The United States, Canada, and Russia have the larg-est output of natural gas from methane deposits.. As a re-sult, modern coal-mining practice removes as much methane from coal deposits
Trang 1Bowes, D R., ed The Encyclopedia of Igneous and
Meta-morphic Petrology New York: Van Nostrand
Rein-hold, 1989
Bucher, Kurt, and Martin Frey Petrogenesis of
Metamor-phic Rocks 7th completely rev and updated ed New
York: Springer, 2002
Philpotts, Anthony R., and Jay J Ague Principles of
Ig-neous and Metamorphic Petrology 2d ed New York:
Cambridge University Press, 2009
Raymond, Loren A Petrology: The Study of Igneous,
Sedi-mentary, and Metamorphic Rocks 2d ed Boston:
McGraw-Hill, 2002
Winter, John D An Introduction to Igneous and
Metamor-phic Petrology 2d ed New York: Prentice Hall, 2010.
Web Site
U.S Geological Survey
Metamorphic Rocks
http://vulcan.wr.usgs.gov/LivingWith/
VolcanicPast/Notes/metamorphic_rocks.html
See also: Asbestos; Corundum and emery; Garnet;
Gneiss; Graphite; Kyanite; Marble; Mica; Plate
tecton-ics; Slate; Talc
Methane
Category: Mineral and other nonliving resources
Where Found
Methane is found throughout the crust of the Earth
The United States, Canada, and Russia have the
larg-est output of natural gas from methane deposits
Methane is also found in mud volcanoes The
decom-position of landfill materials has resulted in the
pro-duction of significant amounts of methane, and
sev-eral landfill sites in the United States have been drilled
into as a source
Primary Uses
The main use of methane is as a fuel source It also has
several industrial uses
Technical Definition
Methane is a naturally occurring gas composed of one
atom of carbon and four atoms of hydrogen This
sta-ble chemical compound has the formula CH4and is
classified as a hydrocarbon
Description, Distribution, and Forms Methane, a product of the decomposition of plant and animal remains, can be found throughout the Earth’s crust in varying amounts Where it is found in greater concentrations, methane is the primary con-stituent in natural gas deposits, which are the target of oil and gas exploration efforts worldwide Methane is also found in coal deposits as an integral part of the coalification process and can be recovered from wells drilled into the coal in the same manner in which oil and gas are obtained
History Methane was considered a waste by-product of oil pro-duction in the past, and trillions of cubic meters es-caped into the atmosphere in worldwide operations Beginning in the 1950’s methane-based natural gas was seen as a viable energy source Several interstate pipelines have been constructed in the United States, primarily to deliver the gas from its origins in the Gulf Coast and Midwest to the metropolitan areas of the Northeast As late as the 1960’s, natural gas had little value in some areas, and wells drilled for oil that dis-covered natural gas instead were frequently aban-doned for lack of markets
Beginning in the 1980’s, methane was touted by some as the fuel of the future It is clean burning, rel-atively inexpensive, and fairly easily transported throughout the United States Its supply is forecast to continue for hundreds of years Research has at-tempted to substitute methane-based natural gas as a motor fuel in cars, trucks, and locomotives, and many vehicles have been converted to use it Its use as a mo-tor fuel will undoubtedly increase as more facilities are constructed to service existing and future vehi-cles
Obtaining Methane
In spite of its advantages, methane has a significant disadvantage: It is explosive if mixed with air in a range of 5 percent to 15 percent by volume, and it has been blamed for several coal-mine disasters As a re-sult, modern coal-mining practice removes as much methane from coal deposits as possible in advance of mining and maintains the methane-air mixture in the mining environment below 1 percent by volume Since methane is not life-sustaining, its accumulation
in underground coal mines can also cause a condition known as “firedamp,” which may asphyxiate mining personnel if undetected
Trang 2Uses of Methane
Methane is an excellent fuel for fuel cells Fuel cells
produce electricity directly from the interaction of
hy-drocarbon and a catalyst This interaction is not
de-pendent on combustion but is a heat-producer, giving
rise to the utilization of waste heat in various ways It
is expected that future fuel cell research, together
with advances in the transportation sector, will place
a greater demand on methane resources
Charles D Haynes
Web Site
U.S Environmental Protection Agency
Methane
http://www.epa.gov/methane/
See also: Fuel cells; Methanol; Oil and natural gas
chemistry; Oil and natural gas reservoirs
Methanol
Categories: Energy resources; products from
resources
Methanol is manufactured by the oxidation of natural
gas or the reaction of carbon dioxide with hydrogen It
has numerous chemical uses and has potential as a
partial replacement for gasoline.
