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Diamond Cut

about cut

The cut of a diamond refers not to its shape, but to the balance of proportion, symmetry and polish achieved by the diamond cutter. The extent of how well the diamond is cut is directly related to the diamond’s overall beauty. When a diamond has been correctly cut, the diamond’s ability to reflect and refract light is greatly enhanced. By understanding the way that light moves through diamond crystals, modern diamond cutters have established a specific set of proportions and angles that are known to harness the diamond’s internal brilliance and to show it in its best light.

Types of Reflection


Brilliance, or brightness, refers to the white light that is reflected back to the eye from the diamond. Light enters through the top of the diamond (the table), is broken down into a rainbow of spectral colors, and is reflected back and forth in the interior of the gem by bouncing off the mirror-like facets. Light exits through the table, recombining as white light.

dispersion (fire)

Dispersion is the rainbow of colors that is reflected back to the eye from the diamond. Light enters through the top of the diamond, is broken down into a rainbow of spectral colors, and is reflected back and forth in the interior of the gem by bouncing off the mirror-like facets. When it leaves through the crown, it stays separated and reaches the eye in flashes of color.


Scintillation is the play of light you see with movement of the diamond, demonstrated by sparkling on the diamond's surface. A diamond is evaluated on its ability to reflect and refract light in all directions.

Diamond characteristics

From the crown to the culet, get familiar with the anatomy of a diamond and with the measurements that play a key role in determining its cut.


The flat surface at the top of the diamond.


The top portion of a diamond, from the girdle to the table.


The narrow rim around the widest part of a diamond, separating the crown from the pavilion. Also referred to as the setting edge, where a diamond is held when set in jewelry.


The lower portion of a diamond, from the girdle to the culet.


The facet or point on the bottom of the diamond's pavilion.


The height of a gemstone, from the culet to the table. Determined as a percentage of the overall diameter of the gem.

Learn More about Diamond Characteristics

The Brilliant Earth Diamond Education Guide will help you choose the ideal gemstone for your ring. Learn about diamond shapes and the four C’s, as well as how to maximize the value of your diamond to fit your budget.

request the guide

diamond cut chart

Cut is considered to be the most important of all of the diamond characteristics, as a well-cut diamond will often appear larger than a poorly-cut diamond of the same carat weight, and have the appearance of enhanced color and clarity.

The quality of cut is determined by how well the symmetry, polish, and proportions of the diamond produce the most attractive balance of the three different types of reflection. Several proportion factors have the most immediate impact on a diamond's ability to reflect light correctly. The table size and depth of a diamond relative to the diameter greatly impacts the light return from a diamond. A well-cut diamond is proportioned so that most of the light entering the gem exits back through the top of the stone, perfectly balancing the white light (brilliance) with intense flashes of fire (dispersion). A poorly-cut diamond, with facets cut only a few degrees out of alignment, can result in light exiting through the bottom of the diamond, known as light leakage, instead of from the top where it is visible. This creates a diamond with dulled brilliance from poor light performance within the gem, making the center of the gem look dark.

GIA, considered to be one of the most respected laboratories for grading natural diamonds, uses the following language on their certificates to grade cut for round diamonds: Excellent, Very Good, Good, Fair, Poor. A GIA Excellent cut will be listed as either Ideal or Super Ideal on the Brilliant Earth site. Brilliant Earth uses specific diamond characteristics, such as cut grade, polish, and symmetry to distinguish between Ideal and Super Ideal. If a cut grade is not available from a grading laboratory, such as for fancy shaped diamonds, Brilliant Earth combines the characteristics above along with depth, table, secondary measurements, and subjective factors to assess the cut grade of the diamond.

In an effort to standardize cut grades across different grading systems, we assign IGI cut grades of Excellent and Ideal to our grades of Ideal or Super Ideal depending on the diamond’s unique characteristics, such as symmetry and polish. IGI is one of the preferred grading laboratories for lab created diamonds, since it currently provides the most detailed grading reports for lab diamonds. HRD Antwerp is also a leading grading laboratory for lab created diamonds, especially in Europe. Because HRD Antwerp does not provide cut grade, we determine cut grade using diamond characteristics including proportion, polish, and symmetry.

super Ideal Cut to the most exacting standards. These diamonds have the most desirable dimensions and are proportioned to return the maximum possible light. Round diamonds will show a "hearts and arrows" facet pattern.
Ideal Exquisite quality cut to create the optimal combination of brilliance and fire. Reflects nearly all light that enters the diamond. Top 3% of diamond quality based on cut.
Very good Superior quality cut that reflects nearly as much light as the ideal cut while at a substantially lower cost.
good Premium quality cut to optimize the size without sacrificing quality or beauty. Reflects most light that enters.
fair Adequate quality cut that reflects some light while maximizing weight. While not as brilliant as a good cut, still a quality diamond.
Poor Not carried by Brilliant Earth.