Tailings

Tailings are the waste left after ore has been processed and the valuable metal or mineral taken out. EPA's uranium mill rule defines them as "the remaining portion of a metal-bearing ore after some or all of such metal, such as uranium, has been extracted" (40 CFR 192.01(m)).

The U.S. Bureau of Mines' Dictionary of Mining, Mineral, and Related Terms (1968) describes tailings as "the gangue and other refuse material resulting from the washing, concentration, or treatment of ground ore," and as the portions of washed ore "regarded as too poor to be treated further."

Tailings are not waste rock

Waste rock is material removed to reach the ore and never processed. Tailings have gone through the mill. Because the ore was crushed and ground, tailings are usually fine-grained, and they may carry the chemicals used to treat the ore.

BLM rules for tailings on public land

Under 43 CFR subpart 3809, the operator of a mine on public land must:

• Dispose of "all tailings, dumps, deleterious materials or substances, and other waste produced by the operations ... so as to prevent unnecessary or undue degradation" (43 CFR 3809.420(b)(2))
• Design, build, and operate "all leach pads, tailings impoundments, ponds, and solution-holding facilities according to standard engineering practices to achieve and maintain stability and facilitate reclamation" (43 CFR 3809.420(b)(12)(i))
• Show waste rock and tailing disposal areas on the maps in a plan of operations (43 CFR 3809.401)

Tailings are also part of the financial guarantee. BLM may release up to 60 percent of the guarantee for an area once backfilling, regrading, drainage control, and "stabilization and detoxification of leaching solutions, heaps, tailings, and similar facilities" are complete there (43 CFR 3809.591(b)).

Old tailings

EPA's definition of a mine for its ore mining discharge rules includes "secondary recovery of metal ore from refuse or other storage piles, wastes, or rock dumps and mill tailings" (40 CFR 440.132(g)). Old tailings can still hold recoverable metal, which is one reason mining claims are sometimes located over historic mill sites.

Why it matters in research

Tailings on a tract raise questions a buyer or operator needs answered: who created them, under which mining claim or mill site, whether a plan of operations and financial guarantee covered them, and whether reclamation was completed. The answers are in BLM case records, the mining claim history, and county records.