On the other hand, if you for example hover the mouse over a sandstone wall in your game, and a tooltip pops up saying "This wall is made of sandstone. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust." then it could be argued that this is not a citation, but the substantial part of that text has been copied verbatim from Wikipedia. Which would make it a derived work (or a plagiate if you don't attribute either).
I have absolutely no problem putting the citations into the game for the excerpts of the text that I use if that was the issue.
But I suppose I will play it safe, and just do my own research as you suggested if even posting citations after the text still may cause an issue. It is a little extra work but I can do that. I greatly appreciate all your responses, there was a bit more to doing this than I originally thought!
Just one more question just to be safe:
In the worst case scenario that for some reason I got called out for violating some copyright in my game by posting text from another website. Could I just immediately remove the text in question to avoid any other legal issues? Or is there a "It's too late, I caught you" clause?