Well, you could build your own Geiger counter.
Here's mine. Yes, it works. I installed a 1/4" jack on the side so I can run the click output through guitar effects pedals, then into a PA system. When paired up with a Theremin, you'd swear you were in a 1950's B-movie.
I love the music from a Theremin. From my favorite inventor, Nikola Tesla.
Kinda learned how a Geiger counter worked when I was in college. Took the cover off the detector tube and turned it on. You know, it runs really HIGH voltage :o.
RE: the radioactive cast iron, there was a story years ago, maybe an urban legend, about radioactive cobalt being recycled accidentally contaminating iron and steel. Either in Asia or Mexico. Could happen.
Red glazed Fiesta Ware is also radioactive. It's from the red pigment.
Tom