Ask a lawyer for an informed opinion. They’ll (hopefully) have the tools to determine what this easement means for you as a potential homeowner on the parcel. The Maine Geological Survey has an item in their FAQ of some relevance.

I don’t know how common these kinds of easements are in Maine, but I would not purchase any real property that could be used and abused at the whim of a corporation with a team of well paid lawyers.

You might ask a local lawyer who knows your rights, not international nerds at Lemmy.

Don’t buy land with an easement you don’t want on it. You can tell the seller to talk to the company and have them negotiate the removal of the easement as a condition of sale. They might be willing to buy back the mineral rights.

But barring that if this is a non-negotiable for you don’t buy it.

Knowing your state/municipality would probably help, but as someone whose family member was involved in a similar situation, there’s literally nothing you can do. And for that matter, if you do anything in developing that land that might impact the mining company’s access, you’re going to be paying for those damages, too.