As far as I can find, what a mine is mining has very little to do with its environmental/safety impact. The literature focuses on style of mine (pit, shaft, whatever) and almost never mentions the actual product. I guess intuitively, any random chunk of rock is going to have a whole bunch of different stuff in it, some of it poisonous, and what you intend to keep doesn't affect what's down there.

Thorium is conceptually viable and should be researched, but is not even close to being ready for the kind of mass deployment needed to be relevant for dealing with climate change. Basically anyone who's trying to pitch a reactor idea that isn't "copy a recent safe reactor ad nauseum" has accidentally fell for someone or another's marketing pitch.