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 Presidium Adamas Tester is designed to quickly identify diamonds, moissanites, and simulants, making it a useful tool for jewelers or enthusiasts checking small stones. Its standout feature is the industry’s thinnest tip, which can test very small diamonds (down to 0.02 carats) and diamond melees, especially when paired with the optional micro probe. This improves accuracy for tiny stones that other testers might miss. The interchangeable probe tip allows users to replace a worn or damaged tip without losing testing time.

The tester provides clear results on a bright LED screen and powers off automatically to save battery. It runs on three AAA batteries, but also includes a USB cable and adapter, adding flexibility for power sources. Its compact, ergonomic shape makes it comfortable to hold and easy to carry, supporting portability well.

Some users report that accuracy can sometimes vary, and the need to purchase the micro probe separately for the smallest stones may be inconvenient. Battery life is decent but depends on usage. This device suits those seeking a reliable tester for quick checks on smaller diamonds with the convenience of a replaceable probe, though it might not be the ideal choice for heavy professional use or those wanting an all-in-one solution.

The GemTrue APEX 5-in-1 Diamond Tester is a versatile and user-friendly tool designed to identify natural diamonds, lab-grown diamonds, moissanite, and other simulants with high accuracy. It stands out with its professional-level precision, thanks to advanced technology and an automatic calibration feature that removes the need for manual adjustments, helping ensure reliable results each time you test a gemstone. The device features a colorful touchscreen that simplifies operation by clearly labeling different testing modes, making it easier even for beginners to use without confusion.

Its compact pen-like design is lightweight and comfortable to hold, which enhances portability and makes it convenient for use both in a workshop or on the go. Measuring just 5 inches long and weighing only 8 ounces, it’s easy to carry and store. The included Rosenthal Collection polishing cloth is a nice touch for maintaining both the tester and your gems in good condition. While the product has excellent user feedback and a strong set of features, it may feel a bit specialized for casual users who test gems infrequently or don’t require multi-stone identification.

This tester represents a solid choice for jewelers, gemologists, and serious collectors needing a reliable, portable, and straightforward device for identifying a wide range of gemstones.