Types of Subsurface Mining

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Minerals and Mining

Minerals

• Concentration of naturally occurring elements in/on Earth.

• Formed over millions of yrs  non-renewable resource.

What We Mine?!?

• Metallic minerals: Iron, Copper, Aluminum • Non-metallic minerals: salt, clay, sand • Energy minerals: coal, oil, uranium

Crushed Iron Sodium Chloride Crystal “Dur”rty Coal

Ore

• Rock that has metallic mineral. • Usable stuff is the mineral • Non-usable is called

gangue

 landfill

Gold Gangue

Smelter s

• Used to remove mineral from gangue in an ore  major polluters (Runescape!).

Bauxite Most Important Aluminum Ore

Oxygen: The Most Abundant Element in the Earth’s Crust

Finding Mineral Deposits

• Use aerial photos and satellite images to see rock formations.

Finding Mineral Deposits

• Use planes w/ Geiger meter (uranium) or magnetometer (iron)

Geiger Meter…Only $460!

Magnetometer… Only $700!

Finding Mineral Deposits

• Drilling a deep well and extracting ore samples.

Exploration Drilling

Surface Mining

• Minerals must be shallowly deposited. • Removed rock and soil is called

overburden

or

spoil

.

Types of Surface Mining Open Pit Mining

• Dig hole and remove ores • Fe, Cu, and Sand

Types of Surface Mining

Dredging (Sand)

• Draglines scrape up underwater mineral deposits

Types of Surface Mining

Area Strip Mining

• Cut new strips away; spoil placed on side, mineral taken out.

Types of Surface Mining

Mountaintop Removal

• Use TNT, huge shovels, and large machines to remove top of a mtn and expose coal underneath.

Case Study Gold: Cyanide Heap Leaching

• Cyanide sprayed on low grade gold ore

Heap

in a giant heap (pile).

• Gold flows down w/ cyanide and is collected at bottom of heap.

Case Study Gold: Cyanide Heap Leaching

• Toxic to birds and mammals.

• Leach ponds can overflow  H 2 O pollution • Leaky liners?

Leach Liner

Subsurface Mining

• Used to remove minerals deep in Earth’s surface.

• Less env. Impact

Types of Subsurface Mining

Room and Pillar

• Machines are used to cut out minerals and are placed on a shuttle car.

Scraper

Types of Subsurface Mining

Longwall Coal Mining

• Moveable steel props support cave while machinery cut off coal onto a conveyor belt.

Environmental Damage

• Collapse/subsidence of land from subsurface mines. • Causes houses to tilt, sewer lines crack, gas mains break.

Environmental Damage

• Wind/water carry away [by erosion] toxic mining waste. • Goes in food webs and watersheds.

Environmental Damage

Habitat Loss!!

My Home!!!

Environmental Damage

• Transportation of minerals  warming, lung probs. global

Environmental Damage Acid mine drainage

• Bacteria eat FeS in spoil  H 2 SO 4  create runs off into streams

Surface Mining Reclamation and Control Act

• Mining ops must reclaim area after land has been used and abused. • Must put aside $$$ to reclaim before mining op’s begin. • States oversee Act. • Land put back, trees grow, no toxic runoff!

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