Below you’ll find our collection of Questions & Answers.

Do you have more questions?

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Why should I buy GemPen?


  • Screens hundreds of stones in a matter of minutes in the GemPen Travel Case
  • Stones don’t have to be handled individually
  • Visible to the eye and not locked up in a compartment when performing a screening.


  • Screen gemstones in the field and when meeting clients
  • Battery powered and re-chargeable
  • Reduces risks and enables safer decisions while trading gemstones


  • Stones of all sizes can be screened
  • Works great for melee.


  • Rough, polished and mounted (even closed back settings)
  • Synthetic diamonds, rubies & sapphires and most known treatments.


  • Filters for GemPen will be developed for new types of synthetics and treatments
  • Filters for GemPen will be developed for other gemstones
  • GemPen Academy is continuously updated.


  • Exclusive design
  • Designed and assembled in Sweden
  • Custom built powerful Xenon UV light source

What is GemPen?

GemPen® is a portable battery powered tool especially designed for jewellers & gemmologists to screen diamonds, rubies & sapphires for synthetics & treatments.

How does it work?

After GemPen is turned on and directed towards a gemstone a fluorescing effect will occur. By analyzing this effect, certain conclusions can be deducted. GemPen gives instant indicative results. GemPen utilizes unique combinations of Xenon UV-wave lengths and filtering, provoking variable fluorescences in gemstones. With this USOF (Ultra Spectrum Optical Filtering) technology, GemPen showcases unique effects, providing results on treatments and synthetics normally not visible with lower output UV-light products. The combination of calibrated lighting and filtering distinguishes GemPen from less powerful UV-light devices – with consistent results and broader use cases. GemPen Premium comes with four different filters used on differing occasions based on gemstone and manipulation type. For optimal results, all four filters should be used, in particular to indicate treatments.

Can GemPen distinguish between natural diamonds and synthetics on the market?

We have achieved positive indications distinguishing natural diamonds from most existing synthetic diamonds, both CVD grown and HPHT grown.

Can GemPen identify other treatments such as?

• Glass fillings: Yes

• Heat, Beryllium and Cobalt: Yes

• HPHT colour enhancement: Yes

• Irradiation: Yes

Is GemPen giving indicative or conclusive results?

The results are indicative. GemPen is a screening tool that helps with the interpretation of the identity of diamonds, rubies and sapphires. It is up to the professional gemmologist to interpret the results. You can consult the following information:

• GemPen Test Tree
• GemPen Fluorescence Colour Map
• GemPen Diamond Map
• GemPen Gemstone Map

Can GemPen indicate between different types of synthetic diamonds?

We have achieved positive indications between most synthetic grown diamonds, CVD’s (Chemical Vapor Deposition) and HPHT’s (High Pressure High Temperature, both BELT and BARS).  The professional user can usually see the difference between HPHT grown and CVD grown stones. **Refer to our Diamond Map

  • HPHT diamonds will usually strongly fluoresce and intensely phosphoresce (keep glowing) for several seconds, sometimes much longer.
  • CVD diamonds can fluoresce in a range of different colours and emit a more subtle intensity and length of phosphorescence. The fluorescence colour of synthetic CVD diamonds may vary due to variations in the manufacturing process of different manufacturers.

How long does one battery charge last?

Estimate continuous user-time of approximately 1 hour and it will take 4-5 hours to fully charge.

See ‘Battery’ info on our website for charging instructions: https://gemometrics.com/battery/

What is the difference between GemPen and diamond testers?

Diamond testers only determine whether it is a diamond or a simulant (such as moissanite or cubic zirconia). GemPen will give an indication if it is a natural, synthetic or treated diamond. When using GemPen, it is important to know the identity of the stone before testing. GemPen doesn’t substitute diamond testers but complements them.

What is the difference between GemPen and synthetic diamond testers?

GemPen works on both CVD grown and HPHT grown diamonds in all sizes. GemPen works on rough, polished and mounted stones (including those with closed backs) and can also indicate treatments such as HPHT-treatment on natural diamonds.

Do you still require laboratory testing?

GemPen is an excellent screening device to get a quick indicative result. If in doubt, further testing is recommended.

Should I use other tools together with GemPen when testing gemstones?

Yes, GemPen is a complementary tool. It is necessary to conduct prior tests to ascertain the type of gemstone that is screened.