Diamond Tester

How Do Diamond Testers Work?

You may get embarrassed by them or elevate your confidence; either way, diamond testers are there to help you know whether you are putting on an authentic piece of jewelry or a cheap copy. Diamond testers have become extremely popular thanks to YouTubers and other TV presenters. Having somebody walk up to you with a camera and a diamond tester may not be the most pleasant experience if you know your diamond is not real. However, if you are confident about the authenticity of your jewelry, then having a YouTuber walk up to you with a diamond tester would be a great feeling.

 In gemology (the study of gemstones), it is important to tell the difference between minerals by their physical properties. A refractometer or a spectrophotometer can be used to determine if a diamond is real by the way it reflects light, but these types of equipment are too bulky. They would be inconvenient to move around, so diamond testers were introduced to detect an authentic diamond accurately. 

In this article, I will be shifting the spotlight from the diamonds to the diamond testers; we will take a closer look at this item, how it is produced, and how it functions.

What Is A Diamond Tester?

You may have seen a YouTuber walk up to someone with a portable device to confirm the authenticity of their diamonds; well, that’s basically what a diamond tester is; it is a small device that is used to check if a gemstone is an authentic diamond based on the way it conducts thermal or electrical energy. Most diamond testers would only test for one of these energies. In contrast, an advanced diamond tester would implement both testing methods to determine if a gemstone is an authentic diamond accurately.

How Does A Diamond Tester Work?

Diamond testers are usually small rectangular devices with a built-in light display and a pointy tip similar to a needle; this tip needs to be placed on the gemstone. If it is an authentic diamond, it would indicate that with a light or a sound. You have to gently place the needle on the stone for a couple of seconds. The diamond tester would calculate the thermal conductivity of the stone, and if it is an actual diamond, it will give off beeping sounds accompanied by a red or green light.

People who study gemology or mineralogy would know that different gemstones conduct heat differently, so a diamond tester takes advantage of the fact that a diamond would conduct heat differently from glass or cubic zirconia. The diamond tester would transmit heat into the stone and calculate how fast the heat travels around the stone to get an accurate result. This process happens from half a second to a full second, with newer diamond testers becoming even faster. 

Some modern diamond testers also measure the electrical conductivity of gemstones; it is then combined with the result from the thermal conductivity test to determine if the gemstone is an authentic diamond.

Diamond Testers Versus Synthetic Diamonds

A diamond tester would detect a diamond simulant like cubic zirconia or rutile, but it will not be able to distinguish between a real diamond and a lab-grown diamond; this is because a lab-grown diamond has the same physical properties as a naturally formed diamond; its major component is carbon, and it is also as hard as real diamonds.

Another gemstone that will fool the diamond tester is moissanite. Moissanite looks very similar to diamonds in appearance; it is also nearly as hard as diamonds. It is the second hardest material on earth after diamonds (diamond comes in at ten on the Mohs scale, while moissanite follows behind at 9.25).

How To Differentiate Between Simulated And Real Diamonds?

We can agree that not everyone possesses a diamond tester, and not everybody is willing to walk around with a diamond tester in their pockets. If you try to get a diamond from an individual but you are not sure whether it is a simulated or authentic diamond, there are some simple tests you can conduct to ascertain whether the diamond is real or fake.

These tests are very easy and fast to conduct, so you don’t need any fancy equipment or skill, and you do not need a diamond tester for these tests.

Look for imperfections –  Naturally formed diamonds may not always be perfect; they usually have some internal imperfections beneath that perfect external surface, making them unique. However, an artificially engineered gemstone is made to look expensive, so it is usually flawless. Natural diamonds get these internal imperfections because of environmental factors during their formation.

Tip: place the stone in question underneath a microscope and check for internal or external imperfections. Take note that these imperfections are not surface scratches.

Check how the stone reflects light – Simulated diamonds like moissanite and cubic zirconia tend to sparkle a lot due to their higher refractive index; they give off a rainbow-like light reflection which may be spotted if the stone is inspected closely. On the other hand, real diamonds do not sparkle as much as these simulated diamonds, and they tend to give off only white lights when they sparkle.

Tip: Hold the stone directly under a light source and check if you would get a multicolored light reflection.

Conduct a scratch test – Diamonds are the hardest material on earth; they are durable and resistant to scratches, whereas most simulated diamonds wear out with time. You would not notice visible scratch marks on diamonds, so before making a purchase, confirm if the gemstone scratches easily; if it does, you are looking at a simulated diamond and not an authentic one.

Tip: rub the gemstone against sandpaper; if you notice smudges or a lot of scratches, then it is a diamond simulant and not the real thing.

