​​​​Holloway Cut Adviser HCA Diamond Proportions Calculator Tool

Is the Holloway Cut Adviser for Diamonds Accurate?

The secret to successfully selecting a diamond online is heavily reliant upon having access to gemological tools used by diamond grading professionals to make their diamond buying decisions… tools such as the ASET Scope, Ideal Scope, Hearts and Arrows Scope, Gemological Microscope and computerized proportions analysis all provide the insight which I need as a professional diamond buyer to make informed decisions every day, but first you need to be able to narrow down the thousands of options available to a select few which are worthy of your consideration and the Holloway Cut Adviser is an excellent tool designed for that purpose.

To be perfectly honest, I don’t use the Holloway Cut Adviser during my diamond selection process because I rely on my 30+ years of experience as a diamond buyer to know what combinations of proportions are most likely to produce the levels of light performance which I expect from a round brilliant cut diamond.  However, I think that the Holloway Cut Adviser (HCA) is an excellent diamond buying tool which can be used by consumers to narrow down the myriad of options that are presented to them as they shop for diamonds online.

Clarity of Gemological Terms:

Now before I get too far along in my review of the Holloway Cut Adviser let’s take a moment to become familiar with some of the gemological terms which I’ll be using throughout this article and which are used frequently on this diamond education website:

“Light Performance” refers to the amount of light which is entering a diamond and being directed back up towards the viewer as a direct result of the angle and degrees of the facet planes or primary “mirrors” of a diamond.  The two most critical reflective surfaces or “mirrors” are the crown and pavilion angles which work together to direct light through the diamond.  If the crown and pavilion angles of the diamond are too steep or too shallow, the majority of light will “leak” out the sides of the diamond and the diamond will appear dull and lifeless.

“Brilliance” is reflected white light or white sparkle and it is primarily controlled by the crown angle of the diamond in combination with the number and size of “virtual facets” which are created and controlled by the consistency of facet shape and alignment.

“Dispersion” or “Fire” is reflected colored light or flashes of colored light and is largely controlled by the crown angle of the diamond in combination with the number and size of “virtual facets” which are created and controlled by the consistency of facet shape and alignment.

“Scintillation” is the sparkle which is created by the diamond being in motion, or which is created as you move around the diamond, much the same way that a piece of cut crystal will sparkle whether you or it are moving…

“Visual Performance” refers to the “Sparkle Factor” of a diamond which is a direct result of the number and size of virtual facets created by the facet structure of a diamond.  To create a high degree of visual performance with a relative balance of brilliance and dispersion and a high degree  of scintillation, a diamond cutter must carefully align the facets not only to meet at the facet junctions (meet point accuracy) but also so that they precisely align with each other from top to bottom and across the stone as if the facets were aligned on a three dimensional clock of sorts… very few diamond cutters actually achieve this type of harmony within the facet structure of a diamond, even within the realm of round brilliant zero ideal cut diamonds.

Hearts and Arrows Diamonds = Increased Visual Performance:

Gemological laboratories such as the GIA and AGS do NOT take visual performance into account during their diamond grading process and thus consumers must rely on images of the diamond as seen through a Hearts and Arrows scope to make this determination:

The three photographs pictured above show three examples of hearts patterns exhibited by three different round brilliant ideal cut diamonds as seen through a hearts and arrows scope.  All three of the diamonds have proportions within the center range of the spectrum allocated by the AGS Laboratory for the zero ideal cut proportions rating and scored extremely well on the Holloway Cut Adviser in terms of estimated light performance.  The diamond on the left is a 0.927 carat, G-color, VS-1 clarity, Signature Hearts and Arrows Diamond from Brian Gavin and the pattern is a text book rendition of a perfect hearts pattern… the hearts are relatively consistent in size and shape, the clefts of the hearts are not split or broken, the tips of the hearts are not twisting, the arrow heads are not twisting and there is even shading and coloration throughout the image which indicates that this diamond is not suffering from Azimuth Shift and will exhibit optimum visual performance or sparkle factor.

