I think that the cost(or even profits) of filling a mine back in after excavation should be considered from the beginning. Hell we could even sell the futures now to recoup the cost of building a mine tomorrow.
I believe that's how the US superfund was supposed to work (tax miners now so we can use that money to fix the damage they did if they won't) but this is no longer the case.
Wouldn't that require knowing how far down/across you're going to dig? Most mines have a known seam to begin with, but a lot of exploration and geology work comes later when there's a big hole to work from. There's only so much you can tell at the surface before you start.
You can (and a less corrupt industrialized country's government sometimes will) require that they give you the money [or lock it into a fund they don't control] before they get permission to make the hole bigger. You need government inspections (so they can't make it bigger without permission) to make this possible, but those are needed for safety anyway.
If you let them, they'll eventually walk away leaving you with a toxic mess and a hole in your budget. The same thing applies for a government securing clean-up funding or a musician securing royalties from a label/ publisher, make sure you get paid first, if you're supposedly getting paid last it will always turn out that whoops, there is no money left, thanks for making us rich, bye.