After a mineral ore has been mined, crushed, and stripped of all concentrates valuable enough to be smelted, the remaining pulverized rock debris is called tailings. Being of no economic use, these loose waste materials are dumped near an active mine into tall, barren tailings piles, whose sides slope according to the angle of repose. A large mining operation turns the Earth inside out as it buries surrounding landscapes under vast, pyramid-shaped mountains devoid of vegetation. A tailings pile is typically the most prominent physical evidence of a mine.
Halfway down they passed the tailings pile of a small coal mine, unworked for years. A dribble of sulfurous water leaked from the portal; decayed locust props, warped by the overburden, shored up the roof of the tunnel.
— Edward Abbey, The Fool's Progress