Strip Ratios in Mining

Chapter 4.5
Mine wastes management
Mining wastes is generated during the process of extraction, beneficiation and processing of
minerals. Extraction is the first phase that consists of the initial removal of ore from the earth.
This is normally done by the process of blasting, which results in generation of large volume of
waste (soil, debris and other material). This is useless for theindustry and is normally just stored
in big piles within the mine lease area, and sometimes, on public land. The bigger the scale of the
mine, greater is the quantum of waste generated. Opencast mines are therefore more pollution
intensive as they generate much higher quantities of waste compared to the underground mines.
Open-pit mines produce 8 to 10 times as much waste as underground mines.1Once the ore is brought to the surface, it is processed to
extract the mineral, which itself generates immense
quantities of waste. That’s because the amount of
recoverable metal in even high-grade ores is generally just
a small fraction of their total mass. Moreover, as the
higher grade mineral deposits are getting exhausted, the
mineral industry is generating more and more quantity ofwaste, as they have to now depend on lower grades of
reserve. For example, in the United States, the copper ore
mined at the beginning of the 20th century consisted of
about 2.5 percent usable metal by weight; today that
proportion has dropped to 0.51 percent.2

The precious the mineral, more
the waste
In gold mining, it is estimated that
only 0.00001 percent (that’s onehundred thousandth of1 percent) of
the ore is actually refined into gold.
Everything else is waste.
Source: Anon, 2006, Dirty Metal,
Mining Communities and Environment,
Earthworks,
Oxfam
America,
Washington, pp 4

There is no estimation on how much waste is generated by this industry globally. But, everyone
agrees that the quantity is so HUGE that is unimaginable. For example, the production of 1
tonne ofcopper generates 110 tonnes of waste ore and 200 tonnes of
overburden.3 Thus, globally the copper industry in 2004 generated 3348 million
tonnes of waste material to produce 10.8 million tonnes of copper metal. 4 In only
5 years between 2000 to 2004, the global copper industry generated 16709
million tonnes of waste material. It is anybody’s guess how much this industry
must have generatedsince it started. And when production of one metal is
generating so much of waste, how much the entire industry would be generating.
Every year, mines in the United States generate waste equivalent in weight to nearly nine times
the trash produced by all US cities and towns combined.5 The total amount of waste ore (not
including overburden) that has been generated to date by the US metals miningindustry probably
exceeds 90 billion tons.6 In India, a conservative estimate puts generation of overburden
(excluding waste produced during processing) at 1861 million tonnes in 2006.7
1

Anon, 2006, Dirty Metal, Mining Communities and Environment, Earthworks, Oxfam America,
Washington, pp 4
2
Gary Gardner and Payal Sampat, 1998, Mind over Matter: Recasting the Role of Materials in OurLives,
Worldwatch Institute, Washington, DC, p. 18
3
Anon, 2006, Dirty Metal, Mining Communities and Environment, Earthworks, Oxfam America,
Washington, pp 4
4
Production of copper taken from L E Taylor et al., 2006, World Mineral production 2000-04, British
Geological Survey, Nottingham, UK, pp 15-17
5
Anon, 2003, Resource Conservation and Recovery Act Orientation Manual (Washington, DC:U.S.
Environmental Protection Agency (EPA),
6
Anon, 1985, EPA, Report to Congress: Wastes from the Extraction and Beneficiation of Metallic Ores,
Phosphate Rock, Asbestos, Overburden from Uranium Mining, and Oil Shale, p. ES-17.

Though most mining wastes, such as overburden, are inert solid materials, the industry also
generates waste that is toxic in nature. Some of these toxic are...