MINERALS

MINERALS

General Classification of Nonrenewable Mineral Resources The U.S. Geological Survey classifies mineral resources into four major categories: Identified: known location, quantity, and quality or existence known based on direct evidence and measurements.

Undiscovered: potential supplies that are assumed to exist.

Reserves: identified resources that can be extracted profitably.

Other: undiscovered or identified resources not classified as reserves

General Classification of Nonrenewable Mineral Resources

Examples are fossil fuels (coal, oil), metallic minerals (copper, iron), and nonmetallic minerals (sand, gravel).

Figure 15-7Figure 15-7

GEOLOGIC PROCESSES Deposits of nonrenewable mineral resources in the earth’s crust vary in their abundance and distribution.

A very slow chemical cycle recycles three types of rock found in the earth’s crust: Sedimentary rock (sandstone, limestone). Metamorphic rock (slate, marble, quartzite).

Igneous rock (granite, pumice, basalt).

Fig. 15-8, p. 343

ErosionTransportation

Weathering

Deposition

Igneous rock Granite, pumice, basalt

Sedimentary rock Sandstone, limestone

Heat, pressure

Cooling

Heat, pressure, stress Magma

(molten rock)

Melting

Metamorphic rock Slate, marble, gneiss, quartzite

ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES

Minerals are removed through a variety of methods that vary widely in their costs, safety factors, and levels of environmental harm.

A variety of methods are used based on mineral depth. Surface mining: shallow deposits are removed.

Subsurface mining: deep deposits are removed.

Mining Regulations The General Mining Act of 1872 is a United States federal law that authorizes and governs prospecting and mining for economic minerals, such as gold, platinum, and silver, on federal public lands. This law, approved on May 10, 1872, codified the informal system of acquiring and protecting mining claims on public land, formed by prospectors in California and Nevada from the late 1840s through the 1860s, such as during the California Gold Rush.

Open-pit Mining Machines dig holes and remove ores, sand, gravel, and stone.

Toxic groundwater can accumulate at the bottom.

Figure 15-11Figure 15-11

Area Strip Mining Earth movers strips away overburden, and giant shovels removes mineral deposit.

Often leaves highly erodible hills of rubble called spoil banks.

Figure 15-12Figure 15-12

Contour Strip Mining Used on hilly or mountainous terrain.

Unless the land is restored, a wall of dirt is left in front of a highly erodible bank called a highwall.

Figure 15-13Figure 15-13

Mountaintop Removal Machinery removes the tops of mountains to expose coal.

The resulting waste rock and dirt are dumped into the streams and valleys below.

Figure 15-14Figure 15-14

Environmental Impacts of Mining Acid Mine Drainage Erosion and Sedimentation Cyanide & Other Toxic Releases Dust Emissions Habitat Modification Surface and Groundwater Contamination

Coal mining affects the environment

Strip mining causes severe soil erosion and chemical runoff Acid drainage = sulfide minerals on exposed rock surfaces react with oxygen and rainwater to produce sulfuric acid

Mountaintop removal causes enormous damage

Coal mining harms human health

Subsurface mining is harmful to human health Mine shaft collapses Inhalation of coal dust can lead to fatal black lung disease

Costs to repair damages of mining are very high These costs are not included in the market prices of fossil fuels, which are kept inexpensive by government subsidies

Mining companies must restore landscapes, but the impacts are still severe Looser of restrictions in 2002 allowed companies to dump rock and soil into valleys, regardless of the consequences

Now what do we do with it? Once the ore is mined and hauled to the surface, it must be processed Tailings are what is left behind once the valuable portion of the ore is removed.

Gangue is the commercially worthless minerals associated with a valuable find.

Mining Impacts

Metal ores are smelted or treated with (potentially toxic) chemicals to extract the desired metal.

Figure 15-15Figure 15-15

Gold Processing Gold is treated with a Cyanide compound which produces a Gold-Cyanide complex which is soluble Problem: Hydrogen Cyanide gas is toxic

Hyperaccumulation Hyperaccumulator plants accumulate inordinate amounts of one or more Trace Elements (TE)s in their above ground biomass. Hyperaccumulators species may accumulate one or more of a range of TEs that currently includes nickel, manganese, zinc, cadmium, thallium, copper, cobalt and arsenic.

Hyperaccumulation may have applications in mining in the future.

