How to use the presidium gem tester

Written by linda richard
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How to use the presidium gem tester
Diamonds and simulants can be checked with the gem tester. (Jasmin Awad/Photodisc/Getty Images)

The Presidium Gem Tester measures the heat conductivity of a gemstone and will test gemstones like diamond, topaz, sapphire or ruby. In addition to diamond being the hardest mineral, it is also the most heat-conductive. This makes it ideal for testing with the gem tester, although handheld diamond testers are also available. The Presidium Gem Tester is larger than a handheld instrument, and it tests other gemstones. It includes a colour stone estimating function that distinguishes gemstones from glass, ruby or emerald from garnet, and sapphire from tanzanite. It does not distinguish between natural and synthetic stones.

Skill level:
Moderately Easy


  1. 1

    Clean and dry the gemstone to be tested. This gem tester tests diamonds, but also tests sapphire, emerald, jadeite, ruby, topaz and spinel.

  2. 2

    Plug the gem tester into a power source or use batteries if you prefer. This gem tester uses two AA alkaline batteries.

  3. 3

    Remove the cap on the probe and make sure the tip is clean. Turn the instrument on and wait about 20 seconds for warm-up.

  4. 4

    Perform a practice test with the test disc for diamond or simulant on the tester, using the probe to push on the disc. The test disc is on the front of the tester and is used like a sample stone. Within 2 or 3 seconds, you should see the dial move to the area for the diamond or simulant.

  5. 5

    Push the probe into the gemstone so that the probe wire tip retracts. When you test, it checks the heat conductivity and identifies the stone.

  6. 6

    Watch the dial move. If it moves to the green area, the stone is a diamond. Readings in the red area are other gemstones, identified on the gem tester screen in the area of the dial. This gem tester can be used for loose or mounted stones of any type.

Tips and warnings

  • Take care of the gem tester by replacing it in the soft case and the hard case after each use.

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