Chapter 15 Geology, Minerals, and Mining Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

This presentation will help you understand: Mineral resources and their contributions to society Mining methods Social and environmental impacts of mining Sustainable use of mineral resources

Minerals and mining We extract raw minerals from beneath our planet’s surface Turn them into products we use everyday Rock and resources from the lithosphere contribute to our economies and lives Rock = a solid aggregation of minerals Mineral = a naturally occurring solid chemical element or inorganic compound It has a crystal structure, specific chemical composition, and distinct physical properties Minerals are nonrenewable, so we need to be aware of their finite and decreasing supplies

ECONOMIC GEOLOGY & MINERALOGY Economic mineralogy is the study of minerals that are valuable for manufacturing and trade. Public policy in the U.S. has encouraged mining on public lands as a way of boosting the economy and utilizing natural resources.

Most economic minerals are metal ores (ores are minerals with high concentrations of metals). Metals are elements that easily give up an electron and thus have a positive charge (cations). Metals consumed in the greatest quantity by world industry (metric tons annually) are: Iron (740 million) Aluminum (40 million) Manganese (22.4 million) Copper (8 million) Chromium (8 million) Nickel (0.7 million)

Nonmetal Mineral Resources Sand and gravel production for road and building construction make up the greatest volume and dollar value of all nonmetal mineral resources. This includes brick and concrete construction, paving, sandblasting and glass production. Evaporites include halite (rock salt), gypsum, potash Sulfur deposits are mined mainly for sulfuric acid production (industry, car batteries, some medicinal products). Limestone is used to make concrete and building stone. Pulverized, it is used to neutralize acidic soil. Soils

Strategic metals and minerals are ones that a country uses but cannot produce itself Wealthy industrial nations often stockpile strategic resources, especially metals. Of the 80 industrial metals and minerals, between one-third and one-half are considered strategic resources.

Minerals are everywhere in our products

ENVIRONMENTAL EFFECTS OF RESOURCE EXTRACTION Geologic resource extraction involves the physical processes of mining and the physical or chemical processes of separating minerals, metals, and other geologic resources from ores or other materials. Ore - a rock in which a valuable or useful metal occurs at a concentration high enough to make mining it economically attractive

We obtain minerals by mining We obtain minerals through the process of mining Mining = in the broad sense, it is the extraction of any resource that is nonrenewable We mine minerals, fossil fuels, and groundwater Mining = in relation to minerals, it is the systematic removal of rock, soil, or other material to remove the minerals of economic interest Because minerals occur in low concentrations, concentrated sources must be found before mining

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 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 mining the ore, 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

Processing minerals has costs Processing minerals has environmental costs Most methods are water- and energy-intensive Chemical reactions and heating to extract metals from ores emit air pollution Tailings = ore left over after metals have been extracted Pollutes soil and water They may contain heavy metals or acids (cyanide, sulfuric acid) Water evaporates from tailings ponds, which may leach pollutants into the environment

We also mine nonmetallic minerals and fuels Nonmetallic minerals include sand, gravel, phosphates, limestone, and gemstones $7 billion/year of sand and gravel are mined in the U.S. Phosphates provide fertilizer “Blood diamonds” are mined and sold to fund, prolong, and intensify wars in Angola and other areas Substances are mined for fuel Uranium for nuclear power Coal, petroleum, natural gas are not minerals (they are organic), but they are also extracted from the Earth

Economically useful mineral resources

Mining and Processing Extraction and separation Ore = rock with high concentration of valuable or useful metal Must be economically feasible 1% Cu ore 0.0001% Au ore

Mining Underground, tunnel mining is very dangerous due to: Gas Inhaling Particulate Matter Tunnel Collapse Placer mining Strip-mining or open-pit mining Tailings - surface waste deposits Groundwater contamination Spoil banks - acid and sediment runoff

Implications of Resource Extraction Mining Placer Mining - Hydraulically washing out metals deposited in streambed gravel. Destroys streambeds and fills water with suspended solids. Strip, Open Pit or Mountain Removal Mining Large scars on land surface. Tailings Toxic runoff Surface Mining Control and Reclamation Act (SMCLRA) (1977) requires better restoration of strip-mined lands, especially if the mined land is classified as prime farmland. Difficult and expensive. Often more than $10,000.00 per hectare. 50% of US coal is strip mined.

Mining methods and their impacts People in developing nations suffer war and exploitation because of the developed world’s appetite for minerals In 2009, raw materials from mining gave $57 billion to the U.S. economy After processing, minerals contributed $454 billion 28,000 Americans were directly employed for mining Large amounts of material are removed during mining Disturbing lots of land Different mining methods are used to extract minerals Economics determines which method to use

Strip mining removes surface soil and rock Strip mining = layers of soil and rock are removed to expose the resource Overburden = overlying soil and rock that is removed by heavy machinery After extraction, each strip is refilled with the overburden Used for coal, oil sands, sand, gravel Destroys natural communities over large areas and triggers erosion Acid drainage = sulfide minerals form sulfuric acid and flow into waterways

Strip mining destroys the environment Strip mining removes soil Discolored water is a sign of acid drainage

Environmental Effects of Mining

A mining method: subsurface mining Accesses deep pockets of a mineral through tunnels and shafts The deepest mines are 2.5 mi Zinc, lead, nickel, tin, gold, diamonds, phosphate, salt, coal The most dangerous form of mining Dynamite blasts, collapsed tunnels Toxic fumes and coal dust Acid drainage, polluted groundwater Sinkholes damage roads, homes, etc.

