Cutting emerald (beryl)
Emerald is the green variety of beryl, colored mainly by chromium, vanadium or both. Its refractive index is low, so it needs a steep pavilion to keep head-on light in the stone. It typically has inclusions and some brittleness, so cutters usually give it a step cut with cropped corners: the shape that took its name.
Its dispersion is low, so a cut has to show color, not fire. This is another reason why step cuts suit it so well.
Emerald optical properties
Where a property has a range, we calculate angles from the lower refractive index. It gives the stricter limit.
The top ten cuts in emerald
In emerald, the DG-M5 Cut performs best of the 11 brilliants we score: 90 for brilliance, 46 for fire and 85 for scintillation. The DG-Anteros Cut follows at 86, 52 and 80, then the DG-Vitruvio Cut at 78, 40 and 98. Of the three, the DG-M5 Cut has the highest brilliance and the DG-Anteros Cut has the most fire.
| Cut | Brilliance | Fire | Scintillation |
|---|---|---|---|
| DG-M5, House cut | 90 (T73 benchmark 78) | 46 (T73 benchmark 39) | 85 (T73 benchmark 80) |
| DG-Anteros, Brilliant | 86 (T73 benchmark 78) | 52 (T73 benchmark 39) | 80 (T73 benchmark 80) |
| DG-Vitruvio, Brilliant | 78 (T73 benchmark 78) | 40 (T73 benchmark 39) | 98 (T73 benchmark 80) |
| DG-Broken Hearts and Arrows, Brilliant | 78 (T73 benchmark 78) | 39 (T73 benchmark 39) | 86 (T73 benchmark 80) |
| DG-Miliano, House cut | 67 (T73 benchmark 78) | 34 (T73 benchmark 39) | 98 (T73 benchmark 80) |
| T73 Round Brilliant, Benchmark | 78 | 39 | 80 |
| T105 Round Brilliant, Brilliant | 71 (T73 benchmark 78) | 34 (T73 benchmark 39) | 90 (T73 benchmark 80) |
| T57 Round Brilliant, Historic cut | 78 (T73 benchmark 78) | 40 (T73 benchmark 39) | 72 (T73 benchmark 80) |
| Old European, Historic cut | 64 (T73 benchmark 78) | 42 (T73 benchmark 39) | 81 (T73 benchmark 80) |
| DG-Rafaello, House cut | 54 (T73 benchmark 78) | 28 (T73 benchmark 39) | 96 (T73 benchmark 80) |
In emerald, the Oval Cut performs best of the 23 jewelry cuts we score: 55 for brilliance, 71 for fire and 87 for scintillation. The Teardrop Cut follows at 54, 63 and 81, then the Trillion Cut at 63, 48 and 80. Of the three, the Trillion Cut has the highest brilliance and the Oval Cut has the most fire.
| Cut | Brilliance | Fire | Scintillation |
|---|---|---|---|
| Oval, Jewelry cut | 55 (T73 benchmark 78) | 71 (T73 benchmark 39) | 87 (T73 benchmark 80) |
| Teardrop, Jewelry cut | 54 (T73 benchmark 78) | 63 (T73 benchmark 39) | 81 (T73 benchmark 80) |
| Trillion, Jewelry cut | 63 (T73 benchmark 78) | 48 (T73 benchmark 39) | 80 (T73 benchmark 80) |
| Pear, Jewelry cut | 56 (T73 benchmark 78) | 59 (T73 benchmark 39) | 76 (T73 benchmark 80) |
| Asscher, Jewelry cut | 62 (T73 benchmark 78) | 55 (T73 benchmark 39) | 72 (T73 benchmark 80) |
| Trilliant, Jewelry cut | 68 (T73 benchmark 78) | 41 (T73 benchmark 39) | 79 (T73 benchmark 80) |
| Cushion, Jewelry cut | 74 (T73 benchmark 78) | 27 (T73 benchmark 39) | 85 (T73 benchmark 80) |
| Square, Jewelry cut | 68 (T73 benchmark 78) | 38 (T73 benchmark 39) | 78 (T73 benchmark 80) |
| Emerald Square, Jewelry cut | 66 (T73 benchmark 78) | 46 (T73 benchmark 39) | 72 (T73 benchmark 80) |
| Marquise, Jewelry cut | 43 (T73 benchmark 78) | 51 (T73 benchmark 39) | 86 (T73 benchmark 80) |
Brilliance is the share of face-up light that the stone returns. Fire is the share of that light that splits into color. Both come from our face-up light census. Scintillation is the sparkle that facets give as a stone moves, and we read it from the facets of each cut. We score 37 cuts, with the same figures as the Cut Performance Wheel, where you can compare any cut with any other in emerald. Mazarin, Peruzzi and Old Mine, historic cushions, are in neither list. Each measured cut’s own page shows its figures in all seven gemstones. A simulation of the geometry, not a grading report.
Emerald: questions
What pavilion angle should I use for emerald?
For a round design, at least 39.4°. At that angle or steeper, light that arrives straight down reflects off both sides of the pavilion, beyond the critical angle of emerald (39.4°). Then it leaves through the table. The angle is the larger of the critical angle and (180° − critical angle) / 4. Faceters usually cut a degree or two steeper, for light that arrives off the axis. Fancy shapes vary, so every cut page lists its own figure.
What is the critical angle of emerald?
39.4°, from a refractive index of 1.577. Light that strikes a facet from inside the stone at less than this angle from the normal of the facet passes out. At a larger angle, it reflects.
Which cuts work best in emerald?
We add brilliance, fire and scintillation together. By that total, the DG-M5 Cut, the DG-Anteros Cut and the DG-Vitruvio Cut are the best brilliants in emerald. By the same total, the best jewelry cuts are the Oval Cut, the Teardrop Cut and the Trillion Cut. We score 37 cuts in all, and this page ranks the top ten of each.
How much does emerald weigh compared with diamond?
Emerald has a specific gravity of about 2.72, and diamond has 3.52. So a stone of the same size weighs about 0.77 times as much as the diamond.