You obviously want to test this thing. I’ve heard uraninite can be found here:
Příbram: 49.677N 14.060E & 49.643N 14.002E
Jáchymov: the Eva mine, and I think Barbora looks like another candidate
It’s fairly inconvenient to hold this up close to everthing. I found an unused piece of aluminium pipe, so I decided to make a Geiger stick. Later, when I realised that aluminium pipes are so cheap and easily available, I reprinted it for a 10 mm pipe, and found out 1 metre is too long.
The handle has the "grooves" 2 cm apart and it ended up working very well for my hand. In general it’s all surprisingly solid, considering the naïve design and low number of iterations.