Background
Methanol (also called methyl alcohol and wood
alco-hol) is a colorless liquid with little taste or odor It boils
at 64.51° Celsius and has a melting point (and triple
point) of−97.56° Celsius At 20° Celsius it has a vapor
pressure of 97.60 torrs, a density of 0.7913 gram per
milliliter, and an index of refraction of 1.3284 Its
mo-lar mass is 32.04 grams Methanol is completely
solu-ble in water and most organic solvents It has a flash
point of only 11° Celsius and is thus highly flammable
Methanol forms numerous binary and ternary
azeo-tropic combinations with a variety of compounds, so it
is difficult to purify
Methanol is of considerable importance: It has
long been considered a major industrial organic
chem-ical, and it has more recently been identified as a likely
automotive fuel source The world production
capac-ity for methanol is more than 22 million metric tons
per year By 2013, worldwide consumption of
metha-nol is estimated to reach 58 million metric tons, more than one-half of which will be consumed in China, the world’s largest producer and consumer of methanol Primary Uses
A major portion of the methanol produced is used for the production of methyl esters such as methyl acr ylate, methyl methacr ylate, and methyl tere-phthalate, which are used in the manufacture of high-volume polymers Methanol has been used to prepare formaldehyde, but now more direct formaldehyde synthetic methods have somewhat reduced that us-age Because formaldehyde is used in enormous quantities for production of synthetic water-based polymers, such as the phenolic and urea resins (em-ployed in plywood manufacture, for example), even the reduced formaldehyde production from metha-nol is important A growing use for methametha-nol is its reaction with isobutene (2-methylpropene) for the synthesis of methyl tertiary-butyl ether, a gasoline ad-ditive that is used in winter in many large cities to re-duce air pollution Another group of major uses of methanol is for the chemical synthesis of acetic acid, methyl chloride, vinyl acetate, vinyl chloride, ethylene glycol (antifreeze), and other compounds Methanol
is also used as a solvent and extracting medium Some methanol is used for the preparation of synthetic pro-tein
Methanol has an octane number value of 100; therefore, fuel uses for methanol have been proposed repeatedly During the 1970’s, as petroleum prices skyrocketed, a number of processes for producing methanol for fuel purposes from wood or other bio-mass sources were considered Vehicles capable of using methanol or a gasoline-methanol mix were de-veloped As gas prices softened in the late 1990’s, automakers shifted attention to ethanol, which is more economical to produce, as methanol prices rose Methanol continues to be used as a fuel for drag race cars, and it is widely used in China as an automo-bile fuel Even though methanol combustion prod-ucts (almost entirely carbon dioxide and water) are nonpolluting and automobile engines can be easily modified to burn methanol, U.S automakers have shifted their attention from methanol to hybrid and electric vehicles
Methanol Production Before 1930 the most common production method was the anaerobic destructive distillation of
Trang 3woods at temperatures below 400° Celsius However,
this method produced low yields (about 21 liters per
metric ton of wood) of very impure methanol Small
amounts of relatively impure methanol produced in
this manner are added to commercial ethanol to
“de-nature” it and prevent the commercial alcohol’s use as
a beverage Fermentation processes used to produce
