Diamond or Cubic Zirconia?

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In the market for jewellery? Before buying anything, read our guide on Diamonds and Cubic Zirconias and make an informed choice!


Gemologists agree that Cubic Zirconia is the finest diamond substitute because it comes closer than any other gem material to matching the characteristics of a diamond. Most people, even trained gemologists, cannot tell the difference with the naked eye.

Below is a short comparison of the actual specifications of Diamonds vs Cubic Zirconias.

Diamond - 10
CZ - 8.5

Refractive Index (Brilliance)
Diamond - 2.417
CZ - 2.15

Specific Gravity
Diamond - 3.515
CZ - 5.8

Almost a Diamond?
In appearance, cubic zirconia looks almost exactly like a good quality diamond, although there are some slight differences:

Fire and Brilliance
CZ has slightly less brilliance (sparkle) than diamond, while having more fire (flashes of rainbow colors). The overall effect is so similar to diamond that trained gemologists often require special equipment to tell them apart.

There are very few substances on earth harder than CZ. With a hardness rating of 8.5, CZ comes closer to matching diamond�s perfect 10.

CZ is about 75% heavier than diamond. As such, a CZ�s size is referred to in carats only as in comparison to diamonds. CZs are more accurately measured in millimeters, referring to the diameter. (A 6.5 mm cubic zirconia is equal in size to a one-carat diamond and actually weighs about 1.75 carats.)

Because CZ is grown in a laboratory in a controlled environment, any crystals that fall short of perfect clarity are simply not used. The finest CZ gems are perfect in clarity.
Overall, a top quality Cubic Zirconia can look as good or even better than a Top Quality Diamond. With more Fire and Sparkle than the average Gemstone, Cubic Zirconias are the best option for the fashion forward on a tight budget.

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