Fig. 15-10, p. 344

Natural Capital DegradationExtracting, Processing, and Using Nonrenewable Mineral and Energy Resources

StepsSteps Environmental effectsEnvironmental effects

Mining Disturbed land; mining accidents; health hazards, mine waste dumping, oil spills and blowouts; noise; ugliness; heat

Exploration, extractionProcessing

Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat

Transportation, purification, manufacturingUse

Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat

Transportation or transmission to individual user, eventual use, and discarding

Mining Waste Subsidence is a phenomenon where the surface collapses directly above a subsurface mine.

Spoils are the unwanted rock and other waste left over after mining either on the surface or subsurface

Tailings are the materials left over after the process of separating the valuable fraction from the worthless fraction of an ore.

What to do with the waste Incorporate the mine waste into

Concrete for buildings Backfill for roads Extraction of other minerals

ENVIRONMENTAL EFFECTS OF USING MINERAL RESOURCES

The extraction, processing, and use of mineral resources has a large environmental impact.

Figure 15-9Figure 15-9

SUPPLIES OF MINERAL RESOURCES

The future supply of a resource depends on its affordable supply and how rapidly that supply is used.

A rising price for a scarce mineral resource can increase supplies and encourage more efficient use.

SUPPLIES OF MINERAL RESOURCES

Depletion curves for a renewable resource using three sets of assumptions. Dashed vertical lines represent times when 80% depletion occurs.

Figure 15-16Figure 15-16

SUPPLIES OF MINERAL RESOURCES New technologies can increase the mining of low-grade ores at affordable prices, but harmful environmental effects can limit this approach.

Most minerals in seawater and on the deep ocean floor cost too much to extract, and there are squabbles over who owns them.

Getting More Minerals from the Ocean

Hydrothermal deposits form when mineral-rich superheated water shoots out of vents in solidified magma on the ocean floor.

Figure 15-17Figure 15-17

USING MINERAL RESOURCES MORE SUSTAINABLY

Scientists and engineers are developing new types of materials as substitutes for many metals.

Recycling valuable and scarce metals saves money and has a lower environmental impact then mining and extracting them from their ores.

Fig. 15-18, p. 351

Solutions

Sustainable Use of Nonrenewable Minerals

• Do not waste mineral resources.

• Recycle and reuse 60–80% of mineral resources.

• Include the harmful environmental costs of mining and processing minerals in the prices of items (full-cost pricing).

• Reduce subsidies for mining mineral resources.

• Increase subsidies for recycling, reuse, and finding less environmentally harmful substitutes.

• Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste.

• Have the mineral-based wastes of one manufacturing process become the raw materials for other processes.

• Sell services instead of things.

• Slow population growth.

Controls Surface Mining Control and Reclamation Act of 1977: regulates active coal mines and reclaims abandoned mines Standards of Performance. Permitting. Bonding. Inspection and Enforcement. Land Restrictions.

SMCRA

SMCRA and its implementing regulations set environmental standards that mines must follow while operating, and achieve when reclaiming mined land.

RequirementsSMCRA requires that companies obtain permits before conducting surface mining. Permit applications must describe what the premining environmental conditions and land use are, what the proposed mining and reclamation will be, how the mine will meet the SMCRA performance standards, and how the land will be used after reclamation is complete. This information is intended to help the government determine whether to allow the mine and set requirements in the permit that will protect the environment. Bonding. SMCRA requires that mining companies post a bond sufficient to cover the cost of reclaiming the site. This is meant to ensure that the mining site will be reclaimed even if the company goes out of business or fails to clean up the land for some other reason. The bond is not released until the mining site has been fully reclaimed and the government has (after five years in the East and ten years in the West) found the that the reclamation was successful. Inspection and Enforcement. SMCRA gives government regulators the authority to inspect mining operations, and to punish companies that violate SMCRA or an equivalent state statute. Inspectors can issue "notices of violation," which require operators to correct problems within a certain amount of time; levy fines; or order that mining cease. Land Restrictions. SMCRA prohibits surface mining altogether on certain lands, such as in National Parks and wilderness areas. It also allows citizens to challenge proposed surface mining operations on the ground that they will cause too much environmental harm.

Case Study: The Ecoindustrial Revolution

Growing signs point to an ecoindustrial revolution taking place over the next 50 years.

The goal is to redesign industrial manufacturing processes to mimic how nature deals with wastes. Industries can interact in complex resource exchange webs in which wastes from manufacturer become raw materials for another.

Case Study: The Ecoindustrial Revolution

Figure 15-19Figure 15-19