10 Best Diamond Testers 2026 in the United States

The HMKIS Diamond Tester Pen is designed for both novices and experts who need to verify the authenticity of diamonds quickly and accurately. One of its standout features is the dual power supply option, allowing users to choose between a Type-C or a 9V power source, which enhances accuracy and stability. The tool is user-friendly, requiring no professional knowledge to operate; users simply select the diamond size and place the tester on the gemstone. The audible signals and LED indicators make interpreting results straightforward, which is great for anyone needing quick assessments.

Portability is another strong point, as the device is lightweight (120 grams) and compact, making it easy to carry for on-the-go testing. Additionally, the inclusion of a 60X LED Jeweler's Loupe enhances its functionality, allowing for detailed inspections of not just diamonds, but also various collectibles and antiques.

The HMKIS diamond tester requires careful handling; incorrect use, such as not touching the panel or testing unsuitable items, can lead to inaccurate results. Users must also ensure they select the correct diamond size before testing, which could be a minor hassle for some.

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.

The tester is simple to operate, featuring a clear analog dial that can differentiate between 16 types of gemstones, including diamonds and moissanites. This ease of use is beneficial for those who may not be very tech-savvy, as it keeps the testing process straightforward.

There are some drawbacks to consider. Despite its user-friendly design, calibration issues can arise during shipping, which may require assistance from the manufacturer. Additionally, the reliance on AA batteries may be seen as a minor inconvenience for some, as it requires regular replacements. While it generally delivers consistent and reliable results, the quality can vary slightly based on calibration and user proficiency. Being aware of this can help manage expectations.

The SAM by Presidium Diamond Tester is a reliable tool designed to identify diamonds and a wide range of moissanites, including those with low electrical conductivity. This makes it especially useful for jewelers who deal with various types of gemstones. One of its standout features is its advanced processing and detection algorithm, which ensures the fastest startup and testing time in the industry.

The highly sensitive thermoelectrical probe further enhances its accuracy and precision in identifying gemstones across a carat range of 0.01 to 10 carats. Users will appreciate the ease of use and safety features, making it suitable for both professionals and enthusiasts. The LED display adds to its user-friendly experience, providing clear and easy-to-read results.

In terms of portability, the tester is lightweight (1.94 ounces) and compact (6.69 x 1.2 x 1.1 inches), making it convenient to carry around. It also offers versatility in power options, being able to run on USB or 3 AAA batteries, with an impressive battery life allowing for approximately 2,000 continuous tests. Despite minor drawbacks, such as the need to purchase additional batteries, the SAM by Presidium Diamond Tester is a dependable and efficient tool for testing diamonds and moissanites.