Top 8 Best Diamond Testers | 2021 Reviews + Guide

It is extremely exciting to encounter a real diamond, but imagine if the one you bought turns out to be a rip-off? Those who are not familiar with a diamond’s characteristics and structure may easily believe that a particular colorless gemstone is a real diamond when it turns out to be a different stone. That is why it is crucial to identify how to spot a fake diamond. 

You might have heard that there are plenty of ways to identify whether a diamond is authentic or fake. The problem with these methods is they tend to be unreliable. It is where diamond testers come in, one of the fastest and accurate ways to spot an original diamond. 

A diamond tester is a compact handheld device shaped like a pen with a small, needle-like tip placed on the stone to be tested. It gives off audible or visual indicators to signal that a diamond is real. Its principle of operation is based on how gemstones conduct heat differently. A diamond tester detects the rate at which heat passes through the stone. 

This buying guide brings you an updated list of the best diamond testers in the market, including its essential features and a benefits analysis to help you find which one works best for your needs. You will also find the reputable brands known for manufacturing diamond testers and an in-depth buying guide of the factors to consider when buying a diamond tester. 

Read on and check out the highly recommended diamond testers today. 

Top 8 Best Diamond Testers Reviewed

  1. High Accuracy Professional Jeweler Diamond Tester by HDE – Best Overall
  2. Diamond Selector II by StillCool – Best Value
  3. Diamond Tester + 60X LED Magnifying Glasses by Molo – Editor’s Choice
  4. Gem Tester II by Presidium
  5. Diamondmate-C Electronic Diamond Tester by Presidium
  6. Ultratester 3+ by GemOro
  7. Adamas Diamond Tester by Presidium
  8. Testerossa by Gemoro

#1. High Accuracy Professional Jeweler Diamond Tester by HDE – Best Overall

High Accuracy Professional Jeweler Diamond Tester

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  • Utilizes large and small switches for diamond testing
  • Protective leather carry case included
  • Emits audible sound for easy reading differentiation
  • Comes with a small diamond testing tray
  • Battery-powered for easy convenience
  • Low battery indicator

If you’re looking for an instant and easy way to compare real and fake diamonds, this diamond detector from HDE is a great recommendation. The High Accuracy Professional Jeweler Diamond Tester is a portable, battery-powered diamond tester in a quality leather carrying case. Due to its small and compact design, this device is easy to carry and provides quick and precise readings. 

This professional diamond selector can offer you peace of mind as it gives accurate and reliable readings in identifying an authentic diamond. The unit comes with a low battery indicator and emits an audible sound to differentiate between readings. It also includes large and small switches for testing diamonds. 

The HDE Professional Diamond Tester requires a single 9V battery to operate with a small testing tray. Plus, this easy to use diamond tester is applicable for both novice and experts alike. 

Works for novice and expertsDoes not detect moissanite
Portable and compactRequires batteries
Easy to read results

#2. Diamond Selector II by StillCool – Best Value

Diamond Selector II

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  • A portable electronic diamond testing device
  • Delivers quick and accurate results
  • Comes with LCD and LED indicator
  • Works on thermal conductivity
  • Emits audible sounds for precise reading
  • Includes large and small switches for diamond testing

The StillCool Diamond Selector II is an affordable and highly portable device that allows you to distinguish authentic diamonds from other simulated stones instantly. Powered by batteries, this diamond tester is convenient to use with basic functionality. It can quickly notify you via visual and audible alert if you are dealing with a real diamond or not.

Keep in mind that the Stillcool diamond tester will not yield any reaction once it detects a fake crystal or any form of simulant like cubic zirconia. This handheld testing device is easy to operate and displays a green signal if the diamond is real. Through a simple switching mechanism, this product can also detect large and small-sized diamonds.

The Diamond Selector II is an accurate and safe spot solution for confirming real diamonds. It comes with an instruction manual so you can fully grip how to operate this device. 

