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They say that Gold is King and Silver is Queeen and the last few years, this has certainly proven