There are many other characteristics which are used to describe a diamond. Many of these characteristics directly affect the overall quality of a diamond or its "grade." This glossary will help you understand more about the anatomy of a diamond.
The top portion of a diamond. Extends from the edge of the table to the girdle.
The angle at which a diamond’s facets in the crown intersect the girdle plane. This slope or slant of the facets that encompasses the table is what helps create the “fire” in a diamond. The crown angle also helps to enhance the brilliance of a diamond.
A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond’s pavilion. It’s purpose is to protect the tip of the pavilion from being chipped or damaged. In older, European-style cuts, the culet is rather large and can be seen through the table of the diamond. The preferred culet is not visible with the unaided eye. (graded small or none).
The height of a diamond from the culet to the table. This is measured in millimeters (mm).
The height of a diamond, measured from the culet to the table divided by the width of the diamond. The depth percentage is very important to the brilliance and fire in a diamond. A diamond with a depth percentage that is too low or too high will look dull or "dead."
The narrow band around the widest part of a diamond. The girdle is described by its appearance at its thinnest and thickest points. The descriptions are as follows: extremely thin, thin, slightly thin, medium, slightly thick, thick, and extremely thick. While it is less desirable for a round diamond to display an extremely thin or extremely thick girdle, such girdle widths are more common and acceptable in fancy shapes.
Cutters will also sometimes do additional cutting on the girdle. In these cases, the girdle may be "polished" or "faceted." These characteristics will be noted on the grading report, however, they are generally not distinguishable to the eye and do not improve a diamonds grade.
The lower portion of the diamond from the girdle to the culet.
The flat facet on the top of the diamond or gemstone.
The table percentage is calculated by dividing the width of the table by the entire diameter of the diamond. This figure is very important to the brilliance and sparkle of a diamond. If the table percentage is too high or too low, the diamond will appear dull.