How do you know a diamond is genuine?

Trine Lamm - diamanter og specialfremstillede smykker

Many transparent stones are similar to each other, e.g. white sapphires, zircon, glass and actually also plastic. So how can we see that a diamond is genuine?

Usually I just need a loupe, and with it I can see if a diamond is a diamond, but I have also seen a lot of diamonds, and of course it requires experience.

What do I look for with the diamond loupe? I check that the facets are sharp and polished. A diamond is the hardest gemstone, and therefore it can be cut perfectly. So I check if the facets are polished completely sharp. If it is a zircon or a piece of glass, the facets will break off a little when the stone is used, they will be worn a little, and this can be seen with a loupe.

This is how the facets look on a zircon or a piece of glass after a short time.

I also check that the facets are not reflected in the diamond, because they shouldn’t be in a diamond.

Otherwise you can use a diamond tester, which is a small “pen” which measures the heat in a gemstone. Diamonds do not heat up as quickly as other gemstones. If it is green, it is a diamond, if it is red, it is not a diamond.

BUT .. the world is never quite so simple and there’s one gemstone which can cheat a diamond tester and that’s a stone called Mossanite. Mossanite completely resembles a diamond, and cheats the diamond tester as the only gemstone. But you can tell that it is not a diamond, in the way it reflects its facets inside the stone. Here you use a diamond loupe. A mossanite will look more “busy” than a diamond. You will immediately know that its not a diamond.


Another piece of advice is to breathe on the stone. On both the fake diamond and the real diamond there will be fog, but the fog will disappear faster on a real diamond.

Finally, you can try to read through a diamond. This can of course only be done with loose diamonds. place the stone upside-down on a page with a lot of text and see if you can read through the stone. If you can decipher the writing through the stone, then it is NOT a diamond. A real diamond will reflect the light and therefore make the text unreadable.

But what about the lab made diamonds that we hear so much about nowadays?

That’s a challenge.

The first thing to realize is that most lab grown diamonds are clearly and responsibly disclosed to be man-made. The big scare in the jewelry industry is non-disclosed lab grown diamonds that are sold as natural diamonds. But, it is important to know that the majority of lab grown diamond manufacturers are perfectly honest organizations that are upfront about their products. Some even laser inscribe all of their diamonds to clearly mark them as lab grown. You will be able to see the certificate number on the girdle.

So lab-grown diamonds are sold by diamond dealers who specialize in man-made diamonds.

The best option to tell if a diamond is man-made is to send it to a specialized lab.

Diamond dealers can sometimes even see the difference, as the diamond is too perfect. They also “grow” in a different way than some natural diamonds, and have a square way of growing which you can see under a microscope.

Some man-made diamonds can be magnetic because there are tiny pieces of metal from the cubic where they have been made, still in the diamond. If you hold a magnet over the diamonds, some of the lab-grown will be attracted. It looks pretty funny.

Some lab-grown diamonds will also continue to glow blue long after they have been exposed to UV light. You may have noticed that when you get your nails done, and have your shellac under UV light, some of your diamonds will glow blue. This is perfectly normal and something we see in 10-15% of all diamonds, but the man-made diamonds will sometimes glow blue even after you have taken your hands out of the UV light. I have seen them light up for 15-20 seconds.

These are some of the tricks I use when determining if a diamond is real or not.

Hope you will find them helpful.

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