Sound and light indicatorsNo batteries included
Lightweight and portableHard to set up at first
Ideal for novices

#3. Diamond Tester + 60X LED Magnifying Glasses by Molo – Editor’s Choice

Diamond Tester + 60X LED Magnifying Glass

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  • Designed to deliver fast and accurate results
  • 60X LED magnifying glass
  • Audio indication
  • LED indicator lights
  • Simple calibration for stones of various sizes
  • Carry bag, and 9V battery included 

The Molo Diamond Tester is another device that utilizes heat to identify a diamond’s authenticity. The process is fairly easy, where you will apply the tip on the diamond’s surface, and it will detect how the heat passes quickly through the diamond. The device will indicate on its LED light if the diamond is a real deal or not. The device will not emit any signal if it is crystal, fake, or cubic zirconia,

Many buyers have chosen the Molo Diamond Tester due to the bonus add-ons. The set includes a 9V battery, allowing you to operate the tester instantly and a 60X LED magnifying glass, giving you a close-up look at the diamond. However, the magnifying glass is not considered a professional standard magnifier, but it still makes a handy add-on. 

Comes with battery and carry bagNot as precise as an electric-powered tester
Portable and compactShort battery life
Relatively accurate
ALSO READ:  Top 10 Best Green Diamonds | 2021 Reviews + Guide

#4. Gem Tester II by Presidium

Gem Tester II

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  • Features the industry’s thinnest retractable probe tip
  • Built-in glass test disc and calibration discs for reference
  • Metal alert buzzer to ensure probe tip is in contact with gemstone
  • Easy to read analog display panel 
  • Differentiates between 16 different gemstones
  • Can operate via AC adapter or rechargeable battery

Presidium is one of the industry-leading manufacturers of diamond testers, garnering them three entries on this list. The first entry is the Gem Tester II, a redesigned version that is more portable, compact, and sturdier. It is the perfect diamond tester for those who are always on the go and frequent participants of auction houses. 

This unit ensures quick and easy reading of diamonds, moissanite, and 16 other colored gemstones. Like other diamond testers, it works on the thermal conductivity principle. It is very precise and displays clear results on its analog screen. 

The Gem Tester II has an enhanced in-built calibration, which you can adjust whether you’re indoors or outdoors. It also features the industry’s thinnest retractable gemstone probe tip to detect colored and coated gemstones as small as 0.02 carats. Not only that, it comes with a metal buzzer alert that emits an audible sound once the tip is in proper contact with a gem. 

For convenience and ultimate portability, the Presidium diamond tester can run on two AA batteries. It can also be recharged with an AC adapter. 

Can be used on polished and unpolished diamondsToo pricey
Tests diamonds as small as 0.02 carats
Can run on AA batteries

#5. Diamondmate-C Electronic Diamond Tester by Presidium

Diamondmate-C Electronic Diamond Tester

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  • Industry’s thinnest retractable probe
  • Proven thermal conductivity testing method
  • Thermoelectric tip for enhanced accuracy
  • LED display panel and metal alert buzzer 
  • Low battery indicator
  • Can operate via rechargeable battery or AC adapter

Presidium claims another spot on this list with the Diamondmate-C Electronic Diamond Tester. It is a completely portable diamond tester working on the thermal conductivity principle. It is a compact and neat device with a retractable probe tip, offering consistent pressure on the gemstone’s surface to deliver accurate results.

As the best diamond tester for rough diamonds, this unit features the industry’s thinnest probe tip at 0.6mm with the ability to test diamonds as small as 0.02ct. Readings are instantly provided with its LED light display. The device has no waiting time between tests and consumes minimal power from its rechargeable batteries and AC adaptor. 

The Presidium Diamondmate comes with a fully-protected carrying case that is easy to use, portable, and lightweight. 

