Minerals and the EnvironmentUnit 5: AP Environmental Science (Chapter 26)

Importance of Minerals to Society• Minerals can be linked to almost every aspect of

day to day living.

• The availability of minerals is a measure of the wealth of a society• To maintain standard of living in a wealthy

society like the United States each person requires 10 tons of nonfuel minerals every year

Importance of Minerals to Society• Minerals are nonrenewable resources that are

depleted with use and take long periods of time to replenish

• With depleting supplies, natural sources of minerals become smaller and harder to find making mining processes more costly and potentially harmful to the environment

• Recycling and conservation of mineral resources may be able to slow the rates of depletion

Production and Distribution of Mineral Resources• The structure of the Earth is divided

into several layers distinguished by the types of materials, densities, pressures, and temperatures in each

• During the formation of planets that occurred as the sun was formed, gravitational attraction collected material in the solar nebula and concentrated it into the orbits of the planets that we see today

Production and Distribution of Mineral Resources• The mass of the Earth increased as

scattered material coalesced into a large object rounded by its gravitational pull.

• Heat from the gravitational condensation of materials and continuous impacts from debris formed a molten core at the center of the early Earth

• In this molten “sea” of elements, heavy material sank to the core and lighter materials rose to the surface

Production and Distribution of Mineral Resources• Crust Composition (9 abundant elements)• 45% Oxygen, 27% Silicon, 8% Aluminum, 6% Iron, 5%

Calcium, 3% Magnesium, 2% Sodium, 2% Potassium, 1% Titanium

• Ocean Water Composition ( 5 abundant elements)• 3.5% Dissolved Solids• 55% of solids are chlorine• Other solid materials include zinc, copper, tin, silver,

and gold (also found in the crust in larger amounts)

Production and Distribution of Mineral Resources• Activity in the geologic cycle is responsible for almost all

aspects of mineral production and distribution

• Movement of the tectonic plates redistributes mineral ores trapped within rock layers

Production and Distribution of Mineral Resources• Action at divergent boundaries

leaches metals from ocean water that comes into contact with hot molten rock

• Action at convergent boundaries puts pressure on rock layers forcing them to heat and go through partial melting that moves and collects metal deposits along the boundary

Production and Distribution of Mineral Resources• Igneous processes start with molten rock that cools and crystallizes into minerals• The longer the cooling process, the larger the mineral crystals

• Sedimentary processes collect mineral fragments that are loosened by weathering and erosion then transport and sort them through the movement of water, wind or ice.• Particles are sorted by size, as velocity of the erosion process

decreases larger fragments are deposited before smaller ones• Minerals dissolved in solutions can be deposited once the water

is evaporated away. These fragments become known as evaporates.

Production and Distribution of Mineral Resources• Biological processes contribute to the formation of

minerals through the transformation and concentration of materials like phosphates, calcium and magnesium

• Life has also altered the state of some minerals by changing the environment they were formed in• Gray bed iron deposits – unoxidized iron formed with

little to no atmospheric oxygen present

• Red bed iron deposits – iron oxides form in the presence of oxygen

Production and Distribution of Mineral Resources

• Weathering processes concentrate mineral fragments in soil where they accumulate unless removed by erosion

• The environment and mineral sources of soil can change the type and amount of mineral deposits that form

Production and Distribution of Mineral Resources• Secondary enrichment occurs when

a primary ore comes into contact with acidic water in the soil and oxygen then is leached through the soil as a solution until it becomes deposited when oxygen is no longer present to continue the enrichment through oxidation• Produces ores that are 10 times

richer than the primary ore

Resources and Reserves• Material collected from mineral deposits is sorted

according to the concentration and clarity of the mineral being mined

• Ores are bodies of material from which valuable material can be extracted economically

• Ore minerals represent the valuable portion of an ore deposit

• Gangue minerals represent the other minerals and material present in the ore deposit that are not valuable.

Resources and Reserves• Mineral resources are elements, compounds or minerals that

are concentrated in a form that can be extracted to obtain a usable commodity

• Reserves are a portion of a resource that is identified and from which usable materials can be legally and economically extracted

Resources and Reserves• As economic, political, or environmental conditions change

resources can become reserves

• As a certain metal becomes scarce demand increases and pushes the exploration and discovery of more identified areas of reserves

Use of Mineral Resources

• Minerals are divided up into categories according to their uses:• Metal production• Technology• Building• Chemical manufacturing• Agriculture

• Some mineral resources are necessary for life (salt) while others are desired to maintain a standard of living (technology products)

Use of Mineral Resources

• Most mineral resources are non-metallic• Sodium, Nitrogen, Sulfur, Potassium, and Calcium

• Iron makes up 95% of all metallic resources consumed

• Abundant metals include iron, aluminum, chromium, manganese, titanium and magnesium

• Scarce metals include: copper, lead, zinc, tin, gold, silver, platinum, uranium, mercury, and molybdenum

