The girdle is the part of a diamond gemstone that separates the crown, the top portion, from the pavillion, the lower portion. A girdle is generally the widest part of a cut diamond and establishes the circumference of the gem.
The girdle is the part of a diamond gemstone that typically rests on a setting for jewelry, exposing only the crown. Loose diamonds are measured by the girdle, usually in millimeters, and are rated by varying degrees. Most ratings use a scale system, with a typical range of extremely thin to extremely thick. Medium girdles are considered perfectly proportioned, though thick or thin diamonds do not necessarily decrease value. Extremely thin or thick girdles may affect symmetry or weight distribution, or cause an uneven setting.