Check if it is foggy – diamonds conduct heat excellently, so they will not retain any fog the same way a simulated diamond would. If you have ever blown hot moist air on your mirror or sunglasses, you will notice how it retains fog for some time before it slowly fades away, diamonds do not do this, so it is an excellent way to know fake diamonds.

Tip: bring the diamond to a place with a neutral temperature and blow hot moist air onto the diamond; immediately take a close look at the diamond to spot if it accumulates fog on the surface.

Do a water test – authentic diamonds are very dense, while simulated diamonds are not. This will be good to keep in mind when getting a diamond. If an authentic diamond is placed on water, it will sink to the bottom while a simulated diamond will not.

Tip:  get a cup of water and gently place the stone on the surface; if it sinks to the bottom of the cup, it is likely a real diamond.

The newspaper test – as you already know from the last paragraph, authentic diamonds are very dense, which also affects the way light passes through them. If you place a diamond on a sheet of newspaper, you will not get to see the paper. In contrast, a simulated diamond-like cubic zirconia is clear enough to allow you to see what is in the newspaper.

Tip: place the stone on a sheet of newspaper and slowly move it around; if you can read the newspaper’s content, then you have cubic zirconia and not an authentic diamond.

Why Do You Test For An Authentic Diamond?

Real diamonds, synthetic diamonds, and simulated diamonds all look alike. Still, it is good to get value for money when it comes to buying diamonds, and there is no better way to do this than getting an actual diamond worth the price. You may be wondering why you need to get a real diamond when you could get a copy and save up a couple of hundred dollars; well, there are some reasons why people pick real diamonds over their cheap copies, and I’ve listed some below.

Real diamonds are good investments – diamonds not only serve as a fashion accessory, but you can also resell diamonds if your finances are low. The cost of diamonds is constantly rising, and it appreciates up to 10% every year. This is a good thing to consider when getting a gemstone, and this is why you need to strive to get an authentic diamond rather than a cheap copy. However, getting a real diamond may not be as easy as it seems. With all the synthetic and simulated diamonds in the market, it is advisable always to test diamonds before you purchase them.

Real diamond symbolizes wealth – real diamonds are very expensive. Unlike their synthetic counterparts, they have real history, and getting your hands on one may be a challenge because they are rare. So whenever an authentic diamond enters the market, it usually comes with a hefty price tag that only the rich and those looking to make a statement can afford. Different people buy diamonds for different reasons, but we are all aware that a rare and expensive diamond makes a very strong statement about a person’s class.

Diamonds are perfect for that special occasion – engagement rings usually come with a diamond center stone; this is because diamonds have become the global symbol of commitment and love. The diamond engagement rings gained more popularity after a successful advertising campaign by the diamond company “De Beers.” The advertisements had a slogan that read, “a diamond is forever,” emphasizing the durability of these gemstones. Another reason people seek a diamond ring when getting engaged is because of its aesthetics.

Real Diamonds are very durable – just as I mentioned in the last paragraph; diamonds are very durable, they are the strongest material on earth, and they rank ten on the Mohs hardness scale. Getting a durable stone means it can still retain its physical properties for generations to come, so people often buy diamonds in hopes of reselling them for a higher price or passing them on to their kids.

Simulated diamonds may not be able to stand the test of time, so it is always advisable to get an authentic diamond if you are financially capable of affording one.

Things To Know When Using A Diamond Tester

  • A real diamond may not test positive for the first time if the stone is cold. It is always good to test and wait a minute or two before testing the stone for a second time.
  • If the diamond tester is not turning on, if it keeps the indicator on but does not warm up, or if it gives off a continuous buzzing sound, consider changing the battery. A good quality alkaline battery such as UCAR, Duracell, or Procell would do the trick. They are pretty cheap too.
  • Most diamond testers would become less sensitive if they had a dirty tip. You can clean the tip of the diamond tester by tilting it at a right angle and rubbing it in circular motions on a clean piece of paper.
  • Clean the stone before you test it. You should not do this with soft fabric if you use an older tester because you will add a layer of dirt to the stone, which may interrupt the stone’s reading. To get the best results, clean the stone with isopropyl alcohol and cotton bud. The idea behind cleaning with alcohol is that alcohol evaporates faster without leaving residues behind.


A diamond tester is a portable tool that is designated to test diamonds. A diamond tester would save you from purchasing a fake diamond, and thus you would be getting your money’s worth each time you shop for diamonds.

Despite diamond testers being so popular, not everyone knows how these small devices work, so I’ve made an article about diamond testers and how they work. After reading this article, you will become more familiar with diamond testers and how they work.