Table
This is the flat facet on the top of the diamond. The table of the diamond is the largest of the 58 diamond facets.
Crown
The crown of the diamond is the portion of the diamond above the girdle.
Girdle
The outer ring of the diamond is called the girdle. The girdle is described by its thinnest and thickest points.
Pavillion
This refers to the lower portion of the diamond underneath the girdle
Culet
The culet of the diamond refers to a flat facet diamond cutters add to the bottom of a diamond's pavilion. The purpose of the culet is to protect the integrity of the pavilion from chipping and fractures. Once a diamond is set in jewelry the purpose of the culet is generally negated as the setting will provide adequate protection for the stone. Most modern diamond shapes have either no culet, or very small pointed culet.
Depth
The depth of a loose diamond refers to the height of a diamond from the culet to the table. Depth is measured in millimeters.
Crown angle
This refers to the angle where the diamond's bezel facets intersect with the girdle plane. The positioning of these facets is critical in determining the amount of light dispersion and fire in a diamond.
Table percentage
This represents the diameter of the table facet in relation to the diameter of the entire diamond.
Facet
The various smooth surface areas of a diamond set up and positioned at different angles, allowing light to enter the stone and reflect back to your eye. A round brilliant diamond has a total of 58 facets.
Symmetry
Variations in a diamond's symmetry such as misshapen or misaligned facets are graded in the laboratory report. Although such variations are often undetectable to the naked eye, it is certainly indicative of a diamonds cut quality.
Fluorescence
This refers to an effect seen in diamond when exposed to long wave ultra violet light. Fluorescence is undetectable in most lighting conditions and can only be seen when placed under an intense and direct ultra violet lamp. Fluorescence has no deleterious effect on the integrity of the diamond. Some prefer Fluorescence in diamonds, others do not. It is a matter of personal taste. Fluorescence in lower color diamonds posses a unique desirability as they will make diamonds appear whiter than their actual color grade. For more information on diamond fluorescence read this excellent article on the subject.
See more: http://www.exceldiamonds.com/education/diamonds/anatomy.php
