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 Pen Professional with UV Light is a versatile tool designed for both novices and experts in the jewelry field. It uses thermal conductivity to distinguish real diamonds from fake ones, which is reliable but can sometimes confuse metals for diamonds. The tester is equipped with an LCD display and LED indicators, making it easy to read results. It also emits sounds when a real diamond is detected, which is helpful for quick identification.

The device is simple to use with key operations that don't require professional knowledge, though proper handling and following instructions are crucial for accurate results. It's lightweight (4.2 ounces) and portable, which is great for on-the-go testing. The inclusion of a rechargeable battery is a plus, reducing the need for frequent replacements.

However, users must manually adjust settings based on the size of the gem, which might be a bit cumbersome for some. An additional UV light feature can aid in further verification of diamonds and other gemstones. The tester's popularity among professionals, hobbyists, and business owners is reflected in its positive customer reviews, though occasional issues with accuracy due to user error have been noted. This diamond tester is a practical tool for anyone in need of a reliable, portable diamond testing solution.