mea culpa-- i have mis read it-- (or mis remembered it.) but I don't use "tailings" its not a word in my common vocabulary. I understood it, and but have never used or heard it used locally. It is a "read only" word.

I refer to the lumps of stuff out site a mine pit as "Slag". -- The East Coast of the US doesn't have the same intensive mining as out west, and most of the mines i have visited have been coal mines. and they have slag heaps, not tailing piles.