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