Encyclopedia of Global Resources part 22 potx

C Na 2 CO 3 C 2H 2 O), hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 C 4H 2 O), and artinite (Mg 2 (CO 3 )(OH) 2 C 3H 2 O). The most abundant carbonate mineral is calcite (CaCO 3 ), which comprises limestone, chalk, traver- tine, tufa (sedimentary rocks), and marble (meta- morphic rock). Most limestone forms in warm, shal- low seas, far from sources of land-derived sediment. Chalk is made of the shells of microscopic floating or- ganisms which once lived in the sea. Spring deposits are travertine or tufa, and cave deposits (stalactites and stalagmites) are travertine. These deposits form from the evaporation of groundwater carrying dis- solved calcium carbonate. Marble is limestone which has been changed by heat and pressure. Malachite and azurite are associated with the oxidized portions of copper deposits and with copper veins through limestone deposits. Sodium carbonate minerals are present in associa- tion with dry salt lake deposits in some parts of the world. Theseinclude trona, natron (Na 2 CO 3 C 10H 2 O), thermonatrite (NaCO 3 C H 2 O), nahcolite (NaHCO 3 ), gaylussite (CaCO 3 C Na 2 CO 3 C 5H 2 O), pirssonite (CaCO 3 C Na 2 CO 3 C 2H 2 O), and shortite (2CaCO 3 C Na 2 CO 3 ). History Calcite, because of its abundance, has a rich history. Because calcite can preserve fossil records, its pres- ence helps datecultural artifacts. Chalkhas been used for writing for thousands of years. Obtaining Carbonate Minerals The mostimportant use of calcite isin the production of cements and lime. When limestone is heated to about 900° Celsius, it loses CO 2 and is converted to quicklime or lime (CaO). Mixed with sand, quicklime forms mortar. When mixed with water, it hardens or “sets,” swelling and releasing heat. The most widely produced cement is portland cement (used in con- crete), which is generally made from limestone and silica- and alumina-bearing material such as clay or shale. The raw materials are ground together, and the mixture is heated in a kiln until it fuses into a “clinker,” which is then crushed to a powder. Uses of Carbonate Minerals Lime (CaO) is also used in agriculture to neutralize acid in soils, in the manufacture of paper, glass, and whitewash, and in tanning leather. It is used in refin - ing sugar,as a watersoftener, and asa fluxfor smelting various typesof ores. Fine-grained limestone has been used in lithography (printing). Blocks of cut lime - stone and marble are usedas building stone and orna- mental stone and may be polished. Crushed lime- stone is used as aggregate in concrete and as road metal. Dolomite has uses similar to those of calcite. Several carbonates are metal ores: dolomite and magnesite (ores of magnesium), rhodochrosite (man- ganese), siderite(iron), smithsonite (zinc), strontian- ite (strontium), witherite (barium), cerrusite (lead), malachite and azurite (copper),andtrona (sodium). Magnesite is used in the manufacture of refractory materials capable of withstanding high temperatures, for special types of cements, and in the paper, rubber, and pharmaceutical industries. Strontianite is also used in the manufacture of fireworks, producing a purplish-red flame. Malachite (green) and azurite (blue) are used as pigments. Sodium carbonate and sodium bicarbonate are important in the manufac- ture of washing soda (or sal soda) and are used as cleaning agents and water softeners. They are used in the manufacture of glass, ceramics, paper, soap, and sodium-containing compounds (such as sodium hy- droxide) as well as in petroleum refining. Sodium bi- carbonate, also known as baking soda, is an important part ofbaking powder, isa source ofcarbon dioxide in fire extinguishers and is used medicinally to neutral- ize excess stomach acid. Several carbonates are used as ornamental stone and in jewelry, including mala- chite, azurite, aragonite (alabaster), rhodochrosite, and smithsonite. Pamela J. W. Gore Further Reading Klein, Cornelis, and Barbara Dutrow. The Twenty-third Edition of the Manual of Mineral Science. 23d ed. Hoboken, N.J.: J. Wiley, 2008. Pellant, Chris. Rocks and Minerals. 2d American ed. New York: Dorling Kindersley, 2002. Pough, Frederick H. A Field Guide to Rocks and Min- erals. Photographs by Jeffrey Scovil. 5th ed. Boston: Houghton Mifflin, 1996. Tegethoff, F. Wolfgang, Johannes Rohleder, and Evelyn Kroker, eds. Calcium Carbonate: From the Cre- taceous Period into the Twenty-first Century. Boston: Birkhäuser Verlag, 2001. Tucker, Maurice E., and V. Paul Wright. Carbonate Sedimentology. Boston: Blackwell Scientific, 1990. Warren, John K. Evaporite Sedimentology: Importance in Hydrocarbon Accumulation. Englewood Cliffs, N.J.: Prentice Hall, 1989. 