In the US, mineral rights are land use rights. It allows you to extract minerals, which has priority over some other land use rights. You are responsible for restoring lower priority use rights only to the extent you have deprived them. You are not responsible for any deprivation of use rights you did not create, which existing mines would be.
I have owned water, mineral, grazing, and other rights in the western US in environments where these were all considered valuable. YMMV.
Almost certainly not.
> Owning mineral rights doesn't create liability for existing mines.
I was under the impression that it generally does. However, the documents are generally old paper records (often missing) and fragmented between multiple polities in Pennsylvania. The owners of the mineral rights obviously know who they are but reconstructing the trail from public records is quite time consuming and provides a lot of "plausible deniability".
But, boy, once fracking made those mineral rights worth something, the owners sure showed up and found those "missing" records in a real hurry.