Guide · 4 min read · Updated
Moissanite vs Diamond vs Cubic Zirconia for Iced-Out Watches
Short answer
Moissanite is lab-created silicon carbide. It is nearly as hard as diamond (about 9.25 to 9.5 on the Mohs scale against diamond's 10), shows more than twice diamond's fire (dispersion 0.104 against 0.044) and costs far less. Cubic zirconia is softer (8 to 8.5) and less brilliant. That mix of hardness, sparkle and price is why moissanite is the usual stone for iced-out watch bezels.
Moissanite, diamond and cubic zirconia compared
The three stones used on iced-out watches differ most in hardness and in how they handle light.
| Moissanite | Diamond | Cubic zirconia | |
|---|---|---|---|
| What it is | Silicon carbide (lab-created) | Carbon | Zirconium dioxide (lab-created) |
| Mohs hardness | About 9.25 – 9.5 | 10 | 8 – 8.5 |
| Refractive index | 2.65 – 2.69 | 2.42 | 2.15 – 2.18 |
| Dispersion (fire) | 0.104 | 0.044 | 0.058 – 0.066 |
| Thermal diamond tester | Passes | Passes | Does not pass |
| Relative price | Low | Highest | Lowest |
What is moissanite?
Moissanite is silicon carbide. It occurs naturally but is extremely rare, so the moissanite used in jewelry is created in a lab. It was introduced to the jewelry market in 1998 as a diamond alternative.
Moissanite rates about 9.25 to 9.5 on the Mohs hardness scale, second only to diamond among common gems, so it resists the scratches of daily wear on a watch.
Moissanite vs lab-grown diamond
A lab-grown diamond is a real diamond: carbon, with the same hardness of 10, made in a laboratory instead of mined. Moissanite is a different stone, silicon carbide.
Side by side, moissanite throws more colored flashes and a lab-grown diamond returns more white light. A lab-grown diamond costs more than moissanite, which is why moissanite is the usual choice when a whole bezel is covered in stones.
Does moissanite pass a diamond tester?
Moissanite passes the common thermal diamond testers, because it conducts heat almost as well as diamond. It is still a different stone: a tester that measures electrical conductivity, often sold as a moissanite tester, tells the two apart.
So “passes a diamond tester” is accurate for thermal testers, and it does not mean the stone is a diamond. Our listings say moissanite because that is what the stones are.
What do VVS and D color mean?
VVS stands for “very, very slightly included”: inclusions are extremely difficult to see even under magnification. D is the top of the colorless range on the diamond color scale. Together they describe a stone that looks clear and white rather than cloudy or tinted.
Why not cubic zirconia?
Cubic zirconia is the cheapest of the three and looks bright when new. It is softer, at 8 to 8.5 on the Mohs scale, so it picks up scratches and loses its edge sooner on a piece that is worn every day. It also does not pass a thermal diamond tester.
Pros and cons of moissanite
Moissanite is the practical choice for an iced-out watch, with two honest drawbacks.
- Pro: hardness of about 9.25 to 9.5 on the Mohs scale, so it is scratch resistant in daily wear.
- Pro: more fire than diamond, and it keeps its sparkle because it does not cloud.
- Pro: a small fraction of the price of diamond, which matters when a whole bezel is set with stones.
- Con: it is not a diamond, and it has little resale value.
- Con: its strong rainbow flashes look different from a diamond's whiter sparkle, which some people notice.
Common questions
Is moissanite a real diamond?
No. Moissanite is silicon carbide, a different gemstone from diamond, which is carbon. It is valued in its own right for its hardness and its fire.
Does moissanite get cloudy?
Moissanite itself does not turn cloudy, but any stone looks dull under skin oils, lotion or soap film. Wiping the bezel with a soft cloth restores the sparkle.
Which sparkles more, moissanite or diamond?
Moissanite shows more fire, the rainbow flashes of color: its dispersion is 0.104 against diamond's 0.044. Diamond returns more white light. Side by side, moissanite looks more colorful.
Can you tell the difference between moissanite and diamond?
Often yes, side by side: moissanite shows more rainbow-colored flashes. A jeweler can confirm it with a loupe, because moissanite is doubly refractive, or with an electrical-conductivity tester.
Is moissanite synthetic?
The moissanite used in jewelry is created in a lab. Natural moissanite exists but is far too rare to be cut into gems.
What is a simulated diamond?
A simulated diamond is any stone that imitates a diamond's look without being diamond, such as cubic zirconia. A lab-grown diamond is not a simulant: it is diamond.
Is moissanite better than cubic zirconia?
For a watch worn every day, yes. Moissanite is harder, at about 9.25 to 9.5 on the Mohs scale against 8 to 8.5, so it keeps its polish longer, and it shows more fire.
Can a diamond tester detect moissanite?
A thermal diamond tester cannot: moissanite conducts heat almost like diamond, so it reads as diamond. A tester that measures electrical conductivity does detect moissanite.
Is moissanite scratch resistant?
Yes. At about 9.25 to 9.5 on the Mohs scale, moissanite is harder than sapphire and resists scratches from everyday wear. Only diamond is harder among common gems.
Does moissanite keep its sparkle?
Yes. Moissanite does not cloud or fade. If it looks dull, a film of skin oil or soap is covering it, and wiping it restores the sparkle.
Does moissanite shine like a diamond?
It is just as bright but more colorful. Moissanite's dispersion is 0.104 against diamond's 0.044, so it throws more rainbow flashes, while a diamond returns more white light.
How durable is moissanite compared with a lab-grown diamond?
A lab-grown diamond is diamond, with a hardness of 10. Moissanite is about 9.25 to 9.5. Both are hard enough for a watch worn every day.
How can you test moissanite at home?
Without tools you cannot be certain. Under a 10× loupe, moissanite shows doubled facet edges because it is doubly refractive; a jeweler's electrical-conductivity tester confirms it.
Can moissanite take heat?
Moissanite can temporarily change color when it is heated, starting at around 65 °C (150 °F), and returns to normal as it cools. Keep a stone-set bezel away from high heat.