Synthetic cubic zirconia

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Synthetic cubic zirconia
Chemical composition Zirconium dioxide - ZrO2
Crystal system Cubic
Habit Columnar
Hardness 8.25 - 8.5
Optic nature Isotropic
Refractive index 2.171 - 2.177
Birefringence None
Dispersion High, 0.059 - 0.065
Specific gravity 5.65 - 5.95
Pleochroism None

Synthetic cubic zirconia entered the market as a gemstone around 1976 and is till present the most wide used diamond simulant. Although cubic zirconia is found in nature (as minute crystals inside zircon), the more stable variant of zirconia crystallizes in the monoclinic system (baddeleyite).
The main means of syntheses is through the "skull crucible" or "skull melting" method.

Chemical composition

Zirconia has the chemical formula ZrO2, this material however will not crystallize in the cubic system through syntheses. A stabilizer of yttria or calcium oxide needs to be added to the source powder in order to let it crystallize as isotropic crystals.


As synthetic cubic zirconia (CZ) is mainly used to imitate diamond one can expect the main separation techniques to concentrate on distinguishing between the two.