Digging up ore displaces huge piles of earth and rock, and processing the ore to produce metals generates immense quantities of additional waste. The amount of recoverable metal in ores, including high-grade ores, is generally just a small fraction of the total mass. Everything else is waste.
Many gold mines employ a process known as heap leaching, which includes dripping a cyanide solution through huge piles of ore. The solution strips away the gold and is collected in a pond, then run through an electro-chemical process to extract the gold.
Assembling a leach pad
at Crowfoot Mine, Nevada.
Credit: Phil Hocker/Mineral Policy Center
This method of producing gold is cost effective but enormously wasteful: 99.99 percent of the heap becomes waste. To cut costs, the heaps are often abandoned. Gold mining areas are frequently studded with these immense, toxic piles, some of them reaching heights of 100 meters (over 300 feet), nearly the height of a 30-story building, and can take over entire mountainsides.
For an example of solid waste impacting traditional lands, read the story of the Western Shoshone.
For more information:
Ruined Lands, Poisoned Waters. A section from Dirty Metals: Mining, Communities and the Environment. (621KB)