1. Chapter 23 Topics:
Mineral resources and their contributions to society
Mining methods
Environmental impacts of mining
Sustainable use of mineral resources

2. Mining for … cell phones?
Cell phones and other high-tech products contain tantalum, obtained from an ore called “coltan”
Significant coltan deposits are found in the Congo, mineable with very basic tools and technology
Armed conflict in the region was in part funded by proceeds from this mining

3. Mineral resources
We extract rocks and minerals from beneath the planet’s surface and turn them into products we use everyday
Rock and mineral resources from the lithosphere contribute to our economies and lives
Rock = a solid aggregation of minerals
Mineral = a naturally occurring solid chemical element or inorganic compound that has a crystal structure, specific chemical composition, and distinct physical properties

4. Minerals all around us

5. Minerals obtained by mining
Mining = in relation to minerals, it is the systematic removal of rock, soil, or other material to remove the minerals of economic interest
Mining = in the broad sense, is the extraction of any resource that is nonrenewable (we “mine” minerals, but also fossil fuels and groundwater)
Because minerals occur in low concentrations, concentrated sources must be found before mining

6. Minerals yield metals
Metal = an element that is lustrous, opaque, and malleable, and can conduct heat and electricity
Ore = a mineral or grouping of minerals from which metals can be obtained economically
Economically valuable metals include copper, iron, lead, gold, aluminum, and tantalum…

7. Ores must be processed
The rock is crushed and the metals are isolated by physical or chemical means
Smelting = heating ore above the metal’s melting point and draining away the molten metal
Heap leaching = using chemical reactions that first dissolve and then precipitate specific metals

8. Mineral extraction has impacts
Smelting emits significant heavy-metal air pollution
Tailings = fine-grained, crushed rock material left over after metals have been extracted
Typically contain heavy metals, toxic substances and/or acids (e.g., lead, cyanide, sulfuric acid)
Infiltration through tailings ponds can leach pollutants into the groundwater
Most extraction methods are water- and energy- intensive

9. Non-metals and fuels
Nonmetallic minerals include sand, gravel, phosphates, limestone, and gemstones
$7 billion/year of sand and gravel mined in the U.S.
Phosphates provide fertilizer
Substances are mined for fuel
Uranium for nuclear power
Coal is not minerals (it is organic), but it is extracted using the same methods as metallic ores

10. Strip mining
Strip mining = long strips of surficial soil and rock are removed to expose and remove the resource
Used for coal, oil sands, sand, gravel
Destroys habitats and communities over large areas

11. Strip mining Overburden = overlying soil and rock that is removed
Overburden is used to refill the mined-out strips
But its internal structure is significantly altered
Acid drainage = sulfide minerals in the disturbed overburden oxidize
Sulfuric acid forms
Flows into surface waterways

12. Subsurface mining Ore bodies are accessed using shafts and tunnels
Used for deeply situated and/or “non-tabular” ore bodies (metals, gemstones, phosphate, salt)
Most dangerous form of mining
Blasting, collapsed tunnels
Toxic fumes and coal dust
Acid drainage, polluted groundwater, sinkholes, damage roads, homes, etc.

13. Open pit mining A large open pit is created in the ground
Used for large ore bodies with evenly distributed mineral concentrations (e.g., copper, zinc, iron, gold)
Also used for bulk soil/rock resources – quarries (e.g., sand, gravel, clay, limestone, marble, granite)
Huge amounts of rock are removed
One Utah mine is 2.5 mi across and 0.75 mi deep
Half a million tons of ore and rock removed each day
Habitat loss, aesthetic degradation, acid drainage

14. Bingham Canyon copper mine

15. Placer mining Running water is used to sift riverbed sediments
Used for gold, gems
Debris washed into streams makes them uninhabitable for wildlife
Disturbs stream banks, causes erosion
Harms riparian plant communities

