The bulk of mining and ore processing waste is the the soil or rock that must be removed to gain access to the ore. This waste material includes the overburden from surface mines, underground mine development rock, and other waste rock.
In 1986, the Department of Interior estimated that surface and underground mines in the U.S. generated 2,385 million metric tons (MT) of waste. Of this, metal mines produced 989 million MT (DOI87). Metal mining waste piles cover areas ranging from less than 1 hectare to more than 2,000 hectares, with an average area of about 50 hectares at major mine sites. Some of this bulk material may be considered waste, while other parts of it have economic value as low-grade ore or for use in other applications.
The valuable portion of the crude ore is a small fraction of the total volume of material that must be handled to obtain it. For example, over 6,900 units of material must be handled to obtain one marketable unit of uranium. This is due primarily to the low percentage of metal in the ore and to the mining methods and processes employed. Only iron and aluminum exceed 5 percent of the crude ore in which it is embedded. As high-grade ore reserves dwindle, these percentages are likely to become even smaller. The mining industry is distinct from many other process industries where waste materials make up a relatively small portion of the materials processed.
Several stages in producing product from minerals and ores require handling large volumes of material, much of it waste. Overburden and waste rock must be removed to expose the ore. The ores are then extracted (mined) and then transported to a nearby mill, where they are beneficiated (concentrated or dressed). Mining and beneficiation processes generate four categories of large-volume waste:
- mine waste
- dump and heap leach waste
- mine water.
TENORM may be present in mining wastes. These wastes, most significantly from uranium mining, may be generated in large volumes. Because the waste rock and soil have little or no practical use, they are generally stored on land near the mine site. Follow the links below to learn more about waste generated by mining for different minerals:
- Uranium Mining Wastes
- Fertilizer and Fertilizer Production Wastes
- Aluminum Production Wastes
- Copper Mining and Production Wastes
- Gold and Silver Mining Wastes
- Rare Earths Mining Wastes
- Titanium Mining Wastes
- Zircon Mining Wastes