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Mineral and Rock Resources

Chapter 13

Sulfur crystal, Sicily

photo by J. Carr

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Ore Deposits

Orerock in which a valuable or useful

metal occurs to be economic 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

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Examples of Metals obtained from Ores

Aluminum or Ironappliances andvehicles

Metals for conductors or semi-conductors

Gems, gold, and silverjewelry

Lead from galena

Copper from malachite and azurite

Zinc from sphalerite

Many other metals found in rocks

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Cost Factors

Concentration Factor (CF)

4 to 25,000 times CF

highly variable occurrences

World demand and many market factors

Energy cost

Human/labor cost

Distance to processing or market

Environmental cost - remediation

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Distribution

Globally, very un-even distribution

Some countries have plentyexport nations

Some countries have noneimport nations

Figure 12.1

Un-even distribution is reason wars are

fought

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Types of Mineral Deposits Igneous Rocks and Magmatic Deposits

Pegmatite Kimberlite

Hydrothermal Ores Veins

Relationship to Plate Margins

Sedimentary Deposits Banded iron formation

Evaporite Other low-temperature ore-forming processes

Placers

Metamorphic Deposits

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Mineral and Rock Resources

Examples (the ways we use)

Metalsiron, aluminum, copper, lead,zinc, nickel, cobalt, gold, silver, or platinum

Nonmetallic Mineralssulfides, lime

(calcium carbonate), sulfur, halite, clay,gypsum, or potash

Rock resourcesmost abundant quantity

of earth resources we use Sand, gravel, limestone, quartz-rich sand,marble, granite, and sandstone

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Mineral Supply and Demand

Global demand is always growing

About 2% pre-World War II for most metals

About 10 % World War II to mid-1970s

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

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World Mineral Supply

World demand is always fluctuating

Commodities do not follow fluctuatingtrends

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

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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 strivingto achieve comparable standards of living as

the technologically advanced countries enjoy

Countries that have the fastest-growingpopulations are not well endowed with mineral

deposits and are the less developed countries

of the world!

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New Methods in Mineral Exploration

Fact: the economically easy and profitabledeposits are being depleted

Geophysics is a useful aid to locating newdeposits

Gravity survey Magnetic survey

Electrical property survey

Geochemical survey and prospecting is anincreasingly popular exploration tool

Remote sensing is expanding intoexploration strategies

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Remote Sensing Sophisticated but valuable exploration tools

Useful to detect, record, and analyze energyemitted off the earth Aerial photography

Satellites

Space shuttle, and other manned missions

Remote sensing is backed up by ground truthactivities

old fashioned geologic mapping Advances in the geological sciences are

directed toward intigration of remote sensing,geochemistry, and geophysics

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Marine Mineral Resources Oceansour new mineral frontier

Sea water contains abundant dissolved mineralsand many useful element Most extraction techniques currently used are energy

intensive and expensive

Hydrothermal ore deposits along seafloorspreading ridges are a possible source of manymaterials Currently, they are too deep - of limited benefit

Manganese nodules are widely distributed onthe ocean floors; a promising solution. Many political, environmental, and legal obstacles

must be over come before they can be mined

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Fig. 12.20

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Conservation of Mineral Resources

Overall need for resources is growingmustreduce this expansion

Some mineral resources maybe substituted by

other, more abundant resources

Plastics replacing automobile parts

Recyclingmany metals are successfully

recycled

More recycling is required Not all commodities are easy to recycle

Measures to reduce demand must be the key

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Impacts of Mining Activities

Mining and mineral-processing activities canmodify the environment in various ways

Both underground mines and surface mineshave their own sets of associated impacts

Safety, hazards, and water and air pollutionshould not be overlooked

Very stressful to the environment

Must be carefully planned Must be safe to miners and their neighbors

Must be containedwater and air pollution is amajor problem

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Underground Mines

Generally hard to see where they are locatedArea 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

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Surface Mines

Quarrying extracts rock to be used either intact

(building blocks or facing stone) or crushed(cement-making and road bed)

Open-pit Mine a large ore body located near the surface

Permanent changes to local topography will occur

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 banksare designed to collect the waste rock

Current reclamation law requires that it be return tothe pit and the original soil replaced

Expensive but vital

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Fig. 12.25

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Mineral Processing Mineral extraction is environmental hazardous

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 controlledand not just dumped

Smelting ores to extract metals, often produce metalladen exhaust gas or ash, sulfur oxid,e and acid rainpollution

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