Usable on polished and unpolished diamondsVery expensive
Comes with protective carrying case
Reliable and consistent results

#6. Ultratester 3+ by GemOro

Ultratester 3+

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  • Detects and identifies a wide range of moissanite, diamonds, and white sapphires
  • Features UV-F1 moissanite identification technology
  • Sleek and patented ergonomic grip handle with an angled tip
  • Auto-off function to preserve battery life
  • Bright white LED stone illuminator
  • Visual and audible indicator with LED light bar and ring tone

The next diamond tester comes from Gemoro, the third-generation model called Ultratester 3+. This device has an enhanced sensitivity and accuracy feature to deal with modern synthetics effectively. This handheld diamond testing device has a patented design that utilizes its sleek and ergonomic features to become ultimately portable. 

Gemoro’s diamond testers are known for its great reputation due to its reliability and accuracy to detect diamonds, white sapphires, a wide range of moissanite. The Ultratester 3+ is nothing short of special features. It uses a glowing probe tip cone indicator that gives off a green signal for diamond and red for metal. It also comes with visual and audible indicators with the LED stone illuminator and audio ring tone to denote the stone’s authenticity. 

This unit is powered by three long-lasting NiMH rechargeable batteries and a micro-USB charging system. Its durable probe can easily warm up in just ten seconds and is protected with a spring-loaded cap. When not in use, the unit quickly goes into an auto-off battery saving function. Plus, it is also user-friendly with its patented finger grip pads. 

Comes with compact storage caseSome issues with tip cone indicator
Durable and protected tip
Comfortable handling
Battery save function

#7. Adamas Diamond Tester by Presidium

Adamas Diamond Tester



  • Easy to use interchangeable probe tips
  • Sleek and ergonomic chrome brushed grip
  • Detects colorless diamonds and moissanite
  • Dynamic micro-LED display for clear, visible results
  • USB port for an alternative power source
  • Automatic power off after two minutes of inactivity

Presidium takes another spot with the Adamas Diamond Tester. This innovative device can instantly detect diamonds, moissanite, simulants, and metals. With its optional micro tip, it can identify diamonds as small as 0.02 carats. It has interchangeable probe tips, which you can easily remove once it requires replacement. 

The Adamas Diamond Tester is a highly portable unit that is user-friendly and lightweight. It also comes with a sleek and ergonomic handle and a dynamic LED screen for ease of use. This device can record up to 500 tests in its built-in memory chip.

You will also love its unique looking design with great attention to detail. It can run via three AAA batteries or a USB cable charger. 

Accurate testing on diamonds as small as 0.02 caratsUnsecured battery cover
Provides clear and price results.A little pricey
Dual power source

#8. Testerossa by Gemoro

Testerossa Diamond, Moissanite & White Sapphire Tester

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  • Detects diamond, moissanite, and white sapphire
  • New Enhanced Moissanite Testing Technology
  • UV fluorescence detection and LED stone illumination
  • Retractable probe tip with enhanced durability
  • Powered by micro USB or rechargeable NiMH/AAA Alkaline batteries
  • 10-year probe tip warranty

The Gemoro Testerossa is a highly functional diamond tester that uses ultraviolet fluorescence technology to detect, identify, and separate diamonds from moissanite, white sapphire, and cubic zirconia. It warms up pretty instantly and comes with four lights to indicate the type of stone you are looking at. 

This unit utilizes a New Enhanced Moissanite Testing Technology for lower conductivity stone identification. It comes with a retractable probe tip with better durability and LED stone illumination. It is powered by rechargeable NiMH batteries, AAA alkaline batteries, or micro USB. 

Provides audible and visual indicatorThe battery door comes loose easily.
Can be powered via USB
ALSO READ:  Top 7 Best Yellow Diamond Rings | 2021 Reviews + Guide

Top Pick for Best Diamond Tester: High Accuracy Professional Jeweler Diamond Tester by HDE

As diamonds become a rare and valuable commodity, the demand for fake or cheaper replicas remains high. Unfortunately, buyers tend to be unknowingly tricked into buying what they believe is the real deal only to find out that it is a rip-off. 

You can prevent this from happening if you get yourself a reliable diamond tester. It is a widely-used device among jewelers to check a diamond’s authenticity. This testing device is one of the most reliable and accurate tools to avoid getting fooled with a fake diamond. 

