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Diamond Testers

10 Best Diamond Testers 2025 in the United States

#1

Winner

10.0 score

Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones

Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones

Presidium

10.0 score

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The Presidium Instruments Gem Tester II (PGT II) is a solid choice for anyone needing a reliable diamond tester, particularly hobbyists and professionals in the jewelry field. One of its standout features is the Assisted Thermal Calibration (ATC), which allows users to calibrate the device easily to their environment, enhancing accuracy in testing. This model is designed to be compact and portable, making it easy to transport, which is a significant advantage for gemologists on the go or those attending trade shows.

Rating
10.0
Chosen by1,109
Testing Method
Accuracy
Portability

Most important from
1254 reviews

Testing Method
This machine tests thermal conductivity, offering a reliable method to distinguish glass from precious stones.
Accuracy
Once calibrated, the device works well and easily determines if stones are glass.
Portability
The Presidium Instruments Gem Tester II is portable and customer-displayable, making it convenient for on-the-go gemologists.
#2
9.1 score

Presidium Instruments Gem Indicator (PGI) Handheld Tester for Identifying Diamonds and Common Colored Gemstones

Presidium Instruments Gem Indicator (PGI) Handheld Tester for Identifying Diamonds and Common Colored Gemstones

Presidium

9.1 score

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The Presidium Gem Indicator (PGI) is a handheld diamond tester designed to identify diamonds and a wide range of colored gemstones quickly, usually within 6 seconds. Its standout feature is a retractable, thin probe tip that maintains consistent pressure on stones, helping to improve accuracy. It supports testing up to 31 types of gemstones, which is quite versatile compared to many testers that focus only on diamonds.

Rating
9.1
Testing Method
Accuracy
Ease of Use

Most important from
52 reviews

Testing Method
The tester requires some knowledge of gemstones to use effectively and comes with helpful resources like a downloadable spreadsheet for reference.
Accuracy
Accuracy can be inconsistent, particularly with blue and green stones, which are often misidentified as glass.
Ease of Use
The retractable thin tip is useful for testing smaller gems, improving usability over bulkier testers.
Portability
Portability and the option to power via USB add convenience for on-the-go testing.
Additional Features
The device does not support testing moissanite, a notable limitation for some users.
#3
8.5 score

Valkynos Professional Diamond Tester Pen with 365nm UV Light & Thermal Sensor – Fast 0.5s Detection, Portable Gem Checker for Novice & Experts – Battery Included

Valkynos Professional Diamond Tester Pen with 365nm UV Light & Thermal Sensor – Fast 0.5s Detection, Portable Gem Checker for Novice & Experts – Battery Included

Valkynos

8.5 score

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The Valkynos Professional Diamond Tester Pen is a handy tool designed for anyone who wants to quickly check if a diamond is real, whether you're a beginner or more experienced. It uses thermal conductivity to test gems and gives results in just half a second, which is impressively fast. It can accurately identify diamonds as small as 0.02 carats, making it useful for a range of stones. A nice extra is the built-in UV light that helps spot diamond fluorescence, adding another layer of verification. This is something not all testers offer and can help catch fakes that might slip through thermal testing alone.

Rating
8.5
Testing Method
Accuracy
Ease of Use

Most important from
30 reviews

Testing Method
Delivers quick and reliable diamond verification with results in just seconds, making it perfect for casual users and collectors.
Accuracy
Accuracy depends on positioning the tester pin correctly on the stone, emphasizing careful handling for best results.
Ease of Use
The loud beeping sound clearly signals a genuine diamond, though an option to mute it would improve user experience.
Portability
Compact and lightweight design fits comfortably in hand and easily carries in the included protective pouch, ideal for on-the-go testing.
Battery Life
Battery comes included and works out of the box, with replacements readily available to ensure uninterrupted use.
Additional Features
Built-in UV light is a valuable feature for spotting diamond fluorescence, adding an extra layer of authenticity check.

Top 10 Best Diamond Testers 2025 in the United States

#1

Winner

10.0  score
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Presidium

Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones

Testing Method: Thermoelectric probe
Accuracy: Assisted Thermal Calibration
Ease of Use: Simple to operate, clear dial
Portability: Compact and portable
Additional Features: Differentiates 16 types of gemstones

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Chosen by 1109 this week

#2
9.1  score
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Presidium

Presidium Instruments Gem Indicator (PGI) Handheld Tester for Identifying Diamonds and Common Colored Gemstones

Testing Method: Handheld diamond tester with thin probe
Accuracy: Depends on stone and user technique
Ease of Use: Ergonomic design, digital LED screen
Portability: Lightweight, handheld, USB powered
Battery Life: Decent, limited details
Additional Features: Tests 31 gemstone types, retractable tip

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#3
8.5  score
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Valkynos

Valkynos Professional Diamond Tester Pen with 365nm UV Light & Thermal Sensor – Fast 0.5s Detection, Portable Gem Checker for Novice & Experts – Battery Included

Testing Method: thermal conductivity
Accuracy: detect diamonds as small as 0.02ct
Ease of Use: red light and buzzer confirm diamond
Portability: lightweight, compact with protective pouch
Battery Life: runs on 1 9V battery included
Additional Features: built-in UV light for fluorescence

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#4
8.5  score
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HMKIS

HMKIS Diamond Tester Pen, Professional Jewelry Diamond Tester with 60X Jewelry Loupe Magnifier, Diamond Selector for Novice and Expert (Non-Rechargeable)

