I asked DH (geologist) about this and he directed me to a US EPA FAQ about radon and countertops. He also said the presence of radon is a function of the chemistry of the rock, so it seems it might not be definitively tied to a particular granite color. The EPA article has some good information, and links to additional resources.

Here is a link that might be useful: US EPA link

I think your best bet is to test the actual slab you want with a Geiger counter. From what I understand, radon varies from slab to slab.

I think your best bet is to test the actual slab you want with a Geiger counter. From what I understand, radon varies from slab to slab.

According to the reports I've read, testing with a regular geiger counter is not all that helpful. It responds to the potassium in granite (which is not harmful) as well as the uranium (which is harmful). So it is really hard to figure out if a given slab is dangerous until you install it.

Again, based on what I've read online, there is variation from slab to slab. But if one slab of "Niagara Gold" tests high in uranium it is very likely that most (not all) slabs will. For instance "Ubatuba" always tests at or near 0 for radon/radiation.

I am still searching for a more comprehensive list of granite types that have been tested, but here are some links that I've found helpful in my research...

A 2011 study of several different granites (see graph on page 6)
http://wjllope.rice.edu/~WJLlope/-myPublications/JENR_102_620_2011.pdf

A 2010 study (see chart on page 4)
http://www.marble-institute.com/pdfs/Chen_etal_2010.pdf

A proposed study that is looking at a list of suspicious granite types
http://employees.csbsju.edu/dsteck/mnradon/radon_in_homes_with_granite.htm

This study tested 254 named stone types, but does not identify the stones by name in the report. I have contacted the author to see if those results have been published elsewhere.
http://www.aarst.org/proceedings/2009/PRE-AND_POST-MARKET_MEASUREMENTS_OF_GAMMA_RADIATION_AND_RADON_EMANATION_FROM_A_LARGE_SAMPLE_OF_DECORATIVE_GRANITES.pdf

If anyone has additional names of granites that have been tested I'd appreciate know about them.

Oh, also this really helpful study that lists 110 different granite types. See pages 39, 40, and 47 as well as appendix A on page 61.

None of the granite types they looked at exceeded the EPA guidelines for radon emissions. However, "Nile Gold" and "Juparana Bordeaux" are much higher than the others. All things being equal, I'd rather avoid those and stick with something that has tested at or near zero.

Here is a link that might be useful: EH&E Granite Countertop report

There are couple of issues with natural stone, radiation that can be measured with a Geiger counter, and radon gas that is emitted as part of the natural decay of uranium in the rock. Granite also contains heavy metals like Thallium that can be a health risk.

There is no uranium in soapstone, limestone, or marble, so you could certainly choose one of these instead of granite. Or you can stick with Corian.

"Or you can stick with Corian."

In the last few years, there have been numerous concerns about plastics (BPAs, etc). I personally wonder if there aren't potential health risks with just about any product we choose: plastics, metals, natural stones. Not to mention the products we coat these things with: sealers, cleaners, etc. Are the quantities of radon and heavy metals enough to be concerned in terms of how we use countertops in reality? We aren't licking them (presumably) and most of the time we are eating our food off of dishes rather than the bare counter. We aren't lining our entire main floor with radon-emitting granite. Even asbestos ceiling texture is safe as long as the material isn't being damaged and released into the air.

Yeah - I've seen people roll out bread and pie dough on granite surfaces, and little kids lick up milk etc from the counter. It does matter whether there's heavy metal in the stone.

Radiation and Radon are facts of life - we're exposed to them every day. The people who work in Grand Central Terminal are exposed to 120 mrem per year of radiation from the uranium in the granite. If you've never tested your house for radon emissions, it's a little silly to worry about your counter top. But there are some stones that emit more radon than is recommended.

The heroes here are marble and soapstone, although soapstone fabricators have to be careful about talc inhalation.

Curious about quartz and quartzite (ceasarstone and silestone). Are there any reports for those materials?

It is tricky to balance everything - durability, sustainability, health risks, not to mention aesthetics. I did not want to go with granite for the radon reason but soapstone is not going to work for us. We are looking at Paperstone and Ceasarstone/Silestone.

Thanks!

Put a fan in the kitchen. Slices those sisters into nonhazardous particles, and you can feel safe.

Nancy

A fan/proper ventilation will help with the radon. Do not think that it will do much to fix the gamma radiation if you have the misfortune to have a high concentration of uranium in your slab.

We looked at a slab of "Mombasa" over the weekend. Then came home and saw that "Mombasa" has tested positive for radon emission. Not as high as some, but not zero. So the search continues.