a ring AGSL number 104076443012. What is your opinion on this diamond, and what do you think it’s fair value should be?

Thank you very much,
V.

Reply
    Todd Gray says March 21, 2015

    Thank you for your inquiry, however the full carat weight of the diamond is required to look up a diamond by diamond grading report number using AGS Report Check, please feel free to send me the carat weight of the diamond via email: diamonds[at]niceice.com or send me a link to the diamond details page if you found it online. Thank you.

    Reply
      Vik says March 22, 2015

      Thank you very much, Todd, for helping me make a decision. The total carat weight is 1.533

      Reply
        Todd Gray says March 23, 2015

        The proportions of the diamond are not within my preferred range of proportions, and thus it is not a diamond that I would recommend purchasing, unless by chance you have seen it in-person and happen to like how this particular diamond performs in terms of the volume of light return and sparkle factor. The pavilion angle of 40.3 degrees is extremely shallow, it would be better if it were between 40.6 – 40.9 degrees; and the crown angle is extremely steep at 35.6 degrees, note that I prefer that it be between 34.3 – 34.9 degrees, with the potential of having it be 34.2 – 35.0 degrees if combined with the right pavilion angle.

        Note that the ASET image on the diamond quality document issued by the AGSL does indicate that this diamond will be nice and bright, as indicated by the high volume of red, and that the distribution of light being reflected throughout the diamond does appear to be consistent; it is important to understand that “ideal cut diamonds” are cut in a wide range of proportions parameters, in an effort to appeal to the preferences of a broader market than the “super ideal cut diamond” niche which I tend to focus upon, thus which ideal cut diamond to purchase is largely a matter of personal preference, so this commentary is really just my two cents so-to-speak. Everything else about the diamond looks fine…

        Reply
          Vik says March 23, 2015

          Thank you very very much. I truly appreciate your help.

          Reply
          Todd Gray says March 23, 2015

          My pleasure. And for those of you who are reading this commentary, and who would like my input on the diamonds that you are considering, or help finding a diamond, please feel free to take advantage of my free diamond concierge service by submitting an inquiry via that form.

          Reply
Jimmy says January 19, 2015

Mr Gray
I was hoping to see if you could help analyze this diamond I recently bought from Blue Nile. Your knowledge and articles have helped me a lot in deciding what is important, thus if you would be kind to throw in your 2 cents regarding the diamond I bought, I would greatly appreciate it.

$9970. 1.26 carat, GIA ex/ex/ex/no fluorescense. F Color, VS2. Table 55, crown 34.5, pavilion 40.8, depth 61.4, girdle thin-medium faceted (3%). HCA score 1.2

The GIA report can be viewed on bluenile’s website, diamond number LD04310752

This is a spectacular diamond, and even local jewelers were mum about it. They would talk bad about buying online, but then just quiet after seeing the diamond, and just say.. yea it’s a good diamond. The problem is, that it bothers me that it is not inscribed, and by the plotting chart, there is no way for me to identify this diamond with a loupe (I cannot see the inclusions), and neither can the gemologist with a microscope (the clouds) anyways. Because of this, I wanted to send it to AGS for re-grading and inscribe it on the diamond girlde, so it would be interesting to see how it performs when compared to GIA. At your convenience, please do let me know of your thoughts. Thanks in advance

Reply
    Todd Gray says January 20, 2015

    I have no doubt that the 1.26 carat, F-color, VS-2 clarity, round diamond from Blue Nile that you purchased is stunning, because the 40.8 degree pavilion angle should provide a high volume of light return, while the 34.5 degree pavilion angle should deliver a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle) and the 80% lower girdle facets should produce pin-fire type sparkle that is a lot like the sparkle created by the tiny mirrors on a disco ball.

    Based upon the measurements provided on the GIA diamond grading report, the diamond qualifies for the AGS Ideal-0 proportions grade, however this does not necessarily mean that the diamond will meet the criteria for the overall cut grade of AGS Ideal-0, which also takes the light performance of the diamond into account, that is determined using Angular Spectrum Evaluation Technology (ASET) which is proprietary to the AGS Laboratory.

    The diamond inclusion “clouds” is comprised of tiny, pinpoint size diamond crystals that look like sparkling specs of dust, that are located in close proximity to one another, they can be very difficult to locate without higher levels of magnification, I can see why you would want to have the diamond inscribed.

    Reply
Ann says January 8, 2015

I am planning to set this diamond in a tension setting. What do you think?

