Tailings

From Freepedia

Tailings, also called gangue, are the rejected material from mining and screening operations. Tailings are the uneconomic remainders from mining; as mining techniques and the price of minerals improve it is not unusual for tailings to be reprocessed using new methods or more thoroughly with old methods, perhaps to recover minerals other than those originally mined.

Strictly speaking, the gangue is unwanted material which occurs naturally along with or intermingled with the ore being mined and is unavoidably extracted with the ore. When the two are separated in the first stage of the mineral preparation, the waste material, the tailings, is mainly composed of gangue.

In coal production the word 'tailings' refers specifically to fine waste suspended in water and the word 'gangue' is never used.

Large-scale operations often leave huge piles of this material on site. Often, as in the case of riverbed metal extraction, this has buried valuable river-flat soils under the largely worthless and often contaminated tailings. Modern extraction methods have resulted in less damage but land rehabilitation continues to be a major problem and costly consideration.