At first glance the diamond pictured in the center exhibits a pretty good pattern of hearts and arrows, in fact it is near perfect.  However if you look closely you will see that there is some variance in the size and shape of the hearts as well as some twisting of the tips of the hearts and some difference in the shading… in addition, the clefts of the hearts pictured in the one o’clock and seven o’clock positions are slightly split and therefore we can determine that the facet structure of the diamond suffers from a slight degree of Azimuth Shift.

However this diamond is going to exhibit a significantly higher amount of sparkle factor than the diamond pictured to the left which exhibits a rather wonky pattern of hearts or what might be more appropriately referred to as rabbit ears!  While the “Light Performance” of the three diamonds might be essentially equal because the proportions of the diamonds are relatively identical, the “Visual Performance” of the three diamonds will be dramatically different because the variance in facet structure will produce a dramatically different number of virtual facets and the virtual facets produced by the diamond on the right will be significantly smaller than those produced by the diamonds pictured on the left and center and thus the diamond will appear to be less lively.

Holloway Cut Adviser Estimates Light Performance:

The Holloway Cut Adviser is designed to estimate the Light Performance of a diamond by considering the various possibilities which can result from combining all of the possible combinations of measurements, angles and degrees which a round brilliant cut diamond may be cut to… it runs the measurements for total depth, table diameter, crown angle, pavilion angle and culet size through a series of calculations based on a mathematical ray tracing of a diamond shaped model and spits out an estimation for how light moves through the diamond and the relative amount of brilliance, dispersion and scintillation which is likely to be produced by a diamond of those proportions.

And this is why the Holloway Cut Adviser is a good first step in the online diamond selection process, it can help you narrow down the field of possibilities in terms of proportions by helping you determine which diamonds have the potential to exhibit high levels of Light Performance, but then you have to consider the results of other tools such as the Hearts and Arrows Scope, ASET Scope, Ideal Scope and computerized proportions analysis (Sarin, OGI, Helium) to complete the decision making process… Just as you can’t rely on a single tool to work on every part of your house or automobile, you can’t rely on a single diamond evaluation tool to select a diamond.

The HCA as a Diamond Diagnostic Tool:

Let’s say that you’re searching for round brilliant ideal cut diamonds and you run across three diamonds that seem to be comparable in terms of description.  For the sake of argument let’s say that they are all graded by the GIA Laboratory and weigh about one carat and are H color and SI-1 in clarity with a cut rating of GIA Excellent.

Note: Blue Nile changed the format of how deep links were created when they switched their affiliate network from GAN to CJ, and thus the original links to the following diamonds were broken and have been replaced with links directed to their diamond search engine, which is fine since these options have probably sold by now. Please use my free Diamond Concierge Service if you would like me to help you find the best options currently available, but the information that can be obtained by reading the article is still applicable even if the diamond details pages can not be accessed.

Starting with this 1.04 carat, G-color, SI-1 clarity round brilliant ideal cut diamond from James Allen which is priced at $6,180.00 and comparing it to this 1.05 carat, G-color, SI-1 clarity round brilliant ideal cut diamond from Blue Nile which is selling for $7,588.00 which seems like a pretty big disparity of price for two diamonds which appear to be equally graded by the GIA Laboratory with an Excellent cut grade and there is only one point difference in carat weight… one would think that the diamonds would be priced similarly since the characteristics of the diamonds are relatively equal.  So let’s punch the two measurements provided on the GIA diamond grading reports into the H0lloway Cut Adviser, starting with the 1.04 carat, G-color, SI-1 from James Allen which according to the GIA has a total depth of 60.1% with a table diameter of 60% and a crown angle of 32.0 degrees which is offset by a pavilion angle of 41.4 degrees:

