Answer to Question #12846 Submitted to "Ask the Experts"

I checked your FAQs and see a similar question, but this is a little bit different. I see a lot of information indicating that irradiation of gems in a nuclear reactor can render the stones radioactive for a time. Most of the information is about blue topaz. I am a mineral collector and go to a few gem shows each year. About a year ago, I purchased some rose quartz facet rough. I understand that rose quartz is also sometimes irradiated. If the rose quartz was treated by neutrons in a reactor, would there be any risk of this stone being radioactive assuming it were faceted and made into jewelry? The stone is about a 2.5 cm cube. The reason I am concerned is that perhaps the materials at these rock/gem shows may not be as strictly regulated or may have been obtained through eBay, or other channels that are not as closely monitored.

Thanks for a really fun question! I actually did some related work about 10 years ago, looking into topaz irradiation—I know you're interested in quartz, but a lot of the same thinking applies here.

First of all, there aren't many nuclear reactors in the world that are used for irradiating gemstones, and they are all licensed by their various governments. The one I'm familiar with is in Germany—they did the topaz irradiations—but location isn't really all that important. What is important is that all of these reactors have to meet regulatory requirements before they can release the irradiated gemstones to their customers (the stores or dealers), and the stores have to meet requirements as well to sell irradiated items. There are two possibilities—if the gemstones can be shown to have so little radioactivity as to be exempt from regulation then they pose no risk and there are no further requirements. Or, if the gemstones are above exemption limits then the reactor operator needs to make sure that their customer has a radioactive materials license. Further, the customer (the store or dealer) has to be able to prove that each individual stone is safe to distribute (sell). And, believe me, regulators are strict about this! I had to go through about a year of back-and-forth before they'd accept that my client with the topaz could ship it around the country. So just by virtue of the fact that the reactor and the sellers operate in a regulatory environment means that your quartz will not put you (or your family) at risk.

Now, let's have some fun!

Exposing stable atoms to neutrons can cause them to become radioactive. That's how cobalt-60 (⁶⁰Co) is made—stable cobalt-59 (⁵⁹Co) absorbs a neutron and becomes radioactive ⁶⁰Co. So, let's see what's in your rose quartz.

All quartz is silicon dioxide (SiO₂), so we know there's silicon and oxygen. In addition, rose quartz has low levels of titanium, iron, or manganese (maybe even a wee bit of aluminum or phosphorus, although this is very rare and probably doesn't describe your stones). Let's see which of these might absorb neutrons and become radioactive.

Silicon—The only long-lived isotope of silicon is silicon-32 (³²Si), with a half-life of about 160 years. But to produce this would require two neutron captures by silicon-30 (³⁰Si), which makes up only about 3–4% of all silicon. The primary silicon isotope is silicon-28 (²⁸Si), which would require four neutron captures to become radioactive. I won't say that this can't happen, but it's not very likely. There might be some other possibilities (such as a neutron being absorbed and knocking out a proton), but I wasn't able to find much information about those. In any event, I don't think we need to worry much about silicon.

Oxygen—There are no long-lived oxygen isotopes, so barring a neutron-proton reaction we don't have to worry about oxygen either.

Titanium—Titanium does have one relatively long-lived radionuclide, but it's lighter than the stable ones. So, it's hard to create this by neutron absorption unless we have a neutron-proton reaction or something somewhat more exotic. So, we can scratch titanium off our list as well.

Iron—Now we're starting to have some fun! Iron-55 (⁵⁵Fe) has a half-life of about 2.7 years and iron-60 (⁶⁰Fe) clocks in at a whopping 1.6 million years. And both of these can be formed from neutron capture of stable iron nuclides. Of the two, ⁵⁵Fe is less likely since it would have to come from neutron capture on iron-54 (⁵⁴Fe), which only comprises about 6% of natural iron; plus, it's not very good at capturing neutrons. And ⁶⁰Fe would require two neutron captures from iron-58 (⁵⁸Fe), the heaviest stable iron isotope, and ⁵⁸Fe is only a fraction of one percent of all iron. Not much to worry about here either.

Manganese—This one is also a bust since manganese has only two nuclides with a sufficiently long half-life to be a concern, manganese-53(⁵³Mn) and manganese-54 (⁵⁴Mn) and they are also lighter than the stable isotopes. So here, too, unless we postulate one of the more complicated reactions, we don't have to worry about manganese either.

All of this is a very long way of saying that it just doesn't seem very likely that irradiated rose quartz is going to develop long-lived radioactivity. And whatever radioactivity it does form will have to remain within safe limits before the reactor facility can ship it to the end user, and before they can ship it to you. I have to admit that I feel as though I'm letting you down by going to all of this detail, only to conclude that your quartz isn't going to be a big deal. But that's the way it goes.

P. Andrew Karam, PhD, CHP