Cutting aquamarine
Aquamarine has a refractive index of 1.567 to 1.590 and a dispersion of 0.014, a specific gravity of 2.72 and a hardness of 7.5 to 8.0 on the Mohs scale (hexagonal crystal system). It is doubly refractive (uniaxial), with a birefringence of 0.005 to 0.009. Its critical angle, from the low end of the range, is 39.7°, so a round design needs a pavilion of at least 39.7° for head-on light to reflect off both sides of the pavilion and leave through the table.
Aquamarine shares emerald's species (beryl) and its optical constants in our trace (within 0.001 of refractive index midpoint and the same fire spread), so these are emerald's figures. So this page ranks the cuts with emerald's figures, and each cut links its emerald page. Aquamarine's own constants are in the table below, with their sources.
Aquamarine optical properties
Published values, as on the aquamarine glossary page; they change a little from stone to stone. Where a property has a range, we calculate angles from the lower refractive index. It gives the stricter limit. Sources: GIA · International Gem Society · LibreTexts Gemology.
The top ten cuts in aquamarine
In aquamarine, 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) |
In aquamarine, 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) |
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, the same figures as our Cut Performance Index. The Cut Performance Wheel does not model this stone yet. Mazarin, Peruzzi and Old Mine, historic cushions, are in neither list. Each measured cut’s own page shows its figures in every gemstone we trace. A simulation of the geometry, not a grading report.
Aquamarine: questions
What pavilion angle should I use for aquamarine?
For a round design, at least 39.7°. At that angle or steeper, light that arrives straight down reflects off both sides of the pavilion, beyond the critical angle of aquamarine (39.7°). 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.
Why does aquamarine show emerald's figures?
Aquamarine shares emerald's species (beryl) and its optical constants in our trace (within 0.001 of refractive index midpoint and the same fire spread), so these are emerald's figures. Our alias rule: the same species, a refractive index midpoint within 0.005 and a fire spread within 0.002 of the stone whose figures it takes; aquamarine is within 0.001 and 0.000.
What is the critical angle of aquamarine?
39.7°, from a refractive index of 1.567, the low end of its published range. 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 aquamarine?
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 aquamarine. 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 aquamarine weigh compared with diamond?
Aquamarine has a specific gravity of about 2.73, and diamond has 3.52. So a stone of the same size weighs about 0.78 times as much as the diamond.