--| What is Cubic Zirconia (CZ)? |--
Cubic Zirconia (or CZ) is a that is extremely rare in nature but is widely synthesized for use as a diamond simulant. The synthesized material is hard, optically flawless and usually colorless, but may be made in a variety of different colors. Because of its low cost, durability, and close visual likeness to diamond, synthetic cubic zirconia has remained the most gemologically and economically important diamond simulant since 1976.
Cubic Zirconia vs. Diamond
Cubic zirconia is so optically close to diamond that only a trained eye can easily differentiate the two. There are a few key features of CZ which clearly distinguish it from diamond, some observable only under the microscope or loupe. For example:
- Flaws. Contemporary production of cubic zirconia is virtually flawless. Whereas most diamonds have some sort of defect, be it a feather, included crystal, or perhaps a remnant of an original crystal face.
- Index of refraction. CZ has a lower index of refraction than diamond. This allows more light to leak out of a CZ, especially when greasy or wet. CZ's lower index of refraction causes it to have less luster than diamond.
- Cut. Under close inspection with a loupe, the facet shapes of some CZs appear different from diamonds. A diamond has such a high refractive index that having these facets meet at a single point does not cause much loss of fire or reflection. On the other hand, CZ has a considerably lower refractive index than diamond. CZs are often cut with 6-sided crown main facets, so that the star facets do not touch the upper girdle facets. This optimizes the brilliance and fire of the CZs. The optimum angle of the main crown facets is steeper for diamond than for CZ.