mineral - ram's environmental science - home
Post on 10-Jan-2022
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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
Diana Shell SMHS
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.
Diana Shell SMHS
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
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