Web Site U.S. Geological Survey Mineral Information: Zeolites Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/zeolites/ See also: Volcanoes; Water; Water pollution and water pollution control. Zimbabwe Categories: Countries; government and resources Zimbabwe has the second largest reserve of gold on the African continent and the second largest reserve of platinum in the world. The country also boasts the largest elephant herd in the world as well as a sizable impala herd; safari tours have historically been an im- portant means of support for the local population. The Country Zimbabwe isinthe southeastern corner ofAfrica, bor- dered to the north by Zambia, to the east by Mozam- bique, to the west by Botswana, and to the south by South Africa. In 2008, the country’s gross domestic product was estimated at $2.3 billion. Of this amount, agriculture accounted for 18.1 percent, industry ac- counted for 22.6 percent, and the services sector ac- counted for 59.3 percent. The total value of mineral production in Zimbabwe exceeds $500 million per year. The mining sector of the economy employs at least sixty thousand people and accounts for more than 40 percent of the total export revenues of the country. Of the total land area, 49.2 percent is forest, and this consists of mopane and dry Miombo woodland. Grasslands, both low- and high-altitude types, consti- tute another important ecosystem. The Zambezi River, which forms the border between Zimbabwe and Zam- bia, is an important waterway of the country. Gold Africa has about 30 percent of the Earth’s mineral re- serves, including 40 percent of the world’s gold. Gold is the most important mineral commodity of Zimba - bwe and the second-leading export commodity, pro - viding an annual output of $194 million. In 2007, 5.7 metric tons of gold were produced by the country’s mines. Zimbabwepossesses thesecond largestgold re- serves in Africa. The Freda RebeccaMine, located closeto Bindura, north of the capital city of Harare, is said to be the richest in the country. Ninety thousand metric tons of ore are processed at this mine each month. Freda Rebecca is owned by AngloGols Ashanti, a large min- ing firm. Other important gold-mining companies in- clude Falcon Gold, one of the oldest in Zimbabwe; Anglo American; Rio Tinto Zimbabwe; Consolidated Trillion Resources; Independence Gold; Delta Gold; and Reedbuck Gold. Central Rand Gold is a holding company for a number of smaller gold-mining and exploration firms. In addition to traditional, large-scale gold-mining operations, nearly everyone in Zimbabwe pans for gold and seeks the mineral in tailings left from closed mines. Diamonds In Zimbabwe, diamonds, among the world’s most precious minerals, were first discovered in 1997 at Murowa, about40 kilometers from the townof Zvisha- vane in the south-central portion of the country. Three kimberlite pipes containing diamond ore were located at the site. The Rio Tinto Group, which is the third largest producer of rough diamonds in the world and also owns gold mines in Zimbabwe, has worked only two of these kimberlite pipes. Full-scale production isexpected toprocess 181,400metrictons of ore per year. Another important diamond mine in the country is the River Ranch mine, a combination open-pit and underground operation. De Beers owns 75 percent of River Ranch. As of late 2008, diamond production in Zimbabwe totaled approximately fourteen million carats. How- ever, a tremendous amount of illegal mining has oc- curredand contributes toa sizableblackmarket prob- lem. The government is attempting to control the diamond situationandthe accompanying violenceas- sociated with the black market. Platinum Among the world’s scarcest minerals, found at a con- centration of only 0.003 part per billion in the Earth’s crust, platinum is a highly prized metal that is thirty times rarer than gold. Its properties of malleability, ductility, and corrosion resistance make it a valuable component used in many industries. Platinumissome - 1366 • Zimbabwe Global Resources Global Resources Zimbabwe • 1367 Zimbabwe: Resources at a Glance Official name: Republic of Zimbabwe Government: Parliamentary democracy Capital city: Harare Area: 150,883 mi 2 ; 390,757 km 2 Population (2009 est.): 11,392,629 Language: English Monetary unit: Zimbabwean dollar Economic summary: GDP composition by sector (2008 est.): agriculture, 18.1%; industry, 22.6%; services, 59.3% Natural resources: coal, chromium ore, asbestos, gold, diamonds, nickel, copper, iron