Apr 01

Choosing the Best Diamond Cut

What is the best diamond cut and how should you go about choosing your ideal diamond?

What is cut?

When discussing diamonds, ‘Cut’ does not mean shape.
“The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions. The cut of a diamond describes the quality of workmanship and the angles to which a diamond is cut.” (wikipedia)

The cut of a Diamond is the only property, which is totally dependent on man. Each stone loses, on average, more than half its original weight during cutting and polishing. Proportions and angles influence the internal reflection of light as well as the dispersion of light leaving the diamond. This determines the Fire (flash or sparkle of rainbow colours) and Brilliance (brightness or white light return) of the diamond, and ultimately its beauty.

The Round Brilliant Cut diamond is the most common cut and has received the most attention in the trade. There are various other cuts for both round and fancy shaped diamonds. This article only relates to Round Brilliant cut diamonds.

A large number of Round Brilliant Cuts have been defined over the years, each with their own detailed specifications of the various proportions of the diamond. The main purpose of these cutting styles has been to maximise the Fire and Brilliance of the diamond to produce the most beautiful stone possible.

Tolkowsky Ideal Cut

In 1919, Marcel Tolkowsky systematically analyzed the optics of the round brilliant diamond using mathematical calculations that considered both brilliance and fire of diamonds. He estimated the best proportions for cutting round brilliant diamonds.

Tolkowsky published his findings in his book “Diamond Design.” He is generally acknowledged as the father of the modern round brilliant diamond cut. Today’s standards for “ideal cut” diamonds are generally based on Tolkowsky’s findings, with minor changes.

Hearts and arrows

“Hearts and arrows (H&A) is a cutting style for round brilliant diamonds modeled after a pattern popularized by the EightStar Diamond Company. The pattern is a series of eight gray arrowheads when viewed from above the crown with one eye and eight heart shapes when viewed from below the pavilion. H&A viewers eliminate incoming light from certain angles and cause the pattern to appear black or very dark gray. In order to display this pattern flawlessly, the diamond must have excellent symmetry of its major facets, and particular lengths of its lower girdle facets.” http://en.wikipedia.org/wiki/Hearts_and_arrows

Ideal Cut

The term ‘Ideal Cut’ has become more of a marketing term than anything else these days. Numerous diamond sellers have used this term to describe their diamonds, with varying standards and proportions.

Russian Cut

‘Russian Cut’ diamonds typically means that the diamond has been cut and polished in a Russian factory. The cutting specifications may vary from factory to factory.

Other Cuts

There are many and varied ‘cuts’ described in the marketplace. Some are scientifically determined and some are not specified at all. They are merely marketing terms attached to ‘all’ diamonds sold from particular sellers.

Certification cut grade

Some diamond grading laboratories will note a ‘cut grade’ on their certificates. Each laboratory works to a defined set of parameters to evaluate the proportions of the diamond. These proportions are then given a grading depending on how close they are to those defined parameters.

It is important to note that the cut grading parameters vary across laboratories. For example, the AGS and DCLA laboratories base their parameters on the Tolkowsky Ideal while the GIA have developed their own cut grading system.

Regardless of the laboratory, the higher the cut grading, the closer the stone is to the ‘best’ cut as defined by that laboratory. This means that diamonds with a higher cut grade ‘should’ perform better with regards to Fire and Brilliance. Unfortunately this is not always the case. You may find stones that have been graded as an ‘Excellent’ cut grade, but do not perform as well as other ‘Excellent’ diamonds because of the relationship of the proportions of the diamond.

Choosing the best cut

It should be clear from the descriptions above that there is no one distinctly ‘best’ cut. In fact, these and other named cuts are more of a marketing tool than anything else.

A good example of this is the ‘Hearts and Arrows’ nomenclature. Almost all diamonds will display some form of the Hearts and Arrows characteristics. Only very few diamonds will show the perfect Hearts and Arrows formations. The perfect Hearts and Arrows are typically only seen in very well cut stones. Unfortunately, some diamond marketers have used their creative license together with the fact that all diamonds display some form of Hearts and Arrows and market their diamonds as ‘Hearts and Arrows.’ This problem is further compounded by the fact that there is no final industry consensus on which diamonds can be called Hearts and Arrows and which cannot.

Another problem with picking a diamond based on a named cut is each cut is defined with some kind of personal preference in mind. For example the European market historically prefers a slightly larger table to the American market. The popular cuts in the respective regions reflect these preferences.

The process for making your choice is fairly simple.

1. Check the cut grade on the diamond grading certificate to find the better made stones. Stick with ‘Excellent’, ‘Very Good’ or ‘AGS0’ cut grades, depending on the grading laboratory.
2. Examine your short list of diamonds under various lighting conditions. Grading laboratories use fluorescent lighting for diamond grading. This adversely affects the appearance of the stone. Try view the stone under fluorescent lights, incandescent lights and preferably in direct sunlight, maybe near the store window, if the jeweller will allow. This will help you get a feel for the ‘personality’ of the diamond. Compare your short list of diamonds to other diamonds so you can see the effect that cut has on the Fire and the brilliance.
3. Make your decision based on your personal preference. Choose the diamond that ‘feels’ right to you. The one that catches your eye when as you move it around.

Ultimately taste and preference for the overall appearance will determine your choice. There is no doubt that working within definite parameters yields a better stone but in the end your eye should make the final decision. So look around, compare diamonds and see what you fancy.


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