Mining
From the topic outline
• IV. Land and Water Use
– Mining
(Mineral formation; extraction; global
reserves; relevant laws and treaties)
14.3 What Are Mineral Resources and What Are The
Environmental Effects of Using Them?
• Some naturally occurring materials in the Earth’s
crust can be extracted and made into useful
products in processes that provide economic
benefits and jobs.
• Extracting and using mineral resources can
disturb the land, erode soils, produce large
amounts of solid waste, and pollute the air,
water, and soil.
Bellwork
• If your group had been able to secure site
16 for mining of Molybdenum, what would
be your next step? What type of mine
would you most likely have? To whom
would you sell the molybdenum? (Hint: use
your device to research possible answers!)
• What is reclamation?
Minerals
• Mineral Resource: Naturally occurring,
inorganic, material from crust
• Ore: Rock that contains a large
concentration of a mineral
– High Grade Ore: Large amount of mineral
– Low Grade Ore: Smaller amount of mineral
Ore Examples
• If you can’t grow it, you have to MINE it!
Element
Ore
Silicon
Quartz
Aluminum
Bauxite
Iron
Magnetite or Hematite
Calcium
Gypsum or Calcite
Sodium
Halite
Magnesium
Magnesite or Dolomite
Potassium
Sylvite
Copper
Chalcopyrite
Tin
Cassiterite
Lead
Galena
Zinc
Sphalerite
Cookie Mining
• Mining for chocolate ore
• You control your profits
– Choose your “land” (cookie)
– Choose your tool(s)
– Determine how best to mine and how
achievable reclamation will be
– You will be charges for any land that is not
reclaimed
Important Minerals and their Uses
Estimating Mineral Resources
• Key terms used by USGS:
– Identified: location, quantity, and quality
known based on direct measurements.
– Undiscovered: potential supplies assumed to
exist.
– Reserves: identified resources that can be
extracted profitably.
Effects of Mineral Use
• No matter the mineral, all steps use large
amounts of energy and creates pollution.
• High grade = less energy needed
• Low grade = more energy needed
Environmental Effects
–
environmental effects, cont.
•
–
toxic chemicals can also be emitted to the
atmosphere
metal ores are extracted, purified, smelted,
and made into desired products
•
•
•
ore consists of ore mineral and gangue
ore is separated from gangue, smelted to
obtain the metal, and made into products that
are used and discarded or recycled
there can be enormous amounts of air and
water pollution from these processes
Harmful Effects
Environmental Effects
–
mining, processing, and use of mineral
resources uses large amounts of energy,
causes land disturbance, and air and water
pollution
•
•
•
land is scarred and the surface is disrupted;
cleanup may cost billions
subsidence from underground mining can
cause pipelines to break
mining wastes contain toxins, and acid
drainage contaminates streams and
groundwater
Fig 16-14 Pollution of water from
mining
Environmental Effects
–
environmental effects, cont.
•
–
toxic chemicals can also be emitted to the
atmosphere
metal ores are extracted, purified, smelted,
and made into desired products
•
•
•
ore consists of ore mineral and gangue
ore is separated from gangue, smelted to
obtain the metal, and made into products that
are used and discarded or recycled
there can be enormous amounts of air and
water pollution from these processes
Environmental Effects
•
•
•
•
•
Disturbs large area
Prone to erosion
Uses large quantities of water
Must pump water out of mine to keep it dry
Acid Mine Drainage (AMD)
– Pollution caused when sulfuric acid and dissolved lead,
arsenic or cadmium wash out of mines into nearby waterways
Environmental Effects of Gold
Mining
 Gold producers
 South Africa
 Australia
 United States
 Canada
 Cyanide heap
leaching
 Extremely toxic to
birds and
mammals
 2000: Collapse of a
dam retaining a
cyanide leach pond
Black Hills : S. Dakota
Acid Mine Drainage
Finding, Removing, Processing
–
promising underground deposits of
minerals are located by a variety of physical
and chemical methods
•
•
methods include aerial photographs, satellite
images, radiation-measuring equipment,
magnetometer, gravimeter
underground methods are also used such as
seismic surveys, analyzing shock waves from
explosive charges, and use of chemical analysis
of water and plants for leached materials
Extracting Minerals from Deposits
• Surface Mining
– Remove overburden (discarded as spoils) to
get to mineral deposits
• Types
– Open-Pit
– Strip
– Contour Strip
– Dredging
– Mountain-Top Removal
Open Pit Mining
• Machines dig large holes in ground, remove ores
• Toxic water can collect at bottom of pit
Strip Mining
• Similar to open-pit, but only useful when deposits
are horizontal and near surface
Specific kinds of surface
mining
Open-pit mining
Strip mining
• Holes are dug
• Ores are removed
• Iron, copper, gold, sand,
gravel, stone
 Used for horizontal beds of
minerals
 Area strip mining: flat land
 Contour strip mining: hills
 Coal (70%)
Contour Strip Mining
• Used in hilly
or mountain
areas
• Cut terraces
• Remove
overburden
and use to
make new
terrace
Dredging
• scrapes up underwater mineral deposits
Mountain-Top Removal
• Literally remove the top of mountains (!!!)
