Chapter 14Chapter 14

Mineral ResourcesMineral Resources

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Some Important ElementsSome Important Elements

C carbonH hydrogenN nitrogenO oxygenP phosphorus

Br bromineCl chlorineFl fluorine

SymbolsCa calciumFe ironK potassiumNa sodiumS sulfur

Al aluminumHg mercuryPb leadSi silicon

Composition by weight of Earth's crust. Only eight elements make up 98.5% of the crust.

Fig. 3–11

Mineral ResourcesMineral Resourcesmineral resource: a naturally occurring concentration of solid, liquid, or gaseous material in or on Earth's crust that can be processed into useful materials at an affordable cost.• energy resources: coal, oil, natural gas, uranium,

geothermal energy sources;

• metallic mineral resources: iron, copper, aluminum…;- ore is a metal–yielding material that can be

economically extracted;- to be profitable, copper must be concentrated 86

times, gold 1,000 times, & mercury 100,000 times the crustal average;

- the average 18 karat ring produces 20 tons of waste

• nonmetallic mineral resources: salt, gypsum, clay, sand, phosphates, water, & soil.

Mineral Deposits Created Through Igneous Processes• Hydrothermal deposits: Account for most metallic mineral deposits (Zn, Cu, Ag, Au)• Hydrothermal veins: deposits of copper, gold, silver• Some gems: peridotite (olivine) from basalts; amethyst (quartz) • Building materials such as Granite

AmethystGold ore

Hydrothermal DepositsHydrothermal DepositsHydrothermal circulation leaches metals from rocks, then concentrates and deposits them in Volcanogenic Massive Sulfide deposits (VMS).

Sulfur is often the element combined with the metal to make sulfide minerals. Ore minerals and metals found at VMS’s:

Ore mineral Metal

Sphalerite (ZnS) zinc

Chalcopyrite (CuFeS2) copper

Galena (PbS) lead

Mineral Deposits Created Through Metamorphic Processes

• Many gems, including diamonds, rubies, sapphires, and garnets,

• Building materials such as marble and slate

Uncut

Diamonds

GarnetMarble

Mineral Deposits Created Through Sedimentary Processes

• Aluminum• Various phosphates and sulfates

• Gypsum (CaSO4)

• Salt• Uranium

Al reserves

Great Salt Lake, UT

Mineral ResourcesMineral ResourcesThe U.S. Geological Survey (USGS) divides mineral resources into two broad categories:

• identified resources: deposits of a particular mineral resource that have known location, quantity, & quality;

• undiscovered resources: deposits of a particular mineral resource that are assumed to exist, based on geologic knowledge & theory, but for which specific locations, quantities, & quality are unknown.

Al Ore (Bauxite)

Uranium Ore (Carnotite)

Mineral ResourcesMineral Resources

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Reserves are identified resources that can be extracted economically at current prices using current mining technology.

Other resources are identified & undiscovered resources not classified as reserves.

Fig.14–6

Supplies of Mineral ResourcesSupplies of Mineral ResourcesCurrently the U.S. imports more than 50% of more than 24 of its most important non-fuel minerals.

Some non-fuel minerals for which the U.S. has essentially no reserves:

manganese, cobalt, tantalum, niobium, platinum, chromium, nickel, aluminum, tin, antimony, fluorine, asbestos, vanadium;

Some non-fuel minerals for which the U.S. has reserve deficiency:

mercury, silver, tungsten, sulfur, zinc, gold, potash;

(See Fig.14–11)

Mercury

AsbestosFluorite

Some Mining Vocabulary

• Ore: Economic deposit of metal-yielding material– Ore mineral: contains desired metal

– Gangue: waste mineral material

• Overburden: rock/soil on top of resource• Spoil: waste material from overburden• Beneficiation: separation in a mill of the ore

mineral from the gangue– Tailings: waste from this process

• Smelting: separates metal from the ore mineral• Reserves: Identified economic resources• Grade: the percentage of metal content in an ore

Extracting Mineral ResourcesExtracting Mineral Resources

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• strip mining is surface mining in which the upper layer is removed to get at the desired mineral resource (see example, left);

• subsurface mining involves use of drill holes or tunnels to extract mineral resources that are too deep to be accessible by surface mining.

Fig.14–9

Bingham Canyon Copper Mine, UT• The mine provides ~15% of our country’s copper needs• Other metals: gold, silver, molybdenum, platinum and palladium• Mining first began in the 1860’s; mine opened in 1906• Two tons of waste are produced to get one ton of ore, which produces

12 pounds of copper

18 mi SW of Salt Lake City

1863 1915

1930 1944

1964 1981 1999

Bingham Canyon

Mine Through Time

It is the largest man-made hole on Earth (over ½ mile deep). It is one of only 2 man-made structures that can be seen from space.

Economics of Mineral ResourcesIn a free market, rising demand and lowering supply of

a resource should lead to rising costs, a reduction in demand, a search for substitutes, better/more efficient technology, etc. But this is not happening in many developed nations because:

• Mining companies get subsidies such as depletion allowances, exploration costs for free, public lands almost free.

• Final cost of goods is only a small fraction of the cost of mineral resource, so scarcity of resource does not affect demand.

• Mineral costs are low because mining companies are not responsible for most environmental costs.

Environmental Effects of Extracting Mineral Resources

• Scarring of land surface • Runoff of waste sediment into nearby rivers.

• Acid (H2SO4) seeping into groundwater and streams, often carrying with them dissolved heavy metals

• Toxic chemicals used in extraction process leaking into soils and water: arsenic, cyanide (cyanide heap leaching p. 353), lead, mercury, cadmium

• Air pollution from smelting plants: SO2, soot, particulates of arsenic, cadmium, lead, and other toxic elements found in ores

Environmental Effects of Mineral ExtractionEnvironmental Effects of Mineral Extraction

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Pollution & degradation of water quality by runoff of acids & toxic chemicals from surface & subsurface mining.

Fig.14–14

Environmental Effects of Mineral ExtractionEnvironmental Effects of Mineral Extraction

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Some harmful effects of mineral extraction, processing, & use.

Fig.14–13

U.S. 1872 Mining LawU.S. 1872 Mining Law

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Under an 1872 U.S. mining law (p. 338), any person or corporation can assume legal ownership of public land (other than wilderness or park) by filing mining claims & paying nominal cost for the land (often $6 to $12 per hectare). 1 hectare = 25.4 acres• no provision for reclamation of damaged land;

• any country may also file claims and obtain minerals on U.S. public lands;

• environmentalists want the law to include the following:- prohibit buying of public land, but allow leasing;- require environmental impact assessment before leasing;- set standards for preventing & controlling pollution &

environmental degradation;- make mining companies legally & financially responsible for

environmental cleanup & restoration.

Areas with abandoned mines

In Washington, most mining has occurred in the Cascades, the Kettle Range

and the Selkirks. Most of the known mines are on U.S. Forest Service and

Bureau of Land Management (BLM) turf

Where mines have polluted waterThe U.S. Geological Survey mapped streams and headwaters tainted with run off from hard-rock mines, releasing this version to the public in 1996. At the request of the EPA, Geological Survey specialists spent more than two years in the late 1990s producing a more current and detailed map based on satellite data and information from the EPA and most state governments. Only four copies of the newer map were produced. Members of Congress and state officials, fearing damage to tourism and development in their states, have blocked release of the new map.