How To Tell Cubic Zirconia From Diamond

Cubic zirconia and diamond are popular gemstones for engagement rings and other jewelry. Both can be cut into various shapes and sizes and set in different types of metal settings. However, while both gemstones may look quite similar, some ways to spot cubic zirconia from diamonds exist.

What is Cubic Zirconia?

Cubic Zirconia, also known as CZ, is a crystalline form of zirconium oxide. It is a colorless, much less expensive man-made gem that appears quite like a diamond. In fact, to an untrained eye, it can be challenging to tell the two apart. While these stones may look similar, they have very different mineral structures - diamonds are carbon, and CZs are zirconium dioxide. And it is for this reason that CZ is categorized as a diamond simulant or diamond alternative.

How to Tell Cubic Zirconia from Diamond

As mentioned above, cubic zirconia is often praised for its diamond-like appearance. To the naked eye, they look quite similar. The ultimate way to tell them apart is to take them to a jeweler or gemologist who will be able to test them with official equipment. However, there are also a few inspections you can make at home that will give you a good guess between the two.


Cubic zirconia tends to be completely colorless, while diamonds can range in color from completely colorless to yellow or brown and are graded on a scale from D to Z, where D signifies a completely colorless stone. Since cubic zirconia is man-made, manufacturers control the whole process. CZ can be made flawless, while diamonds will always have some tiny inclusions or blemishes. However, most people prefer the look of a diamond with flaws, as they feel it makes the diamond look more ''real'' and unique. 

If you look at both stones under natural light, a diamond gives off a white light (brilliance), while cubic zirconia disperses light into rainbow colors. This excess dispersion is due to cubic zirconia's much lower refractive index (2.171 – 2.177) than a diamond (2.417 – 2.419) and a higher dispersion (0.058 – 0.066) than a diamond (0.044).


Diamonds are the hardest known natural material on Earth, rating a 10 on the Mohs hardness scale, while cubic zirconia rates an 8-8.5. This difference in hardness means that cubic zirconia will scratch more easily than a diamond.

In cut stones, cubic zirconia tends to have dull, rounded edges, while diamonds' facets stay sharp. Diamonds rarely show polish marks, but if they do, they will be in different directions on different facets. On the other hand, cubic zirconia will show polishing marks in the same direction on adjoining facets.


Since diamonds are much harder than cubic zirconia, they are more difficult to cut and polish, adding to the cost. A flawless 1-carat diamond cost about $7000 or more, while a flawless 1-carat cubic zirconia can be purchased for less than $20. Lab-grown diamonds often cost almost half of a mined one, but still, they are much more expensive than CZ. However, unlike CZ, diamonds retain some market value and can be passed down for generations as a family heirloom and keepsake. 

The Bottom Line

Cubic Zirconia and diamond are very similar. However, some key characteristics set them apart. They include appearance, hardness, and cost. Cubic zirconia is a good choice if you are looking for a cheaper alternative to diamonds that still looks beautiful. However, diamonds are the better choice if you're looking for a harder and more valuable stone.

But whichever path you take, it's important to know what you're getting into. You can contact Scott & Co. Fine Jewelers to learn more or visit our store in New Oxford and choose your custom jewelry design.