60/60 or ideal cut. How do you know what to choose?

Recently, I had the opportunity to examine two very similar diamonds, one cut to near Tolkowsky ideal AGS0 specifications and one cut to near what dealers refer to as 60/60 make. 60/60 refers to 60% table, 60% depth. Diamond dealers would consider both of these cut styles as very good cutting, but the ideal spec stone has a distinct advantage in the Internet marketplace. It got me thinking about why that is the case. Both of these diamond looked very good and not all that different than one another. Why does one, the ideal cut, hold such an advantage?

I used Sarin, DiamCalc and Verigem to measure, compute and reveal the physical differences, the calculated differences and to read their actual light return statistics. Yes, there is quite a difference. No doubt about it, we can both see substantial variance in the Ideal-Scope, ASET scope and H&A images between these two stones. We can also see the expected differences in the measurement of aspects of light return from them, as well. However, it is with our eyes that we perceive things, and visually, these diamonds are far more alike than different in beauty and appearance.

The debate about ideal cut diamonds outperforming other cuts is not in question. In my opinion, there is no doubt that the measurements we take serve to prove the case for higher performance of ideal cut stones. The images we take with I-S and ASET further bolster the case of ideal cuts, too. However, we can still question whether these performance numbers and images prove anything in lieu of the still highly attractive, very good appearance of the non-ideal stone example. There is no doubt we could construct lighting scenarios where the 60/60 diamond might outperform an ideal diamond. Scientists can be very inventive and statistics can be used to prove or disprove nearly anything. We must be very careful that science and statistics are used fairly. Although I believe science and statistics are being used properly right now, there is a place for showing that alternative choices may look very competitive. We just don’t have the same science in place to show a balanced viewpoint at this time.

What I can say for certain, is that the existing images and numbers serve the purpose of marketing ideal cut diamonds more than for marketing other very good alternative styles of cut. Everyone in the diamond trade wants to give consumers a safe course to follow in selecting diamonds in stores or on the Internet. Especially when buying a distant, unseen diamond, one would want to have a good assurance that the diamond will be very beautiful and have no durability issues. This suits the case for the ideal cut and the attractiveness of the I-S, ASET and other images further this cause. If one would search for non-ideal diamonds the choices are far less reliably made since the sellers hardly ever want to not represent their non-ideal diamond as anything but a great choice or a wonderfully beautiful stone, too. We know better, but salesmen often paint a somewhat better picture of their merchandise than reality. However, there are excellent looking diamonds which are not cut to ideal specifications. The ideal specifications are limiting choices for both cutters and consumers. The trade has not generally figured out how to successfully and objectively describe diamonds which fall outside of the ideal parameter configuration. If we had such a tool to give objective advice, it would be all well and good, but right now we are left with the need for consumers to trust sellers. That is not the kind of assurance most skeptical consumers would be willing to accept. We all understand and cooperate by supplying the kinds of images which consumers take comfort in, such as I-S, ASET and H&A. These images bolster the case for ideal cuts while we have no similar visual strategy for widening the choices to beautiful, but non-ideal selections.

Compromise in weight, color and clarity is the norm with selection of a diamond. Compromise in cut appears to be the most dangerous compromise, but within reason it need not be the case. In spite of the wonderful I-S, ASET and H&A images available for ideal cuts, there is plenty of room for selection of slightly less than ideal cut diamonds.

I suggest that for those who want to broaden their searches for reasons of affordability or for simply a larger selection, extend your search parameters by using the AGA/NAJA Cut Class 1A though 1B range for round diamonds.

Table 52% to 60%
Crown Height 13.5% to 16.8%
Crown Angle 33 to 35.1
Pavilion Depth 42.5% to 43.5%
Total Depth 58.3% to 62.99%
Girdle thickness V. Thin to Medium OR Thin to Sl. Thick
Polish / Symmetry Excellent to V.Good

I’d also suggest using a similar strategy for selection of fancy shape diamonds, too. Use the AGA/NAJA Cut Class charts to help you find fancy shapes from 1A through 2A range. Below is the chart for princess cuts.

Table % 74%-59.%
Crown Height % 16.9%-8%
Girdle Thickness V. Thin to Sl. Thick OR Thin to Thick
Total Depth %. 75%-64%
Polish/Symmetry Excellent to Good

Charts for all the common shapes may be found here: https://www.pricescope.com/tools/AGA_NAJA_Cut_Class_Grader
The reason I’ve have taken the time to write this is to shed light on the ongoing controversy about choosing an ideal cut or what’s called a 60/60 cut round diamond.
60/60 is completely inadequate to describe enough details of a diamond for a consumer to be comfortable with how it is cut, yet when used by an honest and knowledgeable diamond dealer to describe a beautifully cut diamond, it can be a shortcut name for a possibly viable alternative choice. The consumer needs to know quite a bit more than table % and depth % to make any sort of informed decision so a 60/60 description needs substantially more information provided to a potential purchaser. From years of experience, I can’t recommend putting yourself in the hands of a seller who says “60/60 and trust me”. It may be a good beginning to a relationship deserving of trust, but trust is earned over time, not given without forethought.
by David S. Atlas, GG(GIA) Sr Mbr(NAJA) ASG(AGA)
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