Mining
•What is it?
•Why do we do it?
•What does it do to the Earth?
•How can we be more sustainable?
 Naturally occurring in earth’s crust
 Must be extracted, processed
 Examples
 Energy (oil, coal, natural gas, uranium)
 Metallic minerals (aluminum, iron, copper, gold)
 Nonmetallic minerals  Aggregate: sand, gravel
 Fertilizers: potash, phosphorous
 Evaporites: gypsum, halite (salt)
 Building Materials: limestone, marble
 Nonrenewable!
 A rock that contains a mineral.
 Must contain profitable amount
 High grade = large amount of desired mineral
 Low grade = smaller amount of desired mineral
Mineral Resources
1. Magma (Igneous):
 Cooling process causes mineral containing rocks to form
 Gold, silver, lead, mercury, copper (found in veins of quartz)
 Hydrothermal
 Copper, lead, zinc, silver, gold, sulfur
 Manganese nodules (sea floor deposits)
 Steel processing
2. Sedimentary Processes
 Placer Deposits (river gravels)
 gold
 Evaporites
 Halite, gypsum, borax (soap)
3.
Weathering
1.
Bauxite (aluminum), Fe oxides (pigments)
Mineral Resources
 Identified
 Known location, quantity
and quality based on direct
evidence
 Reserves
 Identified resources that
can be extracted profitably
 Undiscovered
 Potential supplies that are
assumed to exist
 Gold
 Electronics, jewelry
 Aluminum
 Packaging, cars, airplanes
 Steel (alloy containing iron)
 Buildings, vehicles
 Sand
 Glass, bricks, concrete
 Limestone
 Cement, concrete, road rock, building materials
Key terms:
1.
Overburden: the soil & rock that lies above the economically
important rock.
2. Gangue: worthless minerals/material that surrounds ore
3. Smelting: using heat & chemicals to turn ore into useable mineral
4. Tailings: piles of waste left behind after extraction, contains gangue
Advantages
Disadvantages
 Income!
 Uses lots of energy
 Revenues for cities,
 Disturbs land
states and countries
 Employment
 Progress – buildings,
cars, electronics
 Erodes soil
 Produces a lot of waste
 Pollutes air, water, soil
Surface mining
 Removal of shallow
deposits
 Overburden removed
 Rock/soil on top of
deposit
 Discarded as “spoils”
 Used in 90% of non-fuel
mineral/rock resources
 Used in 60% of coal
mined in U.S.
Subsurface mining
 Removal of deep




deposits
Often used for coal and
metal ores
Deep vertical shaft is dug
Tunnels must be blasted
Machinery used to reach
deposits
Surface
Subsurface
 Open Pit
 Drift
 Strip
 Slope
 Mountaintop Removal
 Shaft
 Placer
 Hard Rock
 Hydraulic
 Borehole
 Dredging
 Fracking
Open-pit mining
Strip mining
 Holes are dug
 Used for horizontal beds of
 Ores are removed
 Iron, copper, gold, sand,
gravel, stone
minerals
 Area strip mining: flat land
 Contour strip mining: hills
 Coal (70%)
 Used on hilly or
mountainous terrain.
 Unless the land is
restored, a wall of dirt
is left in front of a
highly erodible bank
called a highwall.
Figure 15-13
 Mountain top removed
 Exposes deposits
 Prominent in Appalachian mountains
 Ex. Coal
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
1.
Scarring/disruption of land
 Overburden/Spoils left behind, vegetation can’t grow
well
 H2SO4 – acid runoff
 Sediment, erosion, loss of topsoil
 Subsidence, cave-ins (sink holes), explosions
2. Processing involves many chemicals (sulfuric acid,
mercury, cyanide)
 Creates toxic waste during processing
 Tailings: Often stored in valleys – As, Hg, CN, H2SO4
 Can collapse and get into ecosystem
 Streams/Groundwater polluted with waste material
 Tailings: H2SO4, Hg, CN (Cyanide)
 Overburden: Sediment
 Overburden: H2SO4 – leaches heavy metals such as As, Cd,
Pb, Zn
 Air pollution from processing
 Highest industrial air polluter of toxic emissions!
3.
Forests removed
 Loss of Biodiversity
 Increased Erosion
4.
Disease (subsurface)
 COPD – chronic bronchitis, emphysema
 Black lung disease
Tailings:
 Clean up and restore mining sites
 500,000 surface sites in U.S.
 $70 billion to clean up
 Subsurface disturbs <1/10 the land that surface mining
disturbs
 Produces less waste
 But…causes cave ins, explosions, fires, diseases, deaths
 Designed to encourage mineral exploration on U.S.
public lands and populate the West
 Individuals could “claim” land
 Must spend $500 to improve land
 Could pay $6-12 for land owned by all U.S. citizens
 Could build, sell, lease, use it for whatever
 Frozen in 1995
 Some land still being transferred at 1872 prices!
 1992 modification: must post bonds to cover clean up
cost in case of bankruptcy
 Mining companies trying to weaken
 Established a program for regulating surface coal
mining and reclamation activities
 Established mandatory uniform standards for these
activities on state and federal lands
 requirement that adverse impacts on fish, wildlife and
related environmental values be minimized
 reclamation of land after mining was completed
 Created an Abandoned Mine Reclamation Fund for
use in reclaiming and restoring land and water
resources adversely affected by coal mining practices.