10 Best Diamond Testers 2025 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 Diamond Tester Professional is designed for both novices and experts with its straightforward testing method. Equipped with a high-tech chip, it provides quick results, distinguishing natural diamonds in just a second. The UV light feature is a standout, assisting in evaluating the fluorescence and quality of diamonds—a useful tool for more in-depth analysis. Its ease of use is enhanced by a simple operation procedure where the user holds the conductive panel and the probe should be positioned vertically, making it fairly intuitive even for beginners.

For accuracy, the tester uses a clear LED display with a color-coded scale from 1 to 8, giving precise readings on gemstone authenticity. The built-in light and buzzer alarm system further aid in indicating diamond authenticity with visual and audible cues, although some might find the warm-up time of 25 seconds a bit slow compared to other models.

Portability is a strong point for this pen-style tester. With dimensions of 5 x 1.18 x 0.8 inches and weighing only 3 ounces, it’s compact and easy to carry. It runs on a standard 9V battery, which is included, making it convenient to use on the go without worrying about finding a power source. However, users should note the battery life might vary depending on usage frequency, which could be a limitation for heavier users.

In terms of additional features, the automatic power-off function is practical, conserving battery life when the device is not in use. While its primary function is diamond testing, it can also test other gems and stones, including moissanite, though it may not be as precise for these as for diamonds.

This diamond tester offers good functionality for its price, especially suitable for those who require a portable and easy-to-use device for basic diamond testing. It combines multiple features, making it a versatile tool, though some may find it less efficient for intensive professional use due to its moderate battery life and warm-up time.