Three factors were considered for the top pick, including the brand, price, and consumer reviews. Based on the given criteria, the High Accuracy Professional Jeweler Diamond Tester by HDE claims the number one spot as the best diamond tester.

This innovative device is a portable diamond detector that delivers quick and easy readings on spotting real or fake diamonds. It comes with a durable leather carrying case for extra protection. It is also discreet and compact enough to carry around, perfect for those who are always on-the-go. 

This testing device has a low battery indicator and creates an audible sound to differentiate various readings. It also features small and large switches for testing diamonds. It requires a 9-volt battery and is supplied with a small testing tray. 

This HDE diamond tester is perfect for on-the-go travelers as it comes with a carry case with a compact and portable design. It is also easy to use, making it suitable for experts and novices.

While several brands claim that their products are of good quality, choosing the best unit to provide immediate and most accurate results can be tough. This buying guide has condensed all the top-selling diamond testers in the market and picked the ones that give you the best value for your money.

Best Brands for Diamond Tester

There are always well-established brands and market leaders in every product category, and diamond testers are no exception. This article has included a representative cross-section of various diamond taster brands with an established reputation for quality and accuracy. Check out below for the top diamond tester brands that dominate the market. 


Presidium is a leading manufacturer of gemological instruments that provides accurate and reliable tests and measurements for diamonds and gems, specifically for the diamond and gemstone industry. They started in 1979, making them the first company worldwide to introduce numerous gemological instruments. 

Since the company started, Presidium has been committed to research and developing high-tech testing instruments for the jewelry industry. Their product line ranges from diamond testers, colored gemstone testers, gemstone gauges, and portable carat scales. 

Today, Presidium has reached over 40 countries globally, with more than 130 authorized resellers. They are also a trusted brand in laboratories, gemological institutes, jewelry manufacturers, retail jewelers, diamond appraisal businesses, etc. 


Gemoro is a manufacturer of jeweler supplies, managed by Sy Kessler, a market-leading manufacturer of jewelry tools and equipment. It is a family operated business since 1968 and has continued for more than 50 years and three generations. The company is currently handled by two brothers, Henry and Daniel Kessler, the sons of the former founders of Sy Kessler. 

Today, Sy Kessler takes pride in their massive online inventory of jewelry supplies ranging from magnifiers & loupes, gemstone gauges, diamond color grading, microscopes & photography, solitaire display rings, scales, etc. 

Features to Consider When Buying Diamond Tester (Buyer’s Guide)

Before finally choosing a diamond tester, there are a few essential factors that you should evaluate. These key factors can help you make informed decisions during your selection process and narrow down the best product recommendations. This way, you can guarantee that you invest your money with a quality product that entirely fulfills your requirements. 


It is highly recommended to buy from brands in the professional end of the jewelry market. Choose well-known and reputable companies known for manufacturing diamond testers. Their expertise in making these devices allowed them to introduce innovations to enhance a diamond tester’s accuracy and reliability, which you may find helpful for your diamond testing needs.  

Ease of Use

For those who have never tried a diamond tester before, you need a device that is simple and convenient to use, without the need to set it up for hours and analyze its operation. The best diamond detector should only require a simple flick of a switch to get it started. All you should do is allow the probe tip to touch the diamond and let the heat pass through.

Most units have visual and audible indicators, ready-to-use features, and no waiting time required. If you always bring your testing kit with you and frequently go to auction houses, you should choose a highly portable, compact, and pocket-sized device.  


Quality should always be your top priority, especially if you plan to invest in a high-quality diamond tester. This way, it can help you potentially save more money by eliminating the risk of losing your cash on ripped off units.

Choose a device that is highly durable with an excellent quality build. You may also consider investing in a diamond tester with a protective probe tip and a carrying case for extra protection, which you may find useful when the unit is not in use or is in transit. 

Power Source

Portable diamond testers are either battery-powered or rechargeable. A battery-powered device is a great option for portability. However, you may also consider other secondary options, such as USB charging and power adapter source. Another practical choice is a diamond tester that runs on rechargeable batteries. 


