Dear Dr. Zoomie – I heard that jewelers sometimes irradiate gemstones. Why do they do this (and how is it done)? Is it safe for me to wear jewelry with irradiated gems? I’ve got enough to worry about already!
Well, it is true that a lot of gemstones are irradiated, but they’re completely safe to wear so you can relax a little bit! And now that you’re (hopefully) calmed down a little bit, here’s what happens.
It’s no secret that gems come in a lot of colors and there’s been a tremendous amount of scientific study into why, say, rubies are red and sapphires are blue (both have similar chemical formulae) while diamonds can be pink, blue, colorless, or any of a number of other colors. The general answer is that gemstone color comes from the interaction of the stones with light – some colors are absorbed, some are refracted within the gem, and some are reflected. There’s a ton of sciences, including some fairly heavy-duty physics – that goes into understanding why this occurs and, to be honest, much of it is over my head. But part of the short and (relatively) simple explanation is that different elements absorb (or fail to absorb) different colors of light. The presence of trace amounts of manganese (for example) can give rise to a purple color, iron can turn an otherwise colorless crystal gray or black, copper tints it green or blue, uranium gives us yellow and orange, and so forth. So a crystal’s chemistry can help determine its color.
Colorless gemstones can be artificially irradiated causing a variety of colors. Photo by GIA.
But there’s more than this because light has to pass through a crystal and the structure of that crystal also helps to determine which wavelengths (or colors) of light pass through the crystal, are absorbed, or are reflected. Not only that, but the distribution of electrical charge within a crystal also plays a role. This is where the radiation comes in – ionizing radiation can alter the distribution of electrical charge, and slamming neutrons into a crystal can dislodge atoms from their precise alignment, disrupting the crystal structure. Both of these phenomena will change a gemstone’s color – the most common example is topaz; irradiation can turn a rather boring brown or tan topaz into a lovely blue; light blue if it sits in a beam of high-energy electrons and a deeper blue after being bombarded with neutrons in a nuclear reactor. And other gems are irradiated as well – diamonds can be made yellow (for example), but topaz is the most common.
OK – so that’s why and how it works, but you’re concerned about the health risks, and justifiably so, if only because it would be too bad to spend good money on beautiful gemstone that places you at risk every time you put it on. So what we need to find out is whether or not an irradiated gemstone somehow stores the radiation it’s exposed to, or if it becomes radioactive itself.
The first question is easy – irradiated objects do not store radiation and they don’t re-emit it later. Think of a brightly lit room that lacks windows (light is, after all, just a form of radiation). When you turn the lights off the room gets dark – the chairs, tables, walls and so forth don’t glow with the stored light because the light isn’t stored in these objects; when the lights are turned off the irradiation stops and everything gets dark. Just the same with ionizing radiation – when the irradiation stops, that’s it; end of story.
Having said that, some forms of irradiation can make objects become radioactive. I know that this sounds as though I’m contradicting what I just said, but there’s an important distinction between an irradiated object storing and releasing the radiation it was exposed to versus it becoming radioactive itself. What if, for example, you paint a table with glow-in-the-dark paint that’s activated by exposure to light? In this case, exposure to the lights causes the paint to become activated – it causes chemical changes in the paint. Now when you turn out the lights the paint will glow (but the unpainted table will not), fading slowly over time. The paint is NOT releasing the same light that it absorbed – what the light does is to induce a chemical change in the paint that causes it to glow for awhile. By the same token, hitting a non-radioactive material with neutrons (which are present in a nuclear reactor core) causes some of the atoms to become radioactive. But this only happens with objects that are exposed to neutron radiation or to the very highest energies of beta or gamma radiation, and this can only happen in the core of a nuclear reactor or in very high-energy particle accelerators. And, as with the glow-in-the-dark paint, this induced radioactivity fades relatively quickly. By the time a gemstone is sold any radioactivity that was created has long since faded to undetectable levels and they certainly pose no risk to the buyer (or to the wearer).
Another part of this is regulatory – in order for an irradiation facility to sell their gemstones and ship them to the jewelry store they have to be able to show that the stones meet regulatory criteria – they simply aren’t allowed to ship anything that’s still “hot.” This is another protection against your buying jewelry that might put you at risk.
So – the physics of irradiation are such that only gemstones irradiated in a nuclear reactor can become radioactive at all; everything else will simply have the color changed. Physics also controls the rate at which these gems will become non-radioactive, and this typically happens fairly quickly (a few days to a few weeks). And regulations require that these gems be confirmed to be safe before they can be sold to you. For all of these reasons I feel comfortable saying that, even though your beautiful deep blue topaz might have once spent some time inside of a nuclear reactor, it’s safe for you to wear.
But wasn’t there an incident awhile back where people were hurt by radioactive jewelry?
Yes there was – several people were hurt in fact. But this had nothing to do with irradiated gemstones and we think that all of the jewelry in question was rounded up and accounted for. Here’s what happened.
About a century ago people started using radioactivity to treat cancer. One of the therapies that was used involved putting radioactivity (radium, primarily) into gold capsules. These capsules would be inserted into a tumor and the radiation would destroy the tumor. After they were used (or if they weren’t used) these gold capsules were supposed to be disposed of as radioactive waste. Except that some weren’t – somehow a number of these capsules were sold to gold dealer and melted down into gold that was sold to jewelers and made into jewelry. The whole story is too involved to really get into here, but the short version is that several people got skin burns from radioactive rings before the source was tracked down – a number of scientific and medical papers were written on the subject. Luckily, some perceptive physicians figured out what was happening and contacted the regulators – notices went out and the tainted gold was rounded up and disposed of properly. There might still be minor amounts of this gold out there somewhere, but the vast majority seems to have been rounded up and there haven’t been any reported injuries (or contaminated gold) in the last few decades.
Finally – keep in mind that this involved gold that was contaminated by radioactivity; not gold (or gems) that was irradiated. Again, any irradiated gems you buy are a different kettle of fish and they won’t put you at risk.