What is it? Why do we do it? What does it do to the Earth? How can we be more sustainable? Mining

•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