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Wednesday, December 17, 2008

Tailings,slimes, tailings pile, tails, leach residue, or slickens,Tailings composition,barren rock

Tailings (also known as slimes, tailings pile, tails, leach residue, or slickens) are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore.

Tailings represent external costs of 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, to recover additional minerals. Yesterday's tails can be tomorrow's resource, as seen during the 1990s when the extensive tailings dumps of Kalgoorlie / Boulder in Western Australia were re-processed profitably by KalTails Mining.

In coal and oil sands mining, the word 'tailings' refers specifically to fine waste suspended in water.

Tailings composition

The composition of tailings is directly dependent on the composition of the ore and the process of mineral extraction used on the ore.

Certain types of extraction process, like heap leaching for example, may result in quantities of chemicals used to perform the leaching remaining in the material once leaching has been completed. Older forms of mineral extraction, such as those utilised during the early gold boom years of Australian gold mining, resulted in large heaps of fine tailings being left dotted around the landscape. These tailings dumps would continue to leach residual chemicals into the environment, and if weather conditions allowed it the finer fraction would become windborne, blowing around the townships surrounding the now-dormant mining areas.

Typically, the bulk quantity of a tailings product will be barren rock, crushed and ground to a fine size ranging from coarse sands down to a talcum powder consistency.

Tailings may contain trace quantities of metals found in the host ore, and they may contain minute amounts of added compounds used in the extraction process. Elements are rarely in elemental form, more often as complex compounds.

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