A mining method: open pit mining 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 toxic water

One open pit mine One 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

A mining method: placer mining Using running water, miners sift through material in riverbeds Coltan miners, California’s Gold Rush of 1849 Used for gold, gems Debris washed into streams makes them uninhabitable for wildlife Disturbs stream banks, causes erosion Harms riparian plant communities

A mining method: mountaintop removal Entire mountaintops are blasted off The waste is dumped into valleys For coal in the Appalachian Mountains of the eastern U.S. Economically efficient “Valley filling” = dumping rock and debris into valleys Degrades and destroys vast areas Pollutes streams, deforests areas, erosion, mudslides, flash floods An area the size of Delaware has already been removed

Mountaintop removal is socially devastating Mine blasting cracks foundations and walls Floods and rock slides affect properties Overloaded coal trucks speed down rural roads Coal dust and contaminated water cause illness Local politicians do not help High-efficiency mining reduces the need for workers

Heap-leach extraction is when large piles of crushed ore are sprayed with a alkaline cyanide solution that percolates through the pile to dissolve gold. The effluent is left behind in ponds.

A mining method: solution mining Solution mining (in-situ recovery) = resources in a deep deposit are dissolved in a liquid and siphoned out Salts, lithium, boron, bromine, potash, copper, uranium Less environmental impact than other methods Less surface area is disturbed Acids, heavy metals, uranium can accidentally leak

A mining method: undersea mining We extract minerals (e.g., magnesium) from seawater Minerals are dredged from the ocean floor Sulfur, phosphate, calcium carbonate (for cement), silica (insulation and glass), copper, zinc, silver, gold Manganese nodules = small, ball-shaped ores scattered across the ocean floor Mining them is currently uneconomical Hydrothermal vents may have gold, silver, zinc Mining would destroy habitats and organisms and release toxic metals that could enter the food chain

Restoration of mined sites Governments in developed countries require companies to reclaim (restore) surface-mined sites Other nations (e.g., Congo) have no regulations at all Reclamation aims to bring a site to a condition similar to its pre-mining condition Remove structures, replace overburden, replant vegetation The U.S. 1977 Surface Mining Control and Reclamation Act mandates restoration Companies must post bonds to ensure restoration

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 Remove heavy metals pH is moderated

The General Mining Act of 1872 Encourages metal and mineral mining on federal land Any citizen or company can stake a claim on any public land open to mining for $5 per acre The public gets no payment for any minerals found Once a person owns the land, that land can be developed for any reason, having nothing to do with mining Supporters say it encourages a domestic industry that is risky and provides essential products Critics say it gives land basically free to private interests Efforts to amend the act have failed in Congress

Minerals are nonrenewable and scarce We must recover and recycle our limited supplies Once known reserves are mined, minerals will be gone For example, indium, used in LCD screens, might only last 32 more years Gallium (for solar power) and platinum (fuel cells) are also scarce Reserve estimates are uncertain New discoveries, technologies, consumption patterns, and recycling affect mineral supplies As minerals become scarcer, demand and price rise

Years remaining for selected minerals Scarcity increases prices Industries will spend more to reach further deposits

Factors affecting how long deposits last Discovery of new reserves increases known reserves Minerals worth $900 billion were discovered in Afghanistan in 2010 New extraction technologies reach more minerals at less expense Changing social and technological dynamics modify demand in unpredictable ways Lithium batteries are replacing cadmium-nickel ones Changing consumption patterns affect how fast we exploit reserves (e.g., a recession depresses demand) Recycling extends the lifetimes of minerals

We can use minerals sustainably Recycling addresses: Finite supplies Environmental damage 35% of metals were recycled in 2008 from U.S. municipal solid waste 7 million tons Steel, iron, platinum, gold, nickel, germanium, tin, and chromium Reduces greenhouse gases by 25 million metric tons

CONSERVING GEOLOGIC RESOURCES

Types of Geologic Resource Conservation Recycling is common for aluminum, platinum, gold, silver, copper, lead Steel and iron recycling is easily done at minimills (photo to left). Cars also contain platinum as a catalytic converter catalyst. Substituting new materials (polymers, high-tech alloys, glass cables, etc.)

Recycling of Aluminum - A Big Success Story Aluminum must be extracted from bauxite by electrolysis. This requires lots of energy! Recycling waste aluminum consumes one- twentieth the energy of extraction from raw ore. Nearly two-thirds of all aluminum beverage cans in US are recycled. It makes environmental and economic sense to recycle aluminum. Everyone agrees!

We can recycle rare 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 1.2 billion cell phones sold each year contain 200 chemicals and precious metals Phones can be refurbished and resold or dismantled and their parts reused or recycled Only 10% of cell phones are recycled Recycling reduces demand for virgin ores and reduces pressure on ecosystems

Conclusion We depend on minerals and metals to make the products we use Mineral resources are mined by various methods Contributing to material wealth But causing extensive environmental damage (habitat loss, acid drainage, etc.) Restoration and regulations help minimize the environmental and social impacts of mining Maximize recycling and sustainable use of minerals 46