Moissanite vs Cubic Zirconia: What Is the Difference?
Both are laboratory-made and colourless, but they are different materials. Moissanite (silicon carbide) is harder, at 9.25 against 8 to 8.5 on the Mohs scale, more brilliant (refractive index 2.65 against about 2.15) and keeps its polish for decades. Cubic zirconia (zirconium dioxide) is much cheaper and much heavier; with years of daily wear its facet edges abrade and its surface dulls.
Side by side
| Moissanite | Cubic zirconia | |
|---|---|---|
| Material | Silicon carbide (SiC) | Zirconium dioxide (ZrO₂) |
| Hardness (Mohs) | 9.25 | 8 to 8.5 |
| Toughness | Excellent | Good, but brittle |
| Refractive index | 2.65 to 2.69 | 2.15 to 2.18 |
| Dispersion (fire) | 0.104 | 0.058 to 0.066 |
| Specific gravity | 3.22 | 5.6 to 6.0 |
| Thermal diamond tester | Reads as diamond | Does not |
| Typical use | Fine jewellery for daily wear | Fashion jewellery |
Brilliance and fire
Moissanite's higher refractive index returns more light as bright white sparkle. Both stones show more coloured fire than diamond, but moissanite's dispersion is higher still. Side by side, a new cubic zirconia can look convincing; the difference shows over time.
Why cubic zirconia goes cloudy
Cubic zirconia is hard by most standards, but noticeably softer and more brittle than moissanite. With daily wear the sharp facet junctions gradually abrade and fine scratches accumulate, so the stone loses its crispness and collects a film that is hard to clean away. GIA notes rounded facet junctions as a sign of softer simulants. Moissanite, second in hardness only to diamond among common gems, keeps sharp facets and a high polish for decades.
Weight
Cubic zirconia is very dense: a stone weighs roughly 1.7 times as much as a diamond of the same size, and nearly twice as much as moissanite. Loose, that difference is easy to measure; set in a ring, you may feel it in larger stones.
Price and when each makes sense
Cubic zirconia costs very little and is a sensible choice for costume pieces, for travel, or for trying a shape before committing to it. Moissanite costs more, though far less than diamond, and is made to be worn every day for a lifetime, which is why we use it in every Luhusati piece.
How to tell them apart
- Thermal tester: moissanite reads as diamond; cubic zirconia does not.
- Loupe: moissanite is doubly refractive and can show doubled back facets; cubic zirconia is singly refractive.
- Wear: on an older piece, rounded or nicked facet edges point to cubic zirconia.
- Weight: a loose cubic zirconia is markedly heavier for its size.