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What is the volume
you need to move
to access the useful ore?
5
7
8
9
11
12
13
14
4
3
2
1
0
6
10
15
16
17
18
19
20
21
22
23
23
24
25
26
27
Million tonnes
Source : Worldwatch Institute, 1997.
Iron
Copper
Gold
Zinc
Aluminium
Manganese
lead
Nickel
Tin Tungstene
Waste-rock
Ore
Regardless of the type of raw material, its extraction always
comes with an environmental cost. Most mining leaves a lasting
and damaging environmental footprint. For example, during the
extraction of common metals like copper, lead or zinc from the
earth both metal-bearing rock, called ore, and “overburden”, the
dirt and rock that covers the ore are removed. At a typical copper
mine around 125 tonnes of ore are excavated to produce just one
tonne of copper. The amount of earth moved is mind-boggling
and mining now strips more of the Earth’s surface each year than
does natural erosion.
Waste rock
includes the overburden and mine de-
velopment rock. Industry uses the term “overburden”
to refer to the soil and rock that covers an ore body.
Similarly, mine development rock refers to material
removed from underground mines to access the ore
body. These waste rocks are non-mineralized, or
contain insufficient minerals to process economically.
They are typically hauled from the mine site to waste
dumps for disposal.
Tailings
are the waste products generated during the
recovery of the minerals. Typically, the ore is crushed
or ground to a particle size of less than 0.1 mm in order
to release the valuable constituents. Water and small
amounts of chemical reagents are usually added during
this process to enhance the separation of the minerals
from the ore. (United Nations Environment Programme/
International Council on Metals and the Environment,
1998). The tailings are usually dumped into tailings
dams or erodable dumps (the latter designed so that
the tailings gradually wash into a nearby waterway).
Mine water
is the water that collects in both surface
and underground mines. It comes from the inflow of
rain or surface water and from groundwater seepage.
During the active life of the mine, water is pumped out
to keep the mine dry and to allow access to the ore
body. Pumped water may be used in the extraction
process, pumped to tailings impoundments, used for
activities like dust control, or discharged as a waste
(Environmental Protection Agency). The water can
be of the same quality as drinking water, or it can be
very acidic and laden with high concentrations of toxic
heavy metals.
WASTE FROM CONSUMPTION AND PRODUCTION