Lab Grown Diamonds
Fancy Shapes: What to Check for Each One
No laboratory grades cut on anything but rounds β so for every other shape, you are the cut grader.
Written by the Mapple Gems workshop, Surat Β· Updated 13 September 2026
Short answer
Every fancy shape has one characteristic failure. Oval and pear: the bow-tie. Marquise: asymmetry and two vulnerable points. Emerald and Asscher: they show colour and inclusions with nothing to hide behind. Cushion: crushed-ice versus chunky, which changes the look entirely and is rarely stated. Princess and radiant: corners that need prong cover. All of them need rotating video in ordinary light, because no laboratory issues a cut grade for any of them.
Fancy shapes are where the most value and the most risk sit. They are cheaper per carat than rounds, they often look larger, and they have no cut grade β which means the difference between a beautiful stone and a mediocre one is entirely yours to spot.
Shape by shape
| Shape | The characteristic failure | Best ratio |
|---|---|---|
| Oval | Bow-tie; uneven shoulders | 1.35 β 1.45 |
| Pear | Bow-tie; a point off the centre line | 1.45 β 1.55 |
| Marquise | Asymmetric halves; two exposed points | 1.90 β 2.10 |
| Emerald | Shows colour and inclusions | 1.35 β 1.50 |
| Asscher | Same, plus corner symmetry | 1.00 β 1.05 |
| Cushion | Crushed ice vs chunky β usually unstated | 1.00 β 1.20 |
| Radiant | Corners; can look shallow | 1.20 β 1.40 |
| Princess | Corner chipping; light leakage at corners | 1.00 β 1.05 |
The bow-tie is the fancy-shape fault nobody can show you in a photograph β because it only exists in motion. In elongated brilliants β oval, pear, marquise β light passing through the middle of the stone can be blocked by your own head and hand as you look at it, throwing a dark band across the centre shaped like a bow-tie. A slight bow-tie is normal and present in almost every oval. A pronounced one sits there permanently and is the first thing you will see for the next thirty years. It appears on no grading report, and a still photograph is chosen from hundreds of frames at the angle where it shows least. Only rotating video in ordinary indoor light reveals it. If a seller offers only stills on an oval or pear, that is the one thing you cannot let go.
Oval and pear: the symmetry check
Beyond the bow-tie, these two are where hand-cut variation shows most.
Halve the outline mentally down its long axis β the two sides should mirror each other. Uneven shoulders make a correctly set stone look crooked on the finger, and no setting can correct it. On a pear, additionally check that the point sits on the centre line: a point even slightly off-axis reads as a wonky ring forever.
And on both, insist on a V-prong over the point. A round prong beside the point rather than over it is a construction fault, not a style choice.
Emerald and Asscher: the honest shapes
Step cuts have a handful of large open facets and no scattered sparkle to hide behind, which makes them the most revealing shapes there are.
Two consequences. Go one grade higher on both colour and clarity than you would for a brilliant β VS2 as a floor on clarity, and one step up the colour scale, particularly in white metal. And check the corner symmetry on an Asscher, where the four cut corners should be even; unevenness there is obvious once seen.
The compensation is that these are the calmest, most classic shapes, and for moissanite specifically they read the most diamond-like β few large facets separate less dispersion at once.
Cushion: the question nobody answers
βCushion cutβ covers two quite different stones, and listings almost never say which.
- Crushed ice β many small facets producing a busy, glittering, granular sparkle. More fire, more scintillation.
- Chunky or antique β fewer, larger facets producing broad defined flashes and a more vintage character.
These look genuinely different on the hand and people usually have a strong preference once they have seen both. Ask which you are being sold, and ask for video β it is the single most useful question on a cushion and it costs nothing.
Princess and radiant: the corners
Both are square-ish brilliants, and both concentrate their vulnerability at the corners.
A princess has sharp, unprotected corners which are the thinnest geometry on the stone β each needs a prong over it, and a bezel or protective V-corner setting is better still for daily wear. A radiant has cut corners, which is inherently more robust, but they still want prong cover.
On both, watch for light leakage at the corners in video β corners that stay dark while the centre flashes indicate proportions that are not returning light there.
The universal checklist
- Rotating video, ordinary indoor light, not a lightbox.
- No permanently dark zone as the stone turns. Flashing on and off is correct; staying dark is not.
- Symmetrical outline, checked by halving it mentally.
- Crisp facet junctions rather than a slightly blurred pattern.
- Dimensions and ratio in millimetres, checked against the expected size for the weight.
- Girdle in the middle of the range β extremely thin risks chipping, extremely thick hides weight.
Six checks, all doable from a two-minute video and a report, and between them they cover every shape above.
Keep reading
Frequently asked questions
What is a bow-tie in an oval diamond?
A dark band across the centre of an elongated brilliant, caused by light through the middle being blocked by your own head and hand. A slight one is normal in almost every oval; a pronounced one is permanent. It appears on no grading report and a still photograph is chosen at the angle where it shows least β only rotating video reveals it.
Do fancy shape diamonds have a cut grade?
No β only round brilliants receive a formal cut grade, because their proportions are standardised enough to grade consistently. For every other shape you judge from rotating video: no permanently dark zones, symmetrical outline, crisp facet junctions, and dimensions matching the expected size for the weight.
What is the difference between crushed ice and chunky cushion?
Crushed ice has many small facets producing a busy, granular sparkle; chunky or antique cushions have fewer, larger facets producing broad defined flashes and a vintage character. They look genuinely different on the hand, listings rarely say which, and asking is the single most useful question on a cushion.
Do emerald cuts need a higher colour and clarity grade?
Yes β one step higher on both than you would take for a brilliant, with VS2 as a clarity floor. Step cuts have large open facets and no scattered sparkle to hide behind, which makes them the most revealing shapes for both tint and inclusions. The compensation is that they are the calmest and most classic.
On an oval or a pear, insist on video.
The bow-tie is the one fault a photograph is guaranteed not to show you.
Leave a comment