"Can you explain how to judge diamond visual performance online? I'm having difficulty deciding between a few since I can't view the stones for performance. Thanks in advance and for all the useful advice you provide." — Dave.
In the first place, it's easier than you might think to judge diamond visual performance online. Consequently, you can tell a lot about a diamond based on the information provided by the two vendors you reference in your email:
In that case, let's take a look at the factors that dictate light performance.
Characteristics of Diamond Visual Performance:
The first thing to remember is that your diamond's sparkle factor and light performance depend on the cut quality. That might seem rather obvious, but there is more to the picture than meets the eye.
Under those circumstances, most people make a critical mistake by only relying on the diamond grading report. In that case, their perception of cut quality depends on the cumulation of proportions, polish, and symmetry grades.
Those factors are essential to diamond visual performance but do not account for optical precision or Azimuth Shift. Consequently, the overall cut grade on the lab report only takes the following factors into account:
Major gemological laboratories like the AGS and GIA do not evaluate Optical Precision when determining the cut grade of a diamond. That seems counterintuitive since it has a significant impact on visual performance.
Fine-tune Your Search for Diamond Visual Performance:
It helps to know what you're looking for if you're searching for diamonds online. Otherwise, you're going to waste a lot of time sifting through thousands of options with subpar performance.
It's also important to realize that the AGS Ideal and GIA Excellent classifications represent a range or spectrum of inclusion. Under those circumstances, it makes sense to focus on the middle of the spectrum:
Any variation from the proportions above may significantly reduce the diamond visual performance. Be that as it may, the degree of optical precision will also influence the sparkle factor.
Perspective Is the Pinnacle of Understanding:
In a moment, we're going to look at the four diamonds that David referenced explicitly in his email. We're going to walk through the selection, or rather the elimination process.
First, we'll look at the proportions, polish, and symmetry grades of the diamond as outlined above. Then we're going to get into the nitty-gritty hidden factors of evaluating diamond visual performance.
In that case, we'll look at the images of the hearts and arrows pattern. We're also going to evaluate the ASET and Ideal Scope images. But first, I want to remind you that these four diamonds have an overall cut grade of AGS Ideal or GIA Excellent.
Under those circumstances, they are among the Top 1% of the annual production for round brilliant cut diamonds. So, they're all excellent options in their own right, but we're looking for "the one" that is the Cat's Meow.
Option #1 - Diamond Visual Performance Evaluation:
The first diamond to consider is a 1.62 carat, H-color, VS-2 clarity, GIA Excellent cut round diamond from James Allen. Under normal circumstances, the filters I have in place would preclude this diamond because the 62.3% total depth is steeper than I prefer.
In that case, you're paying a premium for diamond carat weight hidden in total depth instead of the visible outside diameter. The 41-degree pavilion angle is also too steep and will not produce as much light return as a pavilion angle between 40.6 - 40.9 degrees.
If this client did not ask about this diamond specifically, we would not be discussing it. After all, my presets for total depth and table diameter would have prevented me from seeing this diamond in the first place.
Consequently, the light pink and semi-translucent areas visible under the table facet indicate a moderate amount of light leakage. In that case, the 41-degree pavilion angle is a factor, but so is the degree of optical precision, as will be shown below.
This link contains the presets we use to Search for James Allen Diamonds. In that case, you only need to verify that the crown/pavilion angle offset is within the range we recommend above.
Use an H&A Scope to Judge Optical Precision:
The Hearts image shown here indicates a variance in the size and shape of the hearts. Simultaneously, the tips of the hearts are twisting and bleeding into the little arrowheads in the middle.
That is an indication that there is a difference in the length of the lower girdle facets. There is also likely an Azimuth shift, which is a variance in the facets' alignment.
Consequently, it requires a lot of skill to align the diamond facets properly from the perspective of 360-degrees. Not only that, but it can also take up to 4X longer to polish a diamond to exhibit a higher degree of optical precision.
That is why James Allen True Hearts Diamonds cost more than their standard ideal cuts. When judging diamond visual performance online, remember that the sparkle factor is higher when there is less Azimuth shift. The more precise alignment of the facets will produce more virtual facets, which creates a more vivid and intense sparkle.
