system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why did it take so long until radioactivity was discovered

In my country, uraninite was mined alongside silver at least since the 15 century, useless at the time. It is kind of strange to me that nobody noticed anything "weird" about it for such a long time (or did they?)

Is the concentration too small in this form to have effect? Even if they piled it up in junk heaps along with everything that wasn't silver? Or were the people working with it already too ill to notice anything extra going on (mining was not a particularly safe or healthy occupation for a very long time)? Or did they actually know something is weird about it? After all, what did tip off Marie Curie that there's something odd about this mineral?
gpt
So the thing about radiation, outside of the most extremely high concentrations it isn't going do much of anything immediately where you can really easily see cause and effect. Those super high concentrations don't exist naturally, they have to be refined into that.

Even in modern times after something like the chernobyl disaster only 31 people directly died from it, the rest of the effects are long term increases in things like cancer rates which we can really only figure out because of statistics and having a huge sample size.