Lab-grown diamond and moissanite are the two stones most people weigh up once they've decided against a mined diamond. Both are grown rather than mined, both are real gemstones, and both look like a diamond at a glance. They are still different materials, and each has something the other doesn't. We sell moissanite, but this is meant to help you choose, so we've said where lab-grown diamond wins.
Is moissanite a lab-grown diamond?
No. “Lab-grown” describes how a stone is made, not what it is. A lab-grown diamond is diamond, crystallised carbon, made in a lab instead of a mine. Moissanite is also made in a lab, but it is a different crystal altogether: silicon carbide. So moissanite is a lab-grown gemstone, never a lab-grown diamond, and an honest seller won't call it one.
The difference shows in the light. Moissanite bends light more strongly than diamond and splits it into colour more than twice as much, so it throws more rainbow fire; diamond's sparkle is whiter and calmer. The rest of this guide compares the two stone by stone.
What each stone is
Lab-grown diamond
A lab-grown diamond is a real diamond — pure carbon — grown by one of two methods, HPHT or CVD. It has the same refractive index (2.42), dispersion (0.044) and hardness (10) as a mined diamond.
Moissanite
Moissanite is silicon carbide. It was first found in a meteorite in 1893, but natural moissanite is extremely rare and occurs only as tiny grains, so every moissanite gem is grown in a lab. It is not a diamond and isn't sold as one. More in what is moissanite?
Side by side
| Property | Moissanite | Lab-grown diamond |
|---|---|---|
| Material | Silicon carbide (SiC) | Carbon |
| Refractive index | 2.65–2.69 | 2.42 |
| Dispersion (fire) | 0.104 | 0.044 |
| Hardness (Mohs) | 9.25 | 10 |
| Cleavage | None | Yes, like all diamond |
| Refraction | Double | Single |
| Price | R 2 400 at 1.00 ct (ours) | At least twice as much at the same size |
| Resale | No established market | Low |
How they look
This is the difference most people notice, and it comes down to two numbers.
Fire. Moissanite's dispersion is 0.104, more than twice a diamond's 0.044. It splits light into colour far more strongly, so it throws noticeable rainbow flashes, especially in sunlight and in larger stones. Some people love that; others find it too lively.
Brilliance. Moissanite also has the higher refractive index (2.65–2.69 against 2.42), so it returns plenty of bright sparkle. A lab-grown diamond's sparkle is whiter and more restrained — the classic diamond look. If that's what you picture, a lab-grown diamond will give it to you and moissanite won't quite.
Moissanite is doubly refractive and diamond isn't. Under a loupe some moissanite shows slight doubling of the facet edges; good cutters orient the stone to minimise it, and it can't be seen with the eye.
Hardness and everyday wear
Diamond is the hardest gem there is, at 10 on the Mohs scale, and lab-grown diamond is no different. On scratch resistance, it wins. Moissanite, at 9.25, is just behind — harder than sapphire (9) — and well suited to an engagement ring worn every day.
Hardness isn't the whole story. Moissanite is tough and has no cleavage planes, so it is less prone to chipping than diamond. Both stones hold up to daily life.
Colour and clarity
Both are graded on the same letter scale for colour: D, E and F are colourless; G, H and I near-colourless, with a faint warmth that shows most in larger stones and white metal. Moissanite is stable — it doesn't cloud, fade or change colour. We sell only DEF colourless, VVS clarity moissanite, so every stone we offer sits at the top of both scales. See our grading guide for what the grades mean.
Price
This is where the gap is widest. Lab-grown diamond prices have fallen steeply in recent years, but a lab-grown diamond still costs at least twice as much as a moissanite of the same size, and more for higher grades. Here is what our round moissanite costs, DEF colourless and VVS clarity:
| Size | Weight (DEW) | Moissanite SA price |
|---|---|---|
| 6.5mm | 1.00 ct | R 2 400 |
| 7.5mm | 1.50 ct | R 3 200 |
| 8mm | 2.00 ct | R 4 000 |
DEW is diamond-equivalent weight: moissanite is a little lighter than diamond, so its size is described by the weight a diamond of that size would have. Every one of our ten cuts is priced by weight alone. The full list is in our moissanite price guide.
Resale and value
Neither stone is an investment. Because lab-grown diamond prices keep falling, their resale value is low. There is no established resale market for moissanite at all. Buy either one because you want to wear it. What moissanite keeps is its looks: it doesn't cloud, fade or change colour.
Which should you choose?
Choose lab-grown diamond if
- You want a diamond — the material, the name and the classic white sparkle.
- Maximum scratch resistance matters most to you.
- The higher price fits your budget comfortably.
Choose moissanite if
- You love fire and colour in a stone.
- You want a larger stone, or top colour and clarity, for the same money.
- You want a stone that is hard, tough and stable enough for daily wear, at a fraction of the cost.
If you're also weighing up mined diamond, our moissanite vs diamond comparison covers it. When you're ready, browse our stones — each is shown at true size on a hand, calibrated to your screen with a bank card, and comes with a certificate of authenticity, a lifetime warranty, free tracked courier and 14-day returns. Questions? Contact us.
Is moissanite a lab-grown diamond?+
No. Both are grown in a lab, but a lab-grown diamond is carbon and moissanite is silicon carbide. They are different gemstones with different properties.
What is the difference between moissanite and a lab-grown diamond?+
Moissanite has more than twice the fire (dispersion 0.104 against 0.044) and a higher refractive index, so it shows more rainbow flashes. Lab-grown diamond is harder (10 against 9.25) and has a whiter sparkle. Lab-grown diamond costs at least twice as much at the same size.
Which is better, lab-grown diamond or moissanite?+
Neither is better overall. Choose lab-grown diamond for the classic diamond look and the highest scratch resistance; choose moissanite for more fire and a much lower price, with hardness and toughness that suit daily wear.
Is moissanite cheaper than lab-grown diamond?+
Yes. A lab-grown diamond costs at least twice as much as a moissanite of the same size. A 1.00 ct round moissanite costs R 2 400 at Moissanite SA, in DEF colourless and VVS clarity.
Can you tell moissanite from a lab-grown diamond?+
Up close, often yes: moissanite shows more coloured fire, and under a loupe some stones show facet doubling. A thermal diamond tester can read moissanite as diamond, but a moissanite tester, which measures electrical conductivity, tells them apart.