ore, vanadium, lithium, tin, platinum group metals Land use (2005): arable land, 8.24%; permanent crops, 0.33%; other, 91.43% Industries: mining (coal, gold, platinum, copper, nickel, tin, clay, numerous metallic and nonmetallic ores), steel, wood products, cement, chemicals, fertilizer, clothing and footwear, foodstuffs, beverages Agricultural products: corn, cotton, tobacco, wheat, coffee, sugarcane, peanuts, sheep, goats, pigs Exports (2008 est.): $1.321 billion Commodities exported: platinum, cotton, tobacco, gold, ferroalloys, textiles/clothing Imports (2008 est.): $1.915 billion Commodities imported: machinery and transport equipment, other manufactures, chemicals, fuels Labor force (2008 est.): 4.039 million Labor force by occupation (1996): agriculture, 66%; industry, 10%; services, 24% Energy resources: Electricity production (2006 est.): 9.467 billion kWh Electricity consumption (2006 est.): 11.59 billion kWh Electricity exports (2006 est.): 34 million kWh Electricity imports (2006 est.): 2.867 billion kWh Natural gas production (2007 est.): 0 m 3 Natural gas consumption (2007 est.): 0 m 3 Natural gas exports (2007 est.): 0 m 3 Natural gas imports (2007 est.): 0 m 3 Oil production (2007 est.): 0 bbl/day Oil imports (2005 est.): 15,800 bbl/day Oil proved reserves ( Jan. 2006 est.): 0 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. Harare Namibia South Africa Angola Mozambique Botswana Zambia Malawi Zimbabwe Indian Ocean Swaziland times used as a component of dental fillings and as a catalyst in the catalytic converters of automobiles. It also serves a number of important functions in the manufacture of laboratory equipment such as cruci- bles, tongs, funnels, and combustion instruments. Additionally, platinum is valued by many people for jewelry. Leading worldproducers ofplatinum areSouth Af- rica (with 80 percent of the planet’s share of produc- tion), Russia, and Canada. Although Zimbabwe pro- duces approximately only 2 percent of the world’s platinum group metals, this product is an important export for the country. Found in nickel and copper ores, platinum is also found in nativedeposits,includ- ing those along Zimbabwe’s Great Dyke, a geological feature that runs north to south for about 550 kilome- ters through the central portion of the country. Plati- num depositswere found inthis area in1925,but only in more recent times has mining become profitable. Union Carbide began trial mining between 1966 and 1975 at the Mimosa Mine, now Zimbabwe’s old- est. Obtained by Zimasco Ltd. in 1992, Mimosa pro- cesses approximately 27,000 metric tons of ore per month for a production total of 2,400 kilograms of platinum eachyear. Theminealso supplies palladium and rhodium, other platinum group metals. In 2007, 1,850 kilograms of palladium and 190 kilograms of rhodium were produced. The Zimplats Mine, also a large producer of plati- num group metals,produced 3,000 kilogramsof plati- num, 2,440 kilograms of palladium, and 264 kilo- grams of rhodium in 2007. Other important mines along the Great Dyke includeHartley Platinum, Ngezi, and Unki.Ngezi’s production totaled2,550kilograms in 2006, and Unki was expected to generate about 1,644 kilograms by 2010. Lithium Although Zimbabwe is not one of the world’s leading producers of lithium, the country is still important as a lithium exporter because reserves of this alkali metal are rare. Chile is the leading producer of lith- ium, followed byArgentina. Australia, Brazil, Canada, Portugal, and Zimbabwe are the other nations for which lithium is a vital export. Lithium has many uses in industry. It has been used in glass manufacturing for many years because it lowers the melting point of glass and allows for con - tainers to be made with thinner walls as well as with lighter weight.Thermalandshock-resistant cookware is manufactured using lithium, and the metal acts as a catalyst in synthetic rubber and plastic production. Lithium carbonate in a pharmaceutical formulation provides a valuable drug for treating manic depres- sion. Probably the most important modern use of lith- ium has been as a component of rechargeable batter- ies. Lithium batteries are used as the power sources for 60 percent of all cell phones and 90 percent of all laptop computers. In 2000,Zimbabweproduced 38,000metrictons of lithium; production increased by 110 percent be- tween 2003 and 2004. Subsequent figures are difficult to obtain because of the continuing instability of Zim- babwe’s political and economic situation. The Glen Cove Mine, operated