17 Gold Man's relationship to gold has always been quite different from his association to stone,copper,bronze,or iron.Because of this a separate chapter is dedicated to this metal.If iron is consid- ered to be the metal of strength and will,gold may be perceived to appeal,instead,to the forces of the heart.In antiquity,gold was the metal of the gods and was used to create religious ves- sels,utensils,and sculptures,but also ornaments and articles for adornment.In some ancient cultures,gold was not owned by in- dividuals but belonged to the gods and their representatives on earth.Many poets have lauded gold,which they associated with the sun and its warmth and with wisdom. Eventually,however,gold became the symbol of wealth and monetary stability.To satisfy the lust for gold and thus provide the means for a luxurious living for a few selected people and to have the means to pay soldiers,the most brutal wars have been fought and atrocities were committed.Two examples of such be- havior are that of the ancient Romans and of the conquistadors who came to South and Central America.The power and wealth of empires such as those of the Sumerians,the Egyptians,the British,the Mesopotamians,or the Romans were largely based on their possession of gold and their trade with it. Today,about 60%of the world's gold (i.e.,38 million kg)is said to be held by governments and central banks.It is suppos- edly used to back the paper currencies of their respective nations U.S government sources claim that Fort Knox holds currently (May 1996)$54.9 X 109 worth of gold.Nevertheless,the rumor stubbornly persists that only a small portion of this gold remains presently at Fort Knox.Most of it is said to have been shipped to London in 1967/68 by the Johnson administration and was sold there in an ill-fated attempt to keep the price of gold at $35 per ounce.Despite numerous attempts by concerned citizens, who even offered to pay for an audit of the gold reserves,no such
17 Man’s relationship to gold has always been quite different from his association to stone, copper, bronze, or iron. Because of this, a separate chapter is dedicated to this metal. If iron is considered to be the metal of strength and will, gold may be perceived to appeal, instead, to the forces of the heart. In antiquity, gold was the metal of the gods and was used to create religious vessels, utensils, and sculptures, but also ornaments and articles for adornment. In some ancient cultures, gold was not owned by individuals but belonged to the gods and their representatives on earth. Many poets have lauded gold, which they associated with the sun and its warmth and with wisdom. Eventually, however, gold became the symbol of wealth and monetary stability. To satisfy the lust for gold and thus provide the means for a luxurious living for a few selected people and to have the means to pay soldiers, the most brutal wars have been fought and atrocities were committed. Two examples of such behavior are that of the ancient Romans and of the conquistadors who came to South and Central America. The power and wealth of empires such as those of the Sumerians, the Egyptians, the British, the Mesopotamians, or the Romans were largely based on their possession of gold and their trade with it. Today, about 60% of the world’s gold (i.e., 38 million kg) is said to be held by governments and central banks. It is supposedly used to back the paper currencies of their respective nations. U.S government sources claim that Fort Knox holds currently (May 1996) $54.9 109 worth of gold. Nevertheless, the rumor stubbornly persists that only a small portion of this gold remains presently at Fort Knox. Most of it is said to have been shipped to London in 1967/68 by the Johnson administration and was sold there in an ill-fated attempt to keep the price of gold at $35 per ounce. Despite numerous attempts by concerned citizens, who even offered to pay for an audit of the gold reserves, no such Gold
17·Gold 367 audit has been conducted since 1950 by the treasury department. Moreover,it is said that the gold in Fort Knox is mostly only 90% pure because it is derived from gold coins which went out of cir- culation in 1930.