Moissanite vs Diamond: An Honest Comparison
At arm's length most people cannot tell moissanite from diamond. Up close they differ: diamond is harder (10 vs 9.25 on the Mohs scale) and its sparkle is whiter; moissanite is more brilliant and throws noticeably more coloured fire. Both are durable enough for a ring worn every day, and moissanite costs a fraction of the price of a diamond of the same size.
Side by side
| Moissanite | Diamond | |
|---|---|---|
| Material | Silicon carbide, lab-grown | Carbon, natural or lab-grown |
| Hardness (Mohs) | 9.25 | 10 |
| Toughness | Excellent, no cleavage | Good to excellent, has cleavage planes |
| Refractive index | 2.65 to 2.69 | 2.42 |
| Dispersion (fire) | 0.104 | 0.044 |
| Weight for the same size | About 9% lighter | Reference |
| Thermal diamond tester | Reads as diamond | Reads as diamond |
| Electrical tester | Conducts | Does not conduct (rare blue type IIb excepted) |
| Price | A fraction of diamond | Highest |
Sparkle: brilliance and fire
Two different things make a stone sparkle. Brilliance is white light returned to your eye; it depends on the refractive index, and moissanite's (2.65) is higher than diamond's (2.42). Fire is white light split into spectral colours; it depends on dispersion, and moissanite's (0.104) is about 2.4 times diamond's (0.044).
In practice a diamond flashes mostly white with touches of colour; a moissanite flashes white and throws visible rainbows, especially in daylight and in stones above about 1.5 carats. Some people love that liveliness; others prefer diamond's cooler restraint. Neither is better. It is a matter of taste, and the only reliable way to know yours is to see both in natural light.
Durability
Diamond is the hardest gem, but hardness is resistance to scratching, not to breaking. Diamond has cleavage planes and can chip if struck hard at the wrong angle. Moissanite is slightly softer but very tough and has no cleavage; GIA rates its toughness as excellent. Both will outlast the metal they are set in. For an engagement ring worn every day, either is a sound choice.
Colour and clarity
Diamonds are graded on a colour scale from D (colourless) to Z, and colourless stones are priced at a steep premium. Early moissanite had a slight tint, but today's stones are routinely colourless and eye-clean, so you are not paying extra for the top grades. Every Luhusati stone is graded D colour, VVS1, on its GRA report.
Size and carat weight
Because moissanite is less dense, it is usually sold by diamond-equivalent weight: a 6.5 mm round moissanite is called 1 carat because a 1 carat round diamond measures about 6.5 mm, though the moissanite itself weighs a little less. What matters on the hand is the millimetre size, which is why we list both on every piece.
Can people tell the difference?
Not at a glance. A trained eye may notice the extra fire, and under a loupe moissanite's double refraction can make the back facets look doubled. A standard thermal diamond tester reads moissanite as diamond; a dual tester that also measures electrical conductivity identifies it correctly. We explain this in detail in does moissanite pass a diamond tester.
Price and value
A moissanite costs a small fraction of a natural diamond of the same size and less than a comparable lab-grown diamond. Neither moissanite nor lab-grown diamond holds resale value the way a natural diamond can, so buy moissanite to wear, not as an investment. Many people choose it precisely so the budget can go to the setting, a larger stone or a second piece.
Which should you choose?
- Choose diamond if the material itself matters to you, if you prefer a whiter, quieter sparkle, or if resale value is a consideration.
- Choose moissanite if you want a large, colourless, durable stone with more fire, at a price that leaves room for the design you actually want.
If you are deciding on a centre stone, our rings list the stone size in millimetres and carats, and our solitaires such as Aurelia Pavé and Oriane carry 3 carat stones.