by Bikita Minerals Ltd., contin- ues production and is considered to have a remark- ably high-quality grade of lithium. This particular mine has provided the United States Atomic Energy Commission with about 30 percent of its lithium hy- droxide stockpile. Chromium Zimbabwe boasts more than 50 percent of the world’s reserves of chromite, and together South Africa and Zimbabwe possess 90 percent of Earth’s supply of this valuable ore. Chromium is vital in the production of stainless steel, nonferrous (non-iron) alloys, metal- plating processes, and the manufacture of refrac- tories. Like lithium and platinum, chromium is im- portant as a catalyst for manufacturing processes. For the United States, the only domestic source of chro- mium is through recycling, so the country imports much ofits neededsupplyfrom SouthAfricaand Zim- babwe. The two major Zimbabwean chromite mines are Mutorashanga and the Torwood and Valley Mine. The large companies of Zimasco and Zimbabwe Al- loys International own both the ore-mining and ferrochromium production components, allowing for the vertical integration of this industry. Tobacco Zimbabwe is one of the world’s major tobacco export- ers, ranking seventh, as of 2009, after Brazil, the United States, India, Malawi, Italy, and China. For many years, the country ranked as one of the top four tobacco producers in theworld. Tobaccoaccountsfor more than 50 percent of Zimbabwe’s total agricul - tural exports and represents 30 percent of the coun - 1368 • Zimbabwe Global Resources try’s total exports. Sales of the crop earn about seven times more than sales of corn, about twenty-two times more than cotton, and sixty times more than soy- beans. Virtually all the tobacco crop (98 percent) is exported because there is little domestic production of cigarettes. Tobacco production provides employment for ap- proximately 5 percent of the country’s labor force and also contributes to employment for those in the coal-mining, transportation, hospitality, and service sectors of the economy. Most tobacco farming is done by about two thousand large-scale, commercial grow- ers who utilize modern farming techniques, includ- ing irrigation. Theselargegrowers accountfor95 per- cent of total crop production and plant on about 87 percent of the available land. About sixteen thousand small-scale dryland farmers raise theremaining 5 per- cent of the country’s tobacco. Three types of tobacco are grown in Zimbabwe. Flue-cured tobacco is raised in the parts of the coun- try with better rainfall totals, and this encompasses areas north and east of the capital of Harare. Burley tobacco is grown in the northeastern and eastern highland regions, where there is both good rainfall and high humidity, which is necessary for the curing of this particular type of tobacco. Oriental tobacco is grown primarily by small-scale farmers in Masvingo Province. Most tobacco farmers practice a five-year rotation schedule and grow other crops within the rotation cycle. Soybeans, wheat, corn, and livestock are all pro- duced on tobacco land, and some farmers have turned to less traditional crops such as export roses, vegeta- bles for sale to grocery stores, coffee, and paprika. The changeto agreater diversityof cropsbecamenec- essary because of the worldwide campaign to reduce the use of tobacco products such as cigarettes. For most of the 2000’s, Zimbabwe produced an av- erage of 181,000 metric tons of tobacco per year, but in the later years of the decade, production totals dropped steeply. Fewer than 54,000 metric tons were produced in 2008. As mentioned, the global health campaign against tobacco use has contributed signifi- cantly to a drop in production, but severe drought and shortages of diesel fuel and fertilizer have also affected this agricultural sector adversely. Cotton Cotton is Zimbabwe’s second most important agricul - tural export. Approximately 200,000 small farms pro - duce 98 percent of the cotton crop in the country. The amount of cotton produced has been steadily in- creasing. In 2007, production totaled 99,700 metric tons; in 2008, 370,000 hectares were planted and har- vested, with seed cotton production reaching 300,000 metric tons and lint production 123,000 metric tons. Average yield was 0.81 metric ton per hectare. Since 1994, the small-scale cotton growers in Zim- babwe have sold their seed cotton to the Cotton Com- pany of Zimbabwe (Cottco). This companyisthe larg- est buying, processing, and marketing operation in the country,althoughCargill