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•What is it?•Why do we do it?
•What does it do to the Earth?•How can we be more sustainable?
Mining
Naturally occurring in earth’s crustMust be extracted, processedExamples
Energy (oil, coal, natural gas, uranium)Metallic minerals (aluminum, iron, copper,
gold)Nonmetallic minerals -
Aggregate: sand, gravelFertilizers: potash, phosphorousEvaporites: gypsum, halite (salt)Building Materials: limestone, marble
Nonrenewable!
Mineral Resources
A rock that contains a mineral.Must contain profitable amount
High grade = large amount of desired mineralLow grade = smaller amount of desired
mineral
Ores
Mineral Resources1. Magma (Igneous):
Cooling process causes mineral containing rocks to formGold, silver, lead, mercury, copper (found in veins of
quartz)Hydrothermal
Copper, lead, zinc, silver, gold, sulfurManganese nodules (sea floor deposits)
Steel processing
2. Sedimentary ProcessesPlacer Deposits (river gravels)
goldEvaporites
Halite, gypsum, borax (soap)
3. Weathering1. Bauxite (aluminum), Fe oxides (pigments)
Mineral ResourcesIdentified
Known location, quantity and quality based on direct evidence
ReservesIdentified resources
that can be extracted profitably
UndiscoveredPotential supplies that
are assumed to exist
GoldElectronics, jewelry
AluminumPackaging, cars, airplanes
Steel (alloy containing iron)Buildings, vehicles
SandGlass, bricks, concrete
Limestone Cement, concrete, road rock, building
materials
How do we use minerals?
The life cycle of a metal resource
Key terms:1. Overburden: the soil & rock that lies above the
economically important rock. 2. Gangue: worthless minerals/material that surrounds ore3. Smelting: using heat & chemicals to turn ore into useable
mineral4. Tailings: piles of waste left behind after extraction,
contains gangue
AdvantagesIncome!Revenues for cities,
states and countriesEmploymentProgress – buildings,
cars, electronics
Uses lots of energyDisturbs landErodes soilProduces a lot of
wastePollutes air, water,
soil
Mining: the good and the bad
Disadvantages
Surface miningRemoval of shallow
depositsOverburden removed
Rock/soil on top of deposit
Discarded as “spoils”Used in 90% of non-fuel
mineral/rock resourcesUsed in 60% of coal
mined in U.S.
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
Mining Methods
Subsurface mining
Surface
DriftSlopeShaftHard RockBoreholeFracking
Examples of Mining Methods
Subsurface
Open PitStripMountaintop
RemovalPlacerHydraulicDredging
Open-pit miningHoles are dugOres are removedIron, copper, gold,
sand, gravel, stone
Used for horizontal beds of minerals
Area strip mining: flat landContour strip mining: hillsCoal (70%)
Specific kinds of surface mining
Strip mining
Contour Strip Mining
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 removedExposes depositsProminent in Appalachian mountainsEx. Coal
Surface mining method: mountain-top removal
Eureka!Gold MiningPlacer Deposits (gravity
separation)Panning SluicingDredging
Hard Rock DepositsOpen pitHydraulic mining
(sometimes with Hg)Subsurface - S. Africa 12,
800 feet undergroundCyanide is used to extract
gold
Harmful Environmental Effects of Mining
1. Scarring/disruption of landOverburden/Spoils left behind, vegetation can’t
grow wellH2SO4 – acid runoffSediment, 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,
H2SO4Can collapse and get into ecosystem
Streams/Groundwater polluted with waste materialTailings: H2SO4, Hg, CN (Cyanide)Overburden: SedimentOverburden: H2SO4 – leaches heavy metals such
as As, Cd, Pb, ZnAir pollution from processing
Highest industrial air polluter of toxic emissions!
Harmful environmental effects of mining
3. Forests removedLoss of Biodiversity Increased Erosion
4. Disease (subsurface)COPD – chronic bronchitis, emphysemaBlack lung disease
Harmful effects, cont’d
Tailings:
Clean up and restore mining sites500,000 surface sites in U.S.$70 billion to clean up
Subsurface disturbs <1/10 the land that surface mining disturbsProduces less wasteBut…causes cave ins, explosions, fires,
diseases, deaths
How do we fix this?
Designed to encourage mineral exploration on U.S. public lands and populate the WestIndividuals could “claim” land Must spend $500 to improve landCould pay $6-12 for land owned by all U.S. citizens
Could build, sell, lease, use it for whatever
Frozen in 1995Some land still being transferred at 1872 prices!1992 modification: must post bonds to cover
clean up cost in case of bankruptcyMining companies trying to weaken
1872 U.S. General Mining Law
Established a program for regulating surface coal mining and reclamation activities
Established mandatory uniform standards for these activities on state and federal landsrequirement 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.
SURFACE MINING CONTROL AND RECLAMATION ACT OF 1977
SMCRA