Quick answer
The core difference in moissanite vs cubic zirconia: moissanite (silicon carbide) scores 9.25 on the Mohs scale and throws far more fire, while cubic zirconia (zirconium dioxide) scores about 8 to 8.5, so it scratches and dulls with years of daily wear. To tell them apart, check the fire, the weight (CZ is about 1.8 times heavier) and a tester.
On the first day, a good cubic zirconia and a moissanite can look close. Both are colorless, both are made in a lab, both sparkle. The difference shows up in the details, and over time.
We sell both, so we will be straight with you: moissanite is the better stone for a piece you wear every day, and CZ still has a real place in a jewelry box. Here is why.
Key takeaways
- Moissanite is harder (9.25 vs 8 to 8.5) and keeps its crisp facets for decades.
- Moissanite shows about 1.6 to 1.8 times the fire of CZ.
- CZ is much heavier: 1.7 to 1.9 times the weight of a moissanite of the same size.
- CZ costs less and suits fashion pieces, travel and trying a trend.
What is the difference between moissanite and cubic zirconia?
Cubic zirconia (CZ) is synthetic zirconium dioxide, held in a cubic crystal structure by a stabilizer such as yttrium or calcium oxide. It has been mass-produced for jewelry since the late 1970s, and its low material cost made it the most popular diamond simulant in the world, according to its reference entry.
Moissanite is silicon carbide. Henri Moissan found it in 1893 in fragments of the Canyon Diablo meteorite and first took it for diamond. Natural moissanite is extremely rare, so jewelry moissanite is lab-grown. It reached the jewelry market in the late 1990s. The moissanite guide has the full story.
Neither stone is a diamond. The difference is in how they are built: moissanite is one of the hardest gems there is, while CZ is softer than sapphire and much softer than diamond.
Moissanite vs cubic zirconia, side by side
| Moissanite | Cubic zirconia | |
|---|---|---|
| Material | Silicon carbide (SiC) | Zirconium dioxide (ZrO2) |
| Hardness (Mohs) | 9.25 | 8 to 8.5 |
| Refractive index | 2.65 to 2.69 | 2.15 to 2.18 |
| Dispersion (fire) | 0.104 | 0.058 to 0.066 |
| Density | About 3.21 g/cm3 | 5.6 to 6.0 g/cm3 |
| Refraction | Doubly refractive | Singly refractive |
| Heat conduction | High, close to diamond | Low, a thermal insulator |
| Thermal diamond tester | Reads as diamond | Fails |
| Long-term look | Stays bright with cleaning | Scratches and rounded facets over years |
For reference, diamond: hardness 10, refractive index 2.42, dispersion 0.044, density 3.52 g/cm3.
Two lines matter most. A higher refractive index means more brilliance, the white light that bounces back to your eye. Higher dispersion means more fire, the flashes of color. Moissanite leads CZ on both.
Does cubic zirconia get cloudy over time?
It can look that way, yes. CZ does not change chemically, but at 8 to 8.5 on the Mohs scale it is soft enough to pick up fine scratches from normal wear, and it is somewhat brittle. Over months and years, the facet edges wear round and the surface picks up tiny marks. Light no longer exits cleanly, and the stone looks hazy.
Moissanite, at 9.25, sits above sapphire and ruby. The quartz in household dust (7 on the scale) cannot scratch it, and its facet edges stay sharp. When a moissanite looks dull, it is a film of lotion, soap and skin oil, and it rinses off. See does moissanite get cloudy for the full cleaning routine.
Good to know
The Mohs scale is not linear. Each step up is a bigger jump in hardness than the number suggests, so the gap between CZ at about 8 and moissanite at 9.25 is wider than it looks. Keep either stone away from harsh chemicals, and follow our jewelry care guide for the metal.
How to tell moissanite and cubic zirconia apart
You do not need a lab. These five checks, from easiest to most reliable, sort out most stones:
- Look at the fire. Under a single light or in sun, moissanite throws strong rainbow flashes. CZ sparkles too, but its color is softer and its white light glassier.
- Weigh it. Same size, very different weight. A 6.5mm round CZ weighs about 1.6 ct; a 6.5mm moissanite weighs about 0.88 ct. A jeweler's scale settles it.