other alcohols have not been successful for methanol
However, because methanol is found in both plants
and animals and is utilized by bacteria, fermentation
appears to be a likely method if appropriate
microor-ganisms could be identified or if genetically
engi-neered bacteria could be developed for that purpose
The most often used synthetic processes involve
re-actions of carbon monoxide and hydrogen (called
synthesis gas), using catalysts such as copper, zinc, and
chromium oxides at elevated pressures (above 300
at-mospheres) and at temperatures higher than 300°
Celsius The high-pressure process is sometimes
re-placed with a lower-pressure one (below 100
atmo-spheres) at a somewhat lower temperature The
lower-pressure process requires more purified
reac-tants and a more complex catalyst system but allows
the reaction to proceed in simpler reactors The
syn-thesis gas is obtained by treating natural gas
(meth-ane) or petroleum fractions with high-pressure steam
Synthesis gas can also be obtained directly from coal,
and if carbon dioxide is easily available, it may be
more economically desirable to produce the synthesis
gas from the prior reaction of the carbon dioxide with
hydrogen
Toxicity
Methanol, even in minute
quanti-ties, is a powerful poison, acting on
many parts of the nervous system,
particularly the optic nerves
Blind-ness, at least temporary, often results
from its ingestion Methanol is
oxi-dized in the body to formaldehyde
and formic acid, which are the major
direct culprits in methanol
poison-ing Coma and death frequently
oc-cur as a result of methanol
consump-tion
William J Wasserman
Further Reading
Blume, David Alcohol Can Be a Gas!
Fueling an Ethanol Revolution for the
Twenty-first Century Santa Cruz, Calif.:
Interna-tional Institute for Ecological Agriculture, 2007
Cheng, Wu-Hsun, and Harold H Kung, eds Methanol Production and Use New York: M Dekker, 1994 Kohl, Wilfrid L., ed Methanol as an Alternative Fuel Choice: An Assessment Washington, D.C.:
Interna-tional Energy Program, Foreign Policy Institute, the Paul H Nitze School of Advanced Interna-tional Studies, the Johns Hopkins University, 1990
Lee, Sunggyu Methanol Synthesis Technology Boca
Raton, Fla.: CRC Press, 1990
Minteer, Shelley, ed Alcoholic Fuels Boca Raton, Fla.:
CRC/Taylor & Francis, 2006
Mousdale, David M Biofuels: Biotechnology, Chemistry, and Sustainable Development Boca Raton, Fla.: CRC
Press, 2008
Olah, George A., Alain Goeppert, and G K Surya
Prakash Beyond Oil and Gas: The Methanol Economy.
Weinheim, Germany: Wiley, 2006
Paul, J K., ed Methanol Technology and Application in Motor Fuels Park Ridge, N.J.: Noyes Data, 1978 Supp, Emil How to Produce Methanol from Coal New
York: Springer, 1990
Web Site Alternative Fuels and Advanced Vehicles Data Center, U.S Department of Energy
Methanol http://www.afdc.energy.gov/afdc/fuels/
methanol.html
An Indy Racing League car refuels with methanol during a 2003 race (Getty Images)
Trang 4See also: Biofuels; Biotechnology; Energy
econom-ics; Ethanol; Methane; Petroleum refining and
pro-cessing; Plant domestication and breeding; Synthetic
Fuels Corporation; Wood and charcoal as fuel
re-sources
Mexico
Categories: Countries; government and resources
Mexico is second in worldwide silver production; the
metal has been mined in the region since 1546
One-seventh of the annual global production of silver comes
from Mexico Mexico is the sixth largest producer of
pe-troleum worldwide The crude oil industry accounts
for one-third of the nation’s annual revenue and is
controlled by a government-operated company.
