Educational Guides
How optical properties reveal whether a stone is natural or a simulant
Every gem species bends light at a characteristic angle, measured as the refractive index. Natural diamond sits at 2.417–2.419. Cubic zirconia is lower at 2.15–2.18, and moissanite is higher at 2.648–2.691. A refractometer can distinguish these instantly. If a stone's RI doesn't match diamond's narrow range, it is not a natural diamond — no further testing needed for that property.
Key Values
- • Diamond: 2.417–2.419
- • Cubic Zirconia: 2.15–2.18
- • Moissanite: 2.648–2.691
- • Sapphire: 1.76–1.78
- • Glass: 1.50–1.54