180 • Carbonate minerals Global Resources Web Site Carbonate-hydroxylapatite Mineral Data http://webmineral.com/data/Carbonate- hydroxylapatite.shtml See also: Carbon cycle; Crystals; Evaporites; Lime; Limestone; Minerals, structure and physical proper- ties of; Sedimentary processes, rocks, and mineral de- posits. Carnegie, Andrew Category: People Born: November 25, 1835; Dunfermline, Scotland Died: August 11, 1919; Lenox, Massachusetts Carnegie established the Carnegie Steel Company, which he eventually sold for $250 million. The explo- sive growth of the steel industry that Carnegie’ssuccess exemplified initiated the final phase of the Industrial Revolution; it ultimately led, for example, to the mass production of automobilesand the exploitationof a va- riety of resources worldwide. Biographical Background In 1848, Andrew Carnegie moved from Scotland to the United States. He began working in an Allegheny, Pennsylvania, cotton millfor $1.20 perweek. Later, he moved to Pittsburgh, becoming involved in the rap- idly growing railroad business. Carnegie soonbecame the superintendent of the Pittsburgh division of the Pennsylvania Railroad. By investing wisely in what be- came the Pullman Company and in oil lands, Carne- gie established the foundation for his fortune. Impact on Resource Use Following service in the War Department during the Civil War, Carnegieleftthe Pennsylvania Railroad and formed acompany to build iron railroad bridges.This led to the next step: the production of steel. He founded a steel mill and began using the new Besse- mer process of makingsteel. The extensive useof steel that resulted from Carnegie’s work led to a greater ex- ploitation of iron ore deposits in the United States and abroad. The need for oil and rubber, which grew alongside the booming steel industry, also acceler - ated resource exploitation and had profound effects on succeeding generations. By 1899, the Carnegie Steel Company controlled 25 percent of steel production in the United States. Two years later, Carnegie sold the company to J. P. Morgan, whoorganized it into the U.S.Steel Corpora- tion, the first billion-dollar corporation in the United States. When Carnegie was thirty-three years old, with an annual income of fifty thousand dollars, he declared that a person should never seek to build a fortune un- less intending to give the surplus for benevolent pur- poses. Although he did not always follow his own ad- vice, he did eventually give more than $350 million to philanthropic projects, including the endowment of seventeen hundred libraries, the Tuskegee Institute, and the Peace Palace at The Hague in the Nether- lands. Glenn L. Swygart See also: Bessemer process; Capitalism and resource exploitation; Iron; Steel; Steel industry. Global Resources Carnegie, Andrew • 181 Andrew Carnegie was the leading figure in the steel industry at the end of the nineteenth century. (Library of Congress) Carson, Rachel Category: People Born: May 27, 1907; Springdale, Pennsylvania Died: April 14, 1964; Silver Spring, Maryland Carson made a major contribution to the environmen- tal movement in the United States by educating the public about the natural geological evolution of the Earth and the dangers associated with the widespread use of chemicals. Her book Silent Spring was pub- lished in 1962. Biographical Background Rachel Carson was educated at the Pennsylvania Col- lege for Women in Pittsburgh and Johns Hopkins University in Baltimore, Maryland. She did research at the Woods Hole Marine Biological Laboratory and subsequently worked for the U.S. Fish and Wildlife Service in Washington, D.C. Impact on Resource Use Carson published Under the Sea-Wind (1941); The Sea Around Us (1951), which received the National Book Award for nonfiction; The Edge of the Sea (1955); and her most famous work, Silent Spring (1962). Her writ- ings took a naturalist’s approach to explaining the ocean environment and the origin of the Earth, and they were praised for their clear explanations in lay terms. The Edge of the Sea revealed Carson’s growing in- terests in the interrelationshipsof Earth’s systems and a holistic approach to human interaction with nature. In Silent Spring Carson warned of the environmental contamination that results from widespread use of pes- ticides, particularly dichloro-diphenyl-trichloroethane (DDT). She described how the ecology of the soil had been largely ignored in the rush to apply chemicals, drew attention to the effects on wildlife where chemi- cal mixing in runoff channels turned streams into le- thal cauldrons of chemical soup, and accused