How to Test Gem Stones

Written by graham rix
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How to Test Gem Stones
To have a gem thoroughly tested for colour and clarity, you will need to submit it to a body of professional gemologists. (Jeffrey Hamilton/Photodisc/Getty Images)

The most important reason for testing a gemstone is to establish whether it is a real or some kind of cheaper alternative, such as paste or glass. This is something you can do reasonably effectively yourself, with the help of an ultraviolet torch. If you want to tell one gemstone from another, you will need an electronic tester. Beyond that, gemstones can be tested for commercially important factors such as strength of colour and clarity, the absence of flaws or inclusions. For that kind of testing, you will need to submit the gemstone to a professional body of gemologists.

Skill level:
Moderately Challenging

Things you need

  • Ultraviolet (U.V.) torch
  • Electronic gem tester

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  1. 1

    Place a gemstone in a dark room or shade it from the light under a cloth, then shine the beam from an ultraviolet (U.V.) torch on it. If the gemstone is genuine, then it will fluorescence; by contrast, costume jewellery won't react to the light. This is a useful blanket test for gemstones.

  2. 2

    Test the gemstone with an electronic gem tester. This is a hand-held device with a probe which looks rather like a pen. You use it by simply applying the probe to the gem. The result read out on the dial will distinguish between a wide number of the most common coloured stones.

  3. 3

    Send your gemstone to be appraised by a body of professional gemologists. They will subject your stone to a battery of tests and return it to you with a detailed written assessment which can be extremely useful should you wish to sell the gem later. Only unmounted gems can be sent for appraisal by a gemologist.

Tips and warnings

  • Ultraviolet (U.V.) torches are available from high street home security stores.
  • Gem testers are available from online jeweller's accessories stores.

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