Sounds a bit weird: Would mining a thorium rich deposit have higher environmentally related costs? Isn't the thorium itself valuable as well?
Yes, absolutely!
> Isn't the thorium itself valuable as well?
Not at present. It's basically a waste byproduct at the moment. If it becomes widely used as a nuclear fuel in molten salt reactors, that might change. It is used in a few alloys, etc, but there aren't a large number of industrial uses for it.
People have a hard time understanding what the six-seven orders of magnitude difference in energy density between nuclear and chemical fuels means in practice. Basically, even if the entire world switches to being powered only by thorium, thorium will still mostly be a waste product.
For the amount of digging you need to power a single coal plant you could power the entire earth and still have most of your production idle.
Mining's a messy business, it's not like you just bring a lead box with you and drop an occasional nugget of thorium in while you get on with your other work.