Diamond Testers in 2021 – Which One Should You Use?

Choosing a diamond tester is an easy task. Which one you opt for depends on what you want to use it for. Do you want a simple ‘yes’ or ‘no? Do you want to test small diamonds? What about the option to test for other gemstones too?

Let’s take a look

Diamond Testers

Table could not be displayed.

What are the best diamond testers to buy?

Diamond Selector II V2Cheapest Diamond Tester Pen

KKMOON Diamond Selector II
  • LED lights and tone audio results.
  • Easy calibration for stones of various sizes.
  • Reliable and accurate testing.
  • Includes carry case.
  • Lightweight design with tough plastic housing.
  • Matched with a testing platform for loose stones.


The cheapest of diamond detectors is the Diamond Selector II. It comes in at a very budget price and is well received by customers with many positive reviews.

Perhaps not the most well-built diamond tester, although this a great choice for general use, I wouldn’t recommend it for a jeweller who is relying on the accuracy in a shop or when buying and selling.

Very simple to use and comes with its very own carry case. The display is very easy to interpret and uses both LED and sound to alert you of whether you have a real diamond or not.

Highly recommended for those who just want to perform tests on diamonds casually, but I really don’t believe this is good enough for professional use.

That being said at this price and with this many positive reviews, it really is a bargain!

Presidium DiamondMate-C Electronic Tester –Most accurate Diamond Detector

Presidium DiamondMate C
  • Low battery consumption and low battery indication ensure the tester is always with power.
  • Uses the latest technology and thermal conductivity to detect and test for diamonds and simulants.
  • Metal detector function will alert the user when contact has been made with the gem mounting and not the stone.
  • Instant recovery time in between tests with no wait.
  • 1 Year Manufacturers Warranty

Delving into the more professional range of diamond detectors Presidium is one of the leading brands.

The Presidium DiamondMate-C is a quality, well-constructed durable piece of kit that uses the latest tech and thermal properties to run its accurate and stable tests.

Results are given instantly and this Presidium diamond detector pen has one of the thinnest pin probes you will find in the industry allowing you to test very small diamonds.

It features a rechargeable battery that can be charged via a USB lead and will also tell you if you are making contact with the mount and not the stone when performing the tests.

Presidium is a Jewellers main choice and the DiamondMate-C can be found in many Jewellery stores nationwide.

A great bit of kit, very accurate, and highly recommended if you are serious about testing diamonds.

Presidium Refractive Index Meter IIBest Diamond Tester

Presidium Refractive Index II


  • Pinhole Light reflectivity measure on a wide oval-shaped platform.
  • Cover cup included with a blackout interior to make sure the light reflectivity measurement is correct.
  • When testing it will instantly display a direct R.I reading on the digital LED display panel index.
  • In-built Refractive Chart for referencing diamonds and simulants above R.I reading of 1.8
  • 8 Piece Gem Stone Holder built-in.
  • Pocket-sized Refractive Index Chart R.I readings for 55 types of stone.
  • PRIM II PC software to help users find out further information on the possible coloured gemstone using extensive data on the various gemstone properties.
  • Gemstone Dictionary with 57 gemstones? properties (R.I, Color, Hardness, S.G. Value), country of origin and other related information.
  • USB port for alternative power source and connectivity.


The PRIM II is one of the most advanced diamond testers available on the market, it uses refractive light technology and is one of the only diamond detectors that are able to easily determine the difference between diamond and moissanite. It can also test many other gemstones.

It features a clear LCD screen that displays the results of the refractive light test, you can then compare the results to the scales shown on the decal allowing you to determine what stone you have.

Presidiums refractive index meter also has an extensive CD library for your PC allowing you to further identify all kinds of gemstones. If you are going to be testing diamonds regularly then I stand by the fact that this is one of and if not the best you can buy.

It’s lightweight, compact, and well built and can either run on batteries or via the AC adaptor.

Detector Reviews number one choice!


What is a diamond tester?

Diamond testers are electronic devices that are used to test for real diamonds and other gemstones.

They are usually pen-shaped hand held devices that indicate through LED display or audible sound if a suspected diamond is real.

How does a diamond tester work?

The smaller, readily available handheld diamond testers work on the principle that gemstones and diamonds each conduct a different amount of heat.

The diamond tester measures the speed of heat travelling through the stone and then calculates if it is correct for a diamond.

If it is you will be alerted by LED lights or an audible sound.

There are other more accurate testers that use an electric pulse or refractive light.

Do diamond testers really work?

Yes! Diamond testers really do work, and many jewellers will confirm this.

They are perhaps the most reliable test you can perform to authenticate the diamond. Although, diamond testers that measure heat conductivity may return a false positive for moissanite stones as the speed of heat travelling through these stones is similar to diamonds.

There are now models that combine both heat and electricity to test making it very accurate, they are more expensive but are worth it

How do you use a diamond tester?

Assuming you have the pen-shaped handheld device, all you need to do is press the top of the diamond tester onto the suspected diamond at a 90-degree angle.

Depending on the model of tester you have, you will either have LED lights or an audible sound indicating the presence of a real diamond.

Written by Danny Nash

I love metal detecting, history and sharing that with you. Read more of Danny's articles.


Wait! Before You Go...

Get your copy of The Beginners Ultimate Guide To Metal Detecting, today

Almost There!

Enter your name, email address and click DOWNLOAD NOW to receive your Free eBook