How to tell if a Diamond is real?

How to Tell if a Diamond is Real

Is my Diamond real? This is one of the questions I get asked the most and is the reason why I created this blog post.

Another inspiration for this post was reading some of the articles online that rank on page one of google that simply give bad information and advice. So as a diamond specialist and a diamond grading tutor, I decided to write a post containing accurate information to help you.

Take it to a Jewellery Professional

Quick tests at home are a good way to give you an idea if your diamond is real or not but honestly, the best way to tell if your diamond is real, is to take it someone who knows what they are talking about.

Being able to accurately identify not only whether or not the stone is a diamond or not, along with assessing the quality of the stone takes a lot of training and experience.

The best people to take it to are jewellery valuers, gemmologists or diamond graders and these can be found in independent jewellers and pawnbrokers, specialist auction houses, gem labs or they may have their own business. An experienced jeweller should also be able to tell the difference.

What is a Fake Diamond?

I see this term a lot on the internet and from a gemmological standpoint, there is no such thing. Instead we call them diamond simulants as they look like a diamond but are a different gemstone, the two main ones are:

  • Cubic Zirconia (CZ)
  • Synthetic Moissanite

Many other gemstones including glass, quartz, colourless sapphire, white topaz and colourless spinel can all be used to imitate diamond but for this post, I will stick to the main ones listed above.

How to Check That Your Diamond is Real

Use an Electronic Tester

Electronic testers are not always 100% accurate but they do provide a way to quickly and easily test a stone and are a popular tool with jewellers and pawnbrokers.

If you are going to buy an electronic tester, then you want to go for a dual tester as this will give you the most accurate results. Separate diamond and moissanite testers do have their limitations.

A diamond tester will not be able to differentiate between a diamond and moissanite.

A moissanite tester will not be able to differentiate between a diamond and a CZ.

Before using your electronic tester, always read the instructions so that you know how to use the tester properly and also what results you can get from it.

*The tests below will give you an indication of whether or not your stone is a Diamond but a trained professionals opinion should still be sought*

The Read Through Test (Line or Dot Test)

One of the quickest and easiest tests you can do. All you need is a loose gemstone and a piece of lined paper, place the stone table (the large facet on the top of the stone) down with the line running approximately through the middle of the stone.

If the stone is a Diamond or Synthetic Moissanite then you will not be able to see the line, if the stone is a CZ or any other type of simulant then you will be able to see the line through the stone.

*This test only works with Round Brilliant Cut Diamonds

Weigh the Stone

We use a unit of measurement called carats for describing the weight of a gemstone and all gemstones have different density, which means that stones of the same size but of different material can have different weights.

And it is for this reason that weighing the stone on specialist carat scales can indicate if you have a diamond or not. There are many websites that have charts for diamond weights and many cover all different styles of cut but I will give you a couple of examples:

  • 4mm Round Brilliant Cut Diamond = Approximately 0.25 carats (25 points)
  • 5mm Round Brilliant Cut Diamond = Approximately 0.5 carats (50 points)

If you weigh a 5mm round stone for example and it weighs a lot more or less then you probably do not have a diamond as a diamond weights in relation to size only usually vary a little.

The Fog Test

A favourite amongst many older jewellers and jewellery professionals. You simply breath on to the stone and see how long the fog from your breath takes to clear.

Diamonds have excellent thermal conductivity and will quickly dispel the heat from your breath, usually 1-3 seconds but unfortunately Synthetic Moissanite will also clear quite quickly. If the fog takes longer than 5 seconds to clear then the stone is probably not a diamond.

Check for Damage

For this you will need some form of magnification, the best being a jewellers loupe or eye glass with 10x magnification.

Diamonds are the hardest natural material known to man and that means that they are less likely to be chipped or scratched, even after being worn for many years, than than their simulants.

If the stone shows quite a bit of damage, such as chips, scratches or abrasions then it there is a good chance that the stone is not a diamond.

Look at the Quality of the Cut

Due to the combination of Diamonds being very hard and also very valuable, a lot of time, care and attention is taken when the stones are cut and polished.