Through the Kaleidoscope of Virtual Facets:
Virtual facets are internal reflections of light similar to what you might see when looking through a kaleidoscope. Only in this case, the various shapes result from light reflecting through the overlapping facet pattern.
In that case, you'll see more sparkle in hearts and arrows diamonds with more precise patterns. Not only that, but the sparkle factor will be more bold, vivid, and intense. Since the lack of consistency in the hearts' pattern creates light leakage, I would reject this diamond.
Finally, the diamond's primary inclusions consist of cloud, crystal, feather, needles, which are acceptable. The types of inclusions you want to avoid are bruises, cavities, chips, etch channels, knots, and laser drill holes.
Judging Diamond Visual Performance - Option #2:
The second diamond on the list is a 1.66 carat, I color, VS-2 clarity round ideal cut diamond from James Allen. This diamond would typically not cross my path because the total depth is 62.1%.
Nevertheless, this diamond is more interesting because the AGS Light Performance grading platform is more insightful than what the GIA provides.
In this case, the 35-degree crown angle is a good offset for the 40.9 degree pavilion angle. Consequently, that sets the stage for a high volume of light return and a virtual balance of brilliance and dispersion.
The Ideal Scope image reveals a moderate amount of light leakage, as evident by the light pink and semi-translucent sections. This amount of leakage is typical of most standard ideal cut diamonds because they lack a higher degree of optical precision.
Inconsistent Hearts' Pattern:
Despite the proportions, there is a fair amount of inconsistency in the hearts' pattern. Specifically, you'll see that the hearts' are different sizes and shapes. Plus, the space around each of the hearts' is inconsistent, creating some of the leakage shown above.
If you look closely, you will also see that the hearts' tips appear to be twisting. That indicates a difference in the length of the lower girdle facets. Our in-depth tutorial on hearts and arrows diamonds will explain the reason.
The plotting diagram on the lab report indicates the presence of crystals. That means that the larger diamond crystal absorbed tiny diamonds as it formed. In that case, the inclusions are of no consequence, and I'm inclined to keep this diamond on the list.
Option #3 - Review of Diamond Visual Performance:
The third option is this 1.68 carat, I-color, VS-2 clarity, round ideal cut diamond from James Allen. The AGS Laboratory also grades it on the Platinum Light Performance grading platform with an overall cut grade of AGS Ideal-0.
The total depth of 62.2% is grounds for automatic rejection based on the criteria I established at the beginning of this article. However, the 34.9 degree crown angle is a good offset for the 40.8 degree pavilion angle.
In that case, the diamond might exhibit a high volume of light return and a virtual balance of brilliance and dispersion. The Ideal Scope image certainly looks better than the other two options from above. If you look at this Ideal Scope reference chart, I think you'll agree that it falls somewhere between very good and excellent.
The Effect of Optical Precision on Light Performance:
As you can see, there is more consistency in the size and shape of the hearts. There is only a little bit of twisting visible in a few hearts and only slight variance in size and shape.
However, the hearts' pattern still lacks the kind of consistency that produces exceptional light performance. That is why the table facet lacks the consistency of hue and saturation in the Ideal Scope image above.
Hopefully, you are beginning to see the effect of optical precision on diamond visual performance. Significant variations in the size, shape, and spacing of the hearts will create light leakage. For that reason, I think you should limit your search to hearts and arrows super ideal cut diamonds.
Advanced ASET Insight into Diamond Visual Performance:
The fourth option is this 1.726 carat, I-color, VS-1 clarity, Brian Gavin Signature diamond. The proprietary light performance grading report from the AGS Laboratory features the Advanced ASET 30/40 map.
The additional data that Advanced ASET provides makes it easier to judge diamond visual performance. However, I still like to see an actual photograph since the lab report's ASET map is computer-generated.
In that case, you can't use the ASET map to determine the extent of light leakage Fortunately, Brian Gavin provides photographs of the diamond as seen through an ASET and Hearts & Arrows Scope.
When we combine those images with the insight that the high-resolution video offers, it's evident that this diamond is the best choice.