- Use a thermal tester. CZ is a thermal insulator, so a standard diamond tester rejects it. Moissanite conducts heat like diamond and passes. A multi-tester then separates moissanite from diamond.
- Check with a loupe. Moissanite is doubly refractive, so at some angles the back facet edges look doubled. CZ is singly refractive and shows sharp single lines.
- Inspect the edges. On a CZ worn for a few years, facet edges look rounded and the table shows fine scratches. Moissanite edges stay crisp.
One caution: the thermal tester result also explains why moissanite gets mistaken for diamond. We cover it in does moissanite pass a diamond tester.
Two more clues sit outside the stone: the listing and the price. A real moissanite listing names the stone, gives its size in millimeters and its DEW, and states the color and clarity (ours: D color, VVS1). A piece sold as “moissanite” at a costume-jewelry price, with no stone details, deserves a question before you buy.
Moissanite vs CZ price: is the difference worth it?
CZ is cheap to make, and it shows in the price: CZ jewelry usually costs much less than the same design in moissanite. The fair question is cost per year of wear.
For a ring or studs you plan to wear every day for years, moissanite wins. It keeps its look, so you buy once. For a trend piece you may wear ten times, CZ makes more sense. And if you want to know how moissanite compares with a diamond instead, read moissanite vs lab-grown diamond.
| You want | Better choice | Why |
|---|---|---|
| Everyday studs or a solitaire | Moissanite | Stays sharp and bright for decades |
| An engagement or anniversary ring | Moissanite | Hardness 9.25, above sapphire |
| A tennis bracelet worn daily | Moissanite | Dozens of stones, all taking knocks |
| A trend piece or tiny pavé details | CZ | Low cost for a look you may change often |
| Jewelry for travel or the beach | CZ | Less to worry about if it gets lost |
When cubic zirconia is the right choice
We use CZ where it makes sense, and we name it. The Ève CZ snake necklace and the Lettre CZ initial necklace are set with cubic zirconia on 925 sterling silver: light, playful pieces meant for layering, where tiny pavé stones matter more for texture than for fire.
Some of our halo and pavé designs also use small CZ accents around a moissanite center, such as the Aura halo studs. The product page always says which stones are which. The center stone, the one you look at, is D color, VVS1 moissanite.
Moissanite for every day, CZ for fun
Choose the stone that lasts
D color, VVS1 moissanite in sterling silver and 14K gold filled, with free tracked shipping on every US order.
Shop all jewelryFrequently asked questions
Is moissanite better than cubic zirconia?
For everyday jewelry, yes. Moissanite is harder (9.25 versus 8 to 8.5 on the Mohs scale), shows more fire and brilliance, and keeps its crisp look for decades with simple cleaning. Cubic zirconia is cheaper and fine for fashion pieces, but it scratches and loses its sharpness with daily wear.
Does cubic zirconia get cloudy?
Cubic zirconia does not change chemically, but it can look cloudy after years of wear. Its softer surface collects fine scratches and its facet edges wear round, which scatters light. Grime in the setting makes it worse. Cleaning helps with the grime, but it cannot undo scratches.
Will cubic zirconia pass a diamond tester?
No. A standard thermal diamond tester measures how fast a stone carries heat away, and cubic zirconia is a thermal insulator, so it fails. Moissanite carries heat much like diamond and passes a thermal tester. A multi-tester that also checks electrical conductivity is needed to separate moissanite from diamond.
How long does cubic zirconia jewelry last?
It depends on how often you wear it. A CZ pendant worn now and then can look good for years. A CZ ring worn daily takes more knocks and usually shows scratches and dull facet edges much sooner. Moissanite and diamond, being harder, hold their polish far longer in the same conditions.
Can you tell moissanite from CZ by eye?
Often, yes, in good light. Moissanite shows stronger rainbow flashes and a brighter white sparkle, while CZ looks a little glassier. The surest home clue is weight: at the same size, a CZ weighs roughly 1.7 to 1.9 times as much. A jeweler's thermal tester confirms it in seconds.
Keep reading
Written by the Daellia Journal team, Paris. We write about moissanite, metals and the stories behind fine jewelry so you can buy with confidence. Read our moissanite guide or our story.
