Looking for the best diamond tester? Great! In this guide, you’ll learn:
- What is a diamond tester
- How does a diamond tester work
- How to use a diamond tester
- How to read a diamond tester
- Help you find the best diamond tester for your needs
And much more!
Best Diamond Testers: At a Glance
Our TOP Pick | Presidium Multi Tester III • Identifies Diamonds and Moissanites • Tests diamonds as small as 0.02ct • Metal alert buzzer • Industry’s thinnest probe tip (0.6mm)  |
Best Budget | GemOro Ultratester 3+ • Separates Diamond from Moissanite • Detects most difficult F1 moissanite • Metal alert buzzer • Fast warm-up time |
Upgrade pick | Gemlogis Belize • Differentiate an earth-mined and synthetic diamond • Identifies Diamonds and Moissanites • Twin probe tip tester • Testing Range: 0.02ct+ |
 | Presidium – Gem Tester II (PGT II) • Identify diamonds and moissanites • Separates up to 16 colored gemstones • Metal alert buzzer • Built-in Glass and Calibration |
 | SmartPro Gem-Eye-I • Identifies types of common gemstones • Testing stones as small as 0.01ct • Easy Auto Calibration • Bluetooth Ready Device |
There are many ways to distinguish a natural diamond from diamond simulants or other gemstones. For example, using ultraviolet light, water or oil. The easiest way to check is to breathe on the stone; if it’s steam up, it’s not a diamond. These verification methods are inaccurate, and they can be called amateur.
To accurately determine the authenticity of a diamond, it is better to use a special device – diamond tester. The operation of this device is based on thermal and electrical conductivity. Gemstones conduct heat differently, this characteristic can be used to distinguish a diamond from other stones. In order to conduct a test, you need to bring the probe tip of the device to the stone and you will see on the display whether the diamond is real or not.
Our Pick: Presidium Multi Tester III (PMuT III)
Diamond tester Presidium Multi Tester III – the best ratio of price and quality of the offered diamond testers in stores. This device can easily distinguish a natural diamond from gemstones that can be visually confused with a diamond. Moissanite, zircon, cubic zirconia, colorless sapphire looks like a diamond.
Presidium Multi Tester III combine three principles of operation: thermal conductivity, electrical conductivity and metal detector. PMuT III identifies colorless diamonds and moissanites based on their thermal and electrical properties. The metal detector function will help to avoid inaccurate measurements. If during the test the probe tip accidentally touches metal instead of stone, the device will inform you. The size of the probe tip (0.6 mm) allows you to test diamonds as small as 0.02 carats. The test result immediately appears on the bright LED display. Lightweight and portable, the Presidium Multi Tester III can operate on either battery or mains power. The device comes with a protective case. Diamond tester – PMuT III is suitable for both professionals and beginners.
| Pros | Cons |
| Testing gemstones as small as 0.02ct | Product needs to be calibrated prior to use |
| Tests for both diamonds and moissanites | AC adaptor – optional item sold separately |
| Metal alert buzzer | |
| Can be powered by AC adaptor or Batteries |
Second place: GemOro Ultratester 3+
Great diamond tester GemOro Ultratester 3+. A distinctive feature of this device is an elegant ergonomic patented shape and stylish design. This diamond tester can recognize and distinguish a diamond from moissanite and sapphire. The exclusive implemented technology into this diamond tester is capable of detecting the widest range of electrically conductive moissanite, including the new moissanite Forever One (UV-F1).
This device is equipped with a metal detector, which reduces the risk of incorrect tests. Fast warm-up time of the device, allows you to start testing gemstones immediately after switching on. Result of the test is accompanied by light indicators and by a unique sound signal. GemOro Ultratester 3+powered by micro-USB or with 3 AAA batteries. Diamond tester Ultratester 3+ is designed in the USA.
