Of all the gemstones that have been irradiated in recent decades, only blue topaz is still commercially available.
Foto: K. Sieber, www.makrogalerie.de
Radioactivity in gemstones are a sensitive subject. To clarify a common misconception right at the beginning: Not every radioactiv irradiated gemstone becomes radioactive itself as a result of the treatment. Only a very few types of gemstones can be activated by certain irradiation techniques and emit radioactive radiation. Gemstones that are not marked as actively radiating in the following article are NOT radioactive. If you want to know right away which gemstones we are talking of, please scroll down to the "Conclusion" paragraph.
The multitude of natural, radioactive MINERALS and their potential danger is not the subject of this article. This is specifically about artificially irradiated gemstones.
Already at the beginning of the 20th century, it was discovered through systematic research into the causes of color in minerals, that some varieties owe their intense colors to the influence of natural radiation. Smoky quartz and amethyst, violet fluorite, blue salt, yellow sapphires and green diamonds, they all get their color from the influence of natural radioactivity. The source of radiation can be the surrounding rock, and in rare cases, even cosmic radiation. First experiments to imitate these processes artificially were promising.
In the middle of the century, artificially irradiated smoky quartz crystals were produced, but they did not yet achieve commercial significance. It was not until the discovery that colorless topaz could produce intense blue hues by irradiation and subsequent heating that a commercial breakthrough was achieved. Meanwhile, several tons of topaz are irradiated and processed each year.
Types of radiation and their effects on the affected gemstone
The types of radiation gemstones are exposed to range from high-energy electromagnetic radiation (gamma or X-ray radiation), particle radiation (beta radiation) to bombardment with free neutrons and protons. Only the latter irradiation technique can produce elements as a by-product that lead to a noticeable radioactivity of the stone. This collateral radiation can occur, for example, in green and black diamonds when inclusion-rich source material has been used or in blue topaz that has been bombarded with neutrons (and only then). Such neutron-irradiated topaz (typically in the "London Blue" color) may continue to exhibit measurable radioactivity for several years. Therefore, it must first be quarantined until its radioactivity has decayed to the legally specified limits (see below). Blue topaz irradiated with electrons shows lighter hues (trade name: "Electric Blue") and is not radioactive.
Radiation exposure and legal limits
In the European Union, radioactive gemstones and those activated by artificial irradiation may be given to persons only if their specific activity does not exceed 100 Bq per gram.
|The handling of radioactive gemstones (storage, working and processing) is subject to authorization in the EU if the specific activity of the stone exceeds 0.5 Bq/gr.|
Artificial color enhancement by irradiation
The following table lists those gemstones for which a color change is possible due to artificial irradiation. For some types of stones, the irradiation color may fade in sunlight. Such unstable color varieties are marked by an asterisk (*) directly behind the respective color. Gemstones that can actively emit radiation due to irradiation are marked by an [R] behind the respective color. Where there is no [R], no measurable radioactivity has ever been known in the last 50 years until today.
|Gemstone||color before irradiation||color after irradiation||potential radioactivity of irradiated stones|
blass grün bis gelb
grün bis goldgelb
no, respectively not in trade
|* Color is unstable (fades in sunlight)|
|no, respectively not in trade|
|Diamond||farblos, blassfarben||blau, braun, schwarz [R], grün [R]||no, respectively not in trade|
|gelblich, bräunlich||gelb, pink, rot (zusätzlich erhitzt)||no|
|Fluorite||farblos||grün, blau, violett||no|
|rauchgrau, schwarz, violett, hellgrün||no|
|gelb*||* Color is unstable (fades in sunlight)|
|intensiv gelb||no, respectively not in trade|
|Spodumen||rosa||grün*, violett* (selten)||* Color is unstable (fades in sunlight)|
gelb, orange, grün
|braun [R], blau [R]||yes ("Swiss Blue", "London Blue")|
|Tourmaline||blass rosa, blassblau, blassgrün||rosa bis rot||no|
|gelb, pfirsichfarbig, orange|
|dunkel blau, dunkel grün||
[R] Radioactivity possible
In every department store catalog you can find jewelry set with blue topaz. The usual designation is: "blue topaz, treated" and treated in this case means: irradiated and heated.
According to european laws, irradiated stones must be declared as "irradiated" or "treated" without exception. This applies to all business documents, invoices, advertising brochures, inscriptions on stock exchanges, etc.
What is the risk of being exposed to radioactive material?
According to the assessment of the EPI laboratory, the risk is extremely low. In the last 20 years, NO irradiated gemstones have been submitted to the EPI lab that exceeded the above limits.
Compared to other treatment methods, artificial irradiation of gemstones is relatively uncommon. If we put the cost of irradiation in relation to the achievable result, from the point of view of profitability it is obvious that only gemstones that meet the following conditions have a commercial chance:
1. the color should be stable. This is not the case with blue beryl (maxixe type), green spodumene (hiddenite) and partly yellow sapphire.
2. irradiation costs should be lower than the expected sales revenue. Gamma or X-rays are readily available and inexpensive, irradiation with neutrons or protons is much more expensive. Therefore, in general, only stones that also achieve a corresponding market value are treated.
3. natural availability should be low and/or demand should be high.
Essentially, only four minerals meet the above conditions: blue topaz, colored diamond, red tourmaline and smoky quartz. These four are offered for sale in real life. All other gemstone varieties mentioned in this article are extremely rare to find. Black diamond and green diamond have come up for sale now and then in the past with some measurable radioactivity. However, the currently increasingly offered necklaces and bracelets made of black diamond slivers or rough diamonds are all natural (unirradiated) diamonds, with no danger for harm. Remaining is only the blue topaz in the color "London Blue", which may be radioactive. "London Blue" is a dark, slightly grayish hue. Not affected are the ubiquitous light blue, neon blue, radiant light shades. Radioactivity has never been measured in these light-colored blue topazes.
Natural radioactive gemstones
At this point, especially green zircon, which can emit radioactivity, should be mentioned. Sometimes it can contain so many radioactive inclusions that its crystal structure is destroyed (metamict). In apatite and titanite, the natural radioactivity is usually less than the natural background radiation. Heliodor from the Rössing mine in Namibia, Ekanite and Monazite are only interesting for collectors.
|Mineral||Color||Source of Radiation|
|Apatite (*)||blue, green, yellow||Uran (U), Ce, Eu, La, Th und Y|
|Ekanit||green, light brown||Thorium (Th)|
|Heliodor (Rössing deposit, Namibia)||yellow-green||Uran (U)|
|Monazite||brownish yellow||Thorium (Th)|
|Titanite (*)||yellow to brown, green to black||Uran (U), Ce, Eu, La und Th|
|Zircon (metamict)||green||Uran (U), Thorium (Th)|
(*) Radioactivity usually not measurable
Autor: Dipl.-Min. B. Bruder
© INSTITUT FÜR EDELSTEIN PRÜFUNG (EPI)