Testing Method: Select diamond size, place tester
Accuracy: Enhanced accuracy, dual power supply
Ease of Use: User-friendly, no professional knowledge
Portability: Lightweight (120 grams), compact
Additional Features: 60X LED Loupe, dual power supply

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#5
8.5  score
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Presidium

SAM by Presidium, Diamond Tester and Identify a Wider Range of Moissanites

Testing Method: Thermoelectrical probe
Accuracy: Identifies gemstones from 0.01 to 10 carats
Ease of Use: LED display, user-friendly
Portability: Lightweight, compact (6.69 x 1.2 x 1.1 inches)
Battery Life: Approximately 2,000 continuous tests
Additional Features: Advanced algorithm, USB or 3 AAA batteries

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#6
7.9  score
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TEKCOPLUS

Diamond Tester Jewelry Gem Stone Tester Kit – Professional 2-in-1 Tester for Diamonds, Moissanite, Metals, and Gemstones

Testing Method: fine, elastic-tipped probe
Accuracy: accurate for stones as small as 2 pt
Ease of Use: user-friendly
Additional Features: metal detector, 25s warm-up, audible alerts

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#7
7.6  score
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Presidium

PRESIDIUM DIAMONDMATE-C ELECTRONIC DIAMOND TESTER

Testing Method: Electronic
Accuracy: Good
Ease of Use: Minimal setup
Portability: 3.4 x 2.4 x 7.5 in
Battery Life: Decent

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#8
7.6  score
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Presidium

PDMT-A Diamond Mate Electronic Tester A

Testing Method: Thermal Conductivity
Accuracy: Metal detector avoids false readings
Ease of Use: User-friendly
Portability: Weighs 0.4 pounds, portable
Battery Life: Low power usage, battery indicator
Additional Features: Instant recovery, metal detector, warranty

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#9
7.3  score
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Hqdz-td

High Accuracy Professional Diamond Tester Pen, Jewelry Diamond Tester with 60X Mini LED Magnifying&40X Full Metal Illuminated Jewelry Loop Magnifier,Diamond Selector for Novice and Expert

Testing Method: Thermal conductivity
Accuracy: High
Ease of Use: User-friendly, LCD display, LED indicators
Portability: Lightweight, compact, 7 x 1 x 1.5 inches
Battery Life: Decent, 9V battery included
Additional Features: Metal alert, 60X LED magnifying glass

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#10
7.0  score
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Hqdz

Diamond Tester,High Accuracy Jewelry Diamond Tester Professional Diamond Tester Pen Jeweler Tool for Novice and Expert - Diamond Selector II 9V Battery Included(Black Diamond Testers)

Testing Method: Thermal conductivity
Accuracy: High
Ease of Use: User-friendly
Portability: Lightweight, leather pouch case
Battery Life: Standard 9V battery
Additional Features: LCD display, LED indicators, audible sounds

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Buying Guide for the Best Diamond Testers

Choosing the right diamond tester can be a crucial decision, especially if you are in the business of buying or selling diamonds, or if you simply want to ensure the authenticity of your precious stones. A diamond tester is a device that helps you determine whether a stone is a real diamond or a simulant. To make an informed decision, you need to understand the key specifications and features of diamond testers. This guide will help you navigate through the important aspects to consider when selecting a diamond tester that best fits your needs.
Testing MethodThe testing method refers to how the diamond tester determines the authenticity of a diamond. There are two main types: thermal conductivity testers and electrical conductivity testers. Thermal testers measure how well the stone conducts heat, while electrical testers measure how well it conducts electricity. Thermal testers are generally good for distinguishing diamonds from other stones like cubic zirconia, but they may not be as effective with synthetic diamonds. Electrical testers can identify synthetic diamonds but may give false positives with moissanite. Choose a tester based on the types of stones you most frequently encounter.
AccuracyAccuracy is crucial when it comes to diamond testing, as you want to be sure of the results. Higher accuracy testers will provide more reliable results, reducing the risk of false positives or negatives. Accuracy can be influenced by the quality of the tester and the technology it uses. For professional use, opt for a tester with high accuracy to ensure you are making informed decisions. For personal use, a moderately accurate tester may suffice, especially if you are not dealing with high volumes of stones.
Ease of UseEase of use refers to how user-friendly the diamond tester is. Some testers come with simple interfaces and clear instructions, making them easy to operate even for beginners. Others may have more complex features that require a bit of learning. If you are new to diamond testing, look for a tester that is straightforward and easy to use. If you are more experienced, you might prefer a tester with advanced features that offer more detailed analysis.
PortabilityPortability is an important factor if you need to test diamonds on the go. Portable diamond testers are usually compact and lightweight, making them easy to carry around. They often run on batteries, so you don't need to worry about finding a power source. If you frequently travel or need to test diamonds in different locations, a portable tester is a good choice. For stationary use, a larger, more robust tester might be more suitable.
Battery LifeBattery life is a consideration if you opt for a portable diamond tester. A tester with a long battery life will allow you to perform multiple tests without needing to recharge or replace the batteries frequently. This is especially important if you are using the tester in a professional setting where you might need to test many stones in a day. Look for testers with rechargeable batteries or those that use standard batteries that are easy to replace.
Additional FeaturesSome diamond testers come with additional features that can enhance their functionality. These may include built-in UV lights for fluorescence testing, multiple testing modes, or the ability to test other gemstones. While these features can be useful, they may also add to the complexity and cost of the tester. Consider whether these additional features are necessary for your needs or if a simpler model will suffice.

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