Chapter 23 Minerals and Mining

This lecture will help you understand: Mineral resources Mining methods Impacts of mining Reclamation and mining policy Sustainable use of minerals

Central Case Study: Mining for … Cell Phones? Cell phones and other high-tech products contain tantalum Coltan: columbite + tantalum Since 1998, the war in the Democratic Republic of the Congo has killed 5 million Soldiers controlled mining operations and forced farmers and others to work, while taking most of the ore People entered national parks, killing wildlife and clearing rainforests, causing ecological havoc Profits from coltan sales financed the war Most tantalum from the Congo goes to China

The rock cycle 4 4

Earth’s mineral resources We mine and process mineral resources for countless products

We use mined materials extensively We don’t notice how many mined resources we use The average American uses 37,000 lb of new minerals and fuels every year This level of consumption shows the potential for recycling and reuse A child born in 2009 will use 2.9 million lb of mined resources over its life

We obtain minerals by mining We obtain minerals through the process of mining Mining: in the broad sense, it is the extraction of any nonrenewable resource of economic interest Fossil fuels, groundwater, and minerals Because minerals occur in low concentrations, concentrated sources must be found before mining is begun

We extract minerals from ores Metal: an element that is lustrous, opaque, and malleable and can conduct heat and electricity Ore: a mineral or grouping of minerals from which we extract metals Economically valuable metals from ore include: Copper, iron, lead, gold, aluminum Tantalite ore is mined, processed into tantalum, and used in electronic devices

We process metals after mining ore Most minerals must be processed after mining After the ore is mined, rock is crushed, and the metals are isolated by chemical or physical means The material is processed to purify the metal Alloy: a metal is mixed, melted, or fused with another metal or nonmetal substance Steel is an alloy of iron and carbon Smelting: heating ore beyond its melting point, then combining it with other metals or chemicals Modifies the strength, malleability, etc., of metals

Environmental costs of processing minerals Water- and energy-intensive Chemical reactions and heating to extract metals from ores emit air pollution and toxic wastes Tailings: ore left over after metals have been extracted Pollute soil and water Contain heavy metals or chemicals (cyanide, sulfuric acid) Surface impoundments: store slurries of tailings Accidents release pollutants into the environment

We also mine nonmetallic minerals and fuels Sand and gravel provides fill and construction materials Phosphates provide fertilizer Salt, limestone “Blood diamonds” are mined and sold to fund, prolong, and intensify wars in Angola and other areas Poor people are exploited for mine labor Substances are mined for fuel Uranium is used in nuclear power Coal, petroleum, natural gas, oil sands, oil shale, methane hydrate are not minerals (they are organic)

Economically important mineral resources

Mining methods and their impacts Mining provides jobs and money for communities It provides raw materials for products we use Mining has environmental and social costs Large amounts of material are removed during mining, disturbing lots of land Different mining methods are used to extract minerals The method used depends on economic efficiency

Strip mining removes surface soil and rock Strip mining: removal of layers of soil and rock to expose the resource just below the surface Overburden: soil and rock that is removed by heavy machinery After extraction, each strip is refilled with the overburden For coal, oil sands, sand, gravel Causes severe environmental impacts Strip mining destroys natural communities over large areas and triggers erosion

Subsurface mining: underground work Accesses deep pockets of a mineral through tunnels and shafts up to 2.5 miles deep Zinc, lead, nickel, tin, gold, diamonds, phosphate, salt, coal The most dangerous form of mining Dynamite blasts, collapsed tunnels Toxic fumes and coal dust Collapsed tunnels cause sinkholes

Acid drainage Acid drainage: sulfide in newly exposed rock reacts with oxygen and rainwater Produces sulfuric acid Sulfuric acid leaches toxic materials from rock Flows into streams, killing fish and other organisms Pollutes groundwater used for drinking and irrigation Although acid drainage is natural, mining greatly accelerates it by exposing many new rock surfaces at once

Open pit mining creates immense holes Used with evenly distributed minerals Terraced, so men and machines can move about Copper, iron, gold, diamonds, coal Quarries: open pits for clay, gravel, sand, stone (limestone, granite, marble, slate) Huge amounts of rock are removed to get small amounts of minerals Habitat loss, aesthetic degradation, acid drainage Abandoned pits fill with water Acid drainage forms if sulfur is present

