When it comes to reading a diamond grading report, the proportions diagram is probably the section that raises the most eyebrows. It depicts technical information like the table/depth percentages, crown/pavilion angles and upper/lower girdle facet length of the diamond.
However, most of us cannot do anything meaningful with these data apart from comparing them against tables of “recommended proportions”. Fortunately, there is a simple system developed by Garry Holloway that can help you glean deeper into a round diamond’s proportions.
The Holloway Cut Advisor, or as it is most commonly known, the “HCA”, simplifies the process of judging the potential quality and light performance of a standard round brilliant cut.
Let us take a look at how it works and why it can be a handy tool especially if you intend to purchase an engagement ring “blind”.
The founder of HCA, Garry Holloway, is not a newcomer in the industry and has been in the business since the early ’70s. One of his goals is to improve the overall cut quality of diamonds in the market and he is actively involved in cutting edge research work with scientists from Russia and India.
After spending a lot of time in studying round diamonds and understanding how various diamond proportions/angles affect light return, he developed the HCA software.
This program enables the layman to key in variables found in a grading report and provides an instant prediction on the diamond’s visual appeal and performance.
Upon entering data into the HCA software, it will return a score ranging from 0 to 10 (a numerical figure below 2.0 is desired).
Basically, the HCA provides an assessment of a diamond’s potential light return, scintillation, spread and fire based on its cut proportions. It attempts to assess features that are closer to the actual visual appearance of a diamond and the grade is determined based on 4 factors:
Combined, these 4 factors result in the Total Visual Performance of a diamond. An HCA score of less than 2 denotes a diamond that is predicted to have desirable qualities and one that reflects light in an optimal way.
Note: The Holloway Cut Advisor can never replace the tangible information that an ASET/Idealscope or video provides, but it can definitely be considered a useful tool that you can use on your own, for free.
Here’s an example of how you can use it to weed out seemingly similar looking stones based on grading certifications. For comparison’s sake, I chose 2 round diamonds from James Allen which are graded by GIA as Excellent cuts and plugged their cut proportions into the tool.
As you can see, the HCA tool is a very fast and handy tool to help you weed out stones that fall short of having great optics. From the results above, I would instantly reject the diamond on the right based on the HCA findings.
While the diamond on the left receives a 1.2 score, it simply means the diamond passes the initial filtering test. In order to confirm the light performance of the diamond, you need to rely on idealscope or ASET data to find out more details.
Corresponding idealscope images of the diamonds.
The diamond on the left shows a round brilliant diamond with strong light return under the Idealscope (although the light return can arguably be improved). On the right, the image blatantly shows a leaky stone with light loss through the table facet (indicated by the pale ring).
On first glance, the HCA tool might appear to be the smartest application ever created for the diamond shopper. However, a good score on the HCA tool doesn’t necessarily indicate a diamond with best light performance/precision due to a variety of reasons.
The first reason behind having discrepancies is that the HCA tool only utilizes the measurements of 17 out of a total of 57 facets for its analysis. Besides relying on averaged readings, the HCA tool fails to take into account the girdle thickness variations, polish and symmetry ratings.
Also, the HCA tool doesn’t take into account the star facets, upper and lower girdle facet proportions, This means that it cannot accurately reveal whether the scintillation pattern of the diamond takes on a pinfire or a broader flash characteristic.
Combined as a whole, every single facet of a diamond comes together to form a complex relationship which affects its visual appearance and light performance. In fact, I’ve written a comprehensive article about the pitfalls of the HCA tool here.
The next shortfall of the HCA is that it is only applicable for round brilliant cut diamonds. Fancy shapes or modified round cuts cannot be subjected to a similar analysis because the algorithm simply doesn’t work for them.
There are also other factors that can influence the visual appearance and the value of a diamond. For example, a diamond’s HCA score will not reflect potential problems caused by a low clarity grade. Issues that may cause the stone to take up a hazy appearance or have adverse impacts on brilliance cannot be realistically predicted by a computer algorithm.
Taking everything into account, we can say that the HCA score is only useful to a certain degree. However, you need to bear in mind that the tool only provides quick results based on a limited set of data inputs.
Very often, people take the results of the HCA too literally and make the mistake of making a purchase decision without looking at tangible data. The Holloway Cut Advisor is not meant as a tool for selection but rather, a tool to reject poorly proportioned stones.
Once you have weeded out the poor performers which score more than 2.0 on the HCA, you should apply other optical examination tools like the ASET or Idealscope in your final selection process. This will help you cherry pick the most brilliant stone from the remaining diamonds with HCA scores of less than 2.0.
With the advanced computing technology available, the HCA’s usefulness has been severely diminished. Reliable jewelry retailers with transparent business practices are able to provide you with videos and scope data to help you see exactly what you are buying.
Listing at White Flash with video, photos and scope data for easy analysis.