(Source:www.fgmr.com). Gold is used as a means for international payment.As a result, the price of gold fluctuates with the value of the currency of a given country and due to international political events.For ex- ample,gold prices started to rise in 1973 because of the begin- ning of the OPEC oil embargo,and then again starting 1978 due to the increases of gold purchases of Middle Eastern investors as a consequence of upheavals in Iran(US hostage taking)and the invasion of Afghanistan by the Soviet Union a year later(see Fig- ure 17.1).On the other hand,gold prices declined during 1981 and 1991 caused by the conflict in the Persian Gulf,the break- ing up of the Soviet Union,the erosion of gold's role as a safe haven for investors,and worldwide weak economic growth.De- spite of this,the world gold production has steadily increased during the past 100 years(Figure 17.2)probably due to increased industrial uses(computers)and demand for jewelry. It may be argued that a gold-backed monetary system func- tions only as long as the cost of production of gold,and thus its 1,200 1.000 -1992 dollars Current dollars 800 eIIOd 600 400 200 0 1968 19711974'1977198019831986'1989199219951998 Year Figure 17.1.Annual average gold prices in US for one troy ounce of gold.(1 troy ounce =31.1 g;1 "common"ounce 28.35 g).The upper curve adjusts the current price to the unit value in constant 1992 US dollars (correction for inflation).Compiled by E.B.Amey,US Geolog- ical Survey,Minerals and Materials Analysis Section (eamey@usgs.gov)
audit has been conducted since 1950 by the treasury department. Moreover, it is said that the gold in Fort Knox is mostly only 90% pure because it is derived from gold coins which went out of circulation in 1930. (Source: www.fgmr.com). Gold is used as a means for international payment. As a result, the price of gold fluctuates with the value of the currency of a given country and due to international political events. For example, gold prices started to rise in 1973 because of the beginning of the OPEC oil embargo, and then again starting 1978 due to the increases of gold purchases of Middle Eastern investors as a consequence of upheavals in Iran (US hostage taking) and the invasion of Afghanistan by the Soviet Union a year later (see Figure 17.1). On the other hand, gold prices declined during 1981 and 1991 caused by the conflict in the Persian Gulf, the breaking up of the Soviet Union, the erosion of gold’s role as a safe haven for investors, and worldwide weak economic growth. Despite of this, the world gold production has steadily increased during the past 100 years (Figure 17.2) probably due to increased industrial uses (computers) and demand for jewelry. It may be argued that a gold-backed monetary system functions only as long as the cost of production of gold, and thus its 17 • Gold 367 Figure 17.1. Annual average gold prices in US $ for one troy ounce of gold. (1 troy ounce = 31.1 g ; 1 “common” ounce = 28.35 g ). The upper curve adjusts the current price to the unit value in constant 1992 US dollars (correction for inflation). Compiled by E.B. Amey, US Geological Survey, Minerals and Materials Analysis Section (eamey@usgs.gov). 1,200 1,000 800 600 U.S. Dollars 400 200 0 1968 1971 1974 1977 1980 1983 Year 1986 1989 1992 1995 1998 1992 dollars Current dollars
368 17·Gold 2500- 2000- 1500- 1000 PIOD 500 Figure 17.2.World production of gold in metric tons.Source: US Geological Survey,Miner- T als and Materials Analysis 19001020*30'4050'607080902000 Section. Year price,does not drastically drop,or as long as the world supply of gold does not suddenly and excessively increase due to hith- erto unforeseen circumstances.Some economists suggest,there- fore,that the gross national product of a country would be bet- ter suited for supporting a currency.In the late 1800s,many western countries adopted the gold standard,which pledges to exchange paper money for gold at a fixed price.(The United States went on and off the gold standard and finally abandoned it in 1971.)The world's gold production and reserves are given in Table 17.1. Early chemistry and other sciences have greatly benefited from the quest of alchemists to produce gold from less precious ele- ments.Many useful substances have been "accidentally"discov- ered through their experimentations,such as the red stoneware that was invented in 1707 by an alchemist named Johann Friedrich Bottger(who,incidentally,also reinvented,in 1707/08, white porcelain and thus laid the ground for the MeiBen porce- lain manufacture in Germany;see Section 15.2.). Gold is a reasonably good conductor for electricity and heat; it is quite dense and is the most ductile,i.e.,malleable,of all met- als.Indeed,gold can be hammered into thin sheets,only 50 nm in thickness,called gold leaves.Specifically,one gram of gold can be spread out to cover about one square meter.The high es-
