How to tell if a Diamond is real?

A common question people ask is “how can I check to see if my Diamond is real?”, usually by people who have just been given a piece of Diamond jewelry!

And it is understandable as you want to be able to tell people that your sparkly new stone is a Diamond but if you start looking for information on Google or YouTube, you can be given some ‘tests’ that you can do at home to help you answer this question.

But honestly, most of this information is complete and utter nonsense (I decided to use a family-friendly word there) and in this post, I am going to provide you with the right information as to how you can find out if your Diamond is real and also debunk most of these ‘tests’ that are spouted about online.

Just to give you a bit of information on me, I’m a fully qualified Gemmologist with the Gemmological Association of Great Britain and passed their Diamond diploma with distinction (so I know a little bit about testing Diamonds).

How To Find Out if Your Diamond is Real?

The only way to know if your Diamond is real is by taking it to a qualified Gemologist, Diamond specialist or Jewelry Appraiser who has the skills, knowledge, experience and equipment to be able to test the stone and tell you if your stone is a Diamond or not, they may also be able to tell you whether it is natural or lab-grown and the quality of the stone such as Color and Clarity.

This is the only way you can know for sure and as with anything specialized, you take to the people who do this day in, day out and gemologists, diamond specialists and appraisers can be found in independent jewelers and pawnbrokers, specialist auction houses, gem labs or they may have their own business.

What is a Fake Diamond?

A large cushion cut cubic zirconia

Fake Diamond is a term I see a lot on the internet and most people talking about this get it completely wrong as the only way a stone can be a ‘Fake Diamond’ is if it not a Diamond but is sold as a Diamond, for example:

  • If a CZ is sold as a Diamond, then it is technically a Fake Diamond
  • If CZ is sold as a CZ, then it is not a Fake Diamond

If the stone is being sold correctly, then from a gemological standpoint, there is no such thing as a Fake Diamond but there are what are known as diamond simulants, which look like a diamond but are a different gemstone, the two main ones are:

  • Cubic Zirconia (CZ)
  • Synthetic Moissanite

This is because these two gemstones have a similar sparkle and overall look to a Diamond but many other gems including glass, quartz, colorless sapphire, white topaz and colorless spinel have all been used as Diamond simulants in the past.

How to Check To See if a Diamond is Real

With training and pretty basic equipment, it is actually quite simple to check to see whether a stone is a Diamond or not. But telling the difference between a Natural and Lab-Grown Diamond does require some advanced (and expensive) equipment along with training to know what you are looking for, so for this post, I’m just going to be looking at identifying the stone as a Diamond.

Below, I will list the process I use when checking a stone to see if it is a Diamond or not and in terms of equipment, all you need is:

  • A 10x Loupe
  • Daylight Desk Lamp
  • Tweezers if the stone is loose
A jewelers loupe and tweezers

Step 1. Clean The Stone

Sounds simple but cleaning the stone makes identification so much easier, if the stone is loose, then you can just use a simple cleaning cloth but if it is mounted in a piece of jewelry, then you can use warm soapy water and a soft toothbrush or an ultrasonic cleaner.

Once the stone has been cleaned, swill it off with clean water and dry with a lint-free cloth and then avoid touching it without wearing gloves, otherwise, you will put grease and fingerprints on the stone.

Step 2: Observation with the Naked Eye

The second step is to simply look at it with the naked eye and when I’m doing this I am checking the sparkle and the luster of the stone as Diamonds of nearly all cuts will have some kind of life to them (this is quite hard to explain).

But with experience, you just know what a Diamond, Synthetic Moissanite or CZ should look like and their visual appearance is different when compared to some other Diamond simulants such as colorless Sapphire, Quartz or Topaz, which can look a little lifeless when compared to the other three stones, even when they are cut well.

Step 3: Observation Using a 10x Loupe

The next step is to look at the stone under 10x magnification and there are four main things that I look for:

1) Look at the Quality of the Cut/Surface Condition

The very first thing I look at is the quality of the cut and the surface condition of the stone as Diamonds and Synthetic Moissanite are hard materials (10 and 91/4 on the Mohs Hardness Scale), meaning that they are less likely to be chipped or scratched than many other simulants, which are softer (CZ – 8 1/2, Topaz – 8, Quartz – 7).

Now Diamonds and Synthetic Moissanite can get chipped and scratched but it is much less likely and if the stone shows quite a bit of damage, then there is a good chance the stone is not a Diamond.

Diamonds and Synthetic Moissanite usually have a better cut quality and will in most cases have very clearly defined facet edges, facets should be a uniform shape, size and symmetry and all the facet points should meet up properly.

Whereas 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, misaligned facets and many extra facets.

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

2) Look for Doubling in the Stone

After looking at the cut quality and surface condition, 99 times out of 100 you will be able to narrow the stone down to being either a Diamond or Synthetic Moissanite (even very well-cut CZs and Sapphires become easy to spot with experience) and this step, once again just using a 10x loupe can help you differentiate between these two stones.

This is because Synthetic Moissanite are what is known as doubly refractive and when you look through the stone at certain angles, you see two of each facet edge on the opposite side of the stone. Whereas Diamonds are singly refractive, meaning you only see one of each facet edge.

It does depend on the style of cut as to where you look through but with Round Brilliants for example, you look through the kite facets at around a 45o angle at the pavilion facets, in a Diamond the facet edges on the opposite side of the stone will be clear and well defined, whereas the Synthetic Moissanite’s facet edges will be hard to see and define and may have a kind of hazy appearance

How to look for doubling in a Diamond
Single Refraction in a Diamond
Single Refraction in a Diamond
Double Refraction in a Synthetic Moissanite
Double Refraction in a Synthetic Moissanite

With some other styles of cut, I have seen this doubling effect through the table of the stone (that one was very easy to identify!).

