Cut registry › Jewellery cuts › Emerald
Jewellery cuts · Step cut
The step cut everyone knows.
An emerald cut is not a brilliant that fails to sparkle. It is a different instrument, and we can put a number on exactly how different.
The short version
An emerald cut diamond is a rectangular step cut with cut corners and long parallel facets running around the stone, typically 57 to 58 facets.
Its facets are arranged in flat steps rather than the triangles and kites of a brilliant, which is why it produces broad slow flashes instead of fine sparkle.
Definition
A step cut works nothing like a brilliant. Where a brilliant breaks incoming light into many small returns, a step cut reflects it in long, flat planes, so the stone shows large blocks of light and dark that slide across each other as it moves. The trade calls this the hall of mirrors, and it is the entire point of the cut.
The shape comes from lapidary practice on emeralds, where the step cut reduced stress on a brittle stone and showed its colour cleanly. It was adopted for diamond in the 1920s and became the defining Art Deco shape.
That open architecture has one direct consequence, and GIA states it plainly: the long rectangular facets make inclusions far easier to see than brilliant faceting does. An emerald cut is a window into the stone. That is its appeal and its exposure at once.
Proportions
Commonly cited ranges against our measured reference stone. On an emerald, the numbers that decide whether you are happy are clarity and ratio, in that order.
| Measure | Commonly cited | Our reference stone | What it does |
|---|---|---|---|
| Length-to-width | 1.30 to 1.50; around 1.35 most popular | 1.50 | 1.50 is the classic Art Deco proportion. |
| Depth | 61% to 68% | 68.6% | Shallower than a brilliant; the shape spreads its weight. |
| Table | 60% to 70% | 55.0% | The flat top, as a share of the width. |
| Pavilion angle | not commonly published | 41.3° | Decides whether light returns or escapes. |
| Facets | 57 to 58 | 57 | Counted as facets that actually reach the surface. |
GIA issues no cut-quality grade for emerald cuts. The report you should read closely is the clarity grade, and better still, the plotted diagram: on a step cut, position matters as much as grade, because an inclusion under the table has nowhere to hide.
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 | 55.35% | 25.50% | 87.11 | 71.82 | 70.48 | −18.13 |
| Moissanite | 50.84% | 27.23% | 94.53 | 71.82 | 70.25 | −19.57 |
| Cubic zirconia | 58.87% | 24.87% | 92.16 | 71.82 | 72.45 | −19.32 |
| T57 standard, diamond | 92.28% | 1.88% | 78.85 | 71.82 | 88.61 | 0.00 |
Here is the number that matters most on this page. Our reference emerald carries 57 active facets. The round-brilliant standard carries 57. They are effectively the same count, and the emerald scores 71.82 on scintillation against the standard’s 71.82, which is to say the same figure.
So an emerald cut does not sparkle less because it has fewer facets. It sparkles differently because those facets are arranged in flat steps rather than in triangles, and flat steps return light in large blocks rather than small points. If your emerald cut looks calm, that is the design working, not the cutting failing.
What it does give up is light return. Our reference emerald sends 55.35% of entering light back usefully against the standard’s 92.28%, and leaks 25.50%. Its Global score is 70.48 against 88.61. A step cut is not built to maximise return, and it does not.
Where the light is: useful return along the length
Five equal bands from one end to the other, each returning ray binned by where it leaves the crown. Our reference emerald returns 79.6% across the centre against 37.6% at the ends, a spread of 42.1 points. That is the widest spread of any cut we measure here, and it is the measured version of a familiar complaint: the ends of a long emerald cut go quiet while the middle stays alive.
Against the standard
Light return. 92.28% for the round against 55.35% for the emerald, for a Global gap of 18.13 points. This is the largest gap of any brilliant-versus-step-cut comparison on the site, and it is structural rather than a matter of finish.
Sparkle character. Identical facet counts, 57 against 57, and therefore identical scintillation scores. The difference in how they look is entirely a difference in facet geometry. That is a useful thing to be able to demonstrate rather than assert.
Fire. 87.11 against the standard’s 78.85. When an emerald cut does throw colour, it throws it in wide flashes rather than pinpoints.
Face-up size. An emerald cut spreads its weight over a longer, shallower outline than a round, so it usually reads larger for the carat.
Clarity requirement. The one place an emerald costs more rather than less. VS1 is the usual working floor, and VS2 only on a stone verified eye-clean face-up.
Durability. The cut corners are well protected. An emerald cut needs no special setting.
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 emerald returns 50.84% for 70.25 Global, with fire at 94.53 against 87.11 in diamond. Moissanite is doubly refractive, and a step cut’s long clean facets are the easiest place in jewellery to see that doubling, because there is no scatter to hide it.
In cubic zirconia it returns 58.87% for 72.45 Global. Zirconia’s lower refractive index suits this geometry better than diamond’s does, though it gives up hardness to get there.
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 emerald cut diamond is a rectangular step cut with cut corners and long parallel facets arranged in flat steps around the stone, typically carrying 57 to 58 facets. The style comes from lapidary practice on emeralds and was adopted for diamond in the 1920s.
Not because they have fewer facets. Our reference emerald measures 57 facets against the round-brilliant standard’s 57, and scores 71.82 on scintillation against 71.82, effectively the same. The difference is that step facets are flat planes rather than triangles and kites, so they return light in large blocks instead of small points. A calm emerald cut is the design working as intended.
Higher than for a brilliant of the same size. GIA notes that the long rectangular facets characteristic of emerald cuts make inclusions considerably easier to see. VS1 is the usual working floor, with VS2 acceptable only where a specific stone has been verified eye-clean face-up. Read the plotted diagram as well as the grade, because position matters as much as size.
The commonly cited range is 1.30 to 1.50, with around 1.35 the most popular and 1.50 the classic Art Deco proportion. It is an aesthetic decision. Our reference emerald sits at 1.50.
Commonly cited as 61% to 68% depth and 60% to 70% table. Our reference emerald measures 68.6% depth and 55.0% table. An emerald cut is shallower than a brilliant by design, which is part of why it reads large for its weight.
The broad flashes of light and dark that sweep across an emerald cut’s parallel step facets as the stone moves. Because the facets are long flat planes arranged in tiers, they reflect large areas at once rather than breaking light into points, so the stone reads as a corridor of receding mirrors.
No. GIA issues cut grades for round brilliants only, so an emerald report carries symmetry and polish but no assessment of light performance.
Per carat, generally yes, because the shape retains more rough. The saving is partly offset by the higher clarity grade an emerald cut usually needs, so the total cost of a good one is closer to a round than the per-carat figure suggests.
Usually. An emerald cut is shallower than a brilliant and spreads its weight across a longer outline, so more of the stone faces up. Compare face-up millimetres rather than carat weight.
An emerald is rectangular and cut relatively shallow, spreading its weight across the finger. An asscher is square and cut deep, concentrating weight below the table to produce its windmill pattern and the sense of depth the trade calls the endless hallway. Both are step cuts with cut corners.
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 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.