Of the 4 C's used to evaluate a diamond - cut, clarity, color, carat-weight - perhaps the least understood by the general public is cut. After all, even someone looking for the first time at a diamond can often see flaws (which affect clarity), the color, and the relative size of a stone. But, how do you go about evaluating a diamond's cut?

It's actually not a difficult concept to grasp, once you learn that cut determines a gem's brilliance (how effectively it reflects light back toward the viewer's eyes). This is the true artistry of a diamond cutter's work. The biggest flawless diamond with the most amazing color can be ruined by a poor cut that dulls its appearance to the naked eye.

There are, as you probably already know, many popular diamond cuts. They include: round, oval, marquise, pear, heart, emerald, princess, and radiant. While some cuts (round and radiant) are specifically intended to enhance brilliance, a properly cut diamond of any shape should appear sparkly - not dull - in bright light.

There is a lot going on when a diamond cutter does his work, but for a basic understanding, let's concentrate on the three primary aspects: depth, symmetry, and polish. Remember that the main goal when shaping a diamond is to maximize brilliance in the final version.

Depth

Depth refers to how tall a diamond is from top (called the 'table') to bottom (called the 'culet'). The depth partially determines how the expert cutter will angle the many facets (flat surfaces) as he shapes the stone. Ideally, those facet angles will divert incoming light in such a way that it gets routed down, across, and back up through the diamond. Properly done, the result is brilliance. Poorly done, the light leaks through the bottom and/or the sides of the diamond.

Symmetry

Symmetry refers to how well the facets (flat surfaces) are aligned. With perfect symmetry, a diamond looks 'whole.' It pleases the eye from any viewing angle. B

eyond these overall aesthetic qualities, symmetry plays a big role in brilliance. Misalignment or disproportional cuts will wreak havoc on how light travels through the diamond. Just as with poor depth, poor symmetry will cause a diamond to appear dull.

Polish

Polish refers to the smoothness of the surface of every facet that is cut into a raw diamond. This part of the diamond cutting process requires the utmost care and attention to minute detail. With modern technology, polish does not vary nearly as much now as it did in years past. Excellent polish greatly enhances a diamond's brilliance because it creates less diffusion as light enters and exits the diamond. Even a diamond with slight depth or symmetry problems will appear brilliant if the polish is of the highest grade.

To be sure, a lot more is involved than what's covered here. However, for the average diamond shopper, all you need to know is whether the diamond shines with brilliance or appears dull. Specific cut grading details are issued on most diamonds you'll find being sold in stores or from brokers, if you want the in-depth evaluation for investment purposes. But, for most of us, how the diamond looks in terms of brilliance is the way we evaluate it when deciding to shell out our hard-earned money. Now you know why that diamond sparkles (or doesn't) - it's all in the cut!

© John Schwartz (all rights reserved)

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