For the most light, the round brilliant is the best cut for sapphire and ruby in our ray traces. It returns the most light of the ten classic shapes: brilliance 94 out of 100. The cushion (88) and the trilliant (86) come next. Of the ten shapes in sapphire, the oval scores highest for fire: 74, the round brilliant 37.
| Shape | Brilliance | Fire | Scintillation |
|---|---|---|---|
| Round brilliant | 94 | 37 | 80 |
| Cushion | 88 | 36 | 85 |
| Trilliant | 86 | 52 | 79 |
| Princess | 68 | 52 | 78 |
| Asscher | 68 | 53 | 72 |
| Oval | 66 | 74 | 87 |
| Emerald cut | 65 | 47 | 72 |
| Pear | 62 | 56 | 76 |
| Marquise | 55 | 54 | 86 |
| Radiant | 26 | 69 | 74 |
Why
Corundum, the species of sapphire and ruby, has a much lower refractive index than diamond. So light escapes from it more easily, and only well-angled pavilion facets keep it inside. In our traces, the round brilliant does this best of the classic shapes. Its fire is faint to the eye, and body color can hide it.
Ruby and sapphire are both corundum, with the same refractive index and dispersion. So these figures are the same for both. Their color is not part of the trace.
Of all 37 cuts we measure in sapphire, our own DG-M5 returns the most light: brilliance 100.
Compare any two cuts in the Cut Performance Wheel, or turn them in light in the 3D Gemstone Simulator.