Blackbird mine

Abstract: The production of acid from oxidation of pyritic inclusions in mineral mine spoil prevents the revegetation of the overburden and the amelioration of secondary environmental damage due to erosion and/or leaching of this toxic (soluble heavy metal-bearing) material. A total lime requirement must be determined and met in order to control existing acidity and to prevent reacidification as oxidation of pyritic materials in the mine spoil continues. The total lime requirement consists of the summation of the amount of ground limestone needed to neutralize the acidity present due to the buffer capacity of the soil, the acidity generated from complete oxidation of the sulfide-sulfur in the fine, highly reactive fraction (fine sand, silt, and clay-size particles) of the soil, and the oxidation of sulfide-sulfur exposed by weathering of large size material. Spoil samples from the Blackbird Mine, a copper-cobalt mine in east central Idaho, had a total lime requirement ranging from 44 to 72 metric tons of ground limestones per ha, 30 cm deep.