Lab Diamond vs Moissanite: Differences and Which to Buy

Two stones are handed over in the same box, both bright and both colourless, and one is a lab grown diamond while the other is a moissanite. They cost very different amounts, and they are not variations of the same thing: a lab diamond is carbon crystallised in the diamond structure, and a moissanite is silicon carbide. Both are legitimate jewellery materials, both look excellent in a setting, and they wear differently, grade differently and are documented differently.

Last updated: October 11, 2026

Is moissanite as good as a lab diamond?

It is a different material with different properties, so the question is really which suits the purchase.

Moissanite is harder than most gemstones and well suited to daily wear, and it is far less expensive. It is not, however, a diamond: it has a different refractive index, different dispersion and different optical behaviour, and it is not graded on the diamond colour and clarity scales. A lab diamond is diamond in every physical respect except origin, and it is graded on the same scales as a mined diamond.

For buyers whose priority is appearance at the lowest cost, moissanite is a reasonable choice. For buyers who want a diamond that is documented as one — for insurance, resale or because the material itself matters — the lab diamond is the relevant product.

The two materials side by side

Composition, hardness and how each behaves in wear.

Property	Lab grown diamond	Moissanite
Composition	Carbon, diamond crystal structure	Silicon carbide
Hardness	10 on the Mohs scale	Roughly 9.25
Optical character	High refractive index, moderate dispersion	Higher dispersion; more intense fire
Grading	Graded on diamond colour and clarity scales	Not graded on diamond scales
Documentation	Grading report stating origin	Manufacturer specification, not a diamond report
Price	Below natural diamond	Below lab grown diamond
Built to be sold as	Diamond	A separate gemstone

Hardness and wear

Both are hard enough for daily wear; the difference shows up in the setting over years.

Diamond is the hardest material used in jewellery, so a diamond’s edges stay crisp indefinitely under normal wear. Moissanite is slightly softer and, more importantly, it is tougher in some directions than others, which matters mainly in a setting that grips the stone at thin points. In practice both materials serve well in a well-made setting, and the component that wears first is the metal, not the stone.

The practical difference is that a diamond can be re-polished if it ever becomes dulled by long wear, while moissanite refinishing is more limited. That is relevant over decades rather than years.

The optical difference buyers notice

Moissanite has more fire; diamond has more even brilliance.

Dispersion is what splits light into spectral colours, and moissanite has more of it, so in strong light it shows more coloured flashes — sometimes described as rainbow-like. Diamond has a higher refractive index but lower dispersion, so it returns more white light and fewer coloured flashes. Under ordinary indoor lighting the two can look similar; under spotlights or direct sun, the difference is visible, particularly in larger stones.

Neither is a defect. It is a characteristic, and buyers who prefer a quieter brilliance usually prefer diamond, while those who enjoy the coloured flashes often prefer moissanite.

How the two are told apart

Not by eye at a counter, and not by a standard diamond tester in every case.

The clearest indicator is the doubling of facet edges visible under magnification in moissanite, caused by its birefringence — diamond does not do this. Diamond testers that measure thermal conductivity separate moissanite reliably in most designs, while electrical conductivity testers are used specifically to distinguish diamond from moissanite because both conduct heat similarly. In practice, the fastest and most reliable answer is documentation: a diamond comes with a grading report stating origin, and moissanite does not carry a diamond report at all.

That is why the disclosure line on the product page matters more than any instrument a buyer might use.

Price and what drives it

Both are produced rather than mined, but they are produced differently and priced accordingly.

Moissanite is grown in large volumes at low cost, which is why the price gap to a lab diamond is significant even at similar visual sizes. Lab diamonds are produced under diamond growth conditions with lower yield and higher equipment cost, and they are then graded individually, which adds a cost per stone that moissanite does not carry. The result is that the two sit in different price bands by design rather than because one is performing worse.

Where the difference matters most is in a piece with many stones: a bracelet or a line of earrings in moissanite can be built for a fraction of the diamond equivalent. The breakdown of lab grown diamond pricing sets out which factors move the diamond price.

Which to buy

Four situations and the material that makes sense in each.

A piece where the material has to be diamond — for an engagement ring, an heirloom or an insurance schedule: lab grown diamond. A large piece for occasional wear where budget is the constraint: moissanite will deliver the visual effect for far less. A piece with many small stones: moissanite is often the sensible choice, and a diamond line becomes a deliberate premium. And any purchase where the buyer expects to resell: diamond, with the caveat that lab grown resale is weaker than natural, as covered in our notes on certification.

What matters most is disclosure. A piece should be described by its actual material on the product page, the invoice and the packaging, because the failure case here is not choosing moissanite — it is receiving it when a diamond was paid for.

Sources and further reading

• GIA Gem Encyclopedia — diamond and gem material properties
• Gems & Gemology — research on diamond and its lookalikes
• International Gemological Institute — grading and reports
• GIA 4Cs — how diamond grades are defined
• CIBJO Blue Books — nomenclature and disclosure standards
• International Gem Society — gemstone identification reference

Next step: Tell us what the piece is for and whether the material has to be diamond, and we will quote both options against the same specification so the comparison is clear. Lab grown diamond and alternative-material programmes are both supplied. Contact vinico@zkzdiamonds.com or WhatsApp +86 135 3037 8229.

Part of our lab grown diamonds guide.