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Irradiation Treatment

Virtually every blue topaz sold in the market today is the product of irradiation treatment.

Blue topaz is actually very rare in nature, and tends to a very pale blue. The lovely blue topaz gemstones we find today are produced by subjecting clear topaz to electrons from a linear accelerator or by exposing them to neutrons from a nuclear reactor.

The color in topaz is produced from defects in the crystal structure rather than from chemical elements in the stone. So exposing topaz to radiation induces color changes by modifying the way in which the crystal structure absorbs frequencies of light.

Depending on the duration and type of irradiation, and the sort of heating process used afterward, the results vary from light sky blue, to medium Swiss blue and darker London blue. Other slight color variations have been produced and given their own tradenames like "electric blue" and "neon blue". London blue is the scarcest and most expensive type because it requires neutron exposure (the most expensive process), and the longest holding times.

Although the irradiation of gemstones can leave some residual radioactivity, the duration is well-monitored. Government agencies in the USA, and other gem irradiating nations, have strict regulations for the holding and testing of irradiated gems to assure that they are not released to the public until they are safe to handle and wear.

  • First Published: December-16-2006
  • Last Updated: June-05-2014
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    Reproduction (text or graphics) without the express written consent of (SETT Company Ltd.) is strictly prohibited.
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Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

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