10 Best Diamond Testers 2026 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 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 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.