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Chapter 13
Mineral and Rock Resources
Resource terms
• Reserves - have been found and can be recovered
economically with present technology
• Cumulative reserves – includes already consumed materials
• Sub economic or conditional reserves – found but not
profitable to extract
• Undiscovered resources:
– Hypothetical reserves – expected to be found in areas already
discovered
– Speculative reserves –might be found in where deposits not already
known to occur
• Renewable – replaceable on a human timescale
Comparison of population growth and
a. U.S. energy consumption
b. Worldwide consumption of Cu and Al
-not only is the population increasing, but the
consumption of resources per person is rising
Positive correlation between GDP and energy consumption
GDP – Gross Domestic Production, measure of all goods and services produced
Ore Deposits
• Ore – rock in which a valuable or useful metal
occurs to be profitable to mine
• Concentration Factor (CF): CF = Cm/Cmc
– Cm = Concentration factor of the metal in the ore
– Cmc = Concentration of the metal in average continental
crust
• The higher the CF - the richer the ore
• Generally, the minimum CF required to
profitably mine is inversely proportional to Cmc
Cost Factors
• Concentration Factor (CF)
• 4 to 25,000 times CF
– highly variable occurrences
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World demand and many market factors
Energy cost
Human/labor cost
Distance to processing or market
Environmental cost - remediation
Examples of Metals obtained from Ores
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Aluminum or Iron – appliances and vehicles
Metals for conductors or semi-conductors
Gems, gold, and silver – jewelry
Lead from galena
Copper from malachite and azurite
Zinc from sphalerite
Many other metals found in rocks
Distribution
• Globally, very un-even distribution
– Some countries have plenty – export nations
– Some countries have none – import nations
– Un-even distribution is reason wars are fought
Proportions of World Reserves - non fuel minerals
Types of Mineral Deposits
• Igneous Rocks and Magmatic Deposits
– Pegmatite – very large coarse grained igneous intrusive rock
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Feldspars
Tourmaline (A)
beryl
Mica (B)
• Kimberlites – intrusive bodies from deep in
the mantle – contain diamonds
• Hydrothermal Ores – frequently sulfides of metals
– Veins
B. Sulfides form around a spreading
ridge system
C. Black smoker
D. pyrite, iron sulfide, in a basalt
• Relationship of deposits to Plate Margins
– Subduction zones and plate collision
• Sedimentary Deposits
– Banded iron formation – ancient, deposited when oxygen
developed in atmosphere,= and soluble Fe formed iron
oxide deposits
– Evaporite - rock salt deposit
• Other low-temperature ore-forming processes
– Placers, weathered minerals sorted out by stream action
• Metamorphic Deposits
– Graphite
– Asbestos
Mineral and Rock Resources Examples
• Metals – iron, aluminum, copper, lead, zinc,
nickel, cobalt, gold, silver, or platinum
• Nonmetallic Minerals – sulfides, lime (calcium
carbonate), sulfur, halite, clay, gypsum, or
potash
• Rock resources – most abundant quantity of
earth resources we use
– Sand, gravel, limestone, quartz-rich sand, marble,
granite, and sandstone
Mineral Supply and Demand
• Global demand is always growing
– About 2% /yr pre-World War II for most metals
– About 10 %/yr World War II to mid-1970’s, then
slowed from ‘76-’82
– Demand is fluctuating now
• U.S. Mineral Production and Consumption
– U.S. population is only 4.5% of the world but
consumes many times its share of the world supply
China – total Cu consumption now 2x US, but per capita only 40% of the
U.S.
As China increasingly industrializes ----demand will increase.
US mineral production and consumption – per capita consumption:
Total lifetime consumption: total = 3.6million lbs
US share of global consumption of world production
Primary Production = from “new” ore
World Mineral Supply
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World demand is always fluctuating
Commodities do not follow fluctuating trends
Mineral reserves eventual will be depleted
Import/export relationships will fluctuate
Technology often allows more access to
difficult or low grade ore deposits
• Future mineral-resource shortages will occur
and cause international tension
Proportions of US needs for selected minerals supplied by
imports as a % of apparent material consumption
– sources on right
Table 13.2
Minerals for the Future
Some Options Considered
• Consider controlling consumption rates
– Reduce the consumption rates (unlikely)
– Hold these rates steady (unlikely)
• Carefully consider the facts:
– Globally the less developed nations are striving to
achieve comparable standards of living as the
technologically advanced countries enjoy
– Countries that have the fastest-growing populations
are not well endowed with mineral deposits and are
the less developed countries of the world!
