The decade or so following WWII were a strange time in the US. The federal government made itself the only legal purchaser of uranium ore and artificially raised prices to incentivize mining, leading to a brief "Uranium Rush" [1]. Popular songs were sung about uranium prospectors [2]. There were even a couple of educational board games and toys -- with real uranium and other sources of ionizing radiation! -- made to teach kids about uranium and uranium mining [3].
The USGS would assay your samples. A relative who worked there once had the job of reporting to a prospector that while his sample was nicely radioactive, the radioactive chemicals did not occur in nature. I think the prospector may then have threatened to complain to his congressman.