| Pros | Cons |
| Tests for both diamonds and moissanites | Gemstones must have a smooth and full contact on the testing plate to ensure a legitimate test |
| Detects most difficult F1 moissanite | |
| Comes with the perfect accessories | |
| Metal alert buzzer |
Upgrade pick: Gemlogis Belize
Gemlogis Belize is a diamond tester that can surprise even professionals. This unique diamond tester not only distinguish a diamond from moissanite and simulants, but also distinguish natural diamonds (earth Mined) from synthetic diamonds (IIa/CVD/HPHT). Gemlogis Belize is twin probe tip tester. Its patented technology combines a Thermal Probe and Optical Probe. Diamond tester is capable testing both loose and mounted stones. The minimum stone size that can be tested is 0.02 carats. Additionally, the diamond tester can be completed with a “Colorstone Reference Meter”. BLEU – Colorstone Reference Meter allows user to select the colour of the gemstone to give a more definitive indication about the type of gemstone. The Gemlogis Belize Diamond Tester is easy to use but at the same time gives results equivalent to professionals with many years of experience.
| Pros | Cons |
| Combines a Thermal Probe and Optical Probe | Limited Color Range Test: Colorless to near colorless (D – J) |
| Differentiates between natural diamonds (Earth Mined), synthetic diamonds, Simulant & Moissanite | |
| Highly compact and light device | |
| Test loose and mounted stones |
Presidium – Gem Tester II (PGT II)
If you plan to test not only diamonds, but also colored gemstones, Presidium Gem Tester II is the right choice for you. Portable and sturdy diamond tester capable of quickly identify diamonds/moissanites and separates up to 16 common colored gemstones based on their thermal conductivity. No waiting time between tests. The device is equipped with a large, clear analog dial. To obtain an accurate reading, the PGT II is equipped with the function – Assisted Thermal Calibration (ATC). User is now able to easily calibrate the tester according to the testing environment. With this device, you can test both polished and unpolished gemstones. The PGT II is equipped with a thinnest probe tip (0.6mm) for testing gemstones as small as 0.02 carats. Gem Tester II runs on 2 AA batteries or AC adaptor.
| Pros | Cons |
| Separates up to 16 common colored gemstones | Does not differentiate between natural and synthetic colored gemstones |
| Built-in Glass and Calibration (CAL) test discs | |
| Tests polished and unpolished gemstones | |
| Metal alert buzzer |
SmartPro Gem-Eye-I
SmartPro has developed a diamond tester Gem-Eye-I with color estimator display for smoothly and seamlessly testing your Precious stone and diamond. The device operates using the principles of thermal conductivity. High-efficiency gem tester оснащен thinnest probe tip (0.48mm) for testing stones as small as 0.01ct. Metal alert buzzer ensure that probe tip is in contact with gemstone during testing. With Bluetooth and “Smartpro mobile application” you can connect the Gem-Eye-I with your smartphone. The device has an integrated auto-calibration feature for maintaining its testing accuracy. SmartPro Gem-Eye-I runs on 3xAAA batteries or AC adaptor.
| Pros | Cons |
| Testing diamonds as small as 0.01ct | Cannot differentiate moissanite from diamond |
| Auto-calibration before testing | |
| Color stone estimator display | |
| Bluetooth Ready Device | |
| No waiting time between tests |
How to use a diamond tester?
Most diamond testers are very sensitive to external factors. To get an accurate result from your diamond tester, you must meet several conditions. The first thing you should do is to read the manual from your diamond tester. This will help you avoid most mistakes. Below is a list of what can affect the work of a diamond tester:
- Diamond tester must be calibrated
- The operating temperature where you are testing should be between: 65°F- 80°F (18°C- 27°C)
- If your device is powered by batteries, make sure they are charged.
- Make sure to clean the probe tip (For diamond testers with a probe tip)
- Сlean the surface of the gemstone to remove any grease and dirt
- Make sure the gemstones are at room temperature
- Allow the gemstone to cool down, between tests
Where can I buy a diamond tester?