andRomsdalalso have a share of the cotton market. The ginners and mer- chants of these companies provide seed, fertilizer, and pesticides to the growers on credit. In turn, the growers sign contracts promising to sell all of their cotton back to the contractors. Large-scale cotton farming takes place in the cen- tral, northern, and eastern sections of Mashonaland, while most small-scale production is in the Gokwe, Gwanda, and Kezi areas of Zimbabwe. Alber and long staple varieties of cotton are grown on all farms, and the quality of this cotton is ranked as “high” because there are not many contaminants and not much dam- age to the cotton. Although the textile and garment industries have been well established since the 1930’s in Zimbabwe, these industries and the accompanying cotton pro- duction that supports them have experienced a num- ber of problems. Foreign currency problems and the extreme political instability of Zimbabwe have af- fected allof thecountry’sindustries adversely,and the cotton business is no exception. Farmers who have been “resettled” by forced government intervention on former commercial farms are unskilled and have little experience in cotton production. There are also no gins for small farms other than the ones owned by the national companies such as Cottco and Cargill. Extreme drought in the region during recent years has also negatively affected cotton as well as many other crops. Some farmers have begun to break a law that states that all cotton stalks must be destroyed at least fifty days before the next season’s planting. These farmers have been growing cotton by using theprevious year’s stalks, a practice that has led to increased infestation of pink bollworm, one of the primary cotton pests. In spite of these problems, cotton continues to be an im - portant export crop for Zimbabwe and may surpass tobacco as the number one crop of the country. Global Resources Zimbabwe • 1369 Other Resources One of Zimbabwe’s most important resources is its wildlife and ecology: Tourism is the third largest income-producing industry in Zimbabwe, employing about 200,000 people.The country has a varietyof na- tional parks, all ofwhich host an astonishing varietyof flora and fauna. Various licenses for tourists, park fees, and concessions within the parks provide in- come opportunities for local residents. The national parks include Chimanimani, Chizar- ira, Gonarezhou, Hwange, Kazuma Pan, Mana Pools, Matusadona, Matelo,Nyanga, VictoriaFalls,and Zam- bezi. Most of the parks host large numbers of the more common species of savanna wildlife, including roan, sable, impala, eland, cape buffalo, zebra, and elephant. Lions, leopards, and cheetahs are among the large predators that may also be seen in a few of the parks, including Gonarezhou and Kazuma Pan. Chizarira National Park also supports herds of the ex - tremely rare black rhinoceroses. The tsessebe, a sa- vanna antelope, and white rhinoceroses are found in Zambezi National Park. Hwange, the largest game re- serve in Zimbabwe, located close to the Kalahari Desert, is home to hippopotamuses, crocodiles, brown hyenas, gemsboks, and African wild dogs as well as a large elephant herd. Victoria Falls and Zambezi national parks are lo- cated along Zimbabwe’s border with Zambia and are visited as much for the spectacular natural wonder of waterfalls as for the diversity of wildlife. Victoria Falls actually consists of five separate falls, four within Zim- babwe and one (Eastern Cataract) in Zambia. In Zim- babwe, the Devil’s Cataract, MainFalls, Rainbow Falls, and Horseshoe Falls provide awe-inspiring views for the tourist. Since its inception in 1989, the Communal Areas Management Program for Indigenous Resources, better known as CAMPFIRE, has provided money- making opportunities for local people by leasing land to tour companies. However, in order for ecotourism to continue to provide a means of support for Zim- babweans, the political situation in the country must stabilize. Lenela Glass-Godwin Further Reading Bartholomew, D. S. Base Metal and Industrial Mineral Deposits of Zimbabwe. Reprint. Harare: Zimbabwe Geological Survey, 1992. Coakley, George J. The Mineral Industry of Zimbabwe. Washington, D.C.: U.S. Geological Survey, 2000. Duffy, Rosaleen. Killing for Conservation: Wildlife Policy in Zimbabwe. London: International African Insti- tute, 2000. Ebensperger, Arlene, P. Maxwell, and C. Moscoso. “The Lithium Industry: Its Recent Evolution and Future Prospects.” Resources Policy 30, no. 3 (2005): 218-231. George, M. W. Platinum Group Metals. Washington, D.C.: U.S. Geological Survey, 2007. Hulme, David, and Marshall Murphree, eds. African Wildlife and Livelihoods: The Promise and Performance of Community Conservation. Portsmouth, N.H.: James Currey, 2001. See also: Chromium; Cotton; Diamond; Gold; Lith - ium; Platinum and the platinum group metals; South Africa. 