10 Best Diamond Testers 2026 in the United States

The SmartPro Aura Diamond Screener is designed to test both mounted jewelry and loose stones, which makes it quite flexible for different needs. Its standout feature is the ability to detect extremely small stones down to 0.002 carats, using automated screening with options for a quick test or a thorough 360-degree detection. This makes it useful for accurately identifying natural diamonds, CVD and HPHT synthetic diamonds, and common simulants like cubic zirconia.

The built-in smartphone and high-quality camera help automate result processing and even offer certification, adding convenience to the testing process. The device is compact and lightweight enough (around 5 kg or 11 pounds) to be moved if needed, though it’s not ultra-portable like a handheld tester. Its low power consumption suggests it can run for longer periods without frequent recharging. It can handle a large batch of stones (up to 576 at once), including those in transparent bags, which is great for busy jewelers or graders.

The device mainly supports colorless to near-colorless stones (D-K), so it may not be ideal for testing diamonds with stronger color grades. The price and complexity might be a consideration for casual or occasional users. The SmartPro Aura is well suited for professionals or serious hobbyists looking for detailed, automated diamond testing with reliable accuracy and efficient workflow.

The SmartPro Optimum-I Diamond Tester Pen is a versatile tool designed to identify natural diamonds, synthetic diamonds (CVD/HPHT), and moissanite using advanced reflectivity technology. It stands out for its precision, able to test stones as small as 0.015 carats to 10 carats, covering a wide variety of diamond cuts and colors. The built-in 2.4-inch color LCD touchscreen makes the tester user-friendly, providing clear results and an easy way to track how many tests have been performed.

Portability is decent given its handheld design and included protective case, although the product's dimensions suggest it’s not the smallest tester on the market. The device powers via USB, which means you don’t have to worry about battery replacements and can expect reliable battery life without warm-up delays. One useful extra feature is the torch mode, which helps check fluorescence—something valuable when assessing diamonds. This tester works well for both loose and mounted stones and is designed for both right- and left-handed users, broadening its appeal.

This device represents a strong choice for professionals or serious hobbyists needing detailed and accurate diamond testing with modern features. However, it may be less suited for those seeking a very compact or budget option, considering its size and price.

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.