97
directly consumed for mining operations and onsite mineral pre-processing such as flotation,
leaching and coagulation and liquid dumping of
residuals in tailings ponds. Hence modern mining has a substantial water footprint. For instance,
the production of 1 kg of mined gold consumes
an average of 691,000 L of water (Kossoff et al.
2014). It may involve the use of highly toxic substances such as cyanide and mercury, which
brings the risk of accidental releases in toxic
spills from operating mines.
The accumulation of waste materials may
extend from hundreds up to several thousand
hectares on a single industrial mine site. This
threatens soils, freshwater bodies and vegetation
in their wider surroundings through dust generation, mechanical movement and water and wind
erosion acting on waste heaps. Eroded sediments
and dust, whether inert or toxic, can affect human
health directly (e.g. itai-itai disease, a mass cadmium poisoning in Japan) and lead to physical
and chemical deterioration of downstream surface
waters and sensitive ecosystems (Johnson 2003).
Not only spoil heaps present the above threat
to the environment and public health but unrehabilitated abandoned mines as well. Once active
mining ceases, mine facilities and the site must
be reclaimed and closed with the aim of returning
these lands to a stage that resembles, to some
degree, pre-mining conditions. In most cases this
is only partially feasible. In vast areas worldwide,
this has not been achieved, thus the high numbers
of abandoned mine sites left major pollution
legacies.
A primary issue is acid mine drainage (AMD).
In an active mine, water is removed from the site
through pumping to allow mining to proceed.
Once closed, groundwater again migrates into the
mine site. AMD is caused where sulphide minerals (primarily pyrite), common to most metal
mines and coal deposits, react with water and
oxygen to create sulphuric acid. This, in turn, dissolves sulphate salts and heavy metals from the
waste rock heaps and tailings, creating AMD
leachate. Once released into the environment,
AMD is quite toxic to aquatic ecosystems
(Johnson 2003). However, in many cases even
sulphur containing spoil heaps show no contamination in their surroundings (Sütő et al. 2007)
either because pyrite is transformed into more
stable sulphur minerals (e.g. gypsum) or because
the pollution sensitivity of the geological formations near the surface is low impeding the filtration of the leachate into the groundwater. In
countries where environmental regulation and
enforcement is reasonably strict, spoil heaps
form hills and slopes with stability, flora and
fauna not only resembling semi-natural conditions but even providing some profit via hunting
and forestry.
Box 4.3 “Mineral Baby”
Reflecting the new trends in global consumption the Minerals Education Coalition of the
Society for Mining and Metallurgy and
Exploration (SME) developed the “Minerals
Baby” diagram to demonstrate how important
minerals and mining industries are. The iconic
Minerals Baby updated for each year illustrates the volume and diversity of minerals,
metals and fuel an average American will
need in his/her lifetime (Fig. 4.22).
Calculations for the 2018 Minerals Baby are
based on a life expectancy of 78.8 years and
mineral use data from the National Mining
Association, the US Geological Society and
the US Energy Information Administration.
As of 2018, almost 200 tonnes of coal,
2772 hectolitre of petroleum and almost
200,000 m
3
natural gas would be used by an
average American via his/her lifetime together
with 600 tonnes of building material, 10
tonnes of iron and 60 grams of gold. Probably
over the lifetime of an average American the
importance of other minerals and metals,
especially rare earth elements used for data
storage of notebooks, mobile phones and
other mobile devices will increase and the
value of 20 tonnes is expected to increase.
4.1 Changes in the Outer Boundary Zone of the Earth’s Crust
directly consumed for mining operations and onsite mineral pre-processing such as flotation,
leaching and coagulation and liquid dumping of
residuals in tailings ponds. Hence modern mining has a substantial water footprint. For instance,
the production of 1 kg of mined gold consumes
an average of 691,000 L of water (Kossoff et al.
2014). It may involve the use of highly toxic substances such as cyanide and mercury, which
brings the risk of accidental releases in toxic
spills from operating mines.
The accumulation of waste materials may
extend from hundreds up to several thousand
hectares on a single industrial mine site. This
threatens soils, freshwater bodies and vegetation
in their wider surroundings through dust generation, mechanical movement and water and wind
erosion acting on waste heaps. Eroded sediments
and dust, whether inert or toxic, can affect human
health directly (e.g. itai-itai disease, a mass cadmium poisoning in Japan) and lead to physical
and chemical deterioration of downstream surface
waters and sensitive ecosystems (Johnson 2003).
Not only spoil heaps present the above threat
to the environment and public health but unrehabilitated abandoned mines as well. Once active
mining ceases, mine facilities and the site must
be reclaimed and closed with the aim of returning
these lands to a stage that resembles, to some
degree, pre-mining conditions. In most cases this
is only partially feasible. In vast areas worldwide,
this has not been achieved, thus the high numbers
of abandoned mine sites left major pollution
legacies.
A primary issue is acid mine drainage (AMD).
In an active mine, water is removed from the site
through pumping to allow mining to proceed.
Once closed, groundwater again migrates into the
mine site. AMD is caused where sulphide minerals (primarily pyrite), common to most metal
mines and coal deposits, react with water and
oxygen to create sulphuric acid. This, in turn, dissolves sulphate salts and heavy metals from the
waste rock heaps and tailings, creating AMD
leachate. Once released into the environment,
AMD is quite toxic to aquatic ecosystems
(Johnson 2003). However, in many cases even
sulphur containing spoil heaps show no contamination in their surroundings (Sütő et al. 2007)
either because pyrite is transformed into more
stable sulphur minerals (e.g. gypsum) or because
the pollution sensitivity of the geological formations near the surface is low impeding the filtration of the leachate into the groundwater. In
countries where environmental regulation and
enforcement is reasonably strict, spoil heaps
form hills and slopes with stability, flora and
fauna not only resembling semi-natural conditions but even providing some profit via hunting
and forestry.
Box 4.3 “Mineral Baby”
Reflecting the new trends in global consumption the Minerals Education Coalition of the
Society for Mining and Metallurgy and
Exploration (SME) developed the “Minerals
Baby” diagram to demonstrate how important
minerals and mining industries are. The iconic
Minerals Baby updated for each year illustrates the volume and diversity of minerals,
metals and fuel an average American will
need in his/her lifetime (Fig. 4.22).
Calculations for the 2018 Minerals Baby are
based on a life expectancy of 78.8 years and
mineral use data from the National Mining
Association, the US Geological Society and
the US Energy Information Administration.
As of 2018, almost 200 tonnes of coal,
2772 hectolitre of petroleum and almost
200,000 m
3
natural gas would be used by an
average American via his/her lifetime together
with 600 tonnes of building material, 10
tonnes of iron and 60 grams of gold. Probably
over the lifetime of an average American the
importance of other minerals and metals,
especially rare earth elements used for data
storage of notebooks, mobile phones and
other mobile devices will increase and the
value of 20 tonnes is expected to increase.
4.1 Changes in the Outer Boundary Zone of the Earth’s Crust