Certificate:AGS
Shape: Round
L/W/D (mm): 4.46*4.50*2.76
Carat weight:0.33
Color: F
Clarity: IF
Cut: Ideal
Polish:Ideal
Symmetry:Ideal
Depth %:61.50
Table %:55.90
Crown ∠: 35.00
Crown %:15.50
Pavilion ∠:41.00
Pavilion %: 43.30
Girdle: Thin – Slightly Thick
Fluorescence:Negligible

Reply
    Todd Gray says January 9, 2015

    Based upon the numbers, the diamond should exhibit a reasonably high volume of light return, and a virtual balance of brilliance and dispersion; it would be nice to see a copy of the diamond grading report, so that I could provide you with more insight, such as the type of sparkle that is apt to be created by the lower girdle facet length. In addition, it would be helpful to see any reflector scope images, such as ASET, Ideal Scope, or Hearts and Arrows scope photographs, in order to be able to judge the degree of optical precision (this is not graded by the gemological laboratories).

    Generally speaking, the light return of the diamond would be improved if the pavilion angle were between 40.7 – 40.9 degrees, but 41.0 degrees is within tolerance of my preferred range, and works with the 43.3% pavilion depth, but if the pavilion depth were slightly steeper, such as 43.5% then I would have recommended you look for a different diamond, because the odds are that the steeper pavilion depth would prevent light from striking off of the pavilion facets properly.

    I realize that you might not want to post the diamond grading report online, but feel free to send me the number via my Diamond Concierge Service and I will respond via private email.

    Reply
Elizabeth says December 21, 2014

I am considering a 2.3 ct. diamond. The GIA # is 2165498023. Can you tell me if this is a good diamond? I am concerned about the cut grading of Fair, the girdle thickness, and the presence of a small culet. What would be a good price for this stone? Thank you.

Reply
    Todd Gray says December 22, 2014

    Thank you for your inquiry. With no offense intended to my purebred German shepherd, this stone is a dog; and as indicated by the GIA Gem Trade Laboratory, the cut grade is only fair, which is one step above poor. The diamond is essentially cut backwards, the total depth measurement of 55.7% would be better suited for the table diameter measurement; while the table diameter measurement of 61% would be better suited for the total depth.

    The pavilion angle of 40 degrees is extremely shallow, this is likely resulting in a significant decrease in the volume of light return; while the crown angle of 28.5 degrees is also extremely shallow, thereby affecting the balance of brilliance (white sparkle) and dispersion (colored sparkle) to the degree where there really isn’t much of a balance… These two angles represent the primary reflective surfaces of the diamond, they are supposed to reflect light off of each other to intensify sparkle, and then direct the light which enters the diamond, back up towards the viewer, this is not likely to occur in this instance. And the 85% lower girdle facet length is likely to create extremely small, pin-fire type sparkle; and the outside diameter measurements of 8.81 – 8.94 x 4.84 mm, indicate that the outside diameter of the diamond is more than one millimeter out of round, which will give the diamond kind of a flat tire look from a top-down perspective.

    As you’ve indicated the girdle thickness of the diamond is also a concern, very thin girdle edges are prone to being chipped and damaged; and the small culet is likely to show up through the table facet as a small white circle upon close examination of the diamond.

    If you’ve read my blog, then you know this type of diamond is at the far end of the spectrum, directly opposite of what I recommend; since the overall diamond cut quality of a diamond can affect the market price by as much as 60% and this is by far, the worst example of diamond proportions that I’ve ever seen, my approach to estimating the market value would be to put that principle into affect, by taking the list price of this 2.270 carat, H-color, VS-2 clarity, Brian Gavin Signature round diamond, which represents the very best of the best, and which is priced at $32,748.00 and multiply that price X 0.40 = $13,099.00 for the estimated market value of this 2.31 carat, H-color, VS-2 clarity, round diamond which is graded by the GIA with an overall cut grade of Fair, but somehow I’m not even sure if that price is low enough.

    Reply
      Elizabeth says December 22, 2014

      Thank you so much for your valued input. We had a “gut” feeling about this stone, and I guess we were correct to do further research. You just saved us from making a very expensive mistake. We are leery of the many “mall” jewelers, and equally so of buying on-line. Do you have any suggestions? We are looking for a 2-2.5 ct. , H-I-J color, VS1-2 , with a cut that is better than “fair” for sure! The jeweler with the above stone is very reputable- so we are rather upset that we could have just made a horrible purchase. Thank you for any advice you can give us, and for steering us in the right direction!

      Reply
Leslie Yap says November 8, 2014

Hi Todd,

This is a small .56ct D IF EX cut. Very strong Flour. Will this shine?