The Country
Mexico is located in North America, sharing a border
with the United States to the north It is bordered to
the south by Belize and Guatemala in Central
Amer-ica To the east, Mexico borders the Caribbean Sea
and the Gulf of Mexico The country’s western shore
meets the Pacific Ocean, the Gulf of California, and
the Gulf of Tehuantepec Only about one-third of
Mexico is flat A chain of volcanic mountains runs
east-west across the country just south of Mexico City
Plateaus also dominate the landscape The Sierra
Madre mountain chains surround the region’s
pla-teau in a V shape The Sonoran Desert covers the area
east of the Gulf of California Mexico’s economy is the
eleventh largest in the world In 2007, the average
an-nual income was $14,400 A large portion of Mexico’s
income results from oil production The country is a
leading producer of silver and also mines copper,
lead, zinc, and gold
Silver
Mexico is the second leading producer of silver in the
world (2.8 million kilograms in 2007) Four of the top
twelve silver mines (in terms of production) in 2007
were located in Mexico’s silver belt in the center of the
country The majority of silver is taken from mines in
Guanajuato, Pachuca, and Zacatecas
The city of Taxco is one of the oldest mining sites in
the Western Hemisphere Within a year of
conquer-ing the Aztecs in 1521, the Spanish discovered the
value of Taxco By the beginning of the seventeenth centur y, silver mined in Taxco could be found throughout Europe Taxco became known worldwide for its silver wealth For the Spanish, it also was the pri-mary mining site for several precious metals How-ever, as richer and more accessible veins were found, Taxco slowly faded in mining importance
Don José de la Borda, known as the father of Taxco, rediscovered the city’s silver wealth in 1716 He used part of the fortune he made to build schools, houses, roads, and Taxco’s famous Santa Prisca Cathedral Silversmithing and mining was forgotten again dur-ing Mexico’s war for independence The Spanish de-stroyed the silver mines so that Mexican revolutionar-ies could not gain their control
William Spratling, an American professor of archi-tecture, moved to Mexico in 1929 Spratling became interested in Taxco’s silver history He encouraged lo-cal artists to become silversmiths Spratling also cre-ated an apprenticeship program for local silversmiths with promising artistic talent, training them using his own designs Taxco again became world famous for its silver, this time primarily for the jewelry made from the metal Silverware and jewelry are made out of ster-ling silver, which is 92.5 percent silver and 7.5 percent copper Jewelry is often coated with a thin layer of 0.999 fine silver to give it extra shine Britannia silver
is also used for utensils and is 95.8 percent pure silver
In the modern world economy, Taxco is the world leader in silver production Numerous silver stores are located in and around the town’s main plaza Taxco is home to both the Spratling Museum and the Silver Museum In 1937, Spratling created the silver fair as a party for local artists working with silver The fair has become a national event, involving Mexico’s finest silversmiths and some of the world’s best artists
In 1953, Mexico’s president created National Silver Day, which is celebrated the last Saturday of Novem-ber The silver fair starts that Saturday and ends the first Sunday of December each year
Petroleum Petroleum and petroleum-related products have a long history in Mexico Asphalt and bitumen, or pitch, has been used in Mexico since the time of the Aztecs They are believed to have used asphalt to se-cure stone arrowheads on the ends of wooden spears The first time oil was refined into kerosene was in
1876, near the city of Tampico on Mexico’s eastern coast By 1917, large quantities of Mexican oil were
Trang 5742 • Mexico Global Resources
Mexico: Resources at a Glance
Official name: United Mexican States Government: Federal republic Capital city: Mexico City Area: 758,505 mi2; 1,964,375 km2
Population (2009 est.): 111,211,789 Language: Spanish
Monetary unit: Mexican peso (MXN)
Economic summary:
GDP composition by sector (2008 est.): agriculture, 3.8%; industry, 35.2%; services, 61%
