How Does a Diamond Tester Work? (Easy Guide in 2024)

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The best, most effective way of testing for diamonds is with the use of a diamond tester. The reason for this is unlike most other tests that are recommended, the diamond tester takes into consideration the thermal conductivity of the stone and uses what’s known about this gemstone and its conductivity to test the rate of heat transmission or conductivity through the stone.

But how exactly do the diamond testers work? How exactly does it tell you that the gemstone is or isn’t a diamond? And can the tester be used to test for other properties of diamonds? And most importantly, is the diamond tester reliable?

Keep reading to learn more about the diamond testers:


The features of the diamond tester

How Does a Diamond Tester Work

The best way to look at and weigh the effectiveness of the diamond tester would be by taking into consideration the features of the diamond tester and what these different features/ functions do. The most important thing you should know about the diamond tester is that this professional jeweler’s device has been designed uniquely to ensure not just ease of use but also the most accurate readings – and it can be used by experts and novices.

Some of the things that make the diamond tester the most effective tool for testing real diamonds include the fact that the tester has been professionally developed to ensure an accurate result, and it is also fast and precise, and also safe for testing of diamonds. Its portable design is also a great feature as it allows for easy testing of diamonds on the go, and if you are in business, you can run things on the go, and your customers don’t have to come to you.

Ease of use – besides its portable design that makes for ease of use of the tester wherever you are, it comes with small or large switches that further ensure easy and fast testing of diamonds. The sharp, needle-like end that comes in contact with the diamond is also easy to use, emitting an audible sound when it comes in contact with diamonds, metal, or other gemstones. The sound produced is different depending on the material in contact with the tester, which makes it easy for you to differentiate the materials that are being tested and for you to tell if the gem is a diamond or not.

How Does a Diamond Tester Work

Battery-powered – this enhances the portability of the tester, and at the same time, it increases the convenience of using the tester. You only need one standard 9v battery to use the tester.

A high degree of accuracy – this is a feature that you’d be looking for in a diamond tester, and you will be happy to know that the professional diamond tester will accurately test for genuine diamonds, telling them apart from the fakes – well, this is the case, save for the moissanite stone that shares the same thermal conductivity/ properties with diamonds. The beeping from the tester tells you when you have a diamond and when you have a fake or a metal. The volume levels/ bars also help increase the accuracy of the readings and your deductions from the tester.

User-friendly design – since the testers come with a probe on the ends that comes in contact with the test material, a color-coded and calibrated scale that guides the readings for the tester, and the beeping options, it’s rather easy to decipher the results from the readings, and you get to accurately determine if the sample is a diamond or a fake.

The diamond tester is also affordable, allowing for small jewelers and business owners to test their jewelry before selling them. If you love diamond jewelry and would like to test for the authenticity of the pieces you spent a good chunk of money on; this tester would be an ideal fit for you.


How does a diamond Tester work?

Essentially, the diamond tester detects the rate of heat transmission through the gemstone in question. It is used to test for genuine and fake diamonds because it allows you to identify the fakes from the real pieces by displaying different results for the tested stones. In other words, the tester tells you if the gem you are looking at is an actual authentic gem or not; and it does this by measuring the total amount and the speed at which heat travels through that stone. The diamond testers or detectors could also make use of electrical currents or electrical conductivity to measure the number of currents and also the speed at which electricity is traveling through the stone being tested.

But what’s the exact mechanism in which these testers work?

Well, these portable diamond testers test the thermal and electrical conductivity of the test gemstones by use of the probe diamond detectors that feature heated needle tip that is metallic. The tip results in heat transference once you place it on the surface of the diamond, through which you are able to test the thermal conductivity of the diamond. The results from this test tell you if the diamond is real or fake.  Watch the video below!

Is there any science behind these tests? Well, yes. Essentially, electricity and heat are transferred through materials like fake diamonds like the cubic zirconia or even glass, but the heat or electricity transmission through these materials differs from that seen in diamonds. So, by looking at the differences in heat transmission between these materials, you can determine, with an extreme level of accuracy, if the sample material is a real diamond or a fake. Thanks to their high degree of accuracy, the diamond testers save you a great deal in terms of time, effort, and money because you get to test for the diamonds with great ease.

