10 Best Diamond Testers 2026 in the United States
#1
Winner
SmartPro Aura Diamond Screener, Mounted and Loose Stone Testing, 0.002ct Detection, Auto-Detection with 360-Degree View
The SmartPro Aura Diamond Screener is designed to test both mounted jewelry and loose stones, which makes it quite flexible for different needs. Its standout feature is the ability to detect extremely small stones down to 0.002 carats, using automated screening with options for a quick test or a thorough 360-degree detection. This makes it useful for accurately identifying natural diamonds, CVD and HPHT synthetic diamonds, and common simulants like cubic zirconia.
#2
Presidium Instruments Gem Tester II (PGT II) with Assisted Thermal Calibration (ATC) for Identifying Diamonds/Moissanites and Common Colored Gemstones
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
9.4
Testing Method
Accuracy
Portability
Most important from
1334 reviews
#3
Presidium Adamas Diamond and Moissanite Tester | World’s First Tester with Replaceable Micro Probe Tip | for Authenticating Diamonds with Included AC Adapter
The Presidium Adamas Tester is designed to quickly identify diamonds, moissanites, and simulants, making it a useful tool for jewelers or enthusiasts checking small stones. Its standout feature is the industry’s thinnest tip, which can test very small diamonds (down to 0.02 carats) and diamond melees, especially when paired with the optional micro probe. This improves accuracy for tiny stones that other testers might miss. The interchangeable probe tip allows users to replace a worn or damaged tip without losing testing time.
Rating
8.2
Accuracy
Battery Life
Ease of Use
Most important from
47 reviews
Top 10 Best Diamond Testers 2026 in the United States
#1
Winner
SmartPro Aura Diamond Screener, Mounted and Loose Stone Testing, 0.002ct Detection, Auto-Detection with 360-Degree View
SmartPro Aura Diamond Screener, Mounted and Loose Stone Testing, 0.002ct Detection, Auto-Detection with 360-Degree View
Testing Method: automated quick or 360-degree screening
Accuracy: detects stones down to 0.002 carats
Ease of Use: smartphone and camera automate processing
Portability: compact, lightweight, movable, not handheld
Battery Life: low power use, longer run time
Additional Features: handles 576 stones; supports D-K colors
Chosen by 1339 this week
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
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
Presidium Adamas Diamond and Moissanite Tester | World’s First Tester with Replaceable Micro Probe Tip | for Authenticating Diamonds with Included AC Adapter
Presidium Adamas Diamond and Moissanite Tester | World’s First Tester with Replaceable Micro Probe Tip | for Authenticating Diamonds with Included AC Adapter
Testing Method: Thinnest tip, interchangeable probe tip
Ease of Use: Clear results, bright LED screen, ergonomic
Portability: Compact, ergonomic, easy to carry
Battery Life: Decent, usage dependent
Additional Features: Auto power off, USB cable, replaceable tip
Smart Pro MAX Diamond Tester - 5-in-1 Thermal & Optical Probe for Moissanite, Lab Diamond & CZ Detection (0.02ct+)
Smart Pro MAX Diamond Tester - 5-in-1 Thermal & Optical Probe for Moissanite, Lab Diamond & CZ Detection (0.02ct+)
Testing Method: dual-technology probe with thermal, optical
Ease of Use: color touchscreen, multilingual voice, rotation
Portability: rechargeable battery, handheld, larger size
Battery Life: rechargeable battery
Additional Features: Bluetooth, 5-in-1 detection, app
SmartPro Optimum-I Diamond Tester Pen - CVD/HPHT & Moissanite Simulant Identifier with LCD Touchscreen
SmartPro Optimum-I Diamond Tester Pen - CVD/HPHT & Moissanite Simulant Identifier with LCD Touchscreen
Testing Method: advanced reflectivity technology
Accuracy: tests stones 0.015 to 10 carats
Ease of Use: 2.4-inch color LCD touchscreen
Portability: handheld with protective case, 7.48x12.99x15.35
Battery Life: USB powered, no replacements needed
Additional Features: torch mode; works on loose/mounted stones
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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
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
SAM by Presidium | Advanced Diamond and Moissanite Tester with Thermoelectrical Probe | Detects Low Conductivity Moissanite | 0.01–10 Carat Diamond Testing Tool
SAM by Presidium | Advanced Diamond and Moissanite Tester with Thermoelectrical Probe | Detects Low Conductivity Moissanite | 0.01–10 Carat Diamond Testing Tool
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
GemOro UltraTester 3+ Diamond Tester | Test Diamond, Moissanite, White Sapphire Gemstone | Precision Tool with Expert Professional Reading & Accuracy
GemOro UltraTester 3+ Diamond Tester | Test Diamond, Moissanite, White Sapphire Gemstone | Precision Tool with Expert Professional Reading & Accuracy
Testing Method: advanced scanning technology
Accuracy: highly accurate for diamonds
Ease of Use: ergonomic design, retractable probe tip
Portability: portable, 9 x 5 x 2 inches
Battery Life: auto-off saves battery life
Additional Features: LED illumination, UV detection, flexible power
Presidium Duo Tester (PDT II) Diamond and Colored Gemstone Tester | Thermal Conductivity and Reflectivity Testing | Assisted Thermal Calibration (ATC) | Professional Jewelry Testing Tool
Presidium Duo Tester (PDT II) Diamond and Colored Gemstone Tester | Thermal Conductivity and Reflectivity Testing | Assisted Thermal Calibration (ATC) | Professional Jewelry Testing Tool
Testing Method: thermal conductivity and reflectivity
Accuracy: Assisted Thermal Calibration (ATC)
Ease of Use: large dial with color-coded indicators
Portability: compact, battery-powered, weighs 0.7 kg
Additional Features: thin probe tip, tests stones 0.02 ct
#10
Presidium Multi Tester III (PMuT III) All-in-One Instrument for Testing Diamonds, Moissanites and Diamond Simulants
Presidium Multi Tester III (PMuT III) All-in-One Instrument for Testing Diamonds, Moissanites and Diamond Simulants
Testing Method: combined testing method
Accuracy: variable; generally good, less reliable stones
Ease of Use: ergonomic design, rubber grip, bright LED
Portability: handheld, lightweight, uses three AAA batteries
Battery Life: decent, depends on usage
Additional Features: thin retractable probe for 0.02 carats
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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.