Presidium Gem Tester II Colored Gemstone & Diamond Tester

The Presidium Gem Tester II (PGT II) is a professional gemstone testing instrument designed for jewelers, gemologists, appraisers, and gemstone buyers. Using thermal conductivity measurement, it helps distinguish diamonds and moissanites from many common diamond simulants while providing reference readings for up to 16 types of colored gemstones.

Compact and portable, the Presidium Gem Tester II features an easy-to-read analog display, a sensitive 0.6 mm retractable probe, and built-in reference discs. It can examine loose or mounted gemstones, including stones as small as 0.02 carats under suitable testing conditions. Whether you're evaluating jewelry at the counter or examining stones at your workbench, this tester provides valuable information for preliminary gemstone identification.

Thermal Conductivity Testing for Diamonds and Gemstones

Different gemstones transfer heat at different rates. The Presidium Gem Tester II measures these differences using a thermoelectric probe and displays the corresponding reading on its analog dial.

The built-in Colored Stone Estimator helps narrow down possible gemstone identities by comparing their thermal conductivity characteristics. Depending on the reading, the instrument can assist with distinctions such as:

• Sapphire vs. Tanzanite: Compare thermal readings to help distinguish these gemstones.
• Ruby vs. Spinel: Identify differences in thermal conductivity between visually similar stones.
• Topaz vs. Amethyst: Use the reference scale to help separate these commonly encountered gemstones.
• Gemstones vs. Glass: Assist in recognizing certain glass imitations during jewelry evaluation.
• Diamond/Moissanite screening: Identify stones that fall within the combined diamond and moissanite thermal conductivity range.

Some gemstone types share overlapping readings. The tester therefore displays possible gemstone groups rather than always providing a single definitive identification.

Features Designed for Professional Gemstone Testing

• 0.6 mm retractable probe: The fine thermoelectric tip maintains consistent contact pressure and allows testing of gemstones as small as 0.02 carats.
• Analog gemstone identification display: Clearly marked conductivity ranges make results easy to interpret.
• 16 colored gemstone types: Helps distinguish between common gemstones using their thermal properties.
• Metal contact alert: An audible buzzer warns when the probe touches a metal setting instead of the gemstone.
• Built-in reference discs: Integrated Glass and Calibration (CAL) discs allow users to check instrument performance.
• Loose and mounted stone testing: Suitable for examining accessible gemstones in jewelry settings or as loose stones.
• Portable power: Operates on two AA alkaline batteries or the included compatible AC adapter.
• Convenient repeated testing: No routine waiting period between tests after initial warm-up, although very small stones may require cooling before retesting.

Practical Applications for Jewelers and Gemologists

The Presidium Gem Tester II can support routine gemstone evaluation in several professional environments:

• Jewelry retail: Perform preliminary checks on gemstones in incoming merchandise and customer jewelry.
• Gemstone buying: Compare thermal conductivity readings when assessing loose stones before purchase.
• Jewelry appraisal: Use thermal testing as supporting evidence alongside visual inspection and other gemological methods.
• Jewelry repair: Examine accessible mounted gemstones during intake and documentation.
• Gemology education: Demonstrate how different gemstone materials respond to thermal conductivity testing.

Technical Specifications

• Brand: Presidium
• Model: Gem Tester II (PGT II)
• SEP Tools SKU: 54-1143
• Testing method: Thermal conductivity
• Gemstone reference capability: Up to 16 common colored gemstone types
• Probe: Retractable thermoelectric tip
• Probe tip diameter: 0.6 mm
• Minimum gemstone size: 0.02 carats under suitable conditions
• Display: Analog conductivity indicator
• Metal detection: Audible contact alert
• Reference discs: Built-in Glass and Calibration (CAL)
• Power supply: 2 AA alkaline batteries or compatible AC adapter
• Battery operating time: Approximately 3 hours of continuous use with alkaline batteries
• Initial warm-up: Approximately 20 seconds
• Recommended operating temperature: 65–80°F (18–27°C)
• Dimensions: 125 x 90 x 70 mm (4.93 x 3.55 x 2.76 inches)
• Weight: Approximately 220 g (7.76 oz), excluding batteries

What's Included

According to the manufacturer's standard package documentation, the Presidium Gem Tester II includes:

• Presidium Gem Tester II testing unit
• Thermoelectric probe pen
• Built-in Glass and Calibration reference discs
• AC power adapter
• Protective carrying case
• User handbook
• Warranty card

Important Testing Limitations

The Presidium Gem Tester II is intended for preliminary gemstone testing and supporting identification, not conclusive gemstone certification.

Diamond and moissanite: Both materials can produce readings within the same Diamond/Moissanite range. A separate moissanite identification method is required to distinguish them.

Natural and synthetic gemstones: The tester cannot determine whether a colored gemstone is natural or laboratory-grown. Additional gemological testing is required to establish origin.

For consistent readings, gemstones should be clean, dry, and allowed to reach room temperature before testing. The probe should contact the gemstone directly, avoiding metal settings. Multiple readings and complementary identification methods are recommended when results are uncertain.

Expand Your Gemstone Testing Capabilities

For additional identification options, browse our selection of diamond and gemstone testers. Professionals who need to examine inclusions, surface features, and jewelry settings in greater detail can also explore our gemological microscopes.

The Presidium Gem Tester II combines portable operation, a sensitive thermal probe, and an accessible analog reference scale, making it a useful instrument for jewelers and gemstone professionals who need practical preliminary testing at the counter or workbench.

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