According the the HCA Tool the diamond is likely to have Very Good Light Return with Good Fire / Dispersion and Good Scintillation with Excellent “Spread” which is the relationship between the total depth of the diamond and the visible diameter and is “worth buying if the price is right”.  Based upon my experience as a diamond buyer, this is an accurate assessment of this diamond and it enables you to decide whether this diamond is “good enough” and “worth buying if the price is right” or to keep looking for something which is more likely to exhibit a higher degree of light return.  By the way, if you look closely at the lab report for the 1.04 carat, G-color, SI-1 clarity, GIA Excellent Cut diamond from James Allen you’ll notice that the “cut rating” is GIA Excellent and the Polish grade is GIA Excellent, but the Symmetry grade is only Very Good (!) so there are a lot of factors to be aware of when comparing “seemingly similar” diamonds because subtle differences in characteristics can have dramatic effects on price.  So let’s take a look at the diamond from Blue Nile:

As can plainly see by the graphic provided above, this 1.05 carat, G-color, SI-1 clarity round brilliant cut diamond from Blue Nile fared much better on the Holloway Cut Adviser than the option from James Allen did… this is not really a surprise to me because I know from experience that a round brilliant cut diamond with a total depth of 60.3% and a table diameter of 57% which has a crown angle of 34.0 degrees which is offset by a pavilion angle of 40.8 degrees is going to exhibit a high amount of light return… but it is unlikely that the average diamond buying consumer knows this and thus they might be inclined to assume that the diamond from James Allen was “the best deal” if they were only comparing diamonds based upon the characteristics listed on the lab report.

Now it is important to realize that I am not suggesting that diamonds from Blue Nile are superior to those offered by James Allen, not in the slightest… both online retailers offer diamonds in a variety of qualities, I merely selected two diamonds with comparable characteristics which represent opposite ends of the spectrum in terms of proportions… both diamonds are actually considered to be “ideal cut” in terms of their proportions, it’s just a matter of how precise a person wants to be in their selection criteria and mine happens to be fairly precise.

How Seriously Should You Take the HCA Results:

Over the years I’ve seen some people get pretty crazy in terms of how much they rely upon the results of the Holloway Cut Adviser during their diamond selection process… and I say this from the perspective of a person who has been labelled as a “diamond snob” by many of my peers and suppliers over the years!

The tendency seems to be the people want to find a diamond like this 0.936 carat, D-color, VVS-1 clarity Signature Hearts and Arrows Diamond from Brian Gavin which scores Excellent straight down the line for Light Performance, Brilliance, Fire and Spread.  The reality however is that a diamond such as this is rare even within the inventory of a precision focused diamond cutter like Brian Gavin. For this statement to make sense, you must first realize that the only way I seem to be able to consistently score an Excellent rating for Spread on the HCA is to keep the total depth of the diamond between 59 – 60.3% and very few round brilliant ideal cut diamonds are cut with a total depth this shallow.  My personal selection criteria allows for a total depth measurement between 59 – 61.8% and I might even go as high as 61.9% if everything else about the diamond is literally perfect.

For instance this 1.095 carat, F-color, VS-2 clarity, Brian Gavin Signature Hearts and Arrows Round Brilliant Ideal Cut Diamond scored Excellent on the HCA for Light Return, Fire and Scintillation because the table diameter is 56.1% and the crown angle is 34.9 degrees and is offset by a pavilion angle of 40.8 degrees and scored Very Good for Spread because of the 61.9% total depth… no big deal, it’s not something which any of us are going to see in the real world and the diamond exhibits a gorgeous pattern of hearts and arrows so we know that the visual performance is going to be top notch and remember this is not something which can be determined using just the Holloway Cut Adviser.

What Nice Ice Knows About the Holloway Cut Adviser:

Enough to be listed as a reference by the patent review board (ROFLMAO):

Honestly I had no idea that the U.S. Patent Office had relied upon an article which I’d written many years ago about the Holloway Cut Adviser during their review of Garry Holloway’s patent application U.S. Patent 7,251,619 but I thought that it was pretty cool when I discovered this earlier today!  I’m always amazed at where my stuff ends up…

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