Buying gemstone jewellery is a big investment. Diamonds are timeless, rare, and enduring — a symbol of forever. Cubic zirconia, on the other hand, offers a stunning, affordable sparkle for everyday elegance.
Cubic zirconia is a synthetic gemstone that strongly resembles diamonds to the untrained eye. While a diamond and a cubic zirconia may look alike, they are not all the same. If you’d like to learn how to tell apart these two gemstones, here are 6 ways to tell a cubic zirconia from a diamond: -
1. Check the Metal Setting
One of the biggest differences you will notice between cubic zirconia jewellery and diamond jewellery is the metal setting. Since cubic zirconia jewellery is more affordable than diamond jewellery, the gemstone is often set in metal that may contain nickel or copper alloy. For example, gemstones set in gold plating or gold vermeil are likely cubic zirconia.
Therefore, inspect the jewellery markings to identify the metal before buying anything. If your jewellery metal features a ‘22k’ hallmark stamp, it is likely made of 22 Karat gold. If the jewellery piece features a ‘22k GP’ stamping, it is gold-plated.
NOTE: Diamonds are occasionally set in slightly lower quality metals, so this cannot fully guarantee whether the gemstone is a diamond or a cubic zirconia.
2. Light Test
Another way to distinguish a cubic zirconia stone from a diamond is by placing the gemstone in direct sunlight. Diamonds are known for their brilliant reflection with a grey and white sparkle. Cubic zirconia, on the other hand, has a more rainbow-like reflection.
NOTE: When conducting the light test on smaller gemstones, you will notice that they may not be as brilliant as the larger gemstones.
3. Fog Test
Did you know that diamonds are known for their remarkable heat-conducting ability, but they don’t retain heat well?
Breathe warm air onto the gemstone’s surface and see how long it takes for the fog to fade. If the fog disappears immediately, the gemstone is likely a diamond. If the fog lasts for over 30 seconds, it is likely cubic zirconia.
NOTE: Depending on how clean the gemstone is, you may also notice some water droplets forming on the surface of the cubic zirconia after the test.
4. Sink Test
Fill ¾ of a glass with room-temperature water and drop your loose gemstones into the glass to see if they float or sink. If the gemstone floats on the water surface, it is likely a cubic zirconia. On the other hand, if the gemstone has sunk to the bottom of the glass, it is likely a diamond because diamonds are denser than water.
Once you are finished with the sink test, use a pair of tweezers to retrieve the gemstones so that you won’t lose them.
NOTE: This test will not work if the gemstones are already set in jewellery.
5. UV Light
Did you know that diamonds have a blue fluorescent glow when exposed to ultraviolet (UV) light? Place the gemstone under a UV light. If the gemstone radiates a blue glow, it is a real diamond. If the gemstone doesn’t glow, it is a cubic zirconia.
6. Opaqueness Test
Diamonds are known to have sharp and outstanding refraction when light passes through them, hence giving them a dazzling appearance. Cubic zirconia and quartz gemstones have a lower refractive index.
To test the opaqueness of your gemstone, draw a black line on a piece of white paper with a permanent marker. Then, set your gemstone over the line to see if you can see the line. If you can see the line underneath through your gemstone, it is likely a cubic zirconia. If you can’t see the line, then it is a genuine diamond.
NOTE: This test will not work if the gemstone is already set in jewellery.
In the end, both diamonds and cubic zirconia have their own unique charm. While diamonds captivate with their rarity and enduring brilliance, cubic zirconia offers an affordable sparkle that’s perfect for everyday wear. By learning to spot the subtle differences, you’ll feel more confident identifying each stone and appreciating it for what it truly is.