PROPORTIONS

Depth 60.7 %
Table 58 %
Crown Angle 33.5°
Crown Height 14.0%
Pavilion Angle 41.2°
Pavilion Depth 43.5%
Star Length 50%
Lower Half 80%
Girdle Medium, Faceted, 3.5%
Culet None

Reply
    Todd Gray says November 8, 2014

    Practically all diamonds “shine” especially while being pumped full of 3the 00 watt halogen lighting that is an integral part of the design of most jewelry stores, however truly well cut diamonds will exhibit a high volume of light return and a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle / fire) even when being starved for light. This however is not likely to be one of those diamonds… The proportions of this diamond are well beyond the preferred range that I specify in the article 15 Seconds to Diamond Buying Success, which I think is a diamond buying tutorial that every person should read before buying a diamond, because it provides a time proven formula for buying exceptional looking diamonds.

    In this particular instance, the total depth and table diameter of the diamond are perfectly fine, however the 41.2 degree pavilion angle is a bit steep, and when combined with the 43.5% pavilion depth, it is likely to result in light not properly striking off of the pavilion facets, thereby reducing the volume of light return; I recommend keeping the pavilion angle between 40.6 – 40.9 degrees.

    In addition, the crown angle is a bit shallow at 33.5 degrees, as is the 14% crown height, thus the diamond is likely to exhibit a higher volume of brilliance than dispersion, or a virtual balance of dispersion; this effect is likely to be heightened by the 80% lower girdle facet length, which tends to produce smaller flashes of light / sparkle; and this is an issue because our eyes can experience difficulty dispersing smaller flashes of light into colored light / fire, and thus this diamond is probably quite brilliant, but not very fiery; of course there is always the possibility that you prefer diamonds that exhibit smaller pin-fire type sparkle, and more brilliance, as opposed to diamonds that exhibit larger, bolder flashes of light, and a virtual balance of brilliance and dispersion.

    Very strong blue fluorescence in a D-color diamond can be a beautiful thing, but it also has the potential to make the diamond look cloudy, or milky, when viewed in direct sunlight where the blue fluorescent molecules would be excited by the UV light; this is something which affects perhaps 2% of gem quality diamonds, so maybe it is an issue, and maybe it is not, but there’s no way to know without looking at it, or working with a vendor who is extremely vigilant about which blue fluorescent diamonds that they allow into their collection.

    I hope that you find this explanation helpful, if you would like further assistance locating diamonds which are likely to exhibit a higher volume of light return, feel free to take advantage of my free Diamond Concierge Service, by submitting a request, and providing me with the range of characteristics that you are looking for, as well as the price range you are working with, and if possible let me know your preference for the type of sparkle: smaller, pin-fire type sparkle (80 – 82% lower girdle facets) or larger, bolder, brighter sparkle (75 – 78% lower girdle facets) all of which of course combined with my preferred set of proportions.

    Reply
Rebecca says November 6, 2014

Hi there!

Thanks for an informative post. Can I get your opinion on the specs for this RB? The crown angle is a smidge outside of the “sweet spot” but everything else seems to check out. I’m also a bit concerned about the 42.9 pavilion depth percentage. I ran this stone through HCA and it scored a 1.2.

1.23cts.
F
Triple Excellent
VS2
56% Table
61.8% Depth
35 deg. Crown angle
42.9% / 40.7 deg. Pavilion depth percentage / angle

Thanks so much!

R.

Reply
    Todd Gray says November 6, 2014

    Based upon the proportions, the diamond has the potential to be a really nice looking diamond; the 40.7 degree pavilion angle should provide a high volume of light return, and the 42.9% pavilion depth measurement is in-line with that pavilion angle; and the 35 degree crown angle should provide a virtual balance of brilliance (white sparkle) and dispersion (colored sparkle) provided that the crown height provides a good balance for that measurement, e.g. it’s not 16% or something like that; and all of this of course is subject to the effects of optical symmetry, e.g. the consistency of facet shape, alignment, and indexing, which is NOT factors taken into consideration in the GIA symmetry grade that is provided on the diamond grading report, that is meet point symmetry, so ask the vendor for ASET Scope, Ideal Scope, and Hearts and Arrows scope images and send them over to me via email diamonds[at]niceice.com if you’d like me to look those over for you, or just send me a link to the stone. Also you make no mention of the girdle thickness, hopefully that’s in the range of thin to medium.

    Reply
      Rebecca says November 6, 2014

      Thanks so much for the quick response Todd!

      Unfortunately that’s all the info I have so far on this stone. I’ll check back once I find out more. Thanks again 🙂

      Reply
Jeff says April 8, 2014

Hey there-
I just purchased a 1.568ct round cut diamond for an engagement ring. I have tried to do as much research as possible before purchase, but I am still a novice when it comes to this subject, so I apologize in advance if I have any “stupid” comments!

The diamond does have an AGS report from 2007 and also has H&A along with the number inscribed on the girdle. Here are the proportions according to the report.