16. Mountain-top removal
Strip mining on steroids… whole mountaintops are blasted off and dumped into the adjacent valleys
Used for coal in the Appalachian Mountains
Economically efficient
Degrades and destroys vast areas
Pollutes streams
Deforests areas,
Causes erosion, mudslides, flash floods

17. Solution mining
Solution mining (in-situ recovery) = resources in a deep deposit are dissolved in a liquid and pumped to the surface for recovery
Used for salts, lithium, boron, bromine, potash, copper, uranium
Less environmental impact than other methods
Less surface area is disturbed
Acids, heavy metals, uranium can move away from mine

18. Undersea mining We extract minerals (e.g., magnesium) from seawater
Minerals are dredged from the ocean floor
Sulfur, phosphate, calcium carbonate (for cement), silica (insulation and glass), copper, zinc, silver, gold
Manganese nodules = small, ball-shaped ores scattered across the ocean floor (currently uneconomical)
Hydrothermal vents may have gold, silver, zinc
Mining would destroy habitats and organisms and release toxic metals that could enter the food chain

20. Restoration of mined sites
Governments in developed countries require companies to reclaim (restore) surface-mined sites
Other nations (e.g., Congo) have no regulations at all
Reclamation aims to bring a site to a condition similar to its pre-mining condition (i.e., remove structures, replace overburden, replant vegetation)
The U.S Surface Mining Control and Reclamation Act mandates restoration; companies must post bonds to ensure restoration

21. Limited effectiveness
Even on restored sites, impacts may be severe and long-lasting
Complex communities are simplified
Fast-growing grasses used to stabilize soil can hinder the growth of forests, wetlands, etc.
Essential symbioses are eliminated and often not restored
Impacted surface water can also be reclaimed through treatment to moderate pH

22. Mining policy Still guided by The General Mining Act (1872)
Encourages metal and mineral mining on federal land
Any citizen or company can stake a claim on public land
The public gets no payment for any minerals found
Supporters say it encourages a domestic industry that is risky and provides essential products
Critics say it gives away valuable public resources nearly for free to private interests
Efforts to amend the act have failed in Congress

23. Minerals resource management
Minerals are nonrenewable and scarce
Once known reserves are mined, minerals will be gone
Indium, used in LCD screens, might only last 32 more years
Gallium (solar power), platinum (fuel cells) are also scarce
Reserve estimates are uncertain
New discoveries, technologies, consumption patterns, and recycling affect mineral supplies
As minerals become scarcer, demand and price rise
We must recover and recycle our limited supplies

24. Factors affecting “supply life”
Discovery of new reserves increases known reserves (minerals worth $900 billion were discovered in Afghanistan in 2010)
New extraction technologies reach more minerals at less expense
Changing social and technological dynamics modify demand in unpredictable ways (lithium batteries are replacing cadmium-nickel ones)
Changing consumption patterns affect how fast we exploit reserves (e.g., a recession depresses demand)
Recycling extends the lifetimes of minerals

25. Sustainable metals use
Recycling addresses:
Finite supplies
Environmental damage
35% of metals in municipal solid waste were recycled in 2008
7 million tons
Steel, iron, platinum, gold, nickel, germanium, tin, and chromium
Reduces greenhouse gases by 25 million metric tons

26. Metal recycling rates

27. E-waste recycling for rare elements
Electronic waste (e-waste) from computers, printers, cell phones, etc. is rapidly rising
E-waste contains significant amount of many rare elements that could be recovered/recycled
Only 10 % of the 1.2 billion cell phones sold each year are currently being recycled
Recycling reduces demand for virgin ores and reduces pressure on ecosystems

28. Take-aways
We depend on minerals and metals to make the products we use
Mineral resources are mined by various methods
Mining causes extensive environmental damage (habitat loss, acid drainage, etc.)
Restoration and regulations help minimize the environmental and social impacts of mining
Strategies for sustainable use of minerals rely heavily on recycling and recovery programs