the chemical companies of aggressive marketing policies that ignored theimpact on the environment. The first Earth Day (April 22, 1970) and the creation of the En- vironmental Protection Agency in 1970 can both be attributed inpart to Carson’s role in changing the way Americans thought about their surroundings. Pat Dasch See also: Environmental movement; Food chain; Pesticides and pest control. Carter, Jimmy Category: People Born: October 1, 1924; Plains, Georgia As the thirty-ninth president of the United States, James Earl“Jimmy” Carter deregulated domestic crude oil prices and established the Department of Energy. Biographical Background Jimmy Carter graduated from the United States Naval Academy and served in the Navy until his father’s death. Assuming his father’s business responsibilities, Carter expanded the family business and ran for politi- cal offices.Hewas elected governor ofGeorgia in 1970. At the end of his term as governor, Carter began a cam - paign for the presidency. He ran against incumbent Gerald Ford in 1976 and won by a narrow margin. 182 • Carson, Rachel Global Resources Rachel Carson’s seminal text Silent Spring helped spearhead the modern environmental movement. (Library of Congress) Impact on Resource Use The years before and during President Carter’s term were times of instability in the world economy. World petroleum demand was increasing, and Congress had capped domestic crude oil prices, discouraging do- mestic petroleum exploration. In 1979, the Organiza- tion of Petroleum Exporting Countries (OPEC) raised crude oil prices by 50 percent. Because most goods were moved to market by gasoline- or diesel-powered transport, theincrease in worldpetroleum prices con- tributed significantly to inflation, which reached an annual rate of 12 percent. Interest rates tracked infla- tion and rose 20 percent,a level unprecedented in the twentieth century. In response to these problems, President Carter proposed an energy program that included creation of a Department of Energy, deregulation of domestic crude oil prices, and promotion of conservation and alternative energy sources. An advocate of environ - mentalism, President Carter was also successful in obtaining congressional action that preserved vast wilderness areas in Alaska. Robert E. Carver See also: Department of Energy, U.S.; Energy eco- nomics; Oil embargo and energy crises of 1973 and 1979; Synthetic Fuels Corporation. Carver, George Washington Category: People Born: July 12, 1861?; near Diamond Grove (now Diamond), Missouri Died: January 5, 1943; Tuskegee, Alabama A pioneering African American agricultural scientist, Carver is best known for popularizing and promoting the economic potentialofpeanuts and sweet potatoesas alternative crops for southern farmers. Biographical Background George WashingtonCarver was born intoslavery near the end of the Civil War near Diamond Grove (now Diamond), Missouri. His early education was spo- radic, thoughhe did attend high school in Minneapo- lis, Kansas. He was briefly a homesteader in Ness County, Kansas, before he returned to school, first at Simpson College inIndianola, Iowa, where hestudied fine arts, then at Iowa State University in Ames, Iowa, where he studied agriculture. AfterCarver completed his bachelor of agriculture degree in 1894, he was ap- pointed to the faculty at Iowa State and received a master of agriculture degree in 1896. Impact on Resource Use Carver immediately began working as director ofagri- culture and director of the agricultural experiment station at Tuskegee University in Alabama. Carver won international acclaim for the educational efforts he began intheearly 1900’sto promote sound conser- vation practices and sustainable agricultural activity in the rural South, which had previously been depen- dent on cotton production. He is best known, how- ever, for popularizing and promoting the economic potential of peanuts and sweet potatoes as alternative crops for southern farmers. He was instrumental in persuading Congress to protect the peanut industry from foreign competition shortly after World War I. Global Resources Carver, George Washington • 183 Jimmy Carter,thethirty-ninthpresident of the United States,wasan early advocate of alternative energy use. (Library of Congress) In the later stages of his career, he investigated the po- tential uses of peanuts and sweet potatoes, which in- cluded uses in dyes, milk substitutes, and cosmetics. Mark S. Coyne See also: Agricultural products; Agriculture indus- try; Agronomy. Cement and concrete Category: Products from resources Cement and concrete have played crucialroles in shap- ing humankind’s physical