Real Diamonds vs. Cubic Zirconia

Cubic zirconia is a synthetic stone that closely resembles diamonds. Compositionally, cubic zirconia (CZ) is the cubic crystalline form of zirconium dioxide. The gemstone is hard, optically flawless, and typically colorless, though it can be made in a number of different colors. Because of the uncanny resemblance between CZ and real diamonds, CZ has become an extremely popular and more affordable alternative to real diamond jewelry. In this post, we’ll discuss some of the differences between CZ and real diamonds and explain how you can tell the difference between them.

CZ vs. Diamonds: Physical & Chemical Properties

Cubic zirconia has a few key features that differentiate it from diamonds, most of which can only be observed at microscopic levels.

  • Dispersion - CZ has a dispersive power of 0.06 compared to diamond’s 0.044, which means the brighter prismatic fire of CZ can usually by seen by the naked eye.
  • Hardness - CZ has an 8.5-9.0 hardness rating compared to 10 for diamonds.
  • Specific gravity - CZ weighs more than diamonds. A CZ will weigh an average of 1.7 times more than a diamond of the same size.
  • Flaws - CZ is virtually flawless, whereas the majority of diamonds have some sort of defect.
  • Refractive index - CZ has a refractive index of 2.176 compared to 2.417 for diamond.
  • Color - CZ is usually entirely colorless, a quality only present in the rarest of diamonds.
  • Thermal conductivity - CZ is a thermal insulator, while diamonds are thermal conductors.

Testing the Difference

To the naked eye, there is virtually no difference between CZ and real diamonds. The only test one might try is to look at two stones and see which outshines or outsparkles the other. With CZ, the shine will be more brilliant than a real diamond because of CZ’s higher rate of dispersion. All other tests to tell the difference require a jeweler’s loupe or microscope. Jewelers will look at the stone under magnification to see if it has any inclusions, or flaws. These will be absent in CZ but are present in almost all diamonds. If you’d really like to know whether your stone is CZ or a real diamond, take it to a professional jeweler. Usually, jewelers do not charge for this service and can make a quick assessment. If he is unsure, he can recommend that you send the stone to a gem lab for accurate identification.

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