1370 • Zimbabwe Global Resources Victoria Falls is one of the many natural wonders found in Zim- babwe. (©Lucian Coman/Dreamstime.com) Zinc Category: Mineral and other nonliving resources Where Found Zinc is widely distributed in the Earth’s crust, with an average crustal abundance of 70 parts per million (0.007 percent). It hasbeen concentrated intoseveral types of ore deposits from which it is mined as the principal metal or as a by-product. The principal ore mineral is sphalerite(ZnS), also knownaszinc blende or marmatite. China, Japan, Australia, and Canada are the world’s largest suppliers of zinc. Primary Uses Zinc is a widely used metal, but its presence is gener- ally not obvious to the public. The largest single use is in galvanizing, a process in which iron or carbon steel is covered with a thin coating of zinc to prevent rust- ing. Zinc is also widely used in brass alloys and other compounds ranging from pharmaceuticals to rubber tires to paints. Technical Definition Zinc (symbol Zn), atomic number 30, belongs to Group IIB of the periodic table of the elements and exhibits some chemical and physical similarities to cadmium. It has five naturally occurring stable iso- topes, with masses of 64, 66, 67, 68, and 70, and it has an average atomic weight of 65.38. Pure zinc is a mal- leable, bluish-whitemetal thatcrystallizesin a hexago- nal structure and that has a density of 7.13 grams per cubic centimeter. It has a melting point of 419.6° Cel- sius and a boiling point of 907° Celsius. Description, Distribution, and Forms Zinc is one of the most widely used metals; however, throughout much of its history it was not recognized as a distinct metal. Zinc is nearly ubiquitous in trace amounts and is essential for the normal growth and development of plants and animals. It occurs in more than twenty metalloenzymes and promotes healing of wounds and burns; furthermore, zinc deficiency has been shown to have severe effects on reproduction and tissue growth in laboratory animals. Zinc defi- ciency insoils leadsto reducedproductivity butcanbe remedied by the application of trace amounts of zinc in fertilizers. Numerous studies of zinc in the environment have demonstrated that severe zinc pollution is extremely rare and that zinc contamination rarely becomes a problem for plants or animals. In general, the only time that zinc concentrations can rise to harmful lev- els is if the pH is very low and the sources of zinc are very large. Zinc is readily adsorbed onto clays or pre- cipitates from solutions atneutral andhigh pHvalues. Zinc and its compounds are relatively nontoxic to hu- mans when taken in normal dosages. Very large dos- ages can cause gastroenteritis; however, reports of such poisoning are limited to a few rare cases of the consumption of acidic beverages having been kept in galvanized containers.Workplace poisoning hasbeen only rarely reported as the result of inhaling zinc dust or fumes; the human body is quite efficient in the elimination of excess zinc. Zinc has been mobilized by fluids in the Earth’s crustandprecipitated intomanytypes of ore deposits. Although there are many zinc-bearing minerals, the only mineralthatserves asan economic source of zinc in mining is sphalerite (ZnS). The principal types of ores are carbonate-hosted lead-zinc ores (Mississippi Valley-type ores, so called because of their abundance in parts of the Mississippi Valley drainage system, es- pecially Missouri), hydrothermal vein deposits, and polymetallic massive sulfide ores formed where hy- drothermal fluids have deposited complex ores in sedimentary basins orin massesof volcanic rocks. The Mississippi Valley-type ores occurin limestone anddo- lomite beds where there has been infiltration of rela- tively low-temperature (75°to150° Celsius)fluidsthat have already leached zinc (and commonly lead) from thick sequences of sedimentary rocks. The zinc is de- posited as the mineral sphalerite, most often as light yellow coatings on, and as fracture fillings in, the car- bonate rocks. This sphalerite typically contains small amounts (0.5 percent) of cadmium and iron and trace amounts (less than 0.1 percent) of