"Some of the worst mining disasters do not happen in mines.
They take place at dams.
After minerals are extracted from mines, there are waste materials — including sand, rock and chemicals. They're known as "tailings" and are permanently stored in dams constructed of earth, rock-fill or concrete.
But the dams can fail — from chemical erosion caused by the tailings and from disasters like floods and earthquakes. And the toll can be devastating."