Moissanite vs Cubic Zirconia: How to Tell Them Apart
Moissanite and cubic zirconia are both made in a lab, both are clear and bright, and both are used in place of diamond. From across a room they can look alike. Up close they differ in what they are made of, how they handle light, how hard they are and how they look after years of wear. Here is how to tell them apart and where each one belongs in a ring.
What each stone is
Moissanite is silicon carbide. It was first found in 1893 in a meteorite crater, and natural moissanite is far too rare for jewelry, so the moissanite in rings today is created in a lab. Cubic zirconia, or CZ, is zirconium dioxide grown into a cubic crystal. It became widely available in 1976 and became a popular diamond imitation, because it is clear and inexpensive to make.
The two are different materials with different properties:
| Moissanite | Cubic zirconia | Diamond | |
|---|---|---|---|
| Material | Silicon carbide | Zirconium dioxide | Carbon |
| Refractive index | 2.65 | 2.15 to 2.18 | 2.42 |
| Dispersion (fire) | 0.104 | 0.058 to 0.066 | 0.044 |
| Mohs hardness | 9.25 | 8 to 8.5 | 10 |
| Specific gravity | 3.22 | 5.6 to 6.0 | 3.52 |
The cubic zirconia figures are from the Gemological Institute of America.
Sparkle
Shown: Charlotte Round Moissanite Side Stone Engagement Ring
The refractive index measures how strongly a stone bends light, and a higher number means more white light comes back to your eye. Moissanite's 2.65 is higher than diamond's 2.42, and cubic zirconia's 2.15 is lower than both. Dispersion measures how much a stone splits light into rainbow colors, which jewelers call fire. Moissanite's dispersion is about 1.6 to 1.8 times that of cubic zirconia.
In practice, moissanite looks brighter and throws more colorful flashes, especially in sunlight and in larger stones. Cubic zirconia sparkles too, with a softer, less lively light.
Hardness and how they age
Hardness decides how well a stone keeps its polish. Moissanite scores 9.25 on the Mohs scale, second only to diamond. Cubic zirconia scores 8 to 8.5, and the GIA describes it as somewhat brittle.
That gap shows over time. A ring meets countertops, keys and grit every day. Over years of daily wear, a cubic zirconia's facet edges can pick up small nicks and its surface fine scratches, and the stone looks less crisp. Moissanite resists that wear and keeps its polish.
A cloudy look is a different matter. On any stone, it usually comes from a film of skin oil, lotion and soap on the surface, and a soak in warm soapy water clears it. Scratches do not wash off, and the softer stone collects them sooner.
How to tell them apart
- Fire. Moissanite shows noticeably more rainbow color when it moves. Look at both stones side by side in daylight.
- Doubled facets. Moissanite is doubly refractive, so through a jeweler's loupe its back facet edges can look doubled from some angles. Cubic zirconia is singly refractive and shows no doubling.
- Weight. Cubic zirconia is much denser. A cubic zirconia weighs about 1.7 to 1.9 times as much as a moissanite of the same size, so a jeweler with a gem scale can tell them apart quickly.
- Testers. A basic thermal diamond tester reads moissanite as diamond, because moissanite also conducts heat very well. Cubic zirconia fails the same test. A multi-tester that also measures electrical conductivity identifies moissanite. See how diamond testers work.
Price
Cubic zirconia is the least expensive of the three. Moissanite costs more than cubic zirconia and far less than a diamond of the same size. What the extra cost buys is the harder stone, the stronger fire and a polish that lasts.
Where each one belongs in a ring
Shown: Gillian Cushion Cut Moissanite Halo Engagement Ring, with a moissanite center and cubic zirconia accent stones
The center stone carries an engagement ring. It is the largest stone, the one people look at, and the one that takes the most wear, so it is where moissanite's hardness and fire matter most. Every center stone in our engagement rings is moissanite.
On some of our designs, the small accent stones in the halo or along the band are cubic zirconia. Stones that small show much less of the difference in fire, and using cubic zirconia there keeps the price of a ring set with dozens of stones within reach. Other designs, such as the Charlotte above, use moissanite throughout.
Whichever you choose, the care is the same: clean the ring every few weeks in warm water with a little mild soap and a soft brush, and take it off for workouts and heavy work. Our jewelry care guide has the details.
Common questions
Is moissanite better than cubic zirconia?
For a ring you wear every day, yes. Moissanite is harder, so it keeps its polish far longer, and it has more brilliance and fire. Cubic zirconia costs less and suits fashion jewelry and small accent stones.
Will cubic zirconia pass a diamond tester?
No. Cubic zirconia does not conduct heat the way diamond does, so a thermal diamond tester reads it as a simulant. Moissanite can pass a basic thermal tester, and a multi-tester identifies it.
Does moissanite get cloudy?
No. Moissanite does not cloud over time. If it looks dull, it has a film of oil or lotion on it, and a clean brings the sparkle straight back.
Can you tell moissanite from cubic zirconia by eye?
Often, yes: moissanite throws more rainbow fire, and the difference grows with the size of the stone. To be certain, a jeweler weighs the stone or uses a tester.
To see how moissanite compares with diamond, read Moissanite vs Diamond or Why Moissanite. For another clear alternative, see Moissanite vs White Sapphire. Browse our moissanite engagement rings.
Share