Natural resources: petroleum, silver, copper, gold, lead, zinc, natural gas, timber
Land use (2005): arable land, 12.66%; permanent crops, 1.28%; other, 86.06%
Industries: food and beverages, tobacco, chemicals, iron and steel, petroleum, mining, textiles, clothing, motor
vehicles, consumer durables, tourism
Agricultural products: corn, wheat, soybeans, rice, beans, cotton, coffee, fruit, tomatoes, beef, poultry, dairy
products, wood products
Exports (2008 est.): $291.3 billion
Commodities exported: manufactured goods, oil and oil products, silver, fruits, vegetables, coffee, cotton
Imports (2008 est.): $308.6 billion
Commodities imported: metalworking machines, steel mill products, agricultural machinery, electrical equipment, car
parts for assembly, repair parts for motor vehicles, aircraft, and aircraft parts
Labor force (2008 est.): 45.32 million
Labor force by occupation (2005): agriculture, 15.1%; industry, 25.7%; services, 59%
Energy resources:
Electricity production (2007 est.): 243.3 billion kWh
Electricity consumption (2007 est.): 202 billion kWh
Electricity exports (2007 est.): 1.278 billion kWh
Electricity imports (2007 est.): 484.2 million kWh
Natural gas production (2007 est.): 55.98 billion m3
Natural gas consumption (2007 est.): 68.29 billion m3
Natural gas exports (2007 est.): 2.973 billion m3
Natural gas imports (2007 est.): 11.69 billion m3
Natural gas proved reserves ( Jan 2008 est.): 392.2 billion m3
Oil production (2007 est.): 3.501 million bbl/day Oil imports (2005): 385,400 bbl/day
Oil proved reserves ( Jan 2008 est.): 13.68 billion bbl Source: Data from The World Factbook 2009 Washington, D.C.: Central Intelligence Agency, 2009.
Notes: Data are the most recent tracked by the CIA Values are given in U.S dollars Abbreviations: bbl/day = barrels per day;
GDP = gross domestic product; km 2 = square kilometers; kWh = kilowatt-hours; m 3 = cubic meters; mi 2 = square miles.
Mexico City
Cuba
Guatemala
Belize
Honduras
United States
Mexico
Caribbean Sea
G u l f o f
M e x i c o
P a c i f i c
O c e a n
Trang 6ing drilled and refined by American
and British companies The Mexican
government then proclaimed in its
con-stitution ownership of all the country’s
mineral rights In 1938, strikes over
wages from foreign-owned companies
led to the creation of Petroleos
Mexi-canos (Pemex) by Mexican president
Lázaro Cárdenas This caused many of
the foreign companies to leave
Mex-ico Pemex is the ninth largest oil
com-pany worldwide, and the largest in
Latin America Pemex is responsible
for exploration, extraction, refining,
transportation, distribution, and
mar-keting of petroleum, petroleum
prod-ucts, and natural gas Between heavy
taxes and direct payments made to the
government, Pemex is responsible for
one-third of Mexico’s annual revenues
Mexico is the world’s sixth largest
producer of crude oil (3.5 million
bar-rels per day in 2007) and is ninth in
ex-ports It ranks seventeenth by amount
of oil reserves However, Mexico has
passed peak production of oil,
deplet-ing its resources, and overall
produc-tion has begun to decline This could
be a serious problem for the country
because of how heavily the government
relies on money from the petroleum
in-dustry In April, 2009, oil production in
Mexico was 1.37 million barrels per day, a figure that
was under the target for the year By 2010, Mexico’s
oil exports were expected to decline by 18 percent
Pemex has begun looking for new oil fields using
seis-mic technology Scientists send a seisseis-mic wave into the
ground and can use computers to measure its
reflec-tion, which tells about the structure underground
Geologists can use this information to help
deter-mine the best places to drill for oil
Natural Gas
Methane is the main component of natural gas In
ad-dition to methane, natural gas can include ethane,
propane, butane, carbon dioxide, nitrogen, and
he-lium Natural gas, like petroleum and coal, forms
from fossil fuels or in isolated natural gas fields
Ex-tensive refining removes almost everything but
meth-ane The natural gas industry in Mexico is run by
Pemex In 2008, Mexico ranked sixteenth in natural-gas production (55,980 million cubic meters) and thirty-fourth globally in proven reserves (392.2 billion cubic meters)