environment. Of all manu- factured construction materials worldwide, concrete is the most widely used. Background Cement is an important construction material be - cause of the ready availability of its raw materials, its capacity to be shaped prior to setting, and its durabil - ity after hardening. When combined with an aggre- gate (such as sand, gravel, or crushed rock), cement becomes concrete—a durable, load-bearing construc- tion material. Cements with the ability to set and harden under- water are called hydraulic cements. The most com- mon of these is portland cement, consisting of com- pounds of lime mixed with silica, alumina, and iron oxide. Gypsum isalsoadded to retard the settingtime. When water is added, these ingredients react to form hydrated calcium silicates that willset into a hardened product. History Cement has been used for construction purposes for the past six thousand years. The Egyptians are known to have used a simple cement, and the Greeks and Ro- mans advanced the technology by creating hydraulic cements from various volcanic materials and lime. Many examples of their concrete structures remain today—some underwater, where they were used in harbors. The quality of cementing materials declined greatly during the MiddleAges but began toimprove again in the late eighteenth century. In 1756, the famed Brit- ish engineer John Smeaton was commissioned to re- build the Eddystone Lighthouse near Cornwall, En- gland. He undertook a search for lime mortars that would resist the action of the water and discovered that the best limestone contains a high proportion of clayey material. For his project he used lime mixed with pozzolana from Italy (the same volcanic material the Romans had used). Smeaton was followed by a number of researchers, including Joseph Aspdin, a Leeds builder, who patented “portland” cement, named for the high-quality building stone quarried at Portland, England. Manufacturing Cement Cement is a manufactured product, made from raw materials that are found relatively easily in nature. Ce- ment manufacturers have a number of sources for lime, but the most common are limestone and chalk. Coral and marine shell deposits are also used as sources of lime, when available. Silica, alumina, and iron oxide are found in clays, shales, slates, and cer- tain muds. Some raw materials contain almost all the ingredients of cement, especially marl (a compact clay), cement rock, and blast-furnace slag. Industrial 184 • Cement and concrete Global Resources Scientist George Washington Carver is best known for his work with agricultural crops such as peanuts. (National Archives) Global Resources Cement and concrete • 185 Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009.Source: Mineral Commodity Summaries, 2009 40,000,000 37,000,000 36,000,000 35,000,000 35,000,000 33,000,000 30,000,000 30,000,000 22,000,000 Metric Tons 1,500,000,0001,250,000,0001,000,000,000750,000,000500,000,000250,000,000 Saudi Arabia Thailand Iran Indonesia Vietnam Mexico Germany Pakistan France Egypt Italy Turkey Brazil Spain South Korea Russia Japan United States India China 40,000,000 47,000,000 48,000,000 48,000,000 55,000,000 56,000,000 61,000,000 67,000,000 89,100,000 175,000,000 1,450,000,000 Cement: Top Producers, 2008 wastes such as fly ash and calcium carbonate are also used as raw materials for cement, but not on a large scale. Raw materials in the form of hard rock—such as limestone, slate, and some shales—are usually quar- ried, but they may also be mined. If the limestone is of low quality, it may need to go througha concentrating process. Softer materials such as chalk, clay, and mud can be dug by various types of machinery, depending on the physical setting and type of material. Once ex- tracted, the raw materials are transported to the ce- ment manufacturing plant by truck, rail, conveyor belt, or pipeline (when in a slurry). At the plant, the raw materials are ground into a fine powder and then mixed in predetermined ratios. The mixing can be done wet, semidry, or dry. In the wet process the materials are ground wet and mixed into a slurry. In the semidry process they are ground dry, then moistened for adhesion; and in the dry pro- cess the raw materials remain dry throughout. After mixing, theraw materials are burnedin a large rotating kiln. Kilns are usually from four to eight me- ters in diameter and from 90 to 200 meters long, and they consist of a steel cylindrical shell inclined slightly from the horizontal. The mixture is introduced at the upper end of the kiln, and as it flows down the incline (with the help of gravity and the kiln’s steady rotation), it reaches a maximum