The facets at the bottom of the pavilion in diamonds are usually intended to come together at a perfect point. Sometimes the cutter polishes a small facet at the point so that it does not get chipped and this facet is called a culet (pronounced que-let).
Diamonds behave as a window if the facets opposite each other are parallel and that is exactly what happens if the culet is too big. Looking through the table facet on top of the crown, a diamond with a culet facet allows you to see out the hole in the bottom.
When a chip, cavity, or indented natural is present on the culet, only the remaining portion of the culet is considered in determining its size. The culet may also be an unpolished natural. If the natural is parallel to the table, it is considered a culet whereas a natural that is not flat or parallel to the table is considered not to be a culet and is reported as none.
The following culet size descriptions are listed with the typical culet size as a percentage of the average diameter for round brilliant diamonds.
- Pointed (None)
- Very Small (less than 1%)
- Small (about 1.5%)
- Medium (about 3%)
- Slightly Large (about 5%)
- Large (about 7%)
- Very Large (about 11%)
- Extremely Large (about 15%)
The culet sizes listed on certifications as they appear at 10X magnification. Culet rated as pointed (none), very small, small or medium are not visible to the eye and are desirable. Large to extremely large culets may be visible to the eye and can be a distraction. Some fancy shapes like the cushion frequently have larger culets than other shapes of diamonds.