How to tell if a diamond is real or fake | Gillian’s Jewellery

Mirror-Back Stones

Firstly, let’s talk about mirror-back stones, which some people refer to as rhinestones. These are diamond simulants that are widely used in costume jewellery. As you can see in the attached video, there is a layer of shiny material on the back of the stone. In most cases, when you find them, half of the layer has already worn off. This is because they are typically fully glued onto the clear plastic stone, and the shiny part has pressed onto the surface. Then, when they come apart, half of the shiny piece remains on the surface while the other half remains on the stone. This wouldn’t happen with a genuine diamond, so it’s a sign that this would potentially be fake.

Cubic Zirconia, or CZ

The second type is called Cubic Zirconia, or CZ, which are synthetic stones created in a laboratory. They are popular alternatives to diamonds because they are dazzling and sparkle like diamonds when exposed to light. Most importantly, they are, as expected, more affordable than diamonds. Cubic Zirconias are hard stones and are often compared to diamonds, but they are softer as diamonds are the hardest gemstone type material in the world. 

How You Can Check

Inclusions, Imperfections

Genuine diamonds usually have inclusions, which are more imperfections within a diamond, and that is the unique identification of each diamond, almost like a fingerprint. This will be discussed in another future post video stay tuned.

Look for Shiny, or Yellow, Material

Coming back to the point, if you ever come across a stone and you’re unsure whether it’s real, then the first thing we’ll ask you to check is if there’s any shiny or yellow material on the back of the stone. If there is, it’s highly likely to be a rhinestone, and you can also use the following simple technique to confirm this without a loupe.  

Looking through your diamond

If the stone is clear, draw a line on a piece of paper and put the stone upside down on top of it as shown in the video. If you can still clearly see the line through the stone, then it’s more likely to be a CZ.  If it’s a real diamond, then you probably can’t tell what’s underneath.

Sandpaper test… but

Another straightforward way to test a stone’s authenticity is to use sandpaper.  Here’s what you need to do, place the stone upside down and move it back and forth on the sandpaper. If you see scratches on the stone, it is a CZ.  If there are no scratches at all, it is likely a diamond. However, it’s important to note that if the stone is not a diamond, it is very likely that the stone will be damaged by this test.  Our suggestion is to use this only as a last resort or ask a professional jeweller.

These are some basic tips that you can use to examine a stone by yourself. Diamonds are a topic that we have spent two years studying and working on, which has provided us with a solid understanding due to our experience and staying up to date with information from the trade. It’s not possible to become a diamond expert simply by reading a couple of articles or conducting research online. Therefore, we recommend finding a local professional jeweller who is experienced and qualified to provide advice if you are looking for a genuine diamond.

Learning How to Choose A Nice Diamond