temperature between 1,300° Celsius and 1,500° Celsius, at which point the raw mate- rials interact to form calcium sili- cates. The heated material exits the kiln in the form of rough lumps or pellets—called clinker—no larger than 5 centimetersindiameter. After the clinker cools, the manufacturer adds gypsum and grinds the mixture into the fine powder known as port- land cement. Uses of Concrete Concrete is generally used in four common forms: ready-mixed, pre- cast, reinforced, and prestressed. Ready-mixed concrete is transported to a construction site as a cement paste and is then poured into forms to make roadways, foundations, driveways, floor slabs, and much more. Precast concrete—cast at a plant and then transported to the site—is used for everything from lawn ornaments to major structural elements. Rein- forced concrete is created by adding steel mesh, rein- forcing bars, or any other stiffening member to the concrete before it sets. Prestressed concrete, the most recently developed form, increases the strength of a beam by using reinforcing steel to keep the entire beam under compression. Concrete is much stronger under compression (pushed in on itself) than under tension (pulled apart). Brian J. Nichelson Further Reading Gani, M.S. J. Cement and Concrete. New York: Chapman & Hall, 1997. Lea, F. M. Lea’s Chemistryof Cement and Concrete. 4th ed. Edited by Peter C. Hewlett. New York: J. Wiley, 1998. Mehta, P. K., and Paulo J. M. Monteiro. Concrete: Microstructure, Properties, and Materials. 3d ed. New York: McGraw-Hill, 2005. Mindess, Sidney, J. Francis Young, and David Darwin. Concrete. 2d ed. Upper Saddle River, N.J.: Prentice Hall, 2003. 186 • Cement and concrete Global Resources Source: Mineral Commodity Summaries, 2009 Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009. Ready-mix concrete 75% Concrete products 13% Contractors (road paving) 6% Building material dealers 3% Other 3% U.S. End Uses of Cement Neville, A. M. Properties of Concrete. 4th ed. Harlow, Essex, England: Longman Group, 1995. Web Sites Natural Resources Canada Canadian Minerals Yearbook, Mineral and Metal Commodity Reviews http://www.nrcan-rncan.gc.ca/mms-smm/busi- indu/cmy-amc/com-eng.htm Portland Cement Association Cement and Concrete Basics http://www.cement.org/basics U.S. Geological Survey Cement: Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/cement/index.html#mcs See also: Clays; Gypsum; Lime; Limestone; Sand and gravel; Shale; Silicates; Slate. Central Arizona Project Category: Organizations, agencies, and programs Date: Established September 30, 1968; substantially completed 1993 The Central Arizona Project (CAP), a series of pump- ing plants, dams, aqueducts, and pipelines stretching more than 540 kilometers, is the largest water transfer project in the United States. Drawing water from Lake Havasu has supported agriculture in southwest Ari- zona and made possible the growth of major cities, while harming several species of fish and animals downstream. Background As the area that makes up the southwestern United States was settled and populated by Europeans in the nineteenth century, the need for more water became apparent. In the early 1900’s, the Southwest looked to the Colorado River basin as a source of water,and ase- ries of laws and court decisions called the “Law of the River” were established to ensure that each state was treated equitably. Decades ofcourt cases attempted to determine the amount of the water to which Arizona was entitled. Through the 1950’s Arizona lobbied for authorization of a Central Arizona Project, and the U.S. secretary of the interior called for a comprehen - sive Colorado River plan to address the future water needs of seventeen Western states. Passed on Septem- ber 30, 1968, Public Law 90-537, 82 Stat. 885 created the Colorado River Basin Project and the Lower Colo- rado River Basin Development Fund, which autho- rized in turn the development of the Dixie Project in Utah and the Central Arizona Project in Arizona and New Mexico. Provisions The Central Arizona Project was designed to move 4,000 square kilometers of water from Lake Havasu, fed by the Colorado River, to agricultural lands in Maricopa, Pima, and Pinel Counties in Arizona, and to Catron, Grant, and Hidalgo Counties in New Mex- ico. Because of high costs and lower-than-expected demand, however, the New Mexico portion of the project was never built. During the years of construc- tion, the economy of Arizona began to shift from agri- culture to industry, and the metropolitan areas of Phoenix, Scottsdale, and Tucson experienced rapid growth. As a result, CAP waters were reallocated, so that over time