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Platinum Group Metals

GOLD - AURUM 79






GOLD

The most malleable of all metals, gold is primarily used in the jewellery industry. Increasingly important areas are electrical contacts and connectors for  telecommunications and electronics. Since gold never corrodes or tarnishes, it is perfect for conducting electric current, even if it is very weak. At last, it has historically provided investors for a safe haven.


PRECIOUS METAL OF THE GROUP 11

Gold (Au), chemical element, a dense lustrous yellow precious metal of Group 11 (Ib), Period 6, of the periodic table. Gold has several qualities that have made it exceptionally valuable throughout history. It is attractive in colour and brightness, durable to the point of virtual indestructibility, highly malleable, and usually found in nature in a comparatively pure form. The history of gold is unequaled by that of any other metal because of its perceived value from earliest times.


PROPERTIES, OCCURENCES & USE OF GOLD

Gold is one of the densest of all metals. It is a good conductor of heat and electricity. It is also soft and the most malleable and ductile of the elements; an ounce (28 grams) can be beaten out to 187 square feet (about 17 square metres) in extremely thin sheets called gold leaf.


ONE OF THE FIRST METALS

Because gold is visually pleasing and workable and does not tarnish or corrode, it was one of the first metals to attract human attention. Examples of elaborate gold workmanship, many in nearly perfect condition, survive from ancient Egyptian, Minoan, Assyrian, and Etruscan artisans, and gold continues to be a highly favoured material out of which to craft jewelry and other decorative objects.


THE ONE MATERIAL

Because of its unique qualities, gold has been the one material that is universally accepted in exchange for goods and services. In the form of coins or bullion, gold has occasionally played a major role as a high-denomination currency, although silver was generally the standard medium of payments in the world’s trading systems.


PAPER-CURRENCY SYSTEMS

Gold began to serve as backing for paper-currency systems when they became widespread in the 19th century, and from the 1870s until World War I the gold standard was the basis for the world’s currencies. Although gold’s official role in the international monetary system had come to an end by the 1970s, the metal remains a highly regarded reserve asset, and approximately 45 percent of all the world’s gold is held by governments and central banks for this purpose. Gold is still accepted by all nations as a medium of international payment.


GOLD 197

Gold is widespread in low concentrations in all igneous rocks. Its abundance in Earth’s crust is estimated at about 0.005 part per million. It occurs mostly in the native state, remaining chemically uncombined except with tellurium, selenium, and bismuth. The element’s only naturally occurring isotope is gold-197. 


HYDROTHERMAL VEINS

Gold often occurs in association with copper and lead deposits, and, though the quantity present is often extremely small, it is readily recovered as a by-product in the refining of those base metals. Large masses of gold-bearing rock rich enough to be called ores are unusual. Two types of deposits containing significant amounts of gold are known: hydrothermal veins, where it is associated with quartz and pyrite (fool’s gold); and placer deposits, both consolidated and unconsolidated, that are derived from the weathering of gold-bearing rocks.


GOLD FROM GREAT DEPHS

Veins enriched in gold form when the gold was carried up from great depths with other minerals, in an aqueous solution, and later precipitated. The gold in rocks usually occurs as invisible disseminated grains, more rarely as flakes large enough to be seen, and even more rarely as masses or veinlets. Crystals about 2.5 cm (1 inch) or more across have been found in California. Masses, some on the order of 90 kg (200 pounds), have been reported from Australia.


THE PRINCIAL SOURCES

Alluvial deposits of gold found in or along streams were the principal sources of the metal for ancient Egypt and Mesopotamia. Other deposits were found in Lydia (now in Turkey) and the lands of the Aegean and in Persia (Iran), India, China, and other lands. During the Middle Ages the chief sources of gold in Europe were the mines of Saxony and Austria. The era of gold production that followed the Spanish discovery of the Americas in the 1490s was probably the greatest the world had witnessed to that time. 


THE ECONOMICS STRUCTURE OF EUROPE

The exploitation of mines by slave labour and the looting of palaces, temples, and graves in Central and South America resulted in an unprecedented influx of gold that literally unbalanced the economic structure of Europe. From Christopher Columbus’s discovery of the New World in 1492 to 1600, more than 225,000 kg (8,000,000 ounces) of gold, or 35 percent of world production, came from South America. The New World’s mines— especially those in Colombia — continued into the 17th and 18th centuries to account for 61 and 80 percent, respectively, of world production; 1,350,000 kg (48,000,000 ounces) were mined in the 18th century.


