Diamond Cut

One of the most defining characteristics of a diamond is its cut. While high grades of color, clarity, and carat weight affect a diamond, it's the cut that determines the symmetry of the stone's facets, its overall proportions, and its ability to reflect light.

An expertly-cut diamond will achieve high levels of brilliance, sparkle, and durability. Even if a diamond is graded well in other areas, a poor cut can result in a dull, muted effect.

Parts of a Diamond

A diamond is comprised of five main parts that affect its shape and radiance. Knowing these terms will help you understand the important components to consider when selecting a diamond.

 
Table The largest facet of the diamond, a table is the flat surface on the top of the stone, resembling a 'table'.
Crown This is the top portion of the diamond, located above the girdle and extending below the table.
Girdle Forming the outer edge of the diamond, this is where the crown and the pavilion meet and is the widest part of a diamond.
Pavilion Located at the bottom of the diamond, the pavilion bridges the girdle and the culet and form at the bottom (culet).
Culet The smallest facet of a diamond, the culet is located at the very bottom of the stone.
 
Light's Effect on a Diamond

There are many factors that affect a diamond’s brilliance, the most important of which is its ability to reflect light. As a diamond passes through a light source, tiny flashes will be visible within the stone.

Table Reflection When light enters the surface of a diamond, a portion of it is reflected back out of the table (top).
Refraction The remaining rays of light travel into the center of the diamond and bounce off its internal walls, an effect known as refraction.
Dispersion As light exits the diamond, dispersion causes the white light to be separated into multiple colors. Some light will escape out the bottom and sides, and some will reflect out of the top of the stone. The light that is reflected is referred to as the 'fire' of the diamond.
 
Diamond Cut and Depth
Shallow Cut Although a shallow cut diamond will create the illusion of a larger stone, it allows light to escape out the sides instead of reflecting off the top, creating a lack of brilliance and sparkle.
Ideal Cut If you're seeking a high quality diamond that beautifully reflects light, this is the cut for you. This premier cut style is well-proportioned and carefully angled to achieve a luminous appearance.
Deep Cut This type of cut poorly reflects light, resulting in a dull, muted appearance.
 

Polish, Symmetry & Cut Grade

A diamond's polish and symmetry are critical to the quality of its cut. For maximum brilliance, every facet of a diamond should be professionally polished after the cutting process. A high quality polish will leave little to no scratches and marks, while a poor polish can result in imperfections on the surface of the diamond, which can lower its value.

A symmetrical diamond will have well-balanced, properly aligned facets, resulting in a high level of fire and brilliance. If the facets are not symmetrical or not optimally shaped, they'll display less sparkle.

A gemologist assigns a cut grade as a means of measuring a diamond's proportions, craftsmanship, quality of polish, and light reflecting properties. A diamond with a high quality cut grade will exude a large amount of brilliance and fire.

A diamond's ratings for symmetry, polish, and cut grade may vary based on which Gemological Laboratory is evaluating it, as each agency uses a different scale. To learn more, visit the Diamond Certification page.

Diamond Cut & Value

The quality of a diamond's cut has a significant impact on its value. A well cut stone sacrifices more of the rough diamond during the cutting process, resulting in a higher market value. It will, however, exhibit better light reflecting properties, exuding greater fire and brilliance. Improperly cut diamonds will have less visual appeal and a decreased value. To ensure the best value, look for a certified diamond with polish and symmetry ratings of 'Good' or better.

source: brilliance.com