Where did you get the geiger counter, and how much did you pay for it?
Radiological stuff isn't really my forte, hobby wise, but I've thought about it now and then, I'd quite like some day to have a try at building my own cyclotron, microtron, or similar particle accelerator on a small scale of course. Not like I have either the money, the miles and miles of space for a huge linac, and of course, my folks would murder me in my sleep when they saw the electric bill even if I could:P:D