Cutting moissanite
Moissanite, silicon carbide, has an even higher refractive index than diamond and more than twice its dispersion, so it shows strong fire. It is lighter than diamond, so the same size weighs less.
It is doubly refractive. Cutters orient the table perpendicular to the optic axis, so the facets seen straight through the table do not look doubled. Their reflections, and the view through the crown, still look doubled. The 3D Gemstone Simulator traces both rays, so its moissanite shows this too.
Cutting a round in moissanite? Diamond proportions lose the arrows and hearts in moissanite. DG-Anteros is re-solved for it and shows both. See the comparison.
Moissanite 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 moissanite
In moissanite, the DG-M5 Cut, drawn for moissanite, performs best of the 11 brilliants we score: 98 for brilliance, 100 for fire and 85 for scintillation. The DG-Vitruvio Cut follows at 86, 97 and 98, then the DG-Miliano Cut, another moissanite design, at 86, 93 and 98. Of the three, the DG-M5 Cut has both the highest brilliance and the most fire.
| Cut | Brilliance | Fire | Scintillation |
|---|---|---|---|
| DG-M5, House cut | 98 (T73 benchmark 86) | 100 (T73 benchmark 97) | 85 (T73 benchmark 80) |
| DG-Vitruvio, Brilliant | 86 (T73 benchmark 86) | 97 (T73 benchmark 97) | 98 (T73 benchmark 80) |
| DG-Miliano, House cut | 86 (T73 benchmark 86) | 93 (T73 benchmark 97) | 98 (T73 benchmark 80) |
| T105 Round Brilliant, Brilliant | 86 (T73 benchmark 86) | 97 (T73 benchmark 97) | 90 (T73 benchmark 80) |
| DG-Broken Hearts and Arrows, Brilliant | 87 (T73 benchmark 86) | 97 (T73 benchmark 97) | 86 (T73 benchmark 80) |
| DG-Rafaello, House cut | 84 (T73 benchmark 86) | 90 (T73 benchmark 97) | 96 (T73 benchmark 80) |
| DG-Anteros, Brilliant | 92 (T73 benchmark 86) | 91 (T73 benchmark 97) | 80 (T73 benchmark 80) |
| T73 Round Brilliant, Benchmark | 86 | 97 | 80 |
| T57 Round Brilliant, Historic cut | 85 (T73 benchmark 86) | 98 (T73 benchmark 97) | 72 (T73 benchmark 80) |
| Old European, Historic cut | 79 (T73 benchmark 86) | 95 (T73 benchmark 97) | 81 (T73 benchmark 80) |
In moissanite, the Portuguese Bird's Nest Cut performs best of the 23 jewelry cuts we score: 82 for brilliance, 95 for fire and 98 for scintillation. The Cushion Cut follows at 74, 93 and 85, then the Square Cut at 82, 91 and 78.
| Cut | Brilliance | Fire | Scintillation |
|---|---|---|---|
| Portuguese Bird's Nest, Jewelry cut | 82 (T73 benchmark 86) | 95 (T73 benchmark 97) | 98 (T73 benchmark 80) |
| Cushion, Jewelry cut | 74 (T73 benchmark 86) | 93 (T73 benchmark 97) | 85 (T73 benchmark 80) |
| Square, Jewelry cut | 82 (T73 benchmark 86) | 91 (T73 benchmark 97) | 78 (T73 benchmark 80) |
| Trilliant, Jewelry cut | 71 (T73 benchmark 86) | 95 (T73 benchmark 97) | 79 (T73 benchmark 80) |
| Marquise, Jewelry cut | 59 (T73 benchmark 86) | 94 (T73 benchmark 97) | 86 (T73 benchmark 80) |
| Trillion, Jewelry cut | 60 (T73 benchmark 86) | 93 (T73 benchmark 97) | 80 (T73 benchmark 80) |
| Radiant Square, Jewelry cut | 71 (T73 benchmark 86) | 93 (T73 benchmark 97) | 66 (T73 benchmark 80) |
| Asscher, Jewelry cut | 64 (T73 benchmark 86) | 94 (T73 benchmark 97) | 72 (T73 benchmark 80) |
| Octagon, Jewelry cut | 67 (T73 benchmark 86) | 94 (T73 benchmark 97) | 66 (T73 benchmark 80) |
| DG-Octagonal Kite, House cut | 71 (T73 benchmark 86) | 95 (T73 benchmark 97) | 60 (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 moissanite. 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.
Moissanite: questions
What pavilion angle should I use for moissanite?
For a round design, at least 39.5°. At that angle or steeper, light that arrives straight down reflects off both sides of the pavilion, beyond the critical angle of moissanite (22.2°). 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 moissanite?
22.2°, from a refractive index of 2.648. 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 moissanite?
We add brilliance, fire and scintillation together. By that total, the DG-M5 Cut, the DG-Vitruvio Cut and the DG-Miliano Cut are the best brilliants in moissanite. By the same total, the best jewelry cuts are the Portuguese Bird's Nest Cut, the Cushion Cut and the Square Cut. We score 37 cuts in all, and this page ranks the top ten of each.
How much does moissanite weigh compared with diamond?
Moissanite has a specific gravity of about 3.22, and diamond has 3.52. So a stone of the same size weighs about 0.91 times as much as the diamond.