Opal vs Moissanite
Moissanite is harder (Mohs 9.25) than Opal (Mohs 5.5–6.5), so it resists scratching better; Opal is softer than quartz dust (7) and needs more care in everyday rings.
Moissanite has the higher refractive index (2.648–2.691 vs 1.450), which a refractometer (over-the-limit reading) can use to separate them.
Moissanite is denser (SG 3.22 vs 2.15); a moissanite of the same size weighs about 50% more.
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| Property | Opal | Moissanite |
|---|---|---|
| Species / material | Opal (hydrated silica) | Silicon carbide |
| Mohs hardness | 5.5–6.5 | 9.25 |
| Refractive index | 1.450 | 2.648–2.691 |
| Specific gravity | 2.15 | 3.22 |
| Crystal system | Amorphous | Hexagonal |
| Birefringence | None | 0.043 |
Values are typical ranges from standard gemmological references; individual stones can vary.
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