The main point of getting a diamond tester is to get a highly reliable unit that will tell you if a diamond is real or not. You need a device that will deliver not only accurate readings but also reliable results. It is an essential feature to consider in any diamond or gemstone detector. Make sure that you read several product reviews and information before buying one.


The price points of diamond testers in the market vary significantly, from affordable to slightly expensive. Devices with high-tech features certainly come at an expensive price. However, you don’t need to get a pricey unit that goes over your budget. As much as possible, consider a range of price points that are budget-friendly. 

Meanwhile, if you are a professional jewelry buyer, gemstone enthusiast, or jeweler, you need to invest in a high-end unit that will last a long time. 

Customer and Product Reviews

Buyers who are still uncertain about a diamond tester’s accuracy, you can always turn to online reviews to assess the pros and cons based on previous buyers’ experiences. Pay attention to what the customers should say about their feedback and real-life experiences, including what they love and what they hate about the product. 


There are plenty of ideas and methods on how to tell if a diamond is real or not. It is not practical to leave it up to chance since some methods or procedures tend to be completely inaccurate and unreliable. This problem can be solved with a diamond tester that gives accurate, reliable, and fast results. This device will never allow any real diamond or gemstone to slip through your hands again. 

While several brands claim their devices as the best diamond tester, choosing one that will provide you immediate, accurate, and reliable results can seem a little tough. This buying guide has condensed and evaluated some of the top-rated diamond testers in the market that will give you the best value for your money. 

After considering the key factors when buying a diamond tester, the High Accuracy Professional Jeweler Diamond Tester by HDE takes the top spot as the best diamond tester. This handy testing device is a portable diamond tester that guarantees quick and easy readings on identifying real or fake diamonds. 

The set includes a protective leather carrying case so you can securely store the device when not in use. Not only that, but it is also discreet and compact enough to carry around, making it ideal for those who frequently bring their diamond tester with them, especially in auction houses. 

It also comes with a low battery indicator and emits an audible sound to differentiate various readings. It also features small and large switches for testing diamonds. Plus, it is powered by a 9V battery and supplied with a small testing tray. 

Hopefully, this buying guide has helped you discover the best diamond tester that suits your needs. It is highly recommended to invest in a highly accurate and portable diamond tester, so you can save more cash in the long run by avoiding any foul scam. 

FAQS (Frequently Asked Questions)

How reliable are diamond testers?

Diamond testers are the most reliable and precise tools to determine a diamond’s authenticity. However, you should be aware that devices that rely on thermal conductivity can easily mistake moissanite for a diamond due to its similarities in how they conduct heat. 

You can avoid this problem by getting a diamond tester that relies on electrical conductivity to test various types of gemstones, including diamonds, white sapphires, and moissanite. It is for this reason that moissanite and diamonds have different ways of conducting electricity. 

What makes a quality diamond tester?

For those who are decided to purchase a diamond tester, you need to consider a few key factors to ensure you are getting a high-quality device. First, ensure that the device utilizes electrical conductivity to set apart a diamond from moissanite. Some brands available on the market combine the power of electricity and heat testing for better accuracy and reliability. 

Another great feature is a device that comes with a metal detector that tells you if you accidentally come into contact with a metal setting instead of the stone. This feature works best if you frequently test diamond or gemstone jewelry instead of loose stones. 

If the tester cannot recognize a metal, it can denote that you are holding a genuine diamond. It can prove to be misleading, especially if you unknowingly touch the metal setting, even if the mounted diamond is fake. 

How do diamond testers work?

A diamond tester’s operation principle is based on the fact that various gemstones conduct heat differently. Heat passes through a diamond differently than it would through glass or cubic zirconia. A diamond tester detects the rate at how the heat moves through the stone by getting it into contact with a probe tip. The device will deliver a signal via an audible or visual indicator, whether it is a real diamond or not. 

Other diamond testers utilize electrical conductivity to test diamonds and gemstones. They are also based on a similar heat principle, but they use electricity instead of heat.

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