Cut registry › Jewellery cuts › Asscher
Jewellery cuts · Step cut
The square emerald, cut deep.
An asscher is not a square emerald cut. It is a deeper stone with a different job, and the depth is what produces both the windmill and its one measurable weakness.
The short version
An asscher cut diamond is a square step cut with cut corners and concentric step facets descending to a small culet, typically 58 facets.
Its signature is the windmill: four dark blades that appear to spiral into the centre of the stone, produced by those concentric facets over a deep pavilion.
Definition
The asscher was developed by the Asscher brothers of Amsterdam and first cut in 1902, which makes it the first diamond cut to be patented. It was revived in the early 2000s and is now firmly associated with Art Deco design, although it predates the movement by two decades.
Its facets run in concentric squares from the girdle down to a small culet. Looking straight into one, the eye follows those squares inward and reads them as a receding corridor, which the trade calls the endless hallway. The four dark blades crossing that corridor are the windmill.
The comparison with the emerald cut is a depth story rather than an outline story. An emerald cut is cut shallow and spreads its weight across the finger. An asscher is cut deep and concentrates its weight below the table, which is what generates the depth effect and also why an asscher looks smaller for its carat weight.
Proportions
Commonly cited ranges against our measured reference stone. On an asscher, depth is not a compromise to be minimised. It is where the shape’s whole visual effect comes from.
| Measure | Commonly cited | Our reference stone | What it does |
|---|---|---|---|
| Length-to-width | 1.00 to 1.05 | 1.00 | Square by definition; anything longer is an emerald cut. |
| Depth | 61% to 68% | 50.7% | Depth is what produces the endless hallway. |
| Table | 60% to 68% | 60.0% | The flat top, as a share of the width. |
| Pavilion angle | not commonly published | 49.8° | Decides whether light returns or escapes. |
| Facets | 58; Royal Asscher 74 | 58 | Counted as facets that actually reach the surface. |
Certificates usually describe an asscher as a square emerald cut, since GIA does not use the trade name. There is no cut-quality grade for either. The branded Royal Asscher, cut by the same family firm, carries 74 facets and is a different stone from a generic square emerald cut.
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 | 69.28% | 11.33% | 80.17 | 72.44 | 78.36 | −10.25 |
| Moissanite | 64.47% | 11.92% | 93.68 | 72.44 | 79.11 | −10.71 |
| Cubic zirconia | 73.80% | 14.67% | 88.50 | 72.44 | 80.85 | −10.92 |
| T57 standard, diamond | 92.28% | 1.88% | 78.85 | 71.82 | 88.61 | 0.00 |
Our reference asscher returns 69.28% of entering light usefully and leaks 11.33%, for 78.36 Global against the standard’s 88.61. It reaches that on 58 active facets, essentially the same count as the round-brilliant standard’s 57, so almost none of its score is bought with facet count. Among the eleven twenty-one jewellery cuts we measure it places seventh in diamond, which is a strong result for a step cut carrying no more facets than the standard.
Its weakness is movement, and it is the one figure on this page a buyer is most likely to have noticed already. The asscher holds 79.11 of its face-up return at a 20° tilt, against the round brilliant’s 90.41. Only the very shallow square emerald cut sits lower among the jewellery cuts we publish.
That is the measured version of a common complaint: an asscher looks superb straight on and flattens when the hand turns. It is a real property of a deep step cut with concentric facets, not a fault in any particular stone, and no one else appears to put a number on it.
Variants
A grading report describes an asscher as a square emerald cut, and it uses the same words for a plainer square step cut that is not an asscher at all. The library carries both, so they can be compared directly.
| Geometry | Facets | Useful light | Leak | Fire | Global | What differs |
|---|---|---|---|---|---|---|
| Asscher on this page | 58 | 69.28% | 11.33% | 80.17 | 78.36 | The reference stone every other figure here describes. |
| Square emerald | 57 | 63.72% | 17.32% | 83.95 | 76.47 | The plainer square step cut a report also calls a square emerald cut: shallower corners, less depth. |
The asscher is the deeper stone and it returns more light for it. If a report says square emerald cut, that alone does not tell you which of these two you are looking at. The windmill will, and the square emerald cut has its own page.
Against the standard
Light return. 92.28% for the round against 69.28% for the asscher, a Global gap of 10.25 points.
Sparkle character. 58 facets against 57, so the two score almost identically on scintillation, 72.44 against 71.82. As with the emerald cut, the difference in how they look is geometry rather than facet count.
Movement. 79.11 against 90.41. This is the clearest practical difference between the two stones in daily wear.
Face-up size. An asscher reads smaller for its weight than most shapes, because its depth carries weight below the table. Buy on millimetres.
Clarity requirement. Higher than a brilliant. The concentric facets are broad and open, and the eye is drawn down toward the culet where inclusions tend to gather.
Durability. Cut corners, well protected, no special setting required.
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 the asscher returns 64.47% for 79.11 Global, with fire at 93.68. A step cut shows moissanite’s double refraction more plainly than a brilliant does, because there is no scatter in the facet pattern to disguise it.
In cubic zirconia it returns 73.80% for 80.85 Global. Zirconia is soft at Mohs 8.25, and the asscher’s broad open facets show surface wear sooner than a busy brilliant would.
Compare all three for this shape in the Index.
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.
An asscher cut diamond is a square step cut with cut corners and concentric step facets running down to a small culet, typically carrying 58 facets. It was developed by the Asscher brothers of Amsterdam and first cut in 1902, making it the first patented diamond cut.
The four dark blades that appear to spiral toward the centre of the stone when you look straight into it. They are produced by the concentric step facets descending a deep pavilion, and they cross the receding corridor of reflections the trade calls the endless hallway.
Outline and depth. An emerald cut is rectangular and cut relatively shallow, spreading its weight across the finger so it reads large for its carat. An asscher is square and cut deep, concentrating weight below the table, which is what produces the windmill and the endless hallway and also why it reads smaller for its weight.
Higher than for a brilliant. The broad concentric facets display inclusions plainly, and the shape draws the eye down toward the culet where inclusions tend to concentrate. VS1 is the usual working floor, with VS2 acceptable only on a stone verified eye-clean face-up.
Commonly cited as 61% to 68% depth and 60% to 68% table. Our reference asscher measures 50.7% depth and 60.0% table. Unlike most shapes, depth here is not something to minimise: it is what creates the shape’s optical signature.
Because a deep step cut with concentric facets loses more of its return under tilt than a brilliant does. We measure our reference asscher holding 79.11 of its face-up return at a 20° tilt against 90.41 for a round brilliant, among the lowest figures we publish. It is a property of the design rather than a defect in your stone.
No. GIA issues cut grades for round brilliants only, and it does not use the trade name either: an asscher will normally be described on a report as a square emerald cut.
Fifty-eight is standard. The branded Royal Asscher, cut by the same family firm, carries 74. Our reference asscher measures 58 facets that actually reach the surface.
Per carat, generally yes. As with the emerald cut, part of that saving goes back into the higher clarity grade the shape needs.
Often, yes. An asscher carries a greater share of its weight below the table than most shapes, so two stones of equal weight can differ noticeably in face-up size. Compare millimetres rather than carats.
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 asscher 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.
72.44 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.