Surface mining method: mountain-top
removal
• Mountain top removed
• Exposes deposits
• Prominent in Appalachian mountains
• Ex. Coal
Mountain-Top Removal Example
Eureka!
• Gold Mining
– Placer Deposits (gravity
separation)
• Panning
• Sluicing
• Dredging
– Hard Rock Deposits
• Open pit
• Hydraulic mining (sometimes with
Hg)
• Subsurface - S. Africa 12, 800 feet
underground
• Cyanide is used to extract gold
Removing Metals from Ores
• Negative consequences:
– Scarring/disruption of land surface
– Large amount of spoils
– Large amounts of solid waste
– Toxic or acidification of water (H2SO4, etc.)
– Gangue (“gang”)
– Air pollution
14.4 How Long Will Supplies of
Nonrenewable Mineral Resources Last?
• All nonrenewable mineral resources exist in
finite amounts, and as we get closer to depleting
any mineral resource, the environmental
impacts of extracting it generally become more
harmful.
• An increase in the price of a scarce mineral
resource can lead to increased supplies and
more efficient use of the mineral, but there are
limits to this effect.
Depletion of Resources
• Future supply depends
on two factors:
– Actual supply
– Rate of use
• Depletion time
– Use up 80% of
resource
• After depletion:
– Recycle, waste less, use
less, find a substitute,
do without
Economic Depletion
UNDISCOVERED
RESERVES
(known supplies)
Increasing cost
SUBECONOMIC
ECONOMIC
IDENTIFIED
OTHER RESERVES
(potential supplies)
Increasingly uncertainty
• As known resources
are depleted, it
becomes more
expensive and
difficult to get to
new supplies
• We might still have
resources left, but it
will be TOO COSTLY
to utilize them on a
wide-scale
U.S. General Mining Law of 1872
• To encourage mining of “hard rock” minerals
• How it works:
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–
–
–
File claim that you believe land contains valuable minerals
Promise to spend $500 to improve it
Purchase public land for $2.50 to $5.00 an acre (!!!)
Pay $120 a year for each 20-acre parcel of land
• Law frozen in 1995 – by that time, estimated $285
billion of public land “given away” at 1872 prices
• Since clean up requirements only came in 1992, there
are an estimated 500,000 sites that will cost taxpayers
$32-72 billion to clean up!
Example of 1872 Law “Give Away”
• In 2004, a mining company purchased 155
acres of public land near Crested Butte for
$875
• Land could be worth $155 million
• Each year, companies remove $4 billion
worth of minerals each year and only pay
2.3% of the value in tax (compared to
13.2% for oil or 14% for grazing rights)
14.5 How Can We Use Mineral
Resources More Sustainably?
• We can try to find substitutes for scarce
resources, reduce resource waste, and recycle
and reuse minerals.
Reclamation
• The good news: Mining now requires reclamation
• Reclamation: Returning the land as close as
possible to original state.
Copper Basin, TN
Surface Mining Control and
Reclamation Act of 1977
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•
•
•
requires mining companies to restore most
surface-mined land
reclamation efforts are only partially successful
subsurface mining removes coal and various
metal ores too deep for surface mining
subsurface mining disturbs less than 1/10 as
much land as surface mining with less waste,
but is more dangerous and expensive
Restoration of Mining Land
• Creative Approaches
– Wetlands
• Trap and filter pollutants before they get into streams
• Initially expensive, but cost effective compared to using
lime to decrease acidity
– Phytoremediation
• Use of specific plants to absorb and accumulate toxic
materials in soil
Industrial Ecosystems
• Design industrial process to mimic nature
Uneven distribution of minerals
• Most of the nonrenewable mineral resources
supplied by
– Canada
–
–
–
–
United States
8% of world population, consume 75% of
the world’s key metals
Germany
China increasing consumption
Russia
South Africa: self sufficient in all key minerals,
largest producer of gold, chromium and platinum
– Australia
Minerals in Antarctica
• No substantial mineral deposits identified
to date
• Antarctica Treaty (1961)
– Limits activity to peaceful uses (i.e., scientific
studies)
• Madrid Protocol (1990)
– Moratorium on mineral exploration and
development for minimum of 50 years
Finding Mineral Substitutes
• Important goal in manufacturing
• Substitute expensive/scarce mineral
resources for inexpensive/abundant ones
• Examples:
– Using plastic, glass or aluminum in place of
tin
– Using glass fibers instead of copper wiring in
telephone cables
Mineral Conservation
• Includes reuse and recycling of existing
mineral supplies
– Reuse - using items over and over again
• Reduces both mineral consumption and pollution
– Recycling - converting item into new product
• Reduces land destruction from mining
• Reduces solid waste