Moissanite vs Diamond: An Honest Comparison
Published . Updated . 1 minute read.
Editorial review: Optical and hardness values checked against gemological references. Values are approximate and vary slightly by source. Last reviewed .
Moissanite is sometimes marketed as a “better diamond” and sometimes dismissed as a “fake diamond”. Neither label is fair. It is a separate gemstone with its own strengths.
The key numbers
| Property | Moissanite | Diamond |
|---|---|---|
| Material | Silicon carbide | Carbon |
| Mohs hardness | About 9.25 | 10 |
| Refractive index (brilliance) | About 2.65 to 2.69 | About 2.42 |
| Dispersion (fire) | About 0.104 | About 0.044 |
| Optical character | Doubly refractive | Singly refractive |
| Grading | No standard 4Cs system | 4Cs from independent labs |
Higher refractive index means more light returned as brightness. Higher dispersion means more light split into spectral colors, the rainbow flashes people notice in moissanite.
How they look in real life
In soft indoor light the two can look very similar. In direct sunlight, moissanite shows more colored flashes, which some people describe as “disco ball” sparkle. Diamond’s sparkle reads whiter and crisper. Larger moissanites show the difference more than small ones.
Because moissanite is doubly refractive, you may see faceting lines doubled when looking at a large stone from certain angles with magnification. It is not normally visible at arm’s length.
Price and value
Moissanite usually costs a fraction of a similar-looking diamond. It has little resale value, similar to lab-grown diamond. If long-term value matters, a natural diamond is the only one of the three with an established secondary market, and even then resale is far below retail.
Which should you choose?
Choose moissanite if you want a large, very bright stone on a tight budget and like colorful fire. Choose diamond (natural or lab-grown) if you prefer a whiter sparkle, value tradition or want standardized grading.
Frequently asked questions
Can people tell moissanite from diamond?
Most people cannot at a glance. In bright sunlight, moissanite's stronger rainbow fire can be noticeable, especially in larger stones. Jewelers use specific testers or magnification to distinguish them.
Will a diamond tester flag moissanite as diamond?
Basic thermal testers can misidentify moissanite as diamond because both conduct heat well. Combined testers that also measure electrical conductivity are designed to separate them.
Is moissanite cheaper than lab-grown diamond?
Usually, yes, though the gap has narrowed as lab-grown diamond prices have fallen. Compare the specific stones you are considering.
Sources and further reading
- Gem Encyclopedia (Gemological Institute of America)
- Guides for the Jewelry, Precious Metals, and Pewter Industries (16 CFR Part 23) (U.S. Federal Trade Commission, via eCFR)