DIAMOND CUT (PROPORTION, POLISH & SYMMETRY)

Cut is an important parameter because beauty and appearance is defined by the cut. All scintillation and brilliance in any diamond is linked to the cutting. The first aspect to check is whether the diamond is appearing beautiful or not. The cut proportion is dependent on the evaluation of many parameters such as proportion, polish, symmetry, depth%, table %, girdle width, and culet size.

DIAMOND PROPORTION

Because Cut proportion grade provides a single rating which weighs the combined impact of all of the factors listed above on a diamond's visual performance, it is a simple yet vital tool in evaluating a diamond.

There are ideal proportions identified for each shape. Please refer and check that the diamond you are intending to purchase is close to these ideal proportions.

When a diamond is fashioned from a rough stone, the cutter must balance optimal cut (and therefore appearance/ Brilliance/ Lustre / Sparkle) against maximum yield (cutting the diamond to maintain as much carat weight from the rough stone as possible). A Diamond is sold by weight (Carats), therefore more the number of carats the more money the cutter can realise for the diamond. Therefore there is pressure on the cutter to sacrifice appearance for weight. This is why a better cut grade commands a premium in price. The proportion parameter is the single most important parameter that allows the purchaser to identify well cut (excellent to very good graded) pieces from not so well cut (Good to Poor graded) pieces.

At left, the same rough stone (shown in blue) can yield one of two potential diamonds:

1. A too-deep cut diamond (orange) would yield a significantly larger diamond, earning the diamond cutter a larger profit on his investment.

2. A smaller, well cut diamond (white) may sell for less in total than the larger diamond, but it will command a higher price-per-carat not only because of its   superior appearance, but also due to decreased yield from the rough stone.

When a diamond is cut with the proper proportions, light is returned out of the top of the diamond (which gemmologists refer to as the table). If it is cut too shallow, light leaks out of the bottom; too deep and it escapes out of the side.

Cut grade should be a primary consideration when evaluating a diamond’s cut. Only when comparing two diamonds of identical Cut grade should the individual components of Cut (such as girdle width, symmetry, polish, depth%, table %, and culet size) be used as further refinements or tie breakers, especially (in the case of depth %) if one is concerned about how large the diamond will appear.

Buying Tip:

Cut grade should be a primary consideration when evaluating a diamond because Cut determines the beauty and overall appearance. Always select the highest cut grade within your budget, because a poorly cut diamond will seem dull even with excellent clarity and color. Conversely, a well cut diamond can have a slightly lower color (I-J) or clarity (SI1-SI2) and still look beautiful.

DIAMOND POLISH

Polish refers to the degree of smoothness of each facet of a diamond as measured by a gemmologist. When a diamond is cut and polished, microscopic surface defects may be created by the polishing wheel as it drags tiny dislodged crystals across the diamond's surface. Depending on the severity, these defects may disrupt light patterns as the light rays enter and exit the diamond.

Buying Tip:

For diamonds with a polish grade of Excellent to Good, any polishing defects are not visible to the naked eye, and should have no impact on the diamond's overall appearance.

For diamonds with clarity grades of I1 or lower, even a polish grade of Fair is acceptable, since these diamonds already possess internal inclusions that are visible to the naked eye, making any polish markings less relevant.

Poor is the only polish grade that should be avoided regardless of the size or clarity of the diamond.

DIAMOND SYMMETRY

Symmetry refers to how precisely the various facets of a diamond align and intersect. This can include extra or misshapen facets, off centre culets and tables, and wavy girdles.

A diamond with poor symmetry may misdirect light that travels into the diamond, sending it off at slightly wrong angles, and thereby reducing the diamond's brilliance. Often, a diamond cutter will purposefully allow a minor reduction in symmetry as a way of preventing a defect present in the rough stone from being retained as part of the finished diamond.

Buying Tip

A diamond should not be chosen or rejected based solely on symmetry. Because the overall Cut grade already incorporates symmetry, it should be used as the primary determinant when choosing a diamond. When comparing two diamonds of equal Cut grade, symmetry (and polish) can then be used as a further refinement or a tie breaker.