3) Check for Inclusions

The final check is once again and observation but this time we are looking inside the stone to see if the stone has any inclusion and as flawless diamonds are extremely rare, 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.

In most cases, the use of 10x magnification is enough to determine whether the stone is a Diamond or a simulant but it is the knowledge and experience of doing this more times than I can remember that makes this process relatively simple.

Diamond/Moissanite Testers

So we have to talk about Diamond and Moissanite testers as these are many people’s go-to for ‘testing’ Diamonds to see if they are real, including jewelers but are they reliable?

Before I answer that, I feel I should explain the difference between these two types of electronic tester:

The Diamond tester was developed to help people tell the difference between a Diamond and CZ, it does this by testing the thermal conductivity of the stone as Diamonds conduct heat but CZs don’t but a Diamond tester will not be able to differentiate between a Diamond and a Synthetic Moissanite as they are both thermally conductive.

An electronic Diamond tester
Electronic Diamond Tester

The Moissanite tester was developed to help people tell the difference between Diamond and Synthetic Moissanite by testing the electrical conductivity of the stone as most Diamonds are inert (except for Type IIb Diamonds) but Synthetic Moissanite will conduct electricity but the Moissanite tester will not be able to differentiate between a Diamond and CZ because both are inert.

So individually they both have their limitations but you can get a dual tester that tests for both and this should be the perfect tool right?

Not quite as they aren’t foolproof and things like humidity, dirt and not knowing how to use the tester can give you false results and when combined with some stone complications, including:

  • Synthetic Diamonds that contain Boron, which makes them electrically conductive
  • Diamond coated Synthetic Moissanite (yes, it’s a thing!), which makes the electrically inert

This means that these electronic testers shouldn’t be relied upon, they can be used to give you an idea as the stone might be but it is still best to send it to a professional rather than spending money on a tester that still won’t provide a definitive answer.

Home Test Myth Busting

Now that you know what you should do in order to find out if your stone is a Diamond or not, I’m going to go through explain why most of these ‘home tests’ that all of the top-ranking posts on Google and videos on YouTube are completely pointless!

The Read Through Test (Line or Dot Test)

The first test is the Read Through Test, sometimes called the line or dot test and the premise for this is simple as you take the stone, place it table down on a line or dot and with a Diamond, you shouldn’t be able to see the line and with any other stone you should be able to see the line or dot, just like in the image.

Read through test for Diamonds

But there are some drawbacks to this test:

  1. This only works with Round Brilliant cut stones
  2. The stone has to be loose
  3. Synthetic Moissanite will have a similar appearance to a Diamond
  4. With poorly cut Diamonds, you can sometimes see the line/dot

This means that this test is to flawed to provide any kind of definitive answer but it is still a fun thing to play around with when you have some loose stones.

The Fog Test

This one is a favorite amongst many older jewelers and jewelry professionals as you simply breathe onto the stone so that it fogs up and see how long the fog takes to clear.

The fog test is based on thermal conductivity as thermally conductive stones such as Diamond will clear quicker than thermally inert stones such as CZ, which sounds like it could work but once again there are drawbacks to this:

  1. Diamonds and Synthetic Moissanite are both thermally conductive
  2. Sapphires also have a degree of thermal conductivity
  3. The environment such as temperature and humidity will impact on how quick the fog clears on all gemstones

So, just like with the read-through test, there are too many variables to make this a reliable test.

The Water Test

This one is probably the most flawed test on this list as it is said that a real Diamond will sink and a fake one will float…

The test is basically using specific gravity, which is the density of a material in relation to the same volume of water and any material that is denser than water will sink (trying to not get too scientific here) and the reason why it is flawed is that every gemstone has a SG greater than water, which has an SG of 1.

To put this in perspective, here are the SG’s of Diamond and its popular simulants:

  • Diamond – 3.52
  • Synthetic Moissanite – 3.22
  • Cubic Zirconia (CZ) – 5.56
  • Sapphire – 4
  • Spinel – 3.61

This means that these stones will sink as quickly and in many cases quicker than a Diamond, so a completely pointless test.

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!

Conclusion

When it comes to finding out if your Diamond is real, don’t take the chance by doing stupid and pointless tests at home so that you ‘think’ your Diamond is real, just take it to someone who knows what they are talking about, especially as your Diamond could be worth a pretty penny.

A lot of people are embarrassed to ask but don’t be as we aren’t going to judge you for not knowing, we are there to help answer you question (it’s what we trained for and we like looking at stones) and it is exactly the same as taking a piece of art to a specialist so that they can tell you whether it is genuine or not.

Is My Diamond Real FAQ

Some do and some don’t. Not all natural diamonds fluoresce under UV light and even diamonds that do will vary from very weak fluorescence to very strong. The color of the fluorescence can also vary, the majority will show a blue color but other colors such as yellow and green can also be seen.

Yes, you can scratch a real diamond but only with another diamond. Other gemstones such as Sapphire, Spinel or CZ won’t scratch a diamond. Diamond can be chipped by softer materials though, such as metals like steel.

I'm Paul Haywood FGA DGA, the owner and founder of Diamonds and Dials, I'm a fully qualified Gemmologist and Diamond Grader from the Gemmological Association of Great Britain.

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