To many, cut is considered the most important of aspect of a gemstone’s quality and value. Diamond cut affects some of its optical and physical properties including how it reflects light and “sparkles.”

The Diamond Cut Process

Diamond cut refers to how the jeweler physically cuts the diamond stone into its shape and to the proportions and symmetry that achieve optimal light dispersion, which affects a diamond’s quality and price.

Each diamond is cut to very exacting standards. Let’s look at the process to cut a beautiful diamond to better understand the terminology the jewelry industry uses to explain diamond cut factors.

The most common cut, the round brilliant, has 58 facets, or small, flat, polished planes designed to yield the maximum amount of light reflected back to the viewer.

A diamond’s light reflection, known as brilliance, is an extremely important factor in evaluating the quality of a diamond’s cut. A poorly cut diamond will actually lose light and appear dull.

The widest circumference of a diamond is known as the girdle. Above the girdle of a brilliant cut diamond are 32 facets plus the table, which is the largest and topmost facet. Below the girdle are 24 facets plus the culet, or point. 


Proportion diagrams will typically include the following information:

Depth: The height of a gemstone measured from the culet to the table.
Table: Located at the top of the diamond, the table is the largest facet of a diamond.
Girdle: Range of girdle thickness.
Culet: Appearance, or lack thereof, of the culet facet.

A diamond’s cut impacts four aspects of the stone’s optical and physical properties:

Luster: The quality and amount of light that is reflected off just the surface of the diamond. Luster is directly related to the hardness of the stone and the quality of its polish.

Brilliance: The amount of white light that is returned to the eye from both internal and external surfaces. Brilliance is determined by the quality of the diamond’s polish and the number and size of inclusions inside the gem.

Dispersion: The display of spectral or rainbow colors seen coming from the inside of a diamond. Often referred to as “fire,” dispersion is directly related to how well the stone is proportioned.

Scintillation: A diamond will show scintillation, or “sparkle,” when movement is involved. The viewer, the light source or the diamond itself must be in motion for scintillation to occur.

The most important part of choosing a diamond is to choose one that appeals to you personally. While it is beneficial to understand the technical aspects of diamonds, it is most essential to fall in love with your diamond. Visit your local Jewelers of America member jewelry store to work with a professional jeweler who can show you a range of diamonds and explain their unique characteristics.
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