Table: 56.4%
Crown Angle: 34.8%
Crown Height: 15.2%
Girdle: Faceted, 1.6% to 3.8%
Pavilion Angle: 40.7%
Pavilion Depth: 42.9%
Star Length: 54%
Lower Girdle Length: 76%
Total Depth: 61.6%
Cutlet: Pointed

It has a color grade of AGS 2.0 (H)
Clarity grade of AGS 5 (SI1)
Fluorescence: Negligible

This also has a cut grade of AGS Ideal 0
Light Performance 0
Proportion Factors 0
Finish 0
Polish: Ideal
Symmetry: Ideal

I bought this sight unseen because I thought I got a very good price for this loose diamond (less than 10k), but I am worried with it having a report back in 2007 that it may have lost value! Everything about this diamond sounds great and I am hoping I got a good deal on it. Any suggestions what I should do with the diamond when I receive it? I want to get it appraised. Will jewelers send it off to AGS again if they can read the AGS# on the girdle? I appreciate any and all feedback! I guess I am just curious if you think this is a good deal too! Thanks

Jeff

Reply
    Todd Gray says April 9, 2014

    Hi Jeff, the proportions of the diamond are well within the range of preferred proportions which I specify in my article and thus the diamond definitely has the potential to be amazing! The 40.7 degree pavilion angle should produce a high volume of light return, while the 34.8 degree crown angle should produce a virtual balance of brilliance and dispersion, and the combination of the measurements for the star and lower girdle facets should produce nice, broad flashes of light! Definitely sounds like my type of stone! Note that the presence of “H&A” inscribed on the girdle edge, does not necessarily indicate that the diamond is “Hearts and Arrows” as the laboratory must record whatever is inscribed on the girdle edge as part of reporting the characteristics of the diamond at the time they graded it, but the AGSL does not look for, or verify the presence of hearts and arrows as part of their grading process. There should be no issues with submitting the diamond to the AGSL to be re-graded / update the lab report, since they will be able to identify the diamond by the inscription of the diamond grading report which appears on the girdle edge. Sounds like a great find! Congratulations! Oh by the way, if you can make out the inscription and/or have the lab report number, you might be able to look it up using the option to provided on their web site. Feel free to email the lab report number to diamonds[at]niceice.com if you’d like further comment on it, be sure to remind me of the 1.568 carat weight if you do because it is required to find the report.

    Reply
Lynn Arrowood says January 5, 2014

I was just reading some of your comments between the GIA and AGS. I just chose a diamond that was graded by AGS. It is 2.05 D color SI2 with Ideal CUT and light performance, Ideal Symmetry, and Excellent polish. I chose this diamond out of three. I had only requested two of the dimonds to look at, but it just so happened that the jeweler had gotten in an extra diamond. She insisted that i look at it because it was 2.11 carats. That diamond was an SI1, 2.11 carat G color and it was beautiful- however, i did not choose it because it had a strong blue fluorescence. The strange thing was, when she pulled out the GIA report for that diamond, it had an Excellent cut, Very Good polish, and Very Good symmetry, and a strong blue fluorescence. I was shocked by the report. By looking at the diamond, i would have thought it was definately triple excellent! I just couldnt quiet figure out why it looked so good but was not. She kept telling me she couldnt tell the diference between the G and the D but i figure that was because of the fluorescence. Nevertheless, 6 points was not going to sway me to purchase a stone that was a G instead of a D, but to my suprise it was beautiful despite
the fact that the paperwork was not exactly to suit me. I’m still bumfuzzled about this stone. What do you think?

Reply
    Todd Gray says January 6, 2014

    It would be interesting to be able to compare the details on the diamond grading reports for the three diamonds along with a computerized proportions analysis which could provide insight into the facet structure of the diamonds, because being able to do so might provide the answers that you seek. It is possible that the proportions of the G-color diamond were such that they provided excellent light return, which would enable it to rival the D-color diamond in terms of Brightness, which is a term used by the industry to describe both the volume of light return and body color. It is doubtful that strong blue fluorescence in a G-color diamond would boost the color beyond the lower end of the range for F-color, however the brightness of the diamond in terms of the volume of light could certainly make it appear whiter… I’ve certainly noticed that diamonds which are cut to proportions which are optimized to deliver maximum light return and which have a higher level of optical symmetry which enables the diamond to exhibit great contrast, like those produced by Brian Gavin and Crafted by Infinity, tend to face up whiter than diamonds cut to a lesser degree of perfection, but I doubt that I’ll ever see a G-color diamond which I could mistake for a D-color, regardless of the fluorescence rating. Given the same situation, I most likely would have selected the D-color diamond as well, I would much rather have a diamond with zero for light performance and symmetry (the two primary factors of visual performance) and sacrifice a little bit on the polish grade which is much more difficult to ascertain. Good job!

    Reply
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