Diamond Cut

Diagram showing shallow, ideal and deep cut diamonds
The cut defines the make and performance of a diamond. For the general outward appearance, please see shape. Once a fancy color and shape are picked out, cut is usually the most important aspect in choosing a diamond. It is comprised of a combination of properties and is the most subjective property of a diamond.

Basics

The beauty of a diamond largely depends on how well it is cut. Having grown a rough diamond, it is essential to unlock the sparkle and magical scattering of colors that exist within. It is the diamond cutter who brings to life the brilliance and fire of a diamond. It is their experience and craftsmanship that allow each diamond to attain its ultimate beauty – the complex combination of brilliance, luster, light refraction, multiple reflections, color dispersion, and scintillation. In this regard, all diamonds – mined and laboratory-grown – are man-made.

Every AOTC created diamond above certain weight is cut in Antwerp, Belgium, the world-renowned diamond-cutting center, which has traditions going back several centuries. Here, AOTC diamonds are cut for maximum beauty, not weight. Weight is worthless if there is little or no brilliance, fire, and scintillation in the stone.

There are three primary characteristics that make up the beauty of a cut diamond:

  • Brilliance - amount of light returning from the diamond
  • Fire - breaking up of light into spectral colors
  • Scintillation - sparkle associated with movement

The overall proportions of a diamond determine how much light is returned as brilliance from the diamond, back to the viewer.

  • Shallow - Light does not have enough depth to properly return out the top of the diamond. Light is lost out the bottom of the stone.
  • Ideal - The correct proportions allow the maximum amount of light to return
  • Deep - Excess depth causes light to exit the diamond incorrectly. Light is lost out the side of the stone.

Proportions

There are many shapes of diamonds available, and while their ideal range of proportions vary by shape, they all share common terminology:

  • Table - The main facet on the top of the diamond, usually measured as a percent of the diameter.

Larger tables generally return more light, with greater brilliance, though have less scintillation and fire. Smaller tables generally have more fire and scintillation with less brilliance. This is due to the size of the crown angles in relation to the table, and within normal parameters, a larger or smaller table is mainly a personal preference.

  • Depth - The distance from the table to the culet, as a percentage of the diameter.
  • Diameter - Distance between two opposite sides, measured across the center of the stone in millimeters.
  • Girdle - The outer edge of the diamond. This is measured in words and the best girdles are thin, medium or slightly thick. Very thin girdles have to be set more carefully. Thick girdles carry extra weight in the middle of the diamond, but have little impact on the performance.
  • Culet - The point on the bottom of the diamond. This is normally closed, to make a point, though sometimes is a small flat facet that cannot usually be seen with the naked eye. This can optionally be counted as an extra facet.
  • Pavilion - This refers to the lower portion of the diamond, below the girdle. It is measured as the depth from the girdle to the culet, either as a percentage of the total depth, or as the angle of the facet relative to the table.
  • Crown - This refers to the upper portion of the diamond, above the girdle. It is measured as the height from the girdle to the table, either as a percentage of the total depth, or as the angle of the facet relative to the table.

Polish & Symmetry

Polish and symmetry use terms such as 'very good', 'good', 'fair' and 'poor' to describe their quality, so they may seem like a strong guide to determine overall cut, though they are less important to the overall beauty than the proportions noted above.

Polish describes the smoothness and quality of finish on the surface of the diamond. A smooth surface can better let light through. Poor polish can reduce the intensity of the light performance, in the same way it is easier to see yourself in a smooth, flat mirror, than one that is textured or uneven.

Symmetry refers to the alignment of the facets to each other. Properly aligned facets reflect light at the best angles, allowing the light to travel correctly through the diamond. Poor symmetry causes light to be misdirected as it travels through the diamond.

Generally, a 'good' or better rating for polish and symmetry do not adversely impact the beauty of the diamond.

Diamond Cut Charts

Many proportion charts exist for white diamonds and they all vary slightly, though the most well-known is the Tolkowsky Ideal Cut. These typically use mathematical ideals to determine appropriate ranges for depth, table, crown and pavilion angles as well as other important criteria. Our white diamonds list all the appropriate attributes to be measured in cut calculators such as the Holloway Cut Adviser for round brilliants. These charts and calculators should be used to narrow down a selection, but to decide your final choice, all criteria should be considered together, including: color, clarity, polish, symmetry, availability and your budget.

Cut in Colored Diamonds

Ideal cut charts measure the amount of white light return in a diamond, which isn't usually the most important factor when choosing a colored diamond, such as a blue or yellow. The closer a colored diamond is to an 'ideal cut', the more ambient (white) light that enters the diamond will be returned, and thus less saturated color a diamond will exhibit. This same logic applies to white diamonds, in that an ideal cut 'H' color should look ("face up") whiter than a good cut 'G' color, even though the 'H' has more body color. Since the saturation levels vary from one colored diamond to the next, it makes it difficult to categorize the colored light performance based solely on cut proportions.

Our diamonds are cut by experts for beauty, not weight, taking into account specifics of each individual rough diamond. While a colored diamond can accurately be checked against white light return charts, for most people, the color and saturation of colored diamonds are more important criteria than the white light return.

Cut versus Shape

The round brilliant is by far the most studied shape for cut. Its proportion and symmetry allow the application of guidelines better than other fancy shapes. In fancy shapes, such as a princess or cushion, the cut is more complex and cannot be as decisively predicted with charts.

Cut in Grading Reports

With mined diamonds, an AGS '0' or 'Ideal' along with a GIA 'Excellent' are generally considered the 'best cut'. AGS does not currently grade lab-created diamonds and GIA does not currently provide a cut grading or detailed proportion information on their lab-created diamond reports.

Most of our diamonds of .30cts and over are graded by EGL USA. The grading reports from EGL contain all the appropriate percents, angles, measurements and information to determine the make of the diamond. EGL's scale for parameters such as polish and symmetry are Very Good, Good, Fair and Poor.