HOW IMPORTANT IS A DIAMOND’S CUT?

For many men, getting engaged is the first and perhaps the only time they will ever buy a diamond. To prepare themselves, most rightly seek out information about the technical aspects of diamond grading – how else can they expect to make an informed decision?
The problem is the sheer quantity of information that is now available, particularly online. Much of it is confusing or inconsistent, and the issue of ‘Cut’ is often dealt with inadequately.

Immediately obvious is the fact that not everyone attaches the same importance to a diamond’s ‘Cut’. Out of the ‘4Cs’ that define a diamond’s value (colour, clarity, cut, carat weight), in the UK ‘Cut’ tends to receive the least attention. Often it goes entirely unmentioned, with jewellers listing all the other characteristics when quoting a diamond’s price (for example 0.50 ct, G, VS1).

On the other hand, American jewellers tend to focus a huge amount of attention on ‘Cut’, and make heavy use of jargon like ‘Ideal Cut’, ‘Triple Excellent’, or ‘Hearts and Arrows’. So what exactly is a diamond’s ‘Cut’, and how significant is it?

Often diamond ‘Cut’ is confused with ‘shape’. In fact ‘Cut’ is an umbrella term, which groups together several more specific qualities of a diamond. Amongst these are ‘Symmetry’, ‘Polish’, and ‘Proportions’. A diamond’s ‘Symmetry’ refers to the alignment of its facets; its ‘Polish’ refers to the smoothness of its facets; and its ‘Proportions’ describe the relationships between its key dimensions, such as overall depth vs. overall diameter.

The extent to which a diamond sparkles is determined by how effectively it reflects and refracts light. The ‘Proportions’, ‘Symmetry’ and ‘Polish’ of the stone go a long way to establishing this. If the ‘Polish’ is poor, the facets appear dulled. Likewise, the ‘Proportions’ and ‘Symmetry’ need to be a close as possible to a theoretical ideal if the diamond is to sparkle to its full potential.

All these characteristics are graded on a scale that runs Poor, Fair, Good, Very Good, and Excellent. Not every grading certificate will list all of them, and many will include an ‘Overall Cut Grade’ that is a combination of them.

When a diamond is graded ‘Excellent’ for each of the three main characteristics, it is sometimes referred to as ‘Triple Excellent’, though some jewellers also call this ‘Ideal’. The term ‘Ideal’ can also refer to a theoretically perfect round brilliant diamond, originally defined by the mathematician Marcel Tolkowsky in 1919. The term ‘Hearts and Arrows’ refers to the pattern that is sometimes visible when a well cut round brilliant diamond is viewed from its pavilion side. It is generally an indication of quality, but is not synonymous with ‘Triple Excellent’.

So behind all the jargon, what should the first-time diamond buyer be looking for? First of all, he should steer clear of diamonds that have no listed ‘Cut’ grade, particularly stones of one carat. Sometimes, if a rough diamond should have been cut to just under a carat to optimise ‘Symmetry’ and ‘Proportions’, it will be
compromised as the cutter looks to secure the financial premium that comes with stones of a carat or above. The stone's poorly matched dimensions mean that it just won't sparkle as much as it should do.

Beyond that, buyers shouldn’t accept grades below ‘Good’ for any of the diamonds ‘Cut’ characteristics. If this puts a strain on their budget, they should look to compromise elsewhere, perhaps on clarity or carat weight - ‘Cut’ is simply too important.