germanium, gallium, and indium in solid solution. Consequently, the zinc ores serve as the world’s major sources of these rare elements, which are recovered during re- fining. Zinc-bearing hydrothermaldepositscommonly oc- cur as veins from centimeters to meters in thickness associated with granitic to intermediate igneous rocks. The sphalerite in these ores is typically very dark brown to black and contains 5 to 10 percent iron sub- stituting for the zinc; it has commonly been called “blackjack” or marmatite. The zinc ores of the volca - nic and sedimentary deposits are similar mineralogi - Global Resources Zinc • 1371 cally to those of the vein deposits with the sphalerite intermixed with pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ), and galena (PbS). These deposits occur where frac- tures and faults have allowed deeply circulating groundwaters, containing small amounts of dissolved metals, to discharge and precipitate complex masses of sulfides. In recent years modern examples of these types of deposit have been observed forming at oce- anic spreading centers such as the East Pacific Rise. At these sites, hydrothermal fluids issuing from the seafloor fractures are depositing polymetallic sulfide mounds that are rich in zinc. Although all the zinc in ore deposits occurs as sphalerite, much of the zinc forming in modern seafloor deposits is wurtzite, an- other form of ZnS; the wurtzite gradually is converted into sphalerite after deposition. In 2008, world zinc production was about 11 mil- lion metric tons. World reserves are thought to be about 180 million metric tons. The world reserve base, which includes zinc that will likely become eco- nomic to mine, is about 480 million metric tons. United States production is dominated by Alaska, Tennessee, New York, Missouri, and Colorado and has been in the range of 800,000 metric tons per year; total U.S. reserves are about 14 million metric tons, and the U.S. reserve base is about 90 million metric tons. Accordingly, U.S. mines will be able to continue to produce zinc at about the same rates for several de- cades. History Zinc has been found in some bronze and brass arti- facts made five thousand years ago, and a few early ex- amples of nearly pure zinc metal date back to about 500 b.c.e. Significant zincproduction appears to have begun in China in the sixth century c.e. Subsequent large-scale production is known from India about 1000 c.e., but zinc appears in European usage only around the sixteenth century. The technology of zinc smelting is thought to have been developed in China and brought to Europe about 1730. The use of zinc in the United States began in 1835, when it wasdesired to produce alloys forthe manufac- ture of the U.S. standard units of weights and mea- 1372 • Zinc Global Resources Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009.Source: Mineral Commodity Summaries, 2009 1,510,000 660,000 3,200,000 420,000 460,000 1,450,000 770,000 2,840,000 Metric Tons 3,500,0003,000,0002,500,0002,000,0001,500,0001,000,000500,000 United States Kazakhstan China Canada Australia Mexico Peru Other countries Zinc: World Mine Production, 2008 sures. Mining in the United States began about 1850 in rich ores in New JerseyandPennsylvania.A smelter was built in 1859. By 1900 mines had been developed in a number of other states, especially along the Mis- sissippi Valley. Obtaining Zinc Zinc ores are mined by underground and surface mining methods, depending upon the depth of the deposit below the surface. Generally ores must con- tain 2.5 to 3.0 percent zinc or about 4 to 5 percent sphalerite to be economic; this percentage is equiva- lent to a concentration factor of about four hundred times the average abundance of zinc in the Earth’s crust. In orderto recover the zinc,theores are crushed finely enough that the individual mineral grains may be separated by the froth flotation process. This pro- cess selectively removes the sphalerite grains as they attach themselves to small bubbles and float off the surface of a suspension that contains many kinds of minerals. The separation yields a concentrate that contains about 55 to 65 percent zinc, depending upon the purity of the sphalerite. Other valuable metals—such as cadmium, germanium, gallium, and indium—that are present in small amounts in the sphalerite are separated duringselective smeltingand refining. In most smelters, the zinc sulfide is roasted to remove thesulfurand toproduce zinc oxide,which is thenleachedwith sulfuric acidto form a zinc sulfate