In 1995, some control of the natural gas industry was turned over to private industry Pemex continued
to control exploration, production, and firsthand sales Pemex continues to own most of the pipelines throughout the country Private companies handle transportation, storage, and distribution of natural gas In 2005, several natural gas sites were found, which increased production and jobs In 2007, natu-ral gas pipelines became the target of attacks by the Ejército Popular Revolucionario (the People’s Revo-lutionary Army), a small antigovernment terrorist group formed in the 1990’s The attacks resulted in the loss of hundreds of millions of dollars in produc-tion profits
In this 1952 photograph, a worker guides a rock crusher at the Real del Monte silver mine in Mexico Mexico has long been a leader in silver production (Getty Images)
Trang 7In the late nineteenth century, a series of copper
de-posits were found near Santa Rosalía These mines
have been mostly depleted Remaining copper is
pro-duced from open-pit mines near Cananea and La
Caridad Mexico remains the twenty-second largest
exporter of copper in the world In 2007, copper
exports brought in more than $320 million for
Mex-ico The top copper-exporting nation is Chile, where
the industry made $5 billion in 2007 There are
insuf-ficient known reserves to maintain the world’s
cur-rent consumption of copper Scientists estimate that
the world population will deplete the Earth of known
copper by about 2070 if the current rate of
consump-tion continues However, if the demand continues
to increase, the world’s copper might last until only
2035
Mexico’s largest mining company, Grupo Mexico
SAB, has been fighting a lawsuit over control of the
Southern Copper Corporation of Peru American
courts ruled that Grupo Mexico had to return 30
per-cent of its stock in Southern Copper to another
min-ing company, Asarco Asarco, a company based in
Tucson, Arizona, was owned by Grupo Mexico until
2005, when it became board-managed, and the legal
battle started In 2009, Grupo Mexico appealed the
judge’s ruling At the same time, Grupo Mexico was
dealing with a strike among its workers at the
coun-try’s largest copper mine, Cananea, near the U.S
bor-der The strike started over health and safety
stan-dards The company was given permission to fire
fifteen hundred striking workers in 2009 Mexico’s
la-bor board shut down the mine because idle
machin-ery had been looted and damaged beyond repair
Grupo Mexico has worked to reopen the copper pit
with plans to hire two thousand workers to make it
operational
Zinc
In 2006, Mexico was ranked sixth in global zinc
pro-duction, producing 453,893 metric tons Mexico
ex-ported $172.8 million worth of zinc in 2007, ranking
ninth worldwide Canada is the world’s leading zinc
exporter, making more than $546 million in 2007
The largest producer of zinc in Mexico is the state of
Chihuahua The Charcas mine in the state of San Luis
Potosí, in north-central Mexico, is the top
zinc-producing mine Production of zinc in the country
has risen; new mines were opened in 2001, and others
expanded in 2002 A Canadian company, Canasil
Re-sources, found a vein of zinc and silver in the state of Durango The company was exploring a 29-square-kilometer patch of flatland with a geologic intrusion Samples taken of the intrusion in 2006 were found to contain high levels of zinc Canasil expanded its prop-erty in the area to include an addition 1,000 square kilometers to the north and east Early stages of drill-ing began in 2007 Two zones containdrill-ing high con-centrations of zinc at relatively shallow depths were found with the potential to yield a new zinc district in Mexico
Forests and Timber Scientists estimate that in the mid-sixteenth century more than two-thirds of Mexico was forest Today, the tropical forests of the southern and eastern parts of the country are largely all that remain However, Mex-ico contains 1.3 percent of the world’s total forest reserves, and one-quarter of the country is classified
as forest Mexico has more species of pine and oak trees than anywhere else in the world Nonetheless, logging has depleted Mexico’s forests severely Some pine forests in the northern part of the country have been conserved, but the practice is not widespread The national tree is the cypress, which is found near water in semiarid regions Mexico also has a number
