1. Mining
Textbook pages 226 – 230

2. Minerals, Rocks, and the rock cycle
The earth’s crust consists of solid inorganic elements and compounds called minerals that can be utilized
Mineral resource: a concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed into useful materials at an affordable cost.

3. What is a mineral? What is rock?
Naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure
What is rock?
solid, cohesive, aggregate of one or more minerals
Each rock type has a characteristic mixture of minerals

4. Geologic processes
Deposits of nonrenewable mineral resources in the earth’s crust vary in their abundance and distribution
Very slow cycle recycles three types of rocks (and subsequently minerals) found in the earth’s crust
Sedimentary rock (ex: sandstone, limestone)
Metamorphic rock (ex: slate, marble, quartzite)
Igneous rock (ex: granite, pumice, basalt)

5. Mining for Ore An ore is an economically exploitable deposit
What is an economic geological resource?
A mineral that is heavily used in some human endeavor (e.g., metal ores) and therefore is an important part of domestic/international commerce.

6. General classification of nonrenewable mineral resources
The U.S. Geological Survey classifies mineral resources into three major categories:
Identified: known location, quantity, and quality or existence known based on direct evidence and measurements.
Undiscovered: potential supplies that are assumed to exist.
Reserves: identified resources that can be extracted profitably.

8. Environmental effects of using mineral resources
Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm
The methods are used based on mineral depth
Surface mining
Subsurface mining
Shallow deposits are removed
Deep deposits are removed

9. Open-pit mining (surface)
Machines dig holes and remove ores, sand, gravel and stone.
Toxic groundwater can accumulate at the bottom.

10. Area strip mining (surface)
Earth movers strips away overburden, and giant shovels removes mineral deposit
Often leaves highly erodible hills of rubble called spoil banks.

11. Contour strip mining (surface)
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.

13. Mountaintop removal (surface)
Machinery removes the tops of mountains to expose coal
The resulting waste rock and dirt are dumped into the streams and valleys below.

14. PLAcer Mining (surface)
Looking for mineral resources in river/stream beds by sifting through river sediments. Use the flow of water to help separate heavier minerals from lighter sand/mud.
Gold Mining is an example.

15. Underground (“hard rock”) Mining
Underground excavation of hard materials
Accomplished using a variety of equipment and technologies

16. Gangue - Mine Tailings
Worthless minerals that are associated with the valuable minerals in an ore
Concentrating and smelting removes as much of this gangue as possible
“Leftover waste”
Concentrating and smelting removes as much of this gangue as possible
Where can we safely leave the gangue?
Does it represent a potential environmental hazard?
Example: Acid Mine Drainage (AMD) from sulfide ores and coal

17. Mine Reclamation Re-contouring land back to its original topography
Improve soil quality by adding topsoil / nutrients
Replanting with native, fast growing, early successional species
Monitor the site for 5 – 10 years
More difficult in arid areas b/c difficult to grow vegetation

18. Supplies of mineral resources
The future supply of a resource depends on its affordable supply and how rapidly that supply is used
A rising price for a scarce mineral resource can increase supplies and encourage more efficient use.
Rising prices can also place undue pressures on developing nations in which large stores of mineral reserves are located

19. Environmental effects of using mineral resources
The extraction, processing, and use of mineral resources has a large environmental impact.

20. Environmental Damage 4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4
Gaping holes in ground (old open pit mines).
Particulate air pollution
Piles of mine tailings (non-ore removed from mines) = Gaunge
Accidental draining of rivers and lakes.
Disruption of ground water flow patterns.
Loss of topsoil in strip-mined regions (350 to 2,700 km2 in US alone).
Contamination from sulfuric acid (H2SO4) produced through weathering of iron sulfide (FeS2, pyrite) in tailings.
4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4
Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings.
Acid Mine Drainage

21. Mining impacts
Metal ores are smelted or treated with (often toxic) chemicals to extract the desired metal
Example: cyanide for extraction of low grade gold ores