DIAMOND CUT

Diamonds are cut to maximise the sparkle, fire, brilliance and overall visual beauty of a diamond. The cut is a measure of light performance as light hits a diamond. Before a diamond is cut and polished, it is known as a rough diamond. The skin of the rough diamond is opaque and often difficult to see through. Rough diamonds have little to no sparkle. This is because they lack facets or faces that bounce and reflect light. Diamonds sparkle is a result of light performance. As light hits a diamond, it penetrates the diamond, bounces around and reflects within the diamond and ultimately returns light to your eye. That is the sparkle that you see. The cutting of a diamond directly impacts the amount of light performance achieved. The angles, locations, sizes and shapes of facets will determine the diamond sparkle.

CUT SCALE: THE FACTORS

Once a diamond has been cut and polished, it’s cut can be graded. GIA grades cut base precisely measuring the angles and sizes of the facets of a diamond. These include the diamond’s Table, Depth, Girdle, Pavilion, Crown and Culet. Polish and Symmetry can also place a small role. All these factors come together to determine the cut grade of the diamond. Each diamond shape and size have an ideal cut proportion. If you're looking for an ideally cut diamond, simply ask one of the gemologists and they can point out a few diamond options that have ideal proportions.

THE CUT SCALE

Fair & Poor: Diamonds with significant light leakage earn a Fair or Poor grade. These diamonds tend to leak noticeable amounts of light from being too deep or shallow in height. These have little brilliance and are less visually appealing. Fair or Poor cut diamonds do not meet NB Jewellers®’s minimum light performance criteria. This cut category represents the top 35% of gem quality diamonds. Avoid these diamonds as they will not make for sparkling jewellery.

Very Good: Very well-cut diamonds that capture all the potential of the diamond. Very brilliant with minimal light leakage. Diamonds cut often intentional cut to achieve a Very Good grade so that can improve the other characteristics of the diamond such as Colour, Clarity or Carat. The top 15% of gemstone quality diamonds are Very Good cut. Very Good cut diamonds can be a great choice if looking maximise value on the other factors.

Good: Well-cut diamonds that capture light and possess high degrees of sparkle. Good cut diamonds have some light leakage, but overall shine bright. These diamonds can have noticeably larger or even smaller measurements than perfectly cut diamonds of the same shape. Cutters may intentionally cut to Good proportions to achieve a particular look or style. The top 25% of diamonds have a Good cut grade. Good cut diamonds can be a good blend of value and size, however be careful and always ask a gemologist to assess the particular diamond for you before you decide.

Excellent: The highest grade representing the top diamonds in the world. Diamonds with an Excellent cut grade are masterfully crafted and precisely cut to unleash the maximum sparkle and brilliance of a diamond. Little or no light leakage occurs as light passes through a diamond. This premium category represents the top 3% of all diamonds. Excellent cut diamonds are increasing with improvements in manufacturing technology. An excellent cut diamond is always a good choice regardless of diamond shape and size.

LIGHT PERFORMANCE

A diamond’s cut reflects the brilliance and sparkle you see from it. That sparkle is light performance. Light performance is made up of factors such as reflection, refraction, and dispersion. The better and more uniformly a diamond is able to reflect and showcase light, the better of a diamond it is as it will sparkle more in your jewellery.

FINISH: POLISH, SYMMETRY AND FACETS

Other factors that affect the cut grade are Polish, Symmetry and faceting. These are the finish of a diamond. Diamonds are typically cut in two ways: step cuts and brilliant cuts.

Step cuts, such as Emerald cut diamonds and Ascher cut diamonds, have sparkle or fire. They have facets that look like a staircase and are a bit simpler in presentation. They are considered very elegant and maximise the diamond’s scintillation. These cuts are elegant but because they have fewer facets do not reflect light as much as brilliant cut diamonds. While both diamonds have unique beauty, it is important to consider which type of diamond sparkle you want while picking a diamond cut.

Brilliant cuts, most commonly Round cut diamonds or Princess cut diamonds, have maximum diamond sparkle. They possess more facets than step cuts and the facets are triangular and kite-shaped. Brilliant cuts have a high degree of diamond sparkle and maximum the fire and scintillation of a diamond.

The other two attributes of finish are polish and symmetry. Both of these are a result of the manufacturing process. The polish of a diamond is how cleanly smooth the facet surfaces are. If small striated polish lines remain, it may affect light performance and therefore, diamond cut. The other attribute is symmetry. Symmetry is simply the pattern and evenness of the size, shape and location of facets. If the location of a facet is incorrect, the performance of light and therefore the cut grade can be affected. For example, an off-centre table facet may reduce diamond sparkle.

PRICING EFFECT

Like the other diamond C’s, cut grade can have substantial implications on pricing. Today, we see the highest number of Excellent cut or perfectly cut diamonds. The improvement of diamond manufacturing technology allows diamantaires to be more precise in cutting practices. With round cut diamonds, an Excellent cut can have a 5%-10% premium over the next grade, Very Good cut. The same applies from Very Good to Good. 
Fancy shaped diamonds (shapes other than Round cut) do not have GIA assigned cut grades. This is because with fancy shapes, diamonds can have a variety of shapes and lengths/widths all the while still maximising brilliance and sparkle. NB Jewellers® factors in a variety of diamond attributes to assign its own grading standards to fancy shapes.

SELECTING CUT GRADE

Cut is often considering the most important of the 4 C’s of diamonds (carat is more of a preference, not an art or science). When selecting a diamond, it will certainly important to ensure light is not lost. Excellent cuts are most premium and Very Good cuts offer more value. The differences in sparkle are quite subtle, but they are noticeable when compared side by side. We recommend maximising on the cut grade, if possible.

Fancy shapes have less restrictions because beauty is in the eye of the beholder. Still, you can often safely go a grade lower with non-round diamond shapes. Excellent cut fancy shapes are fairly rare.

In the end, it’s your decision and you must remember there are plenty of other factors that influence a diamond. You must choose which factors/attributes matter most to you.