of ceiba trees, which were sacred to the Mayas The Mayas believed that a ceiba tree stood at the center
of the Earth, connecting it with the spirit world over-head Ceiba trees grow in tropical regions, tall with large canopies that house several different species Even in modern deforestation, ceiba trees are often spared
Mexico’s rain forests along the gulf coast and throughout the country are being cut down, and the land burned by farmers to expand their fields This rain forest is part of the Maya Forest, which covers the Yucatán Peninsula, northern Guatemala, and parts of Belize, 5.3 million hectares in total Efforts to pre-serve the forest, and the Mayan ruins within, have been complicated by a rapidly growing population In addition to use as farmland, the forests are being cut down to make room for roads, dams, and other ac-commodations needed to handle an influx of workers and tourists to the region In 1978, the Mexican gov-ernment set up an international sanctuary to protect 331,200 hectares of rain forest However, the Montes Azules Biosphere Reserve continues to shrink each year Support for the preservation of the reserve is worldwide: In 2004, the European Union pledged 31
Trang 8million euros (approximately $44 million) for four
years in an effort to aid the tribes that live in and near
the sanctuary Poverty and population growth have
re-sulted in destruction of the forest
Many valuable types of wood are found in the
tropi-cal forests, including hardwoods such as various oaks
and mahogany The forests also contain cedar and
rosewood Sapodilla trees are found in Mexico’s rain
forests and are the basis of chicle Chicle is a form of
latex that is used in chewing gum In 2000, Mexico’s
forestry imports exceeded exports by $2.46 billion
However, many other products are found in the
for-ests of Mexico, including gums, resins, fibers, oils, and
waxes
Other Resources
Mexico is twenty-fourth in the world in exportation of
nonmonetary gold In 2007, gold exports amounted
to more than $160 million Gold is a popular metal
used in jewelry, sculpture, and coins Gold occurs
nat-urally as granules, nuggets, and large deposits
Lead is another metal that is heavily mined in
Mex-ico Bullets, pipes, pewter, radiation shields, batteries,
and weights are all made from lead Lead is also
poi-sonous and can cause a variety of problems, including
blood and brain disorders, nerve damage, even death
Mexico is also the sixth largest producer of salt in the
world
Jennifer L Campbell
Further Reading
Bowles, Ian, and Glenn Prickett, eds Footprints in the
Jungle: Natural Resource Industries, Infrastructure, and
Biodiversity Conservation New York: Oxford
Univer-sity Press, 2001
Fernandez, Linda, and Richard Carson, eds Both Sides
of the Border: Transboundary Environmental
Manage-ment Issues Facing Mexico and the United States New
York: Springer, 2002
Ibarrarán, María, and Roy Boyd Hacia el Futuro:
En-ergy, Economics, and the Environment in Twenty-first
Century Mexico New York: Springer, 2006.
Joseph, Gilbert, and Timothy Henderson, eds The
Mexican Reader: History, Culture, Politics Durham,
N.C.: Duke University Press, 2003
Meyer, Michael C., and William H Beezley, eds The
Oxford History of Mexico New York: Oxford
Univer-sity Press, 2000
Nobel, John, ed Mexico 11th ed Oakland, Calif.:
Lonely Planet, 2008
Primack, Richard, et al., eds Timber, Tourists, and Tem-ples: Conservation and Development in the Maya Forest
of Belize, Guatemala, and Mexico Washington, D.C.:
Island Press, 1997
See also: Copper; Forests; Gold; Oil and natural gas reservoirs; Silver
Mica
Category: Mineral and other nonliving resources
Where Found Micas are common rock-forming minerals and are widely distributed throughout the world They occur
in igneous, metamorphic, and sedimentary rocks They are mined as sheets or flakes and scrap Sheet mica is primarily found in Brazil, Madagascar, India, and Canada Muscovite flakes are mined in the United States from igneous pegmatites and metamor-phic schists located in North and South Carolina, Connecticut, Georgia, and New Mexico
