Correct me if I'm wrong, but doesn't "end of the pipe" potentially allow you to go back to your tailings and extract more material from previously dead feedstock?
In principle, yes. But it's probably not economically viable. Rare earth oxide prices are in the range of 10-100 USD per kilo. Platinum and gold go for ~1000 USD per ounce. Of course the tailings grades will be different but as far as I know these are the only metals which have gone through significant tailings reprocessing efforts. In SA that's also mainly because they had loads of material that had been mined 100 years ago when recovery was lower. I think copper might also reprocessed in a few places but I would guess only via heap leaching (stick in some plumbing and irrigate your dump with acid).