Diamond Detectors & Testers – All You Need To Know

What is a diamond tester or diamond detector?

Diamond testers or also known as Diamond detectors are specialist electronic devices that use a variety of different technology to test a diamond or gemstones authenticity.

Most commonly you will find them in a pen-shaped hand held device that will alert you via sound or a meter reading if your diamond or gemstone is real.

Do diamond testers work?

Absolutely, diamond testers are the most accurate testing form when testing diamonds and are used by jewellers, jewellery crafters and diamond traders worldwide.

The accuracy of the reading and reliability will largely depend on the diamond tester that you are using, some models now combine multiple tests for greater accuracy. For example heat and electricity current testing.

How do diamond detectors work?

There are multiple types of diamond testers and detectors available and they work using different methods.

The most common types and how they work are as follows:


The diamond detectors that test using heat measure how fast heat travels through the diamond or stone.

The brains of the device then calculate the time it takes and lets you know if your stone is genuine.

Diamond testers that use heat to test the stone can’t differentiate between diamond and moissanite.

Refractive index 

This type of diamond detector uses light to indicate what kind of stone you have in your possession.

It measures the amount of light that is reflected through the stone.

Refractive index can differentiate between diamond and moissanite and some can even identify ruby and sapphire.


A very similar principle to thermal diamond detectors except they use electricity.

Electricity based diamond detectors can differentiate between diamond and moissanite. 

How to use a diamond tester

Using a diamond detector is relatively simple, just pay attention to the results.

Take the diamond detector, for the sake of this guide we are going to talk about how to use the pen shaped hand held diamond tester.

Ensure the probe tip and stone are clean and clear from any dirt or moisture.

Watch for the indication that the diamond or gemstone tester is ready for testing.

At a 90 degree angle depress the nib of the device against the stone you want to test (diamond or gemstone)

Watch the meter on the side of the diamond detector for the authentication of the stone, or listen for the beep.

Best diamond detectors

Best Price

Mid Range


Our Picks


Diamond Selector II

Presidium Multi Tester III

Presidium Duo Tester PDT II


More Info

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Diamond Selector II

The diamond selector II is the cheapest diamond detector we have featured, giving those working with a budget something to consider.


  • Compact & Portable Design
  • Audio Alert (With volume control)
  • Battery Level indication
  • Authenticity Meter

Our thoughts

For the price of this diamond detector, you really can’t go wrong.

Although a basic piece of equipment and probably slightly retro and tacky looking, it does work.

Worth pointing out as we have discussed previously diamond detectors and testers within this budget range use heat to test diamonds, they also give a false positive on moissanite. So be careful.

Take your time to read the instructions before using it and I have no doubt you will be impressed with how accurate it can be.

All in all a working diamond tester for under $30 is something you really can’t complain about.

Diamond Selector II

- Compact & Portable Design
- Audio Alert (With volume control)
- Battery Level indication
- Authenticity Meter

Presidium Multi Tester III

Presidium diamond testers are perhaps the most popular and advanced detectors on the market.

They’ve earnt their reputation by delivering highly advanced and accurate machines and the Multi Tester III is one of their most popular hand held models.


  • Differentiates & displays moissanite & diamond
  • Clear easy view reading meter
  • Thin retractable probe nib
  • Anti-Slip grip

Our Thoughts

Apart from the high price tag, the multi-tester III is a fantastic piece of kit well received by jewellers and traders worldwide.

To ensure the high accuracy of this machine a good tip is to clean the tip and the stone before the test.

Very simple to operate straight from the box making it appealing to beginners as well as diamond traders,  you just wait a couple of seconds and away you go with the testing.

I especially like the rubber anti-slip grip idea as it’s a fiddly process and gives you that extra bit of stability, the tips on the diamond testers are very small so you need to be precise.

Presidium Multi Tester III

- Anti-Slip Rubber Grip
- Clear LED 180 Degree Display
- Separates Diamonds & Moissanite
- Thinnest Retracatable Probe Tip

Presidium Duo Tester  PDT II

Another presidium in our best diamond tester list, the Duo Tester II is an advanced and powerful machine that comes with a higher price tag.


  • Retractable thermoelectric tip
  • Clear analog dial with 15 different gemstone readings
  • Thinnest probe tip of diamond detectors to allow small stone testing
  • Dual tests for higher accuracy

Our Thoughts

The PDT II is an advanced diamond and gemstone tester and is purpose built for people who are regularly testing stones, jewellers and other traders.

A very hi tech diamond tester with high accuracy, largely down to the duo testing.

It’s quite expensive if you’re just going to be testing at home on the odd occasion and cheaper alternatives exist.

That being said still a very powerful bit of kit, that excels with stone identification.

Presidium Duo Tester II PDTII

- Analog Display With 15 Gemstones
- Dual Tests For Higher Accuracy
- Retractable Thermoelectric Probe Tip
- Reflective Index Testing

Other FAQ’s

Do lab grown diamonds test positive on a diamond detector?

Yes lab grown diamonds will test positive on a diamond test or detector, this is because as per a naturally mined diamond they are made from crystalized carbon.

Can a diamond detector be wrong?

In some instances, depending on the detector you are using there are times when your diamond detector could be wrong. Certain things can effect the test results such as a dirty probe, dirty diamond or a cheap diamond tester.

What is the cheapest diamond detector?

I found diamond testers as cheap as $9.99 however the reviews were not very good with lots of people saying that they broke after a few tests.


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