Diana Shell SMHS

OPEN-PIT

STRIP

Contour Strip

Mineral = naturally occurring elements & compounds (PURE) nonmetallic minerals w/ economic value include graphite, quartz crystals,

diamonds, gems, sand, gravel, limestone, salt, phosphate, SULFUR.

metals extracted from earth & consumed most: Fe, Al, Mn, Cu, Cr, Ni.

most minerals are not found pure, but are mixed with other minerals in

ROCKS

Ore = rocks with enough minerals in them to mine at profit (iron ore, etc.)

high grade ores = lots of minerals = very profitable = mineral reserve

low grade ores = few minerals = not profitable now = mineral resource

How are minerals deposited in Earth’s crust?

1. Magmatic concentration: minerals formed in layers as magma cools (heavy

near bottom (iron oxides) & light near top(silicates))

2. Hydrothermal processes: hot water near magma dissolves minerals as it

passes thru rock layers below surface & then

deposits them where hot water breaks thru surface

3. Sedimentation: rivers dissolve minerals and deposits them in new spots

4. Evaporation: as water evaporates out of the ocean or lakes, the water leaves into

the air & any minerals dissolved in it are deposited on the bottom.

Steps to convert mineral deposit to usable product

a) locate deposit b) Mine Minerals c) smelt ore at high temp to separate

spoil from mineral 1. Surface Mining (when deposit near surface)

90% mineral & rock mining/60% coal mining

a. open-pit mine: big holes in ground

(Cu ore, Fe ore, gravel, other stone)

b. strip mining: bulldoze a thin parallel strips, burying

each as you progress, unused debris

called spoil piles

(Coal, phosphate rock – fertilizer)

c. contour strip mining: strip mine on hilly land

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d. dredging ocean floor: drag bucket along ocean floor

Problems Surface Mining

topsoil & vegetation lost = nothing to stop EROSION

require huge, visible tracts of land

Solutions

Restoring the Land: add topsoil, plant trees & vegetation

Surface Mining Control & Reclamation Act: Only requires COAL mines to

reclaim…no others!

use series of wetlands downstream of mining site, cow manure (raises pH of

leached sulfuric acid & precipitates dissolved toxic metals), phtyoremediation – p.340

2. Subsurface Mining: mostly coal & valuable metals that are too deep for surface mining

dig deep tunnels along known mineral “veins” deep underground

disturb far less land than surface mining (more hidden)

dangerous and more expensive than surface mining

Environmental Effects of Mining

General Mining Law of 1872-1996 – established to encourage development

of western lands. They can stake land & buy for $2.50-$5.00/acre and keep all

profits (unlike timber, coal, oil, must pay 12.5% profit to feds) does not require co. to reclaim land, they get profit & trash land (50 are Superfund sites)

erosion of open-pit mines & spoil banks in strip mines if

not restored (1977 Federal Strip-Mining Reclamation & Control

Act: Requires better restoration)

toxic runoff (sulfuric acid, mercury, & cyanide) when

rainwater percolates through piles of mining wastes (spoil banks &

tailings) & floods mines; can go into aquifers, lakes & rivers

good

bad

Restored land in back left

Many metals occur in nature as

SULFIDE deposits. The sulfur in spoil has lead, arsenic, cyanide

dissolved in sulfuric acid.

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Manganese nodules on Pacific Ocean

floor. Used for steel, alloys, etc.

Environmental Effects of Mining (cont.)

Smelting: extract metals from ore by heating

or treating with chemicals smelting produces large amounts of air pollution

and is usually energy intensive

smelting creates lots of air pollution, acid

rain

Increasing Mineral Supply to Meet Demand

reuse & recycle minerals

hope to find new reserves high quality ore in developing nations

use new technology (biomining – p.344) to get minerals out of low-grade

ore at reasonable $$

get Manganese (for steel) rich rocks off deep ocean

floor bottom

use substitutes like silicon & composite plastics (still

negatives to this)

Sustainable manufacturing: minimizing waste during industrial

processes

Industrial Ecology: extension of SM in which “wastes” for one industry

are raw materials for another

Dematerialization: decrease in size & weight of product over time as

technology improves

Slag floats on top of metal

because it is less dense

Wasteland from acid rain

outside Canadian nickel smelter