more water would be designated for municipal and industrial use,andless for agriculture. Impact on Resource Use The purpose of CAP, as it was conceived in the late 1940’s, was to keep agriculture thriving without de- pleting groundwater supplies. By most accounts, this goal was not realized. In addition, the diversion of water from itsnatural course hascreated environmen- tal problems downstream from Lake Havasu, includ- ing the extinction of fish and wildlife, in spite of sev- eral successful conservation efforts along the project itself. Dams along the project provide hydroelectric power, reducing the region’s dependence on other forms of power generation. Cynthia A. Bily Web Sites Central Arizona Project http://www.cap-az.com/ U.S. Department of the Interior Bureau of Reclamation Colorado River Basin Project: Central Arizona Project http://www.usbr.gov/dataweb/html/crbpcap.html Global Resources Central Arizona Project • 187 See also: Hydroenergy; Los Angeles Aqueduct; Three Gorges Dam. Ceramics Category: Products from resources Ceramics are inorganic, nonmetallic materials—such as naturally occurring silicates, oxides, nitrates, car- bonates, chlorides, and sulfates—that are subjected to high temperatures during their manufacture and pro- cessing. Ceramic materials are high strength but brit- tle. As a result of modern research and development, they have multiple and varied uses. Background Paradoxically, ceramic science is one of the oldest yet one of the newest technologies. Much of what is known of prehistoric humans and of the earliest civili- zations has beenlearned fromthe pottery thatwas left behind. This longevity illustrates one of the greatest assets of ceramic materials, their durability. The fact that most of the surviving pieces are fragments gives evidence of the greatest weakness, their brittleness. The term “ceramics” is derived from the Greek term keramos, which means “potter’s clay.” Ceramics is defined in some dictionaries as “the art of making things from baked clay.” “Clay” is used in describing ceramics because it was an essential material in tradi- tional ceramic compositions. The term “baked” is im- portant, since high temperatures are used in most processing of ceramics. Althoughsimple, thisdescrip- tion of ceramics was an accurate one until the time of WorldWar II. In the early 1940’s, the field of materials science, of which ceramics is a part, experienced a push to develop new materials and processing meth- ods. Today, a more accurate present-day description of ceramics might be “the art and science of making and using implements and other articles that are es- sentially composed of inorganic and nonmetallic compounds.” Traditional Ceramics The ceramic industries may be grouped into several divisions according to the products produced. Tradi- tional divisions include whitewares, refractories, abra - sives, structural clay products, glass, cement, and por - celain enamels. Developments in the second half of the twentieth century in the fields of nuclear physics and electronics resulted in many new ceramic prod- ucts, collectively known as technical ceramics. Whitewares are materials such as clay, feldspar, whiting, and potter’s flint that fire to a white color. The mineral mixtures are shaped and then partially melted at high temperatures to produce a dense hard material. The term whiteware is misleading, since products in this class are produced in a wide variety of colors, depending on the amounts of impurities in the raw materials.Common whitewares includeearth- enware, porcelain or other tableware products as well as casseroles and bowls,floorand wall tile, anddecora- tive products such as vases and lamp bases. Important commercial whitewares include laboratory ware such as porcelain crucibles, combustion tubes, and grind - ing balls for the chemist as wellas electrical porcelains such as spark plugs and insulators. 188 • Ceramics Global Resources A worker carries ceramic cylinders in Jungdezhen City,China, home to what is believed to be the oldest egg-shaped ceramics kiln in the world. (Zhang Wu/Xinhua/Landov) Refractories are structural materialsmanufactured for the purpose of withstanding corrosive high-tem- perature conditions in furnaces and process vessels. Refractories have high melting temperatures, good hot strength, and resistance to chemical attack and abrasion. They are made from the refractory clays, ka- olin, magnesite,chrome ore, olivine, and bauxite. For more special services, refractory products are made from synthetic compositionssuch as carbidesand bor- ides. Among the most important users of refractories are the metallurgical industries, including