Transcript 1b. Mining - AIS Moodle

Mining
Mining
• Minerals are naturally occurring
substances found in rocks, soils, or
sediments.
• Minerals deposits that can be mined
profitably are called ores.
• They can be either metallic or non-metallic
Minerals can be classified into 4
categories.
1. Metallic minerals
– Associated with intrusive igneous rock
– These deposits can consist of valuable metals such
as nickel, copper , zinc , lead, and gold
– Metallic minerals must be broken apart and
chemically processed to extract the useful metal from
the mineral.
– At one time magma containing dispersed minerals
was forced up towards the earth’s surface through
fissures.
• Super heated brines
dissolved metallic
elements, which
flowed into some of
these cracks. As they
cooled they solidified
and formed veins.
Veins of gold
2. Fuel minerals
- Found in
sedimentary rock
- formed from the
remains of living
organisms that were
transformed over
time by heat and
pressure into coal,
oil, or natural gas.
3. Industrial minerals (gypsum, potash, rock
salt)
- found mainly in sedimentary rock.
- formed in shallow seas in regions with
hot dry climates.
- as water evaporated, it became more
and more salty
- eventually the salt began ti build up in
layers
- in some cases the seas dried up .
4. Structural minerals
- associated with all types of rocks
- are the products of river, wind, and
glacial deposition
- include sand, gravel, and clay
- used mostly as construction materials
Finding a deposit
• The old fashioned
way of finding a mine
was your prospector
with a pick and
shovel, a gold pan,
and a lot of luck.
• Today, technologies used include, but are
not limited to, exploration geology,
geophysics, geochemistry, and satellite
imagery.
Geology
• Geology is the study of the planet Earth—
the materials of which our planet is made,
the processes that act on these materials,
and the products formed.
• Geologists use ground-mapping
techniques to identify features seen on
satellite images and aerial maps of large
tracts of the continent.
Satellite Imagery
• Ground-based surveys are expensive, and
one can often experience difficulty in
mapping large-scale structures. However,
large geological structures are often
readily visible on satellite imagery.
Geophysics
• Geophysical exploration involves
searching for favorable mineral deposits
using the physical properties of rocks.
• Geophysical investigations groundpenetrating radar studies or the use of
seismic waves to show contrasting rock
types.
• The selected rock units of interest might
then be mapped and sampled.
Geochemistry
• Geochemists can determine the
composition of what lies below the Earth's
surface by sampling soil. Soil at the
surface can carry a chemical signature of
what lies below, because of the movement
of chemicals through the rise and fall of
the water table.
• Positive geochemical results from surface
sampling are followed by a drilling
program. Because of the great expense,
drilling is only carried out when the area is
very likely to contain substantial mineral
deposits.
• Drilling produces either rock fragments, or
'cores' of rock for sampling to determine
whether the mineral deposit contains
worthwhile concentrations of ore minerals.
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Types of Mines
1. Open pit
Used when ore
bodies lie near the
surface
Large hole exposes
the ore body
Waste rock
(overburden) is
removed
2nd cheapest method,
but has the largest
environmental
impact. Why?
2. Strip Mining
• The cheapest and safest method, but can have
a significant impact environmentally on the
surface. Why?
• The ore is close to the surface of the land (30m)
but has one or more layers of rock and dirt on
top of it. To mine the ore, these layers have to
be taken off.
• This mining is done in long, narrow strips. When
the ore is done in one strip, the miners begin to
create another strip next to it. The waste, dirt,
and rock that they take off of the top of the next
strip is put on top of the last one.
3. Underground Mining
• Very expensive and the most dangerous
of the three methods, but has the least
impact environmentally on the earth’s
surface. Why?
• Underground mining is done when the
rocks, minerals, or gemstones are too far
underground to get out with surface
mining.
• Entry into underground mines is by vertical
shafts, or by a sloping tunnel.
• To extract the ore, the components
required to build large pieces of machinery
are taken down the shaft and assembled
in the area where the miners are working.
• All underground mines are ventilated
• http://www.uraniumsa.org/processing/underground.htm
Video Links
• Sustainable practices
• Copper & Molybdenum Mining in Canada