It's natural Uranium. "Highly explosive and radioactive" is just sensation seeking news. Naturally occuring Radon-222 which is also an alpha emitter with a half

It's natural Uranium. "Highly explosive and radioactive" is just sensation seeking news. Naturally occuring Radon-222 which is also an alpha emitter with a half life of 3.8 days instead of 4.68·10e9 years is a lot more radioactive than Uranium-238. It's still a toxic heavy metal.