Note that there are two main types of diamond testers – the conventional and the modern design testers.

The conventional testers feature metallic tips, and they are heated before these tips are applied to the cooler surface of the test material; and as mentioned above, the heat transference rate and characteristics tell you if the sample is authentic or not.

The modern/ newer diamond testers, on the other hand, are able to differentiate the physical properties of real diamonds and their simulants. These testers include the delicate Ceres Diamond Tester with the small copper tip and a very high degree of heat sensitivity that results in a high-accuracy diamond tester that is also very reliable. There is also the Rayner Diamond tester that is ideal for commercial tester, the GIA Diamond pen that uses a visible greasy liquid that leaves visible marks on the non-absorbent diamond surfaces, and finally, the Fluorescence diamond testing that makes use of UV to differentiate real from fake diamonds.


Does the diamond tester accurate?

How Does a Diamond Tester Work

The diamond testers are quite accurate and reliable, and they make the most accurate tools for testing for the accuracy and the authenticity of diamonds.

The only catch is that you cannot rely on the heat-based diamond testers because the results can be misleading where the moissanite is mistaken for the diamond – the moissanite and the diamond are very similar, and they have the same thermal properties.

So, the only reliable way to test and differentiate diamond from moissanite is by use of the electrical-based diamond tester. A tester that uses electrical conductivity can easily and accurately differentiate the two gemstones.


Will Diamond Testers work on Ruby or other Gem Stones?

How Does a Diamond Tester Work

The best part about the diamond testers is that these nifty gadgets can also work on other gemstones like rubies, among other real gemstones.

The reason for this is that the gadget makes use of just the same technology as that used in detecting other gemstones, and it would tell if the gemstone you’re testing is real or not.

The diamond testers also work well on emeralds, sapphires, and many other gemstones.

That said, detection of rubies is not always the easiest, and it can be rather difficult to detect and differentiate rubies from garnets, especially for the rubies that are darker in color. The good news is that the diamond tester would still detect rubies, despite the differences in color.


Do diamond testers work on Lab-Grown Diamonds?

How Does a Diamond Tester Work

At the end of the day, the diamond tester is necessary for the detection of real diamonds and differentiating them from the fakes.

But when it comes to the lab-grown diamonds, these simulated pieces, which are man-made and look exactly like the real diamonds, cannot be detected or differentiated from the real stones.

So, you cannot use the diamond tester to satisfactorily differentiate mined from the lab-grown diamonds.

Generally, the lab-grown diamonds’ chemical makeup is exactly like that of the natural diamonds – the physical properties are the same, too – even to the trained eye.


Heat diamond tester or Electric diamond tester

While the heat diamond testers use the gemstone’s thermal conductivity to test for the genuine gemstones, the electric diamond testers take into account their thermal conductivity.

And given the difference between diamonds and moissanite, it’s worth noting that the electric diamond tester would be more ideal as it gives insights into the differences between these two seemingly similar different gemstones by showing the differences in their electrical conductivity.


Related Q&A

Does a diamond tester work on gold?

While the diamond tester is ideally used to detect gemstones and differentiate diamonds from other gemstones, the mechanism of the tester allows for the testing of metals, albeit indirectly. It can only test/ detect metals, but not specific elements – if the probe comes in contact with gold, for instance, there will be continuous beeping which tells you that the probe is in contact with a metallic piece.

Does a diamond tester work on silver?

While the tester can detect metal, it is not an ideal tool for testing for specific metals such as silver. Tests like the nitric acid test would be more effective.

Does a diamond tester work on sapphire?

Yes, you could use the diamond tester to test for a sapphire.



Diamond testers are based on the heat conductivity principles of the gemstones and the fact that diamonds conduct electricity while the stimulants are often non-conductive.

The diamond tester measures the exact conductivity level of the gemstone, and you can use the results to determine if the piece is genuine or not.

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