A diamond’s cut is not only about its shape, but how effectively the stone can return light back to the viewer's eye. A well-cut diamond will appear very brilliant and fiery; while more poorly cut stones can appear dark and lifeless, regardless of color or clarity.

Not only do well-cut diamonds appear more brilliant, they can also appear larger than other stones of the same carat weight. An ideal stone has both increased brilliance as well as increased diameter relative to more deeply cut diamonds.

Diamond Anatomy

Each and every diamond has its own unique set of properties and proportions:

Diameter: Width of a polished stone, measured from edge to edge.

Table: Largest polished facet located on the top of the diamond.

Crown: The top part of a diamond extending from the table to the girdle.

Girdle: The very edge of the diamond where the crown and pavilion meet.

Pavilion: The bottom part of a diamond extending from the girdle down to the culet.

Depth: The total height of a diamond measured from the table to the culet.

Culet: The small or pointed facet at the very bottom of a polished stone.

Understanding Brilliance, Dispersion & Scintillation

Well-proportioned diamonds exhibit three different properties: brilliance, dispersion and scintillation. As light strikes a diamond's surface, it will either reflect off the table of a polished stone or enter into the diamond. The light that reflects is considered a diamond's brilliance. Brilliance is the flash of white light one will see when looking at a stone. As light travels into a stone, some of rays are divided into flashes of color, which is called dispersion. Fire is the result of dispersion, which is the separation of white light into its spectral colors. As an observer moves a diamond back and forth, the flashes of color are called scintillation.

Putting it all Together

Depth and table percentages can affect the brilliance in a round diamond.

[Please Note: this example is for a round diamond only - fancy shapes have their own set of unique proportions.]

Diamond Table

The table is the top facet of a diamond, expressed as a percentage of the diamond's average girdle diameter. This is the largest facet of a stone, and the one that is presented first. If the percentage is too low or too high, there will be more light leakage and the diamond will sparkle less.

Symmetry Flaws

Symmetry refers to the exactness of the shape and arrangement of facets in a diamond. Although to the naked eye finish features only have a tiny affect on appearance, symmetry is a significant aspect.

Read more about Symmetry Flaws.