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1950-1990
US population grew by 65%
Materials consumption grew by 130%
If less- developed nations are to achieve living
standards remotely comparable to
industrialized nations
– Vast quantities of minerals and energy will be
needed
– US – world’s highest rate of car ownership
• 760 cars per 1000 people
• World average - 120 per 1000
Relationship between GDP and car ownership in east and southeast Asia
- if China just moves up to the line that will be an increase of over 45 million vehicles
Gross domestic product (GDP) refers to the market value of all final goods and services
produced within a country in a given period. It is often considered an indicator of a country's
standard of living.
New Methods in Mineral Exploration
• Fact: the economically easy and profitable
deposits are being depleted
• Geophysics is a useful aid to locating new
deposits
– Gravity survey
– Magnetic survey
– Electrical property survey
• Geochemical survey and prospecting is an
increasingly popular exploration too
• Remote sensing is expanding into exploration
strategies
• Landsat images of S. Africa a. dry, b. wet
season
Remote Sensing
• Sophisticated but valuable exploration tools
• Useful to detect, record, and analyze energy emitted
off the earth
– Aerial photography
– Satellites
– Space shuttle, and other manned missions, ISS
• Remote sensing is backed up by ‘ground truth’
activities
– old fashioned geologic mapping
• Advances in the geological sciences are directed
toward integration of remote sensing, geochemistry,
and geophysics
3 ASTER images from NASA Terra satellite in different wavelengths:
A. Visible and near IR - vegetation as red, water and snow as white, rocks
shades of gray
B. Shorter wavelength – limestone's appear yellow-green, clay shows a purple
C. Thermal IR – carbonates appear green, mafic purple, variations of red
indicate quartz variations
Marine Mineral Resources
• Oceans – our new mineral frontier
• Sea water contains abundant dissolved minerals and
many useful element
– Most extraction techniques currently used are energy
intensive and expensive
• Hydrothermal ore deposits along seafloor spreading
ridges are a possible source of many materials
– Currently, they are too deep - of limited benefit
• Manganese nodules are widely distributed on the
ocean floors; a promising solution.
– Many political, environmental, and legal obstacles must be
over come before they can be mined
Figure 13.18
Manganese nodules
Conservation of Mineral Resources
• Overall need for resources is growing – must reduce
this expansion
• Some mineral resources maybe substituted by other,
more abundant resources
– Plastics replacing automobile parts ,but uses petroleum!
• Recycling – many metals are successfully recycled
– More recycling is required
– US recycled 17 million vehicles in 2005 = 13 m tons of scrap steel
• 100 m tons of new steel produced each year
• Takes much less energy to recycle than produce new from ore
– Not all commodities are easy to recycle
• Measures to reduce demand must be the key
Impacts of Mining Activities
• Mining and mineral-processing activities can
modify the environment in various ways
• Both underground mines and surface mines
have their own sets of associated impacts
• Safety, hazards, and water and air pollution
should not be overlooked
• Very stressful to the environment
– Must be carefully planned
– Must be safe to miners and their neighbors
– Must be contained – water and air pollution is a
major problem
Figure 13.19
Underground Mines
• Generally hard to see where they are located
– Area of disturbance is local
• Miners place the tunnels close to the ore body to cut
down on waste
• Once mines are closed they can be sealed with the
non-ore rock (waste rock)
• Surface collapse general limited and controllable
with modern mine reclamation practices
– Old, abandoned, and forgotten mines are still a
problem
Figure 13.20 A. collapse of land
surface over abandon copper mine AZ
B. subsidence pits – coal mines – WY.
Surface Mines
• Quarrying extracts rock to be used either
• A. intact (building blocks or facing stone) Rock of
Ages, VT
• B. crushed (cement-making and road bed) UT
• Open-pit
– Mine a large ore body located near the surface
– Permanent changes to local topography will occur
– World’s largest open pit – Bingham Canyon , Utah
$6 billion worth of minerals extracted
Figure 13.25 A closer look at the Bingham Canyon mine:
a. huge tailings piles
b. erosion and runoff – copper leached from tailings
• Strip mining
– Most ores occur in a layer that generally is parallel to the
surface
– The ore zone is overlain by vegetation, soil, non-ore rock
that must be removed
– Spoils banks are designed to collect the waste rock
– Current reclamation law requires that it be return to the
pit and the original soil replaced
– Expensive but vital
Wyoming - a. spoils banks
N.Dakota – a. grading and
b. ungraded area revegetation
b. one year after reseeding
Mineral Processing
• Mineral extraction is environmental hazardous
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Ore rock is ground or crushed for extraction
The fine waste material is placed in tailings
The tailings are exposed to wind and weather
Harmful elements such as mercury, arsenic, cadmium, or
uranium can leached out
– The surface and subsurface water systems are too often
contaminated
– Chemicals used in ore extraction must be controlled and
not just dumped
– Smelting ores to extract metals, often produce metal laden
exhaust gas or ash, sulfur oxide and acid rain pollution