Introduction
The culet is a small facet at the bottom of a diamond's pavilion — the lowest point of the stone, directly opposite the table. In a modern round brilliant, the pavilion's eight main facets taper to a point, and the culet is either absent entirely (a sharp convergence) or present as a tiny flat facet where the tip would otherwise be.
Culet size is reported on every GIA grading report for round brilliants, appearing alongside proportion measurements like table percentage, total depth, crown angle, pavilion angle, and girdle thickness. It may seem like a minor detail compared to those proportions, but culet size directly affects what you see when you look at a diamond face-up — and in the case of larger culets, what you see is a dark circle at the centre of the stone that no amount of brilliance can disguise.
How Culet Size Is Graded
GIA grades culet size on an eight-point descriptive scale:
- None (also called Pointed)
- Very Small
- Small
- Medium
- Slightly Large
- Large
- Very Large
- Extremely Large
The assessment is made under 10x magnification by examining the diamond in profile and face-up. Graders evaluate whether a culet facet is present at all, and if so, how large it is relative to the diamond's overall proportions. The grade describes the facet's apparent size — not its absolute measurement in millimetres — so a "Small" culet on a 0.50ct diamond and a "Small" culet on a 3.00ct diamond are visually comparable when viewed through the table.
A grade of None means the pavilion facets meet at a precise point with no flat facet. Under magnification, you see a sharp convergence. This is the standard for modern round brilliant cutting and the most common grade on diamonds cut in the last two decades.
Why Modern Diamonds Have No Culet
The shift toward pointed (None) culets is driven by optics. When the pavilion facets converge to a point, light that has been reflected by the pavilion angle geometry exits cleanly through the crown. There is no flat surface at the bottom to interrupt the light path.
A culet facet, by contrast, is a window. Light that reaches the pavilion tip and strikes a flat culet facet can pass straight through instead of reflecting. The larger the culet, the larger the window, and the more light escapes downward rather than returning to the viewer as brilliance.
This is why cutting technology and market preference have converged on None. Modern precision cutting equipment can bring pavilion facets to a clean point without chipping — something that was more difficult with older tools. The result is a diamond that maximises the total internal reflection described in Pavilion Angle and minimises light loss at the stone's lowest point.
GIA's cut grading system for round brilliants reflects this preference. A culet of None or Very Small has no negative impact on the overall cut grade. Medium and larger culets begin to affect the assessment, and Large or above will typically limit the stone to Very Good or lower.
The Dark Circle: What a Visible Culet Looks Like
When a culet is large enough to be seen without magnification — generally Medium and above — it appears as a dark spot or circle at the centre of the diamond when viewed face-up through the table. The effect resembles a small inclusion sitting at the pavilion tip, but it is not a clarity characteristic. It is a facet.
The mechanism is straightforward. You are looking down through the table and crown facets into the pavilion. At the very bottom, instead of a point that reflects light back, there is a flat facet angled perpendicular to your line of sight. That facet transmits light through the diamond rather than reflecting it. Your eye registers the absence of returned light as a dark area.
The larger the culet, the more prominent the dark circle. A Slightly Large culet is noticeable under close inspection. A Large or Very Large culet is visible at normal viewing distance — it creates a persistent dark spot that moves with the diamond as you tilt it, distinct from the dynamic light-and-dark pattern of scintillation.
This effect is independent of the diamond's clarity grade. A diamond with VS1 clarity and a Large culet will show the dark circle just as prominently as one with SI2 clarity. The culet is not plotted on the clarity diagram because it is a proportion feature, not an inclusion or blemish.
Historical Context: Culets in Older Cuts
Before modern precision cutting became standard, most diamonds were cut with visible culets — often Medium to Large by today's grading scale. There were practical reasons for this.
Older cutting technology made it difficult to bring pavilion facets to a precise point without risking a chip or nick at the tip. A small culet facet protected the pavilion from damage during cutting, polishing, and setting. The culet acted as structural insurance — a deliberate flat surface that was less fragile than a sharp point.
Historical cutting styles such as Old European Cuts and Old Mine Cuts routinely feature Medium to Large culets. These are not defects — they are signatures of the era and the cutting philosophy that prevailed. An Old European Cut was designed for warm candlelight, not the bright white LEDs of a modern jewellery store, and its larger culet was part of a proportional system that prioritised different optical qualities.
If you are considering a vintage or antique diamond, expect to see a larger culet. Evaluate it in context: a Medium culet on a genuine Old European Cut is normal and appropriate. The same culet on a modern round brilliant would be unusual and would suggest either dated cutting or deliberate weight retention.
Culet and Durability
A pointed culet — graded None — is the sharpest and most exposed feature on a diamond. While diamond is the hardest natural material, hardness resists scratching, not impact. A sharp point can chip if struck at the right angle with sufficient force, particularly during the setting process when a jeweller positions prongs or tightens a bezel.
In practice, this risk is manageable. Once a diamond is set in a ring, the pavilion is protected by the mounting — the culet sits inside the setting, shielded from contact. The vulnerability exists primarily during handling before and during setting. A competent jeweller accounts for this, and modern settings are designed to accommodate pointed culets without stressing the tip.
A Very Small or Small culet provides a marginal durability advantage — the tiny flat facet is slightly less fragile than a pure point. The optical cost is negligible: neither grade produces a visible dark circle. Some cutters intentionally leave a Very Small culet as a compromise between optical performance and handling safety.
For diamonds that will be set in open-back designs — where the pavilion is exposed — a Very Small culet is a reasonable precaution. For standard prong or bezel settings, None performs well.
Summary
The culet is where the pavilion ends — either as a point or a small flat facet at the diamond's lowest tip. For modern round brilliants, look for None, Very Small, or Small on the grading report. These grades preserve the light return you are paying for when you select a well-cut diamond with optimal pavilion angle and crown angle. Medium and larger culets create a visible dark circle at the centre of the face-up view — not an inclusion, but a window that lets light escape. If you encounter a larger culet on a vintage diamond, assess it as a period feature rather than a flaw, but factor its visual impact into your evaluation. And remember that culet size, like girdle thickness, is one of several proportion details that contribute to the full picture captured by the cut grade.