a. Acidic drainage from bituminous coal mines containing a high
concentration of acidic sulfates, esp. ferrous sulfate.
See also: acid water
b. Drainage with a pH of 2.0 to 4.5 from mines and mine wastes. It results
from the oxidation of sulfides exposed during mining, which produces
sulfuric acid and sulfate salts. The acid dissolves minerals in the rocks,
further degrading the quality of the drainage water. AGI
Dictionary of Mining, Mineral, and Related Terms