Diamond education
Lab-grown diamond vs moissanite
One is diamond. The other is a different gemstone.
By the CTJ Jewellery team, led by founder Greg Ward · Updated September 2026 · Editorial policy
Key facts
- Lab-grown diamond: carbon
- Moissanite: silicon carbide
- Diamond hardness: 10
- Moissanite hardness: about 9.25
- Moissanite shows more coloured fire
- CTJ doesn’t sell moissanite
Side by side
| Lab-grown diamond | Moissanite | |
|---|---|---|
| Material | Carbon (diamond) | Silicon carbide |
| Hardness | 10 | About 9.25 |
| Sparkle | White brilliance with fire | Stronger rainbow fire |
| Graded as | Diamond (IGI, GIA) | Not graded as diamond |
Why does it matter what you’re shown?
Some jewellers display moissanite or samples in place of the actual diamond. At CTJ, the diamonds and jewellery you see are the actual pieces you buy.