10 Best Diamond Testers 2025 in the United States

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 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.

The digital LED screen provides clear, easy-to-read results, and the ergonomic design with a chrome finish makes it comfortable to hold during use. Portability is a strong point here as the device is lightweight and handheld, with the added convenience of a USB port for alternative power options. While the PGI is reliable for many gemstone types, accuracy can depend on the stone and user technique, so some experience is helpful.

Battery life is decent, though details are limited, which could be a factor for heavy use. This tool is especially suitable for jewelers or hobbyists dealing with multiple gemstone types rather than just diamond testing. The PGI is a practical, easy-to-use tester with good versatility, but users should be mindful of its limitations in absolute precision and battery specifics.

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.