Diamond Cut
The way a diamond is cut, its width, depth, roundness, size and position of the facets determine the brilliance of the stone. Even if the color and clarity are perfect, if the diamond is not cut to good proportions, it will be dull and less impressive to the eye.

Table: Flat, top facet of the diamond.
Crown: Upper portion of the diamond, above the girdle.
Girdle: Part that separates the top and bottom of the diamond. This is the widest part of the stone.
Pavillion: Bottom portion of the diamond, below the girdle.
Culet: The tip of the bottom of the diamond. This is the most fragile piece of the stone.
Diameter: The widest part of the diamond as measured by the girdle width.
Depth: Total height of the diamond measured from the table to the culet.

TABLE
The table of a diamond has a very important influence on the overall brilliance of the stone. The best cut diamonds have a table that is 56-62% of the size of the girdle diameter.

GIRDLE DIAMETER AND THICKNESS
The basis for checking the overall proportions of a diamond is the diameter of the girdle, the part that separates the top (crown) and bottom (pavillion) of the stone. All other measurements are related as a percentage of the girdle diameter.

Because very few round diamonds are absolutely round, the girdle diameter is measured in at least four directions, with the highest and lowest values reported on grading reports. You may see the Measurements section of a grading report look something like this: 5.44 - 5.46 x 5.75 mm. This means that the girdle is 5.46 mm at its widest point, and 5.44 mm at its least widest point. The third number represents the Depth of the diamond, which is the measurement from the top of the table to the culet.

PAVILION
The pavilion is the bottom portion of the diamond, below the girdle. The height of the pavilion greatly contributes to the diamond's overall brilliance. If the pavillion is too long or too shallow in proportion to the rest of the diamond, light will "leak" out from the bottom of the stone resulting in a duller looking diamond.

HOW DIAMOND CUT GRADE IS DETERMINED
The overall cut grade of a diamond is determined by taking into account all of the factors described above and plotting the results into a table. The table below shows the values used in determining the overall cut grade of a diamond. After each factor of the cut receives a grade, the overall cut of the diamond is determined by the lowest grade any of the factors received. For example, even if all measurements are ideal but the table size is only good, the overall cut grade of that diamond will only be good.