In mining, gangue is the commercially worthless material that surrounds, or is closely mixed with, a wanted ore. The separation of the ore from the gangue is a necessary and often significant aspect of mining; it can be a complicated process, depending on the nature of the minerals involved.

For any particular mineral deposit, and at any particular point in time, the concentration of the wanted mineral in the gangue material will determine whether it is commercially viable to mine that deposit. The ease with which the ore can be separated plays an important part too. Early mining ventures with their relatively unsophisticated methods did not often achieve a very high degree of separation of the ore from the gangue. As a result a significant amount of ore often found its way into the tailings dumps of a mine. As the value of an ore increases, or when new and cheaper means of processing the ore are introduced it has often become worthwhile to rework old dumps to retrieve the ore they still contain.

Minerals that were once thought of as gangue, and were dumped as tailings, may at a later date find a commercial use. When this happens the old dumps are often reworked to extract the wanted mineral. For instance in copper mines in the 19th century the mineral arsenopyrite used to be dumped until arsenic became popular as an insecticide later in the century.

[edit] References

• An Elementary Outline Of Mechanical Processes, by G. W. Danforth. 1912; 49. Elimination Of Gangue

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