How Does A Diamond Tester Work?

by Ultimate Jewelry Guide
How Does A Diamond Tester Work?

A diamond tester is a device that measures the quality of diamonds. It can also be called an optical bench or a precision scale. A diamond tester has been available since the mid-1900s and they are used in jewelry stores to determine if the diamond being sold is high quality or not.

This post will give you all of the information you need to know about how this machine works and what it does, so you can buy with confidence!

How Diamond Testers Function

The unique factor about diamond testers is that they use a needle on the top of the device to perfectly detect if the diamond is real. The needle works with thermal connectivity to provide an accurate result. To use a diamond tester, all you need to do is simply place the needle gently on the top of the diamond, and allow it to sit for several seconds. It will calculate the thermal connectivity levels and if they show positive results, the tester will give you an alert. You can easily see the thermal levels fluctuating with the built-in meter on the side, but all this will depend on the model you’re using. 

If the diamond testing device determines that the diamond is real, it will show a positive symbol on the display or make a sound to confirm the positive results. The good thing about using a diamond tester is that it doesn’t take long – usually, it’s a matter of seconds and you’ll have the results. Therefore, you won’t have to wait too long compared to other traditional methods, which normally take longer than just using diamond testers.

However, before buying a diamond tester, you need to ensure you’re dealing with a reliable seller. This will make sure you purchase a genuine device that will test diamonds correctly.

Features Of A Diamond Tester

Most diamond testers come with metal detectors that help to alert you if mistakenly slide the needle off the diamond. This is one of the most essential features of diamond testers because it prevents you from recording any metal activity surrounding the gem. Some diamond testers also feature LED screens. The high-tech LED screen doesn’t necessarily need to beep like other models, but only emits a green or red light to confirm if the diamond is authentic or not. 

Another advanced feature you’ll find in some diamond testers is the magnifier. The magnifier included in a diamond tester helps you to easily view the surface of the gem and examine it closely in order to ascertain whether it has any blemishes or other irregularities. 

It’s also important to note that the diamond testing models that feature a magnifier require batteries to run. But, batteries are also a good thing because they come in handy if you’re using the diamond tester away from a power source, such as outdoors. With a battery-powered diamond tester, you can just pull it out from wherever you carried it and use it instantly. Therefore, having some batteries with you will help you in the process. You should also consider having some extra batteries.

Are Diamond Testers Reliable?

Diamond testers are quite reliable since they are some of the most accurate tools you can use to check the authenticity of a diamond. But, you need to ensure you purchase a good diamond tester if you want accurate results. There is a chance that you’ll find fake diamond testers in the market, which means you need to be cautious when buying one. 

Ensure you look for a reputable and genuine dealer that most prefer buying from to be on the safe side. You also need to know that diamond testers that solely rely on thermal conductivity can easily mistake moissanite for a diamond. This is mainly because these two types of stones are pretty similar in terms of heat conductivity. 

Luckily, there is a way you can solve this issue. All you need to do is use a device that utilizes electrical conductivity to test stones. That’s because although moissanite and diamond have a similarity in heat conductivity, they tend to slightly differ from each other. Therefore, using a device that uses electrical conductivity to test stones will come in handy and eliminate the issue of confusion.

How To Tell If It Is A Good Diamond Tester Or A Bad Diamond Tester?

So, how exactly can you differentiate between a good and bad diamond tester? Most people find it difficult but it’s actually a very easy thing to do. 

If you’re planning on buying a diamond tester, there are several factors you need to check to ensure you purchase the right one. One of these factors is that you need to ensure the diamond tester uses electrical conductivity to be able to differentiate between a diamond and moissanite. The good news is that some of the latest models on the market combine both heat and electricity testing to offer accurate results.

Another excellent feature you need to check is if the diamond tester has a metal detector, which signals when you accidentally touch the metal part setting instead of the stone. This will save you from making the mistake of thinking you’re either dealing with a fake diamond or a real gem. 

If you have a diamond tester that cannot recognize metal, it can easily indicate that you’re holding a real diamond when you mistakenly touch the metal part, even if you’re dealing with a fake diamond. This can lead to inaccurate results and disappointments later on after you finally discover that you either bought or found a fake diamond. 

Other Ways Spot A Fake Diamond 

Aside from using a diamond tester, there are also other ways to spot a fake diamond. Below we’ll discuss these other ways that you can take advantage of to ensure you end up with an authentic diamond.

UV Fluorescence Testing

This test only requires a backlight. What you need to do is go to a dark room and shine the backlight on the diamond. If the diamond glows blue under the backlight, then it shows it’s authentic and not a fake one. But, if the diamond glows another color it’s a good indication you’re dealing with a fake diamond. 

The only exception is if the diamond glows yellow because some of them do that. Overall, if you have a gem that doesn’t glow either blue or yellow under the backlight in a dark room, then rest assured it’s a fake diamond. 

The Fog Test

This is also another ideal test to consider if you don’t have a diamond tester for the job. But you need to ensure the gem you want to test is clean, since dirt and oil may affect the results. All you need to do is hold and breathe on the gem and quickly look at it. Check whether it has fogged up after breathing on it and how long it stays fogged up. 

This is also another way of testing thermal conductivity on a diamond. Therefore, it’s important to note that diamond and moissanite shouldn’t fog up for more than a few seconds. Only a fake diamond will fog up for a while. Unfortunately, this isn’t such an accurate way of testing the authenticity of a diamond, so only use it if you don’t have otherwise.

The Facet Edges Test

What you need for this test is a jeweler’s loupe or a magnifying glass. You can use the loupe or magnifying glass to inspect where the facets meet on the diamond. Check whether they are rounded, abraded, or chipped. 

If the facets of your diamond are rounded, then that’s a clear indication it’s fake. Although diamonds are famous for being the hardest material on earth, they are still destructible. Diamonds can chip and get scratched. Therefore, a highly abraded surface on a diamond is an indication of a softer material, which means it might be a fake diamond.

Weighing and Measuring Test

The fourth test to consider is weighing and measuring the diamond. For this test, you need a highly accurate gem scale, calipers, and a loose gem. You can also use a ruler instead of calipers, although it doesn’t guarantee accuracy.

To test the density, measure the diamond across its widest point and place it on the scale. Check the weight in carats and the width according to the appropriate measurements. You can check out this chart that shows the right measurements of most gems.

The weight and size should match with the one on the chart. The only exception is if your diamond is cut or unusually shallow. Moissanite also has the same density as a diamond, so it might test within the same range. 


I hope this post has helped you understand how a diamond tester works and its benefits to users. But, if you lack the device, there is the alternative of using the other four methods that we’ve outlined above. Additionally, you can conduct more research to find out other better ways of testing the authenticity of a diamond. Just ensure you’re doing the right thing because testing the originality of a gem is a complex process and requires you to be keen and cautious.

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