History of the Grand Canyon

I don't know the details of this case but Uranium ore is usually mainly an alpha emitter. Alpha radiation is stopped by a sheet of paper or your clothes and skin. It is generally only dangerous if you ingest or inhale it when it becomes quite a problem. If you carried a chunk next to your skin for long periods that would be a problem. Or if you breathed the radon gas it emits for a long time in a confined space that might be bothersome. None of that happened. This material was apparently in 5 gallon buckets and the visitors were not selecting a chunk of rock to nibble on or tie around their neck.

So I suspect this is a case of overblown hysteria.

My expertise in this area comes from being a USN Health Physics Tech (they call it Engineering Lab Tech ELT)