Garry Holloway: HCA for Fancies?

[kenny]

Your Holloway Cut Advisor, HCA, is invaluable tool for online shoppers.
Too bad it is only for the round brilliant.

Sorry if you've answered this before but is there any chance we will someday see an HCA for Princess or other cuts?

If so which might be the first fancy to get an HCA?
Isn't Princess the second most common cut?

 

[MissAva]

According a a bridal magazine article this Spring, marquise is the second most popular.

 

[Garry H (Cut Nut)]

Bridal smidal.
yes princess is #2, then probably square emerald at present.

HCA is a parameter-based cut grading system. Dave Atlas from AGA has a rudimentary system for many cuts, and the Japanese were doing very specific ones in the early 80''s. HRD and ScanD had them early on.
Sarin scanners made this the quickest and easiest method. It is also easiest to visualize and explain. However there are problems:
1. The parameters used are for ideally symmetric diamonds rather than ‘real’ stones.
2. Even symmetric stones with can have variations in upper and lower girdle facets angles and azimuth. 3. These cut systems are only practical for round diamonds.
4. Different parameters contribute to a diamonds cut grade independently of each other.
5. Grading only round diamonds for cut quality leads to trade commoditization.

The forth point is now widely understood. Early simplified grading systems rated cut based on each proportion independently, rather than using their combined influence on the optical effects. For example charts of high-quality diamond proportions for “crown angle - pavilion angle" coordinates looked like a rectangle. However we now know that crown and the pavilion angles are interdependent and there are many proportion combinations for new grading systems that conflict with the conventional rectangular grading. HCA was to th best of my knowledge the first such system to do that.
However building a parameter-based database that describes all the possibilities becomes more and more complex. The variables for the simple round include crown and pavilion angles, table, girdle and culet size, upper and lower girdle facet lengths and azimuths; all this creates exponential growth. GIA claims to use 38.5 million data points in its parametric system. That is before including azimuth and symmetry variations.

With fancy shaped diamonds parametric grading may be impossible, and planning of cutting certainly will be.

 

[oldminer]

I appreciate all that Garry has done for us with the HCA and admit that my system is "rudimentary". However, that does not mean it is not of great value in screening for fancy shapes to consider. The systems coming your way at present for princess cuts such as AGS are far more complex then the AGA Cut Class grades and truly better at telling which diamond looks best, but when it comes to rectangles or long shapes such as marquise, oval or pear, then the AGA Cut Class charts will give you a great deal of assistance in choosing a great combination of shape and cut. We''ll leave the light performance to your eyes for now, but AGA and others will measure light performance in these shapes in a short period of time. Also the AGA Shape Selector tool can make communication between consumers and sellers easier. It allows you to set "bulge", "flatness" and "length to width ratio" of the fancy shape outlines and then transmit this to others or print sample copies for your own use.

In advancing the science of judging light performance, AGA and others will not forget that the outline shape of a fancy cut diamond MUST be pleasing to the eye. The diamond must be durable, symmetric, well polished, and have a reasonable depth percentage judged against the average of length, width and diagonal measures. When light performance is judged to be excellent and nothing is found deficient with the cut and outline, then and only then, do we have a truly fine diamond. There are many ways to find compromises that still will look very good to the eye or be a little less than perfectly cut, yet cost a little to a lot less. This is nothing new and will be the way the market handles new information.

 

[Garry H (Cut Nut)]

I made a mistake above - I think Dave was first in the mid to late 80''s with fancy grades. Japanese were maybe early 90''s with round only

 

[oldminer]

I made my first attempt at cut grading in 1985 with a prodcut I called "The Diamond Report Card". It looked like an elementary school''s report card with grades for cut, color, clarity and a plus, neutral or negative factor added on for color, strength and visibility of any UV fluorescence. Color and Cut quality we given higher importance than Clarity even back then. The concept of UV fluorescence having any potential for making a diamond better looking was heresy....... We had lots of fun and some success making those report cards. We called the final grade, a "Suitability Grade" If a stone scored high, it was very suitable for use in an engagement ring. If it scored lower, one might use it in earrings or a pendant, but not a ring. It gave store sales people a numerical, single number, on which to make easy comparisons.

I won''t go so far as to say every score was perfect or that comparing diamonds by a single concocted number is a right thing to do. But back then, it was new information and way ahead of where the market was. Being ahead of the market is something I seem to specialize it. It has been a lot of pleasure.

As they say in dog sledding, "Only the lead dog has a change of scenery".....