This Guardian article talks about how uranium was mined at the beginning of the 1500s. The Guardian is a pretty reputable newspaper as far as I’m aware, so I am willing to believe them. Out of curiosity, I attempted to find out why anyone would mine uranium in the 1500s. A quick google tells me it was only defined as an element by Martin Klaproth in 1789, and the article mentions that uranium’s radioactivity wasn’t discovered until around 1896.
The Wikipedia page mentions ceramic glazing, but also mentions it has been mined since the Roman empire, so I'm not sure what to believe there.
So what did people think they were mining before this? Was it just some kind of heavy stuff? Was there any link between the chemical and people falling ill? Or was it just in such small quantities or handled so little that no one noticed?