The world’s largest open pit mine This Utah mine is 2.5 mi across and 0.75 mi deep; almost half a million tons of ore and rock are removed each day

Placer mining uses running water Using running water, miners sift through material in riverbeds Used for gold, gems Debris washes into streams They become uninhabitable for wildlife Disturbs stream banks Causes erosion Harms plant communities

Mountaintop removal reshapes ridges Entire mountaintops are blasted off “Valley filling”: dumping rock and debris into valleys For coal in the Appalachian Mountains of the eastern U.S. Degrades and destroys vast areas Pollutes streams; deforests areas; causes erosion, mudslides, flash floods, biodiversity loss An area the size of Delaware has already been removed

Mountaintop removal is devastating Mine blasting cracks foundations and walls Floods and rock slides affect properties Coal dust and contaminated water cause illness Lung cancer, heart and kidney disease, pulmonary disorders, hypertension, death The poor people of Appalachia suffer while we benefit from coal-produced electricity Critics argue that valley filling violates the Clean Water Act In 2010, the EPA introduced rules to limit damage

Solution mining dissolves resources Solution mining (in-situ recovery): resources in a deep deposit are dissolved in a liquid and sucked out Water, acid, or other liquids are injected into holes Used for salt, lithium, boron, bromine, magnesium, potash, copper, uranium Less environmental impact than other methods Less surface area is disturbed Acids, heavy metals, uranium can accidentally leak or leach out of rocks and contaminate groundwater

Ocean mining We extract minerals (e.g., magnesium) from seawater Minerals are dredged from the ocean floor Manganese nodules: small, ball-shaped ores scattered across the ocean floor These reserves may exceed all terrestrial reserves Logistical difficulties in mining have kept extractions limited, so far

Restoring mined sites only partly works Governments in developed countries require companies to reclaim (restore) surface-mined sites Reclamation aims to bring a site to a condition similar to its pre-mining condition Remove structures, replace overburden, replant vegetation The U.S. Surface Mining Control and Reclamation Act (1977) mandates restoration Companies must post bonds to cover restoration costs

Restoration of mined sites Even on restored sites, impacts may be severe and long-lasting Complex communities are simplified Forests, wetlands, etc., are replaced by grasses Essential symbioses are eliminated and often not restored Water can be reclaimed Moderate the pH Remove heavy metals

The General Mining Act of 1872 Encourages metal and mineral mining on federal land Any citizen or company can stake a claim on, or buy (for $5 per acre), any public land open to mining The public gets no payment for any minerals found Supporters say it encourages a domestic industry that is risky and requires investment to locate vital resources Critics say it gives valuable public land basically free to private interests People have developed the land (e.g., for condominiums) that have nothing to do with mining Efforts to amend the act have failed in Congress

Minerals are nonrenewable and scarce Many minerals are rare and could become unavailable Once known reserves are mined, minerals will be gone For example, indium, used in LCD screens, might last only 32 more years Gallium (for solar power) and platinum (fuel cells) are also scarce Estimating how long a reserve will last is hard New discoveries, technologies, consumption patterns, and recycling affect mineral supplies As minerals become scarcer, prices rise

Years remaining for selected minerals Time periods can increase if more reserves are found or decrease if consumption increases

We can use minerals sustainably Recycling minerals addresses: Finite supplies Environmental damage 35% of metals were recycled in 2009 from U.S. solid waste 35% of our copper comes from recycles sources Recycling decreases energy use It also lowers greenhouse gas emissions Aluminum from raw sources uses 20 times more energy than from recycled sources

We can recycle metals from e-waste Electronic waste (e-waste) from computers, printers, cell phones, etc., is rapidly rising Recycling keeps hazardous wastes out of landfills while conserving mineral resources Cell phones can be refurbished and resold in developing countries Or their parts can be dismantled or refurbished Today, only 10% of cell phones are recycled Reduces pressure on ecosystems

Conclusion Geologic processes shape Earth’s terrain and form the foundation for living systems We depend on minerals and metals to make our products Mineral resources are mined by various methods Contribute to material wealth But cause extensive environmental damage (habitat loss, acid drainage, etc.) Restoration and regulations help minimize the environmental and social impacts of mining Recycling and sustainable use prolong mineral resources 31 31