Above, we have described the basic principles of diamond testers. If you already know what tests you want to run with diamonds, but have not decided on a model, use our table. The table lists diamond testers from different manufacturers. The first and second columns list the manufacturers and models of the diamond testers. The third, fourth and fifth columns list the key opportunities:
- Can diamond tester identify diamond
- Can diamond tester distinguish diamond from moissanite
- Is diamond tester capable of distinguishing natural diamond from synthetic one
By clicking on the links “view on amazon”, you can find out reviews, users of these devices. You can also find out the price of a particular diamond tester.
| Manufacturer | Model | Identify Diamond | Identify Moissanite | Separate natural diamonds from synthetic | Customer reviews |
|---|---|---|---|---|---|
| Presidium | Multi Tester IIIⓘ | Yes | Yes | No | View on Amazon |
| GemOro | Ultratester 3+ⓘ | Yes | Yes | No | View on Amazon |
| Gemlogis | Belizeⓘ | Yes | Yes | Yes | View on Amazon |
| Presidium | Gem Tester IIⓘ | Yes | Yes | No | View on Amazon |
| SmartPro | Gem Eye Iⓘ | Yes | No | No | View on Amazon |
| Presidium | Diamond Mate-Cⓘ | Yes | No | No | View on Amazon |
| GemOro | Testerossaⓘ | Yes | Yes | No | View on Amazon |
| Cultj | Diamond ComboTester IIⓘ | Yes | Yes | Yes | View on Amazon |
| TekcoPlus | DMTK-83ⓘ | Yes | Yes | No | View on Amazon |
| Presidium | SAMⓘ | Yes | Yes | No | View on Amazon |
| Presidium | Adamasⓘ | Yes | Yes | No | View on Amazon |
| SmartPro | Reade-Iⓘ | Yes | Yes | No | View on Amazon |
| Gemlogis | Mantisⓘ | Yes | Yes | No | View on Amazon |
| Presidium | ARIⓘ | Yes | Yes | Yes | View on Amazon |
| Gemlogis | Lapisⓘ | Yes | Yes | No | View on Amazon |
| Gemlogis | Vistaⓘ | - | - | Yes | View on Amazon |
| Presidium | Synthetic Diamond Screener IIⓘ | - | - | Yes | View on Amazon |
| Presidium | Duo Tester IIⓘ | Yes | - | No | View on Amazon |
| Presidium | Refractive Index Meter II ⓘ | Yes | Yes | No | View on Amazon |
| SmartPro | Screen-I ⓘ | - | - | Yes | View on Amazon |
How much is a diamond tester?
Online stores offer a wide range of diamond testers. Prices for these devices range from a few dollars to several thousand dollars. The average price of a good diamond tester is two hundred fifty dollars. The device for such money is able to distinguish a diamond from moissanite and various diamond imitators. The operation of such devices is based on the principle of thermal conductivity and electrical conductivity. Also, devices of this price category are equipped with metal detectors, which increases the level of testing accuracy. More expensive models of diamond testers are also able to distinguish natural diamonds from synthetic ones.
How does a diamond tester work?
There are several types of diamond testers. The first type of diamond tester conducts a test based on thermal conductivity, electrical conductivity or refractive index. Some manufacturers combine several test methods in one device. Such devices can distinguish a diamond from other gemstones, but such devices will not distinguish a natural diamond from a synthetic one. Diamond testers based on thermal conductivity are the most common devices.
The second type of diamond testers are devices that are able to determine the origin of diamonds. Conventionally, diamonds can be divided into two groups, natural – mined from the ground and synthetic, grown in laboratories. Natural diamonds are more valuable than synthetic ones. Such diamond tester is suitable for people who need to know not only what a diamond is in front of them, but also what type of diamond is in front of them.
Above we have described the two most popular types of diamond testers. Most diamond testers allow you to test loose and mounted stones. There are also devices that combine these two devices in one.
Diamond tester thermal and electrical conductivity?
Diamond tester, which works on the principle of thermal conductivity, electrical conductivity is a device with one or two probe tips. Apply the probe tip of the device to the gemstone and the test result appears on the display – is the real diamond in front of you. Most devices work on the principle of thermal conductivity and electrical conductivity. Gemstones conduct heat differently, this feature helps to distinguish one stone from another. But there are exceptions. For example, diamond and moissanite have the same thermal conductivity, so a diamond tester can confuse and determine the stone incorrectly. Therefore, in order to avoid such a mistake in the device, it must be possible to conduct a moissanite test. Diamond tester can distinguish a diamond from moissanite using electrical conductivity, this indicator is different for these stones. For accurate analysis, choose devices with the ability to conduct moissanite test.