Gemological Institute Of America (GIA) Graduate Diamonds Practice Exam

Are zircon and cubic zirconia considered the same simulant?

Yes, they are the same No, they are different simulants They are both natural gemstones They are types of diamond

Correct Answer:

No, they are different simulants

Explanation:

Zircon is a natural mineral, while cubic zirconia is a synthetic material created specifically as a diamond simulant. They both serve as diamond substitutes, but they aren’t the same substance. Zircon’s crystal structure is tetragonal and it exhibits birefringence, which can cause faint doubled images when viewed through a loupe. Cubic zirconia, on the other hand, is cubic and isotropic, so it does not show birefringence. Differences in refractive index, density, and hardness also separate them: CZ is generally harder and denser than natural zircon, and its fire comes from its very high refractive index and dispersion. Because of these distinct properties, they are considered different simulants.

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