solution. After the solution is purified, the zinc is removed in electrolytic cells and precipitates on large aluminum cathodes. Further refining is accomplished by distilling the zinc in a vapor form, which is then recondensed. Zinc recycling accounts for a relatively insignificant percentage of demand because so much of the zinc is used in forms for which recycling is diffi- cult or inefficient. Uses of Zinc Zinc metal and zinc compounds have broad uses, but many applications are not easily visible or known to those who benefit from them. About 90 percent of zinc is used in the metallic form; the remainder is used as zinc oxide and a variety of other compounds. More that half of metallic zinc usage is for the galva- nizing of iron and steel for construction, transporta- tion, electrical, and machinery purposes. The appli- cation of the zinc, either by dipping the iron and steel into molten zinc or by electrolytic plating, provides a coating that greatly reduces the rusting of iron and steel. Much of the use of such galvanized materials is on the body parts of motor vehicles. Many construc- tion materials, from nails to bridge parts, are also gal- vanized to reduce corrosion. Die-cast zinc materials are also widely used in han- dles, grills, gauges, housings, and assorted hardware, much of it in vehicles. The modern American auto- mobile can contain as much as 18 kilograms of zinc. Zinc isalsoused asasacrificial anode onships, oil rigs, and other structures exposed to seawater. These an- odes corrode as the result of natural electrical cells that develop, and in the process they prevent the cor- rosion of other metals. Beginning in 1983, zinc was used in the minting of United States one-cent coins; the penny is composed of 95 percent zinc. Zinc isa basiccomponent ofthe copper-based alloy brass, which has served humankind for thousands of years. Brass is widely usedinshell casings for ammuni- tion, intubing, inmotors, inrefrigeration equipment, and in communication and electronic devices. Zinc dust and zinc oxide have been used in corrosion- inhibiting primer paints for application on metals. Zinc dust is also used in the manufacture of alkaline dry-cell batteries. Zinc oxide and other compounds Global Resources Zinc • 1373 Source: Mineral Commodity Summaries, 2009 Data from the U.S. Geological Survey, .U.S.GovernmentPrinting Office, 2009. Galvanizing 55% Alloys 21% Brass & bronze 16% Other 8% U.S. End Uses of Zinc such as chlorides, sulfates, and sulfides are widely used in chemical catalysts, welding and soldering fluxes, paints, fungicides and pharmaceuticals, and phosphors for cathode tubes and radar scopes; they are also used as additives in lubricating oils andgreases and in agricultural products. James R. Craig Further Reading Adriano, Domy C. “Zinc.” In Trace Elements in Terres- trial Environments: Biogeochemistry, Bioavailability, and Risksof Metals.2d ed.New York: Springer, 2001. Greenwood, N. N., and A. Earnshaw. “Zinc, Cad- mium, and Mercury.” InChemistry of theElements.2d ed. Boston: Butterworth-Heinemann, 1997. Guilbert, John M., and Charles F. Park, Jr. The Geology of Ore Deposits. Long Grove, Ill.: Waveland Press, 2007. Krebs, Robert E. The History and Use of Our Earth’s Chemical Elements: A Reference Guide. 2d ed. Illustra- tions by Rae Déjur. Westport, Conn.: Greenwood Press, 2006. Massey, A. G. “Group 12: Zinc, Cadmium, and Mer- cury.” In Main Group Chemistry. 2d ed. New York: Wiley, 2000. Nriagu, Jerome O., ed. Zinc in the Environment. New York: Wiley-Interscience, 1980. Rainsford, K. D., et al., eds. Copper and Zinc in Inflam- matory and Degenerative Diseases. Boston: Kluwer Ac- ademic, 1998. Silva, J. J. R. Fraústo da, and R. J. P. Williams. “Zinc: Lewis Acid Catalysis and Regulation.” In The Biolog- ical Chemistry of the Elements: The Inorganic Chemistry of Life. 2d ed. New York: Oxford University Press, 2001. 