Transcript What is a mineral? - Liberty Union High School District

MINING
Textbook pages 226 – 230
Friday, November 18th, 2016
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.
• What
is a mineral?
• Naturally
occurring, inorganic, solid
element or compound with a definite
chemical composition and a regular
internal crystal structure
• What
• solid,
is rock?
cohesive, aggregate of one or
more minerals
• Each rock type has a characteristic
mixture of minerals
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)
•
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.
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.
•
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
•
Shallow deposits are removed
SUBSURFACE MINING
•
Deep deposits are removed
OPEN-PIT MINING (SURFACE)
• Machines
dig holes and remove ores,
sand, gravel and stone.
• Toxic
groundwater can accumulate at
the bottom.
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.
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.
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.
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.
UNDERGROUND (“HARD ROCK”) MINING
• Underground
excavation of hard materials
• Accomplished
using a variety of equipment
and technologies
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”
MINE RECLAMATION
• Re-contouring
topography
• Improve
land back to its original
soil quality by adding topsoil / nutrients
• Replanting
with native, fast growing, early
successional species
• Monitor
• More
the site for 5 – 10 years
difficult in arid areas b/c difficult to grow
vegetation
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
ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES
The extraction, processing, and use of mineral
resources has a large environmental impact.
Environmental Damage
•
•
•
•
•
•
•
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
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