Irradiated Gemstones

In recent months there has been a flurry of interest in irradiated gemstones - primarily blue topaz - on the part of state and federal regulators. Although the actual health risk from these gemstones is negligible, the regulatory risks can be significant. I have been working with jewelry importers and with regulators to try to come up with an approach to this issue so that business can go on as before. At the moment, however, this is something that we're still working on, and I can't give you any easy answers.

What I have here is what information I have been able to find on the matter. There is a combination of scientific and technical information, some regulatory guidance documents, and some articles (including one that I wrote). Hopefully this will be of help to you.

Jewelry Importers

If you are a jewelry importer and you intend to apply for a radioactive materials license, here are some of the steps you will have to take.

Concerned customers

If you have purchased blue topaz or another irradiated gemstone, you should be relieved to know that the radiation dose from these gems is very low, and you don't need to worry about the radiation affecting your health. Even if you wear your jewelry continuously, the radiation dose will be too low to cause skin burns or to give you cancer.

Radiation Safety Professionals

Pure topaz is nearly colorless; the colors in topaz come from trace impurities and small defects in the crystal structure; these can cause small changes in the arrangement of electrons in the crystal that, ultimately, are the cause for the different colors that we see. Impurities are responsible for most of the colors that we see, but color can also be induced by subjecting the topaz to neutron, electron, or gamma radiation. This irradiation can induce defects in the crystal structure, or can change the arrangement of electrons within the crystal, and these changes will cause the topaz to turn blue. Neutrons, being more penetrating and more heavily ionizing than electrons or gammas, cause a deeper blue color than do the other forms of irradiation. Gamma irradiation, of course, will not cause the gems to become radioactive, but neutron bombardment and (to a lesser extent) electron irradiation can cause the formation of radionuclides.

The formula for pure topaz is Al2SiO4(F, OH)2. None of these elements is likely to form long-lasting radionuclides under a neutron bombardment, so irradiating pure topaz is not likely to cause long-lasting problems. However, topaz does not form in isolation, it forms in a magma chamber as liquid rock slowly crystallizes. Every batch of magma has a different set of impurities , depending on the part of the mantel that gives rise to the magma and the rocks that the magma penetrates (and partially melts) as it rises to the surface. Thus, every geographic location will give rise to topaz with slightly different chemistry. This rises from the realm of trivia to importance because many of these impurities can become activated, and some of them form neutron activation products that have half-lives on the order of weeks or months, rather than hours or days (as is the case with pure topaz). Some of the induced radioactivities are summarized in this table.

Partial bibliography

1. Chapter 2 of NUREG/CR 1717
2. Health Risk Assessment of Irradiated Topaz, Nelson KL, Unpublished PhD Thesis, 1991
3. Radioactive Contamination of Manufactured Products, Lubeneau JO and Nussbaumer DA. Health Physics 51(4):409-425. 1986Gemstone Irradiation and Radioactivity, Ashbaugh CE. Gems & Gemology, Winter 1988
4. Radioactive and Radiation Treated Gemstones, Ashbaugh CE. Radioactivity and Radiochemistry 2(1): 42-57
5. Gemstone Irradiation and Radioactivity, Ashbaugh CE. Gems and Gemology, Winter 1998:196-213