At first glance Moissanite resembles diamond and might be mistaken for a diamond, a synthetic (lab grown) diamond or diamond simulant (CZ). When compared with cubic zirconia or CZ (perhaps the world's most popular diamond simulant), the differences are obvious. CZ is an inexpensive simulated diamond look-alike, inferior in almost every gemological property to Moissanite. CZ is mass produced under a myriad of trade names and promoted with various brand names. Please refer to the next section: Commonly Marketed Gemstones & Diamond Alternatives.
CZ is too soft
Hardness is the resistance of a gemstone to being scratched or the facets being worn down. Compared to Moissanite, CZ has less than one half (45%) the hardness of Moissanite as measured using the Knoop indention test: 1370 kg/mm2 vs. 3000 kg/mm2. Therefore, Moissanite is 219% harder. Because CZ scratches easily, it can lose its surface luster after just a few months or years with regular wear.
Although CZ sellers boast that CZ can scratch glass, many gemstones and jewels are ranked above glass in hardness and can easily scratch it as well. Therefore this is no amazing feat.
CZ is not tough enough
Toughness is the resistance to chipping and breaking. Compared to Moissanite, CZ has only 1/3 the toughness: 2.4 PSI compared to 7.6 PSI. Therefore Moissanite is over 300% more resistant to chipping.
Therefore given the substantially inferior hardness and toughness of CZ, it will have a finite life. Given Moissanite's very high hardness and toughness, it will not scratch, chip and wear like a CZ, and with a little care, it will last a lifetime and beyond.
CZ has inferior optical properties
The beauty and sparkle of engagement gemstones is found in their brilliance, fire and luster.
Moissanite is known for its high refractive index of 2.69, which is 25% greater than the refractive index of a CZ. The higher the refractive index of a gemstone, the more brilliance the jewel emits. Therefore, Moissanite's brilliance easily out performs CZ.
Moissanite's dispersion of 0.104 is 58% greater than a CZ (0.044). Therefore Moissanite emits more fire, or flashes of rainbow colored light, than CZ.
The luster of Moissanite is 50% higher than that of CZ. The higher the luster, the greater the amount of light reflected from the surface of the gemstone.
In summary, Moissanite has significantly higher brilliance, fire and luster than CZ.
Optical Anamolies: Windowing
The lower refractive index of CZ causes the stone to exhibit substantially more "windowing" than a Moissanite or diamond and gives CZ what many women refer to as a "glassy" appearance.
Windowing is an optical phenomenon that occurs when light passes through a gemstone without being refracted. If windowing is present in a gemstone the observer can look through the stone at certain angles as if it were a window or can observe large dark areas in the stone (caused by light leaking out the window).
A well cut stone should reflect so much light that nothing is seen behind it. However this statement presumes that you are looking straight down through the top of the stone, and the stone is not tilted at all. Tilting the stone even slightly will change the angles of light hitting the pavilion facets. Each type of gem has its own range of "tilt brilliance". The lower the refractive index the less tilting it takes to window the stone. Since the refractive index of CZ is substantially lower than Moissanite (1.8 - 2.17 compared to Moissanites 2.69), the result is that although a CZ may look pretty when viewed from the top, but when viewed at various angles many dark or black spots can appear, making it easy to spot as a "fake".
CZ strong affinity to dirt
CZ has a very strong affinity to dirt. Another reason many consumers feel that CZ quickly loses its luster and "looks cloudy" is because hand oils, cosmetics, etc. will quickly cling to the gemstone. Given the inferior refractive index of a CZ compared to a diamond or Moissanite, even a little bit of dirt can make the CZ appear dull or lifeless. This in turn requires the wearer to have to clean it often, we have had customers tell us even multiple times a day, to keep it sparkling. Although Moissanite can get dirty with time, it is much more resistant to dirt than CZ and even a diamond, which means it will stay cleaner longer.
CZ lacks stability and durability
CZ is sensitive to heat. When exposed to too much heat, CZ stones will shatter and turn a very opaque, milky color. This can be a problem if you would like to make modifications to your CZ jewelry such as ring sizing. Many jewelers will refuse to perform repairs on CZ jewelry.
Cubic zirconia also naturally tries to bond with CO2 and water which can lead with time to clouding on the surface of the stone.
Conclusion
In the end, CZ is great for cheap fashion jewelry, but is simply too soft for jewelry if you intend to wear it frequently (i.e. bridal jewelry), it has too strong an affinity to dirt, and its optical properties (luster, fire and brilliance) all fall short when compared to a Moissanite. Unlike Moissanite and diamond, CZ will not stand the test of time.
| Toughness | Moissanite is 317% more tough (less likely to chip) |
| R.I. (Brilliance) | Moissanite is 25% more brilliant |
| Fire (dispersion) |
Moissanite has 58% more fire |
| Luster |
Moissanite has 50% more luster |
| Windowing |
CZ demonstrates obvious windowing, giving it a glass-like appearance. Moissanite displays less windowing than even diamond. |
| Affinity to Dirt: | Moissanite requires substantially less cleaning |
| Durability | Unlike CZ, will not shatter when jeweler applies heat |
| Stability: | Unlike CZ, will not react with CO2 and water |