Availability of Mineral Resources• In many cases the issue with minerals is not their

complete depletion, but the cost of mining and recycling the known supplies

• When a mineral becomes limited we can:• 1. Find more sources• 2. Recycle and reuse what has already been obtained• 3. Reduce consumption• 4. Find a substitute

• Choices depend on social, economic and environmental factors

Mineral Consumption• Use of a mineral resource can occur in several ways:• Rapid consumption• Consumption with conservation• Consumption with conservation and recycling

U.S. Supply of Mineral Resources• Domestic supplies of desired minerals are not sufficient

to meet the needs of the U.S. population so it requires import of minerals from other countries

• Mineral resources could exist within the United States but it is currently cheaper, easier, or more practical to import the supplies

• The results of this desire to import are political alliances with countries we would not normally align with because of political or moral differences on policies within the country

Impacts of Mineral Development• The impact of mineral

exploitation on the environment depends on such factors as;• Ore quality, mining

procedures, local hydrologic conditions, climate, rock types, size of operation, topography, and many more interrelated factors.

• The impact varies with the stage of development of the resource.

Impacts of Mineral Development• Exploration activities generally have minimal impacts on the

environment. They include:• Remote-sensing data collection and analysis• Surface mapping• Seismic surveys• Drilling• Radiation and magnetic testing• Electrical resistance• Chemical analysis

• Mining and processing activities can have a large impact on the environment especially as lower grade material is processed

Impacts of Mineral Development• A big debate in mining processes is whether surface or

subsurface mining should be developed in identified areas

• Surface mining is cheaper but comes with more direct environmental impacts

• Currently surface mines cover less than 0.5% of the total area of the United States

Subsurface mining• Disturbs less than 1/10 as much land as surface mining and

produces less waste

• Concerns are that it is more dangerous, more expensive and leaves behind more of the valuable ores

• Techniques to access coal:• mine shafts, slope and drift mines

• Techniques to recover coal:• Room and pillar (60% recovery)• Longwall (80% recovery)

Surface Mining• Surface mining is a broad category of mining in which soil

and rock overlying the mineral deposit called overburden is removed

• Techniques:• Open-pit• Dredging• Area strip• Contour strip• Mountaintop removal

Surface Mining• To separate valuable ores from the gangue, mining

processes use a variety of techniques:• In situ boring (Uranium, Copper)• Heap leaching (Gold, Silver)• Hydraulic mining

Surface Mining• New mining techniques utilize microbes to isolate and purify

valuable minerals

Surface Mining• Surface mining concerns:• Release of harmful trace elements into an

environment• Water pollution• Ecosystem degradation• Changes to nutrient cycles• Increased chances of accidents• Acid mine wash (sulfide release)

Impacts of Mineral Development• Social impacts of mining processes include: • Rapid influx of people into rural areas• Increased stress on local utilities and services• Increased pollution• Economic dependency on the mining industry

General Mining Act of 1872

• Law that authorizes and regulates prospecting and mining for mineral resources on federal lands

• Gave any discoverer of a mineral lode over the age of 18 rights to mine the land

• The price of lands claimed under this act were priced at $2.50-$5.00 per acre, which still stands today

Surface Mining and Reclamation Act of 1977• Primary federal law that regulates the environmental impact

of coal mining in the United States

• Sets environmental standards for the operation and reclamation of mined lands

• Requires permits for mining and bods to cover the cost of reclamation

• Authorizes government employees to inspect mining operations

• Restricts the use of national parks and wilderness areas

Minimizing Environmental Impacts• Most environmental impacts from mining trace back to the

disposal of waste created during the extraction, processing and use of mineral resources

Minimizing Environmental Impacts• Reducing the environmental footprint of mineral

resources can include:

• Environmental regulations at all levels

• On and off-site treatment of waste• Increased use of biological processes for the treatment

of waste (biooxidation, bioleaching and biosorption)

• Application of the 3 R’s of waste management(Reduce, Reuse and Recycle)

Recycling of Mineral Resources• Iron and steel are recycled in large volumes for three

reasons:• 1. Market is huge, and there is a large scrap collection

and processing industry.• 2. Enormous economic burden would result from

failure to recycle. • 3. Significant environmental impacts related to

disposal of over 50 million tons of iron and steel.

• In addition, only 1/3 the energy is required to produce steel from recycled scrap as from native ore.

Minerals and Sustainability

• Simultaneously considering sustainable development and mineral exploitation and use is problematic. • Sustainability is a long-term concept and minerals are

a finite resource

• Human ingenuity will be important because often it is not the mineral we need so much as what we use the mineral for.

Minerals and Sustainability• A measure of the time available for finding the solutions to

depletion of nonrenewable reserves is the R-to-C ratio• R is the known reserves• C is the rate of consumption

• The ratio is a present analysis of a dynamic system in which both the amount of reserves and consumption may change over time.

• The ratio provides a view of how scarce a particular mineral resource may be. Those metals with relatively small ratios can be viewed as being in short supply.• Those resources are identified so we can find substitutes

through technological innovation.