the steel industry. Glasses are ceramics that do not return to crystal- line form after being melted and cooled. These noncrystalline ceramics behave as high viscosity liq- uids. They are essentially rigid at room temperature but gradually soften and flow as the temperature is in- creased. This viscosity allows glasses to be formed by processes that will not work for other ceramic materi- als. Glasses can be pressed into shallow shapes, drawn or rolled into tubes and sheets, blown into hollow shapes, or spun into fibers. Most glasses are naturally transparent to visible light and are commonly used as windows, bottles, lightbulbs, lenses, and optical fibers. The basic ingre- dient in most glasses is silica sand, but a wide range of other materials can be added to produce glasses pos- sessing a wide variety of tailored properties. Borosili- cate glasses are resistant to both chemicals and heat, properties that make them useful both in the home and in the laboratory. Oxides of the transition metals may be added to produce glass of almost any desired color. The porcelain enamels are glassy coatings fused onto metals to provide decoration and protection from corrosion. They are hard, rigid ceramics that are electrical and thermal insulators as well as wear- resistant and chemically inert. Available in all colors, they are found on household appliances, on struc- tures used for food storage, in medical and hospital equipment, and in vessels used in the production of food and chemicals. Technical Ceramics Research after World WarII madepossible a wide vari- ety of nontraditional ceramic products based onhigh- purity synthetic materials processed by special tech- niques. A few items will illustrate the scope of this relatively new field. Ceramics have played an essential role in the devel - opment of the computer industry. The ceramic pro - cess is used in the fabrication of the complex inte- grated circuits that perform the basic operations of a computer on silicon semiconductor wafers. These in- tegrated circuits are packaged on ceramic substrate materials. Oxides and carbides of uranium, plutonium, and thorium are ceramic materials that are used in the production of fuels for nuclear fission reactors. High- strength concrete, often containing lead, is used in shielding structures around nuclear reactors. “Hot cell” windows, made of leaded glass, maintain optical transparency when exposed to radiation. Ceramic materials are also used in virtually all segments of the aerospace industry. Refractory materials are used in building launching pads, rocket nozzles, and heat shields. Lasers, which came into prominence in the 1960’s, utilize the variousquantum transitions thatatoms and molecules undergo to produce intense beams of in- frared, visible, or ultraviolet light. The original ruby laser used as its light-emitting medium a crystalline aluminum oxide ceramic that contained a small amount of chromium. Another important ceramic la- ser is the yttrium aluminum garnet doped with neo- dymium to emit light in the infrared region of the spectrum. As the need for more specialized materials grows, the field of ceramic science will continue to produce more and more exotic materials. Grace A. Banks Further Reading Barsoum, M. W. FundamentalsofCeramics. Rev.ed.Phil- adelphia: Institute of Physics, 2003. Bormans, P. Ceramics Are More than Clay Alone: Raw Ma- terials, Products, Applications. Cambridge, England: Cambridge International Science, 2003. Carter, C. Barry, and M. Grant Norton. Ceramic Mate- rials: Science and Engineering. New York: Springer, 2007. Jones, J. T., and M. F. Berard. Ceramics Industrial Pro- cessing and Testing. 2d ed. Ames: Iowa State Univer- sity Press, 1993. McColm, Ian J. Dictionary of Ceramic Science and Engi- neering. 2d ed. New York: Plenum Press, 1994. Phillips, George C. A Concise Introduction to Ceramics. New York: Van Nostrand Reinhold, 1991. Sfmiya, Shigeyuki, et al., eds. Handbook of Advanced Ce - ramics. 2 vols. Boston: Elsevier/Academic Press, 2003. Global Resources Ceramics • 189 . that included creation of a Department of Energy, deregulation of domestic crude oil prices, and promotion of conservation and alternative energy sources. An advocate of environ - mentalism,. most processing of ceramics. Althoughsimple, thisdescrip- tion of ceramics was an accurate one until the time of WorldWar II. In the early 1940’s, the field of materials science, of which ceramics is a part, . World War I. Global Resources Carver, George Washington • 183 Jimmy Carter,thethirty-ninthpresident of the United States,wasan early advocate of alternative energy use. (Library of Congress) In