Chapter 27

Minerals and the Environment

Importance of Minerals to Society

• Standard of living increases with availability– Success in locating, extracting, importing and

using; measurement of wealth– generally located in small, hidden areas (most

areas exploited)– U.S. uses 10 tons of non-fuel minerals per year– sand, steel and gravel

How Mineral Deposits Are Deposited

• Ore Deposits – formed when metals are concentrated in anomalously high amounts by geological processes– biosphere related and geologic cycle– large; deeply buried; concentrated; accessible

• Mineral resources are usually extracted from ore deposits

How Mineral Deposits Are Formed

• Distribution of mineral resources– Earth's formation– Crust and Ocean

• silicates vs. manganese oxide nodules

• Plate boundaries– Convergent and Divergent

• metallic ores vs. sulfide deposits

• Igneous processes– gravity and density (crystallization) and hot

water (source of most ore deposits)

How Mineral Deposits are Formed, con't.

• Sedimentary processes– water (placer deposits – related to flow and

stream turbulence) and wind– evaporates (calcium, sodium, potassium)

• Biological processes– iron ore deposits– Ca and Na (precipitated)

• Weathering processes– parent rock (bauxite)– secondary enrichment

Resources and Reserves

• Minerals are classified as:– 1. Mineral Resources

• Elements, chemical compounds, minerals or rocks that can be extracted to obtain a usable commodity

– 2. Mineral Reserves• The portion of the resource that is identified and

from which usable materials can be legally and economically extracted at the time of evaluation

Classification of Mineral Resources

• Based on use:– elements for metal production (ores) and

technology– building materials (sand and steel)– chemical industry– agriculture

• Metallic minerals can be classified according to their abundance

Availability of Mineral Resources

• When the availability of a mineral becomes limited, there are 4 possible solutions:

1. Find more sources

2. Recycle and reuse what has already been obtained

3. Reduce consumption

4. Find a substitute

**Choice depends on social, economic and environmental factors

U.S. Supply of Mineral Resources

• Domestic supply:– insufficient for current use– imports– political, economical and military instability

• alliances

Impacts of Mineral Development

• Environmental Impacts– Depends on many factors – ore quality, mining

procedures, hydrologic factors, climate, rock type, size of operation, topography, etc.

– Exploration vs. Mining and Processing• land, groundwater and surface water, air and

vegetation are all impacted• Copper

– topography; air (dust); surface and groundwater (drainage); biological (nutrients, biomass, diversity)

Impact of Mineral Development

• Social Impacts– Increased demand for housing and services in

mining areas– land-use shifts– closing of mines– environmental regulation in reclamation

(consider current trend of surface mining - cheaper)

Minimizing Environmental Impact of Mineral Development

• Federal, state and local environmental regulation (air, sediment and water pollution)– reclaiming;

stabilizing soils; controlling air emissions; treatment of contaminated water

Minimizing Environmental Impact of Mineral Development

• On-site and off-site treatment of waste– engineering and

conservation• controlling sediment

and water

– biotechnological processes

• acid tolerant plants• bacteria

• Three R's

Minerals and Sustainability

• R-to-C Ratio– A measure of the time available for finding the

solutions to depletion of nonrenewable resources

– R = known reserves– C = rate of consumption – provides a view on how scarce a particular

mineral resource may be– small ratios: short supply; find substitutes

through technological innovations

Future of Mineral Mining

• Factors that make more difficult and expensive– depletion of high-

grade ores– increasing energy

costs– less tolerance for

environmental damage

Mining with Microbes

• Biohydrometallurgy– extracting minerals from rock by using

microscopic organisms– Advantages:

• may produce minerals without large-scale excavations• techniques may be used to decontaminate wastes

– Disadvantages:• technology is not yet available for all mining situations• genetically-engineered organisms may pose a threat