Cut registry › Jewellery cuts › Square emerald
Jewellery cuts · Step cut
The name on the report.
A grading report calls an asscher a square emerald cut. It uses exactly the same words for this stone, which is not an asscher. That is a genuine buying problem, and it is measurable.
The short version
A square emerald cut diamond is a square step cut with cut corners and facets in flat parallel tiers, carrying 57 facets on our measurement.
It is also the term a grading laboratory uses for an asscher, which means two different stones arrive described by the same three words.
Definition
GIA does not use the trade name asscher. On a report, an asscher is a square emerald cut. So is a plainer square step cut like this one, which has no windmill and no deep concentric architecture. The report cannot tell them apart. Your eye can, immediately.
What separates them is depth and facet arrangement. An asscher is cut deep, with concentric tiers descending to a small culet, which is what produces the windmill and the sense of a receding corridor. This stone is cut shallow, with fewer tiers and a wider table, so it spreads across the finger instead of drawing the eye down into itself.
Neither is wrong. They are different stones for different reasons, and the point of this page is that you should know which one you are being offered before you agree a price.
Proportions
Trade description on the left, our measured reference stone on the right. Note the depth figure, which is the single clearest difference from an asscher.
| Measure | Commonly cited | Our reference stone | What it does |
|---|---|---|---|
| Length-to-width | 1.00 to 1.05 | 1.00 | Square by definition. |
| Depth | 60% to 70% commonly cited | 49.2% | Far shallower than an asscher, and that is the whole difference. |
| Table | 60% to 70% | 62.5% | Wide, which is what makes it spread. |
| Pavilion angle | not commonly published | 44.1° | Decides whether light returns or escapes. |
| Facets | typically 57 to 58 | 57 | The same count as a round brilliant. |
Because the certificate term covers both stones, depth percentage is the number to read. A square emerald cut in the fifties is this shape; one in the sixties is more likely an asscher. Neither carries a cut grade.
Light
Measured on the census that runs on every cut on this site: 3,200 rays face-up, 2,200 at 20° tilt, on exact facet geometry, against T57 as the standard.
| Material | Useful light | Leak | Fire | Scintillation | Global | vs the standard |
|---|---|---|---|---|---|---|
| Diamond | 63.72% | 17.32% | 83.95 | 71.82 | 76.47 | −12.14 |
| Moissanite | 58.12% | 16.96% | 92.75 | 71.82 | 76.97 | −12.85 |
| Cubic zirconia | 65.31% | 20.71% | 88.59 | 71.82 | 78.51 | −13.27 |
| T57 standard, diamond | 92.28% | 1.88% | 78.85 | 71.82 | 88.61 | 0.00 |
This stone returns 63.72% of entering light usefully and leaks 17.32%, for 76.47 Global against the standard’s 88.61, which places it ninth of the twenty-one jewellery cuts we publish.
Its standout figure is spread: 107.72 on the Index axis, the widest of any cut we measure. That axis reads millimetres per carat from depth, and at 49.2% this is the shallowest stone in the section by a clear margin. A square emerald cut of a given weight covers more finger than anything else here.
It pays for that in movement. Tilt retention reads 78.53 against the standard’s 90.41, among the weakest we publish, which is the usual bargain with a very shallow stone: large face-up, less forgiving as the hand turns.
On 57 active facets, the same count as the round brilliant standard, it scores 71.82 on scintillation, and fire reads 83.95 against 78.85.
Where the light is: useful return across the face
Five equal bands across the stone. This cut returns 58.4% at the centre against 63.2% at the edges, against the round-brilliant control’s 99.1% and 98.1%. A shallow step cut under a wide table gives up its centre first.
Against the standard
Light return. 63.72% against the standard’s 92.28%, a Global gap of 12.14 points.
Face-up size. 107.72 on the spread axis, the widest figure on this site. This is the cut’s real argument.
Movement. 78.53 against 90.41. The cost of that spread.
Clarity. Higher than a brilliant needs. Step facets are open planes and a wide table makes them wider.
Durability. Cut corners, so no protective setting is needed. Safer than a carré.
The baseline for all of this is the round brilliant itself. Its facet plan is set out in the anatomy of a round brilliant, and the measured standard we compare against is T57, the stone Tolkowsky published in 1919.
Materials
In moissanite it returns 58.12% for 76.97 Global with fire at 92.75.
In cubic zirconia it returns 65.31% for 78.51 Global.
Set it against the asscher in the Index and the difference in depth is obvious long before any figure is.
Trade-offs
Questions
The questions buyers actually ask, answered in full. Where the answer is ours to prove, the figure is measured on the Index; where it is an established gemological fact, it is stated as one.
A square emerald cut diamond is a square step cut with cut corners and facets arranged in flat parallel tiers. It is also the term grading laboratories use for an asscher, because they do not use the trade name, which means two visibly different stones can carry the same description on a report.
On paper, often yes. In the hand, no. An asscher is cut deep with concentric tiers descending to a small culet, producing the windmill and the endless hallway. This stone is cut shallow at 49.2% with a wider table, so it spreads rather than drawing the eye down. Read the depth percentage to tell them apart.
They trade different things. We measure this cut at 76.47 Global against the asscher’s 78.36, so the asscher returns more light. This cut spreads much further for its weight, at 107.72 on the Index spread axis, and gives up tilt stability to do it. Choose on which of those you care about.
Yes, and by our measurements more than anything else we publish. It reads 107.72 on the Index spread axis, the highest figure on the site, because at 49.2% it is the shallowest cut in the section. That axis is derived from depth, so it is a claim about millimetres per carat.
Commonly cited ranges run 60% to 70%, but our reference stone sits at 49.2%, which is what makes it spread. A very shallow step cut buys face-up size and gives up tilt stability, and there is no cut grade to tell you where the balance has landed.
Higher than for a brilliant of the same size. Step facets are open planes with nothing to break up the view into the stone, and a wide table makes that view larger still. VS1 is a sensible floor.
No. GIA issues cut grades for round brilliants only. On a square emerald cut the report gives you colour, clarity, carat, symmetry, polish and the shape description, and nothing at all about how the stone handles light.
Yes. The cut corners are the same protection an asscher and an emerald cut have, so no special setting is required. It is considerably safer than a carré, which keeps its corners sharp.
Next
See the whole set on the jewellery cuts index, or the measured house and historic cuts in the cut registry.
Method
Monte-Carlo on exact facet geometry: 3,200 rays face-up plus 2,200 at 20° tilt, cosine-weighted from a 7° near-vertical cone. Useful light is what exits through the crown within 64° of vertical. The same protocol runs on every cut on this site, so the figures are comparable to each other.
They measure our reference geometry for the shape at the proportions listed above, not an average of stones on the market. A square emerald cut to different proportions will read differently. Treat them as a like-for-like comparison between shapes, not as a grade for any individual stone.
Engine estimates, ±2 points, not lab-certified grades. We do not publish the Index symmetry axis on these pages: it scores facet regularity within each pavilion family, which is meaningful for a round brilliant and misleading for a shape whose pavilion is deliberately irregular.
71.82 here against the standard’s 71.82. The term is 100(1−e−n/45) on the count of facets that actually reach the surface, so it is a pure function of facet count and nothing else.