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 U.S. Geological Survey Zinc: Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/zinc See also: Brass; Cadmium; Open-pit mining; Under - ground mining. Zirconium Category: Mineral and other nonliving resources Where Found The known deposits of zirconium constitute 0.028 percent of the Earth’s crust, which is greater than the combined total of all known copper, nickel, lead, tin, zinc, and mercury deposits. Reserves of zirconium minerals are found in Australia, Brazil, China, India, South Africa,Ukraine,Sri Lanka,Russia,and Canada. Deposits in the United States are located in Florida, North Carolina, California, Oregon, Colorado, and Idaho. The largest deposits are in Australia and South Africa. Primary Uses Zirconium is used mainly in ceramics, foundry appli- cations, opacifiers, and refractories, as well as in abra- sives, chemicals alloys, welding rod coatings, and sand- blasting. Technical Definition Zirconium (symbol Zr) is a grayish-white, lustrous metal. It is amember of the second seriesoftransition metals inGroup IVBin theperiodic tableof elements. Zirconium’s atomic number is 40, and its atomic weight is 91.22;it has five stableisotopes and three un- stable isotopes. Zirconium has a melting point of 1,852° Celsius, a boiling point of 4,377° Celsius, and a density of 6.506 grams per cubic centimeter. Description, Distribution, and Forms Zirconium occurs in abundance in S-type stars and has been identified in the Sun and meteorites. Zirco- nium is foundinmany minerals, such as zircon (zirco- nium silicate) and baddeleyite (almost pure zirco- nium dioxide), and it is typically found in igneous rocks (mainly granite and diorite). History Zirconium was discovered by German chemist M. H. Klaproth in 1789, while he was studying some semi- precious stones from Sri Lanka. The name comes from the Arabic wordzargun, which meansgoldcolor, describing the gemstone now known as zircon. Im- pure zirconium was first isolated by Jöns Jacob Ber - zelius by heating a mixture of potassium zirconium fluoride with potassium in an iron tube. 1374 • Zirconium Global Resources Obtaining Zirconium Metallic zirconium is produced commercially by the purification of zirconium tetrachloride by sublima- tion and reduction of the tetrachloride vapor with molten magnesium (the Kroll process). Unless spe- cial separation methods, such as column chromatog- raphy, are used in this process, the zirconium pro- duced contains between 0.5 and 3 percent hafnium, chemical element number 72. Uses of Zirconium Because zirconium has a low tendency to absorb slow neutrons and a remarkable resistance to the corro- sive environments in nuclear reactors, it finds many uses in the field of nuclear energy. Zirconium and its tin-iron-nickel-chromium alloy (zircaloy) are used as coatings for pipes and fuel element jackets in fission reactor cores. Zirconium is also used in deodorants, surgical instruments, pins, screws for bone repairs, spinnerets for the spinning ofrayonfibers, alloys, and powder metallurgy. In powdered form, zirconium is used as an ammunitionprimer, in smokeless flashpow - ders, in blasting caps, and in the manufacture of vac - uum tubes.Various zirconiumcompoundsare usedas catalysts forammonia synthesis,fororganic oxidations, for polymerizations, and in the conversion of sulfur di- oxide to sulfur trioxide. Along with niobium (colum- bium), zirconium is asuperconductor (it canconduct electricity withoutanyresistance) atlow temperatures and is used in the construction of superconducting magnets with potentialapplicationsto the generation of electrical power. Baddeleyite, a compound of zirco- nium and oxygen, can withstand extremely high tem- peratures. It is used for laboratory crucibles (melting pots for metals) and the linings for certain furnaces. Alvin K. Benson Web Site U.S. Geological Survey Mineral Information: Zirconium and Hafnium Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/zirconium/ See also: Alloys; Australia; Brazil; Igneous processes, rocks, and mineral deposits; India; Isotopes, radioac - tive; Minerals, structure and physical properties of; Niobium; Nuclear energy. Global Resources Zirconium • 1375 Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009.Source: Mineral Commodity Summaries, 2009 575,000 31,000 160,000 29,000 405,000 35,000 Withheld 120,000 Metric Tons 600,000500,000400,000300,000200,000100,000 United States India China Brazil Australia South Africa Ukraine Other countries Zirconium: World Mine Production, 2007 . industries. Platinumissome - 1366 • Zimbabwe Global Resources Global Resources Zimbabwe • 1367 Zimbabwe: Resources at a Glance Official name: Republic of Zimbabwe Government: Parliamentary democracy Capital. mixture of potassium zirconium fluoride with potassium in an iron tube. 1374 • Zirconium Global Resources Obtaining Zirconium Metallic zirconium is produced commercially by the purification of zirconium. 50 percent of the world’s reserves of chromite, and together South Africa and Zimbabwe possess 90 percent of Earth’s supply of this valuable ore. Chromium is vital in the production of stainless