Primary Uses Muscovite sheets are used as electrical insulators in the electronic and computer industries Scrap mica is ground and used primarily as a coating material and
in the paint industry
Technical Definition The mica group of minerals is composed mainly of muscovite, KAl2(AlSi3O10)(OH)2; biotite, K(Mg,Fe)3
(AlSi3O10)(OH)2; phlogopite KMg3(AlSi3O10)(OH)2; and lepidolite, K(Li,Al)3(AlSi3O10)(OH)2; although there are thirty known mica minerals Micas are hy-drous aluminum silicate minerals that have a perfect basal cleavage Micas have a hardness of 2.5 to 4 and show a vitreous to pearly luster Muscovite is a type of mica that is colorless and transparent in thin sheets and white to light brown or light yellow in thicker blocks Phlogopite is yellow to brown with a copper-colored reflection off cleavage surfaces Biotite is pri-marily black but can appear dark green or brown Lepidolite has a distinctive lilac to pink color
Description, Distribution, and Forms Micas form monoclinic crystals that inevitably show a perfect basal cleavage Crystals and their cleavage
Trang 9sheets commonly display a hexagonal form
Musco-vite and biotite can be found in thick “books”
contain-ing layer upon layer of thin cleavage sheets, which can
be up to 3 meters across in pegmatites
Micas are common throughout the world
Musco-vite is characteristic of granites and pegmatites In
metamorphic rocks muscovite is the primary
constitu-ent of many mica schists Biotite is found in igneous
rocks ranging from granite pegmatites to diorites,
gabbros, and peridotites It also occurs in silica-rich
lavas, porphyries, and a wide range of metamorphic
rocks Phlogopite occurs in metamorphosed
magne-sium limestones, dolomites, and ultrabasic rocks
Le-pidolite occurs only in pegmatites
History
Mining of mica started as early as 2000 b.c.e in India,
where it was used as medicine, decoration, and paint
Commercial mining of mica in the United States
began in 1803 Mica was used in store windows, shades
for open light flames, and furnace viewing glass When
electronic vacuum tubes were developed in the early
1900’s, mica was used as spacers and insulators in the
tubes, thus beginning its use in the electrical industry
Obtaining Mica The United States has limited supplies of sheet mica but is the largest producer of scrap mica Although there are no environmental problems in mining mica, sheet mica is expensive to mine because of the intense hand labor needed to mine and process the sheets Uses of Mica
Muscovite and phologopite remain important com-mercially because they have a low thermal and electri-cal conductivity and a high dielectrielectri-cal strength Sheet mica is used as electrical insulators, retardation plates
in neon helium lasers, optical filters, and washers
in the computer industry The isinglass used in fur-nace and stove doors from the 1800’s to the present is sheet muscovite Lepidolite is the only mica mined and processed for its composition It is a source of lith-ium, which is used in the production of heat-resistant glass
Scraps and flakes of mica are processed into ground mica and used as a coating on rolled roofing, asphalt shingles, and waterproof fabrics It is also used in wall-paper to give it a shiny luster, as a lubricant when mixed with oils, and as a pigment extender in paint A magnesium-rich alteration product of biotite, vermic-ulite, is used as insulation, packing material, and an ingredient in potting soil
Dion C Stewart
Web Site U.S Geological Survey Mineral Information: Mica Statistics and Information
http://minerals.usgs.gov/minerals/pubs/
commodity/mica/
See also: Lithium; Metamorphic processes, rocks, and mineral deposits; Pegmatites
Mineral deposits See Igneous
processes, rocks, and mineral deposits; Metamorphic processes, rocks, and mineral deposits;
Plutonic rocks and mineral deposits; Sedimentary processes, rocks, and mineral deposits
Drywall joint cement 59%
Paint
13%
Plastics 5%
Other 23%
Source:
Historical Statistics for Mineral and Material Commodities in the United
States
U.S Geological Survey, 2005, scrap and flake mica
statistics, in T D Kelly and G R Matos, comps.,
, U.S Geological Survey Data Series 140 Available
online at http://pubs.usgs.gov/ds/2005/140/.
U.S End Uses of Ground Mica
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