Antique diamond knowledge
An open culet is a small polished facet at the very bottom of a diamond, where a pointed tip would otherwise be. It is common in many historic old mine and old European cuts. Seen face-up, it may appear as a small central opening or dark geometric point. It is not automatically damage or poor cutting. The important questions are whether the facet is intact, how it relates to the surrounding pattern, and how the diamond changes in motion.
Reviewed 14 August 2026. Prepared by the Imperial Cushions editorial team. Laboratory terminology is retained where a report is cited; historical context and visual judgments are identified as interpretation. Stone-specific observations below use public Imperial Cushions dossier images and videos.
What exactly is the culet?
The culet is located at the tip of the pavilion, opposite the table. GIA describes it as a facet placed where the pavilion mains meet. Its practical purpose is to reduce the risk of damage to a sharp point while the diamond is loose. When no culet facet is present and the pavilion mains meet at a point, a grading report may describe the culet as “None.” When a facet is present, GIA uses size descriptions ranging from Very Small to Extremely Large.
“Open culet” is the trade expression most clients encounter. It usually refers to a culet large enough to be visible through the table, especially in an antique stone with broad facets. The apparent opening is not a hole through the diamond. It is the polished bottom facet seen through the stone and influenced by the room, the camera, the observer and the diamond’s other proportions.
Why historic cutters used visible culets
Old mine cuts are commonly associated with a softly squared outline, a small table, a high crown, a relatively deep pavilion, short lower-half facets and a visible culet. GIA notes that the style was common from the early eighteenth century through the late nineteenth century and that examples vary because cutters followed the natural crystal and worked with the tools and priorities of their period.
A polished culet protected the otherwise vulnerable pavilion point. It also became part of the visual architecture of many historic brilliant styles. The result should not be judged by applying a modern round-brilliant preference mechanically. In an antique cushion, the culet may provide a quiet centre around which the broad pavilion reflections switch on and off.
That does not mean every large culet is attractive. GIA’s modern round-brilliant cut research shows that an eye-visible culet can disrupt the face-up pattern. Antique fancy shapes, however, do not receive that modern round-brilliant cut grade. Their culets need to be judged within the individual outline, facet arrangement, depth and movement of the stone.
Open culet, chip or abrasion: how to tell the difference
| Observation | What it may indicate | How to verify it |
|---|---|---|
| A flat, deliberate facet at the pavilion tip | An intentional culet | Review the grading report, pavilion view and magnified video |
| An irregular missing area or fresh-looking break | A possible chip | Inspect at magnification from several angles and check the condition notes |
| Small worn or frosted areas along an edge | Possible abrasion or wear | Use diffused light, dark-field magnification and a condition-focused video |
| A dark centre that moves or disappears on tilt | Often reflection or obstruction, not physical damage | Compare still images with slow movement in more than one lighting environment |
A face-up photograph alone is not enough to diagnose condition. A dark shape can be the camera or observer reflected by the pavilion facets. A crisp geometric culet can look irregular when the stone is tilted. Conversely, a flattering still image can conceal an abrasion or a small chip. Condition should be reviewed separately from the aesthetic question of whether the central pattern is pleasing.
For a fuller condition sequence, see the Imperial Cushions guide to girdles, chips, abrasions and repairs. When a laboratory report is available, our guide to reading a grading report for an antique cut explains what the document can establish and what still requires direct viewing.
How culet size changes the face-up pattern
The larger the culet appears relative to the rest of the pattern, the more likely the eye is to notice it immediately. A small culet may register only as a pinpoint. A medium or large culet may appear as a distinct geometric window. Its visibility also depends on table size, pavilion depth, facet scale, contrast and viewing distance.
In a well-composed antique cushion, a visible culet can create a stable centre while the larger facets around it produce broad flashes. In another stone, the culet may feel too dominant, off-centre or disconnected from the rest of the pattern. None of those impressions can be reduced to the culet description alone. The relationship is what matters.
Compare the culet with the whole proportion set rather than treating it as an isolated number. The guide to old mine cushion proportions explains how table, depth, crown, outline and culet work together. The Antique Cushion Diamond Atlas provides a broader visual framework for comparing historic cushion families.
Two real stones, two different readings
The public dossier for the 8.01 ct H VVS2 old mine cushion gives a spacious face-up view. In the still image above, the central culet is easy to locate because the diamond is large and the surrounding mains are broad. The centre reads as one component in a wider arrangement of light and dark. A still image establishes the outline and the culet’s position, but it cannot by itself establish how active the pattern remains as the stone moves.
The 3.01 ct G VS2 old mine cushion brilliant presents a more compact field. The central feature remains visible, but the visual experience is not simply a smaller version of the 8.01 ct stone. Outline, facet scale and the distribution of contrast change the balance. This is why comparing actual dossiers is more useful than memorizing a preferred culet size.
Why motion matters more than a perfect still
The rotating presentation below shows the actual 3.06 ct G VVS2 old mine cushion brilliant. Watch the centre first. The culet may appear dark in one position, brighten or narrow in another, and then recede as the surrounding reflections reorganize. That change helps separate a normal reflection pattern from a fixed physical feature.
Replay the video at three distances: close enough to see the centre, at normal screen distance to read the whole pattern, and farther away to judge presence. Then review the stone under another lighting setup if one is available. Video compression, screen brightness and a single camera angle can change the apparent size and darkness of the culet, so video is a comparative tool, not a substitute for physical inspection.
A buyer’s culet checklist
- Confirm the terminology. Read the culet description on the grading report, if supplied.
- Request a straight face-up image. Check position, shape and relationship to the surrounding facets.
- Request a pavilion view. A deliberate facet is easier to understand from below.
- Watch slow movement. Determine whether the dark central appearance changes as the stone tilts.
- Inspect at magnification. Separate an intentional culet from a chip, abrasion or extra facet.
- Change the lighting. Use diffused light and smaller direct sources rather than one flattering setup.
- Return to the whole diamond. Decide whether the centre supports the outline, rhythm and presence you value.
Is an open culet a defect?
No. In many antique diamonds it is an intentional and historically characteristic facet. It becomes a negative only when the individual stone’s condition or visual balance makes it one. A chipped culet is a condition issue. A very dominant or distracting culet is an aesthetic judgment. An intact visible culet that works with the rest of the facet pattern can be part of the appeal of an old mine or old European cut.
The best buying decision therefore combines documentation, still images, movement and condition inspection. If the stone is important, ask for the centre to be shown plainly rather than relying on a single beauty image.