The girdle and the culet are two details on a diamond grading report that describe the edge and the bottom of the stone. The girdle is the narrow rim that separates the crown from the pavilion, and it is the edge that usually sits in the setting. The culet is a small facet, or a point, at the very bottom. Both help you understand how the diamond is built, and both are worth reading with the rest of the proportions rather than in isolation.
What the girdle is
The Gemological Institute of America describes the girdle as the narrow section that separates the crown from the pavilion, and as the diamond's setting edge. On a GIA report the thickness is usually given as a verbal description, and often as a range, using a scale from Extremely Thin through Very Thin, Thin, Medium, Slightly Thick, Thick and Very Thick to Extremely Thick. GIA assesses that thickness under 10 times magnification, looking at the stone in profile.
Those words matter because the girdle has two jobs. It needs to be sturdy enough to sit in claws or a bezel without chipping easily, and it should not hide so much weight that the stone looks smaller face up than its carat suggests. GIA is clear that a thin girdle can increase the risk of damage such as chipping, and that a thick girdle can contribute toward a heavier diamond than its face up appearance warrants. We would not choose or reject a stone from a single girdle word alone. We look at the description, at the measurements, and at the diamond with you on a video consultation. Our guide to table and depth explains the other proportion figures that sit alongside this one.
What the culet is
The culet is at the bottom of the pavilion. GIA describes it as a polished facet placed parallel to the table, whose purpose is to protect the point. If there is no culet facet, the report records the size as None. When a facet is present, GIA describes it as Very Small, Small, Medium, Slightly Large, Large, Very Large or Extremely Large. Graders first assess it face up, looking through the table under 10 times magnification. A small culet, or none at all, is common and is usually hard to notice in the hand. A much larger culet can show as a darker area through the table and may change the face up pattern.
How we read them with you
For a standard round brilliant, girdle and culet are among the details GIA considers in the cut grade, together with table, depth and finish. Most fancy shapes do not receive that same cut grade, but the report still usually describes the girdle and the culet. We read those words next to the 4Cs and to why cut matters, then we look at the stone itself.
Nothing is made until you approve the design and the stone in writing. A 70 percent deposit is paid then, making time is 5 to 6 weeks, and the ring is UK hallmarked before insured, tracked FedEx delivery. If you would like to go through a report with us, get in touch, browse the diamonds we can source, or read our guide to how to read a GIA certificate.
Frequently asked questions
What do girdle and culet mean on a diamond report?
The girdle is the narrow rim that separates the crown from the pavilion, and it is the edge that usually sits in the setting. The culet is a small facet, or a point, at the bottom of the stone. Both are described on a standard GIA report.
Can a girdle be too thin or too thick?
GIA notes that a thin girdle can increase the risk of damage such as chipping, and that a thick girdle can add weight that does not show face up. We look at the description on the report and at the stone itself, rather than treating any one word as a pass or fail.
Does every diamond have a culet facet?
No. If there is no culet facet, GIA records the culet as None. A small culet, or none at all, is common. A much larger culet can be visible through the table and may change the face up pattern.
Do fancy shapes show girdle and culet as well?
Yes. Even when a fancy shape does not receive a GIA cut grade, the report still usually describes the girdle and the culet, along with the millimetre measurements. We review those with you when we shortlist stones.