I had the same thought, and wanted to check some strange ore from the desert. Eventually I soldered my own Geiger counter, thanks to the fabulous Safecast proje

I had the same thought, and wanted to check some strange ore from the desert. Eventually I soldered my own Geiger counter, thanks to the fabulous Safecast project. This is it: https://blog.safecast.org/bgeigie-nano/ https://blog.safecast.org/bgeigie-nano/ It cost ~$650, but that's because it uses a very high-end geiger tube, and can detect alpha and beta in addition to gamma radiation. Comparable commercial devices do apparently cost a couple thousand. Low and behold, the desert rocks weren't radioactive. However, taking the counter on an airplane was quite shocking, and gave the cabin crew real concern.