This means that diamonds will have very clearly defined facet edges, facets should be a uniform shape, size and symmetry and all the facet points should meet up properly.

Sharp Facet Edges on a Diamond
Sharp facet edges on a Diamond
Poorly Cut CZ
Poorly Cut Facets on a CZ

With many of the cheaper simulants such as CZ’s, not as much care is taken when cutting and finishing the stone and you will often see that the facet edges have a more rounded appearance, facets can vary in size and shape, lack of symmetry, mis-aligned facets and many extra facets.

Check for Inclusions

Flawless diamonds are extremely rare so there is a chance that you might see inclusions if you have a diamond.

An inclusion is an imperfection within the stone, there are many different types of inclusion that can be found in a diamond and rather than list all of them, I have included a link below to a list of inclusions by the GIA:

GIA list of inclusions

Looking for inclusions does take some practice and in Diamonds with good clarity such as VS or VVS, you will struggle to see them, however with SI and I clarity stones you will be able to see them.

Typically you will not see any inclusions in CZ’s or Synthetic Moissanite as they are both man made and the process has been refined to remove any inclusions.

Look for Doubling in the Stone

The tests mentioned above are all really focused on telling whether or not you have a diamond or a cz. This is because telling a diamond and synthetic moissanite apart is a little more challenging.

Synthetic Moissanites are usually cut and polished to a good standard and as they are harder than cz, they are less likely to get damaged but fortunately there is one definitive test you can do to tell them apart from a diamond.

How to see doubling in a synthetic moissanite

You want to look at the stone in the way described in the image above using a 10x loupe and if you have a Diamond, the facet edges on the opposite side of the stone will be clear and well defined.

If you have a synthetic moissanite then the facet edges will be hard to see and define and may have a kind of hazy appearance, this is because you are seeing two of each facet edge, which is why it is called doubling.

Single Refraction in a Diamond
Single Refraction in a Diamond
Double Refraction in a Synthetic Moissanite
Double Refraction in a Synthetic Moissanite

Pointless Home Tests

Now there are a lot of articles online with some tests that you can do at home, that honestly will just be a waste of your time and I will tell you why below:

The Water Test

This is where you put the stone in a glass of water and apparently a real diamond will size but a fake one will float. This is completely untrue as pretty much every diamond simulant will sink and a CZ, Synthetic Moissanite, White Sapphire and Colourless Spinel will all sink as fast, if not faster than a diamond.

The Heat Test

Possibly the most idiotic test out there! This is where you heat the stone up and then drop it into cold water and a fake diamond will break, according to the internet.

Well a Diamond can break if you do this as well, yes diamonds disperse heat quicker than a cz, spinel or quartz but there may be inclusions in the diamond that heat and cool at different temperatures that can cause the diamond to break and honestly who wants to try and intentionally break a gemstone?

Checking the Sparkle of the Stone

This is flawed on so many levels. First off, unless you have a diamond of the same shape and size to compare it to, how will you know if the stone you have sparkles more or less?

Secondly, the sparkle of a diamond varies from stone to stone, it all depends on the quality of the cut and the number of inclusions.

Thirdly, some styles of diamond cut such as Emerald and Baguette cut hardly sparkle. As you can see, this really is a useless test!

What about Synthetic Diamonds?

Synthetic diamonds are becoming more and more common in the world of jewellery, but how can you tell if your diamond is natural or synthetic?

Unfortunately telling the two apart requires far more advanced equipment that costs thousands of pounds and there are not simple visual tests to tell which one is which but advancements are being made and the equipment is becoming cheaper and more accessible, so more and more jewellers and pawnbrokers will have equipment that can indicate the origin of your diamond.

Is My Diamond Real FAQ


I know that the tests above are far more in depth than most of the other guides out there but what makes this one different is that I teach people how to do this, using the tests I have mentioned above.

Once again, I do want to re-iterate that if you want a definitive answer to your whether your diamond is real or not, please take it to a professional.

Want to Learn More About Diamonds?

If so, I have created an Introduction to Diamonds online course, that takes you through all the basics when it comes to Diamonds, just click the link to check it out!

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