THE WORLD'S LEADING PRODUCER

Russia became the world’s leading producer of gold in 1823, and for 14 years it contributed the bulk of the world supply. During the second era of expanding production (1850–75), more gold was produced in the world than in all the years since 1492, primarily because of discoveries in California and Australia. A third marked increase (1890–1915) stemmed from discoveries in Alaska, Yukon Territory (now Yukon), and South Africa. 


THE WORLD'S SUPPLY OF GOLD 

A major factor in the increase of the world’s supply of gold was the introduction in 1890 of the cyanide process for the recovery of gold from low-grade ores and ores containing minute, particle-sized gold. Gold production continued to rise throughout the 20th century, partly because of the improvement in recovery methods and partly because of the continual growth and expansion of South Africa’s gold-mining operations.


THE 20THE CENTURY 

In the late 20th century, four countries—South Africa, Russia, the United States, and Australia—accounted for two-thirds of the gold produced annually throughout the world. In the early 21st century, China was the world leader in gold production. During this period, Australia, the United States, Russia, Canada, and South Africa also continued to supply large amounts of the precious metal.


PURE GOLD

Because pure gold is too soft to resist prolonged handling, it is usually alloyed with other metals to increase its hardness for use in jewelry, goldware, or coinage. Most gold used in jewelry is alloyed with silver, copper, and a little zinc to produce various shades of yellow gold or with nickel, copper, and zinc to produce white gold. 


THE COLOUR OF GOLD

The colour of these gold alloys goes from yellow to white as the proportion of silver in them increases; more than 70 percent silver results in alloys that are white. Alloys of gold with silver or copper are used to make gold coins and goldware, and alloys with platinum or palladium are also used in jewelry. The content of gold alloys is expressed in 24ths, called karats; a 12-karat gold alloy is 50 percent gold, and 24-karat gold is pure.


HIGH ELECTRICAL CONDUCTIVITY

Because of its high electrical conductivity (71 percent that of copper) and inertness, the largest industrial use of gold is in the electric and electronics industry for plating contacts, terminals, printed circuits, and semiconductor systems. 


EMPLOYED ON SATELLITES

Thin films of gold that reflect up to 98 percent of incident infrared radiation have been employed on satellites to control temperature and on space-suit visors to afford protection. Used in a similar way on the windows of large office buildings, gold reduces the air-conditioning requirement and adds to the beauty. Gold has also long been used for fillings and other repairs to teeth.


AQUA REGIA

Gold is one of the noblest—that is, least chemically reactive—of the transition elements. It is not attacked by oxygen or sulfur, although it will react readily with halogens or with solutions containing or generating chlorine, such as aqua regia. It also will dissolve in cyanide solutions in the presence of air or hydrogen peroxide. Dissolution in cyanide solutions is attributable to the formation of the very stable dicyanoaurate ion.


THE SIMILARITY

Like copper, gold has a single s electron outside a completed d shell, but, in spite of the similarity in electronic structures and ionization energies, there are few close resemblances between gold on the one hand and copper on the other.


MIDAS, KING OF THE PHYRYGIANS

Gold (Au, from the Latin word aurum) is the oldest metal known to mankind. It has always exercised an enormous power of attraction. In mythology, reference is made to the quest for the Golden Fleece by Jason and the Argonauts around 1200 BC. In Asia Minor, Midas, King of the Phrygians, was endowed by Dionysos with the power of turning everything that he touched into gold.



CROESUS, KING OF LYDIA

Croesus, King of Lydia, owed his legendary wealth to gold mines. He struck the first gold and silver coins around 550 BC. In early times gold metallurgy was based on gravimetric separation of the metal by virtue of its high density (19.3).

 

CALIFORNIAN GOLD RUSH

Extraction by the amalgamation technique was introduced around 500 BC. In the 16th century the Spaniards invaded South America and discovered huge gold veins. Later, Kruger discovered the gold deposits of South Africa in 1834. Perhaps the most famous gold discovery, the Californian Gold Rush, followed shortly after.

 

 
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