price, does not drastically drop, or as long as the world supply of gold does not suddenly and excessively increase due to hitherto unforeseen circumstances. Some economists suggest, therefore, that the gross national product of a country would be better suited for supporting a currency. In the late 1800s, many western countries adopted the gold standard, which pledges to exchange paper money for gold at a fixed price. (The United States went on and off the gold standard and finally abandoned it in 1971.) The world’s gold production and reserves are given in Table 17.1. Early chemistry and other sciences have greatly benefited from the quest of alchemists to produce gold from less precious elements. Many useful substances have been “accidentally” discovered through their experimentations, such as the red stoneware that was invented in 1707 by an alchemist named Johann Friedrich Böttger (who, incidentally, also reinvented, in 1707/08, white porcelain and thus laid the ground for the Meißen porcelain manufacture in Germany; see Section 15.2.). Gold is a reasonably good conductor for electricity and heat; it is quite dense and is the most ductile, i.e., malleable, of all metals. Indeed, gold can be hammered into thin sheets, only 50 nm in thickness, called gold leaves. Specifically, one gram of gold can be spread out to cover about one square meter. The high es- 368 17 • Gold 2500 2000 1500 1000 500 1900 2000 Year Gold World Production (metric tons) ’10 ’20 ’30 ’40 ’50 ’60 ’70 ’80 ’90 0 Figure 17.2. World production of gold in metric tons. Source: US Geological Survey, Minerals and Materials Analysis Section
17·Gold 369 TABLE 17.1.World gold production and reserves in 2001 Production of world Reserves of world Country [tons] production [tons] reserves South Africa 400 15.8 19,000 38 USA 350 13.8 5,600 11.2 Australia 290 11.5 5,000 10 China 185 7.3 1,000 2 Canada 160 6.3 1,500 3 Russia 155 6.1 3.000 6 Peru 140 5.5 200 0.4 Indonesia 120 4.7 1,800 3.6 Others (Ghana 69, 725 28.6 13.000 26 Brazil 52, Colombia 22) World total 2,530 100 50.000 100 Source:Drillbits Tailings,September 2002. teem for gold results,however,from its inertness to environ- mental influences combined with a relatively high reflectivity, which is about 93%in the yellow-red spectral region and 98%in the infrared.The latter property makes gold useful as heat shields for satellites,visors in space suits,and for thin,IR-reflecting films on windows.Because of its relatively high conductivity(71%of that found for copper)and its corrosion resistance,gold is used in large quantities by the electronics industry,for example,for conducting pads and for extremely thin wires which connect computer chips with the pins of headers.Further,gold is used in dental restoration.(Dental alloys contain,for example,85.6% gold,12.7%platinum,0.2%iridium,0.1%rhodium and traces of indium,zinc,titanium,iron,etc.)Fine particles of gold (colloidal gold)mixed with glass produces a deep red color.Gold leaves are green-blue in transmission. Native gold,that is,gold in its pure(unoxidized)state,is widely found on all continents and in all climate zones,albeit often in finest distribution.It appears near igneous rocks,occasionally in combination with silver,selenium,tellurium,or bismuth.Gold- bearing rock formations,that is,gold accumulations in cracks of rocks,called vein deposits or lode deposits,include hydrothermal veins which are associated with quartz and pyrite (fool's gold). It is believed that superheated water dissolved gold in the earth's interior which,after rising to the surface,deposited in cracks of rocks.Another theory proposes that liquid,gold-containing rocks (magma)emerged from great depths of the earth,out of which gold eventually precipitated.Crystals as large as 3 cm in size have
teem for gold results, however, from its inertness to environmental influences combined with a relatively high reflectivity, which is about 93% in the yellow-red spectral region and 98% in the infrared. The latter property makes gold useful as heat shields for satellites, visors in space suits, and for thin, IR-reflecting films on windows. Because of its relatively high conductivity (71% of that found for copper) and its corrosion resistance, gold is used in large quantities by the electronics industry, for example, for conducting pads and for extremely thin wires which connect computer chips with the pins of headers. Further, gold is used in dental restoration. (Dental alloys contain, for example, 85.6% gold, 12.7% platinum, 0.2% iridium, 0.1% rhodium and traces of indium, zinc, titanium, iron, etc.) Fine particles of gold (colloidal gold) mixed with glass produces a deep red color. Gold leaves are green-blue in transmission. Native gold, that is, gold in its pure (unoxidized) state, is widely found on all continents and in all climate zones, albeit often in finest distribution. It appears near igneous rocks, occasionally in combination with silver, selenium, tellurium, or bismuth. Goldbearing rock formations, that is, gold accumulations in cracks of rocks, called vein deposits or lode deposits, include hydrothermal veins which are associated with quartz and pyrite (fool’s gold). It is believed that superheated water dissolved gold in the earth’s interior which, after rising to the surface, deposited in cracks of rocks. Another theory proposes that liquid, gold-containing rocks (magma) emerged from great depths of the earth, out of which gold eventually precipitated. Crystals as large as 3 cm in size have 17 • Gold 369 TABLE 17.1. World gold production and reserves in 2001 Production % of world Reserves % of world Country [tons] production [tons] reserves South Africa 400 15.8 19,000 38 USA 350 13.8 5,600 11.2 Australia 290 11.5 5,000 10 China 185 7.3 1,000 2 Canada 160 6.3 1,500 3 Russia 155 6.1 3,000 6 Peru 140 5.5 200 0.4 Indonesia 120 4.7 1,800 3.6 Others (Ghana 69, 725 28.6 13,000 26 Brazil 52, Colombia 22) World total 2,530 100 50,000 100 Source: Drillbits & Tailings, September 2002
370 17·Gold been found in California and even larger ones in Transylvania as depicted in Plate 17.1.Chunks up to 90 kg in weight have been supposedly encountered in Australia.Most of the time,however, quartz rocks contain gold in concentrations of one-hundredth of a percent or less.Gold has been traditionally "harvested"from river beds into which it was washed after the rocks have been eroded by wind and water.The technique of panning is com- monly used.(Due to its high density,gold sinks to the bottom of a slurry of water and rocks.)Small nuggets or flakes of gold have been,and still can be,picked up in streams near surface veins or alluvial deposits.In antiquity,gold-containing mud was passed through sheep skin whose wool was subsequently burned to ob- tain gold dust.The Sumerians 6000 years ago already crushed gold-bearing quartz applying massive stone hammers.Eventu- ally,"surface"gold became scarce and man had to resort to un- derground mining.This was done particularly since about 600 B.C.in the Mediterranean region,as well as in Asia Minor,West- ern and Eastern Europe,Africa,and Asia.It was made possible through advances in ventilation and later by better drainage of the ground water.In antiquity,Egypt was the land richest in gold (and poorest in silver).It derived its gold from the desert region on the Red Sea and from Nubia.(Nub in the Egyptian language means gold.)The Greeks and Romans used scores of slaves and convicts as mine workers who labored under deplorable condi- tions.Rome got most of its gold from Spain.Looting of the gold holdings of other countries likewise filled her treasury. During the Middle Ages,the miners were liberated from slav- ery and became free agents who offered their services to the high- est paying governments.Gold mining,melting,and casting pretty much paralleled similar endeavors developed for copper pro- duction,as described in Chapter 1.This can be understood by knowing that the melting point of gold (1063C)is even 20C lower than that of copper. Discoveries of gold in certain regions of the world led to large migrations of people to these places.Examples are the great gold rush to California in 1849,or to New Zealand in 1861 (which doubled that country's population in six years).The city of Jo- hannesburg in South Africa was founded as a result of a gold rush in 1886,and Canada's Yukon Territory had a similar influx during 1897/98. Over the centuries several chemical methods have been devel- oped to separate gold from its admixtures.Among them is the cyanide leaching process,in which gold from crushed rocks is dissolved by NaCN in the presence of oxygen.Subsequently,the impurities are separated by treating the resulting solution,for
been found in California and even larger ones in Transylvania as depicted in Plate 17.1. Chunks up to 90 kg in weight have been supposedly encountered in Australia. Most of the time, however, quartz rocks contain gold in concentrations of one-hundredth of a percent or less. Gold has been traditionally “harvested” from river beds into which it was washed after the rocks have been eroded by wind and water. The technique of panning is commonly used. (Due to its high density, gold sinks to the bottom of a slurry of water and rocks.) Small nuggets or flakes of gold have been, and still can be, picked up in streams near surface veins or alluvial deposits. In antiquity, gold-containing mud was passed through sheep skin whose wool was subsequently burned to obtain gold dust. The Sumerians 6000 years ago already crushed gold-bearing quartz applying massive stone hammers. Eventually, “surface” gold became scarce and man had to resort to underground mining. This was done particularly since about 600 B.C. in the Mediterranean region, as well as in Asia Minor, Western and Eastern Europe, Africa, and Asia. It was made possible through advances in ventilation and later by better drainage of the ground water. In antiquity, Egypt was the land richest in gold (and poorest in silver). It derived its gold from the desert region on the Red Sea and from Nubia. (Nub in the Egyptian language means gold.) The Greeks and Romans used scores of slaves and convicts as mine workers who labored under deplorable conditions. Rome got most of its gold from Spain. Looting of the gold holdings of other countries likewise filled her treasury. During the Middle Ages, the miners were liberated from slavery and became free agents who offered their services to the highest paying governments. Gold mining, melting, and casting pretty much paralleled similar endeavors developed for copper production, as described in Chapter 1. This can be understood by knowing that the melting point of gold (1063°C) is even 20°C lower than that of copper. Discoveries of gold in certain regions of the world led to large migrations of people to these places. Examples are the great gold rush to California in 1849, or to New Zealand in 1861 (which doubled that country’s population in six years). The city of Johannesburg in South Africa was founded as a result of a gold rush in 1886, and Canada’s Yukon Territory had a similar influx during 1897/98. Over the centuries several chemical methods have been developed to separate gold from its admixtures. Among them is the cyanide leaching process, in which gold from crushed rocks is dissolved by NaCN in the presence of oxygen. Subsequently, the impurities are separated by treating the resulting solution, for 370 17 • Gold
17·Gold 371 example,with metallic zinc,which causes the gold to precipitate. In another process,hot sulfuric acid or nitric acid is applied to gold alloys which dissolves silver and other constituents(but not gold)and thus separates gold from its alloying components if this is desired.In "cementation"(a process which has been in exis- tence since about 550 B.c.),the gold-silver alloy in the form of thin leaves is heated in the presence of salt(NaCl),whereby sil- ver chloride forms,which can be washed out.Gold is so noble that it needs a mixture of nitric and hydrochloric acids (aqua re- gia)to change it into a salt(AuCl3). For jewelry and many utensils and coins,pure gold would be too soft and therefore needs to be alloyed with silver,or possi- bly palladium or platinum,or left unpurified,as was done in an- tiquity;see below.Thus,goods made of gold alloys usually have a broad range of colors.(A 50%gold alloy is known by the term “12 karat'”whereas pure gold is called“24 karat'".) A large number of skilled gold artisans emerged in different cultures through the millennia,as witnessed through splendid artifacts which have been found in numerous burial sites.Among them are finds near Varna (Bulgaria)on the coast of the Black Sea (see Plate 1.4)dating from 4300 B.C.,artifacts from the Sume- rians(4000 B.c.),and particularly from the Egyptians who skill- fully covered wooden or copper articles with gold leaves(called gilding).But solid gold articles were also created by the Egyp- tians.One of the finest examples of this is the inner coffin be- longing to the pharaoh Tutankhamen(1350 B.c.),which was made of solid gold and weighs 110 kg.A number of Irishmen during the second millennium B.c.were likewise gifted gold ar- tisans.They traded their goods between the British islands and Central Europe.This considerably enhanced the wealth of the in- volved people,particularly the British.Other places of gold min- ing and artistic activities emerged in India,China,Greece,and Asia Minor,to mention a few.By the time of the Middle Ages (around A.D.1500),London counted 52 goldsmith shops who had to maintain a certain standard in workmanship before they were accepted in a trades guild.A few examples of art work made of gold are depicted in Plates 17.2-17.5. As implied above,gold coins played an important role in early trade.(To a lesser extent,coins made of silver and even bronze were likewise used.)Probably the first true coins,that is,cast disks of standard weight and value,were manufactured by the Lydians of Anatolia at about 640 B.C.using a natural alloy con- sisting of gold with 20 to 35%silver,which was known by the name electrum.The coins were embossed with the aid of a die that bore the image of a lion.However,the trade value of these
example, with metallic zinc, which causes the gold to precipitate. In another process, hot sulfuric acid or nitric acid is applied to gold alloys which dissolves silver and other constituents (but not gold) and thus separates gold from its alloying components if this is desired. In “cementation” (a process which has been in existence since about 550 B.C.), the gold–silver alloy in the form of thin leaves is heated in the presence of salt (NaCl), whereby silver chloride forms, which can be washed out. Gold is so noble that it needs a mixture of nitric and hydrochloric acids (aqua regia) to change it into a salt (AuCl3). For jewelry and many utensils and coins, pure gold would be too soft and therefore needs to be alloyed with silver, or possibly palladium or platinum, or left unpurified, as was done in antiquity; see below. Thus, goods made of gold alloys usually have a broad range of colors. (A 50% gold alloy is known by the term “12 karat” whereas pure gold is called “24 karat”.) A large number of skilled gold artisans emerged in different cultures through the millennia, as witnessed through splendid artifacts which have been found in numerous burial sites. Among them are finds near Varna (Bulgaria) on the coast of the Black Sea (see Plate 1.4) dating from 4300 B.C., artifacts from the Sumerians (4000 B.C.), and particularly from the Egyptians who skillfully covered wooden or copper articles with gold leaves (called gilding). But solid gold articles were also created by the Egyptians. One of the finest examples of this is the inner coffin belonging to the pharaoh Tutankhamen (1350 B.C.), which was made of solid gold and weighs 110 kg. A number of Irishmen during the second millennium B.C. were likewise gifted gold artisans. They traded their goods between the British islands and Central Europe. This considerably enhanced the wealth of the involved people, particularly the British. Other places of gold mining and artistic activities emerged in India, China, Greece, and Asia Minor, to mention a few. By the time of the Middle Ages (around A.D. 1500), London counted 52 goldsmith shops who had to maintain a certain standard in workmanship before they were accepted in a trades guild. A few examples of art work made of gold are depicted in Plates 17.2–17.5. As implied above, gold coins played an important role in early trade. (To a lesser extent, coins made of silver and even bronze were likewise used.) Probably the first true coins, that is, cast disks of standard weight and value, were manufactured by the Lydians of Anatolia at about 640 B.C. using a natural alloy consisting of gold with 20 to 35% silver, which was known by the name electrum. The coins were embossed with the aid of a die that bore the image of a lion. However, the trade value of these 17 • Gold 371
372 17·Gold coins was somewhat impaired because of the variation in the composition of electrum.Eventually,under the reign of the Egyptian King Croesus of Lydia (560-546 B.C.),purification of gold was accomplished and the quality and weight of gold coins were certified by the government.Similar minting was eventu- ally adopted by the Greeks and finally also by the Romans.The latter used iron dies which were more resistant against wear com- pared to the bronze dies that were used by the Greeks and Egyp- tians.In contrast to this,the Chinese issued square-holed bronze coins utilizing essentially the same size and shape for almost 2,500 years until the twentieth century. In conclusion,gold was probably known to and valued by mankind as early as during the Neolithic or even the Mesolithic time periods because of its color,luster,ductility,its inertness to environmental interactions,and its availability in the native state. Gold played a major role in mythology and folklore and allowed beautiful pieces of art to come into existence.On the other hand, gold also brought hardship,pain,and tears to many people around the world because of the desire for its possession. Suggestions for Further Study L.Aitchison,A History of Metals,Wiley,New York (1960). R.W.Boyle,Gold,History and the Genesis of Deposits,Nostrand Reinhold,Inc.,New York (1987). T.A.Rickard,Man and Metals,Arno,New York (1974)
coins was somewhat impaired because of the variation in the composition of electrum. Eventually, under the reign of the Egyptian King Croesus of Lydia (560–546 B.C.), purification of gold was accomplished and the quality and weight of gold coins were certified by the government. Similar minting was eventually adopted by the Greeks and finally also by the Romans. The latter used iron dies which were more resistant against wear compared to the bronze dies that were used by the Greeks and Egyptians. In contrast to this, the Chinese issued square-holed bronze coins utilizing essentially the same size and shape for almost 2,500 years until the twentieth century. In conclusion, gold was probably known to and valued by mankind as early as during the Neolithic or even the Mesolithic time periods because of its color, luster, ductility, its inertness to environmental interactions, and its availability in the native state. Gold played a major role in mythology and folklore and allowed beautiful pieces of art to come into existence. On the other hand, gold also brought hardship, pain, and tears to many people around the world because of the desire for its possession. L. Aitchison, A History of Metals, Wiley, New York (1960). R.W. Boyle, Gold, History and the Genesis of Deposits, Nostrand Reinhold, Inc., New York (1987). T.A. Rickard, Man and Metals, Arno, New York (1974). 372 17 • Gold Suggestions for Further Study
