How to Tell the Difference Between a Diamond and Cubic Zirconia
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How to Tell the Difference Between a Diamond and Cubic Zirconia
For anyone considering fine jewelry, one of the most common questions is: “How can I tell if a stone is a real diamond or just cubic zirconia?” While both can look dazzling to the untrained eye, there are some very real and noticeable differences that can help you spot the distinction without needing professional tools.
1. The Facet Edges
A facet is one of the many flat surfaces that are cut into a gemstone to bring out its sparkle. On a genuine diamond, the facet edges are extremely sharp and precise—so sharp, in fact, they are almost indiscernible to the naked eye. This crispness comes from diamond’s hardness, which allows it to take a cleaner, finer polish.
By contrast, cubic zirconia (CZ) has facet edges that appear softer and less sharp. Instead of blending seamlessly, they often show up as distinct lines where each facet meets. This creates a less refined look when compared side-by-side with a diamond.
2. The Girdle of the Stone
The girdle is the narrow band that runs around the widest part of a gemstone—basically its “equator.” On diamonds, the girdle is often left rough and unfinished or cut into tiny facets. Both styles are signs of careful diamond cutting.
Cubic zirconia, on the other hand, almost always has a smooth, highly reflective girdle. That mirror-like shine along the edge is a quick giveaway that you might not be looking at a diamond.
3. Facet Abrasion
Because diamonds are the hardest known natural material, they resist wear in ways softer stones cannot. While diamonds can chip under extreme force, they rarely show facet abrasion—the wearing down or rounding of facet edges.
Cubic zirconia, being softer, is far more prone to facet abrasion. Over time, the sharpness of its cut fades, leaving duller edges and less brilliance. If you notice worn-down facets on a frequently worn stone, there’s a good chance it isn’t a diamond.
4. Brilliance and Fire
Diamonds and cubic zirconia also differ in the way they handle light. Diamonds have a high refractive index, giving them a unique brilliance and sparkle that appears crisp and bright white. CZ, however, tends to give off more colorful flashes, sometimes with a “rainbow-like” effect. While pretty, it lacks the refined scintillation of a true diamond.
5. Density and Weight
Cubic zirconia is denser than diamond, which means that a CZ stone will weigh more than a diamond of the same size. Jewelers often use this weight difference to quickly identify stones.
6. Thermal Conductivity
One of the most reliable tests (used by jewelers) is thermal conductivity. Diamonds disperse heat quickly, while cubic zirconia does not. Diamond testers are specifically designed to take advantage of this property.
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Final Thoughts
While cubic zirconia can make for an affordable and attractive alternative to diamonds, knowing the difference ensures you always get what you pay for. By examining facet edges, the girdle, potential facet abrasion, and light performance, anyone can learn to spot the telltale signs.
If you’re shopping for fine jewelry and want the assurance of genuine, high-quality stones, trust professionals who provide transparent details and certification.
👉 Discover authentic, timeless pieces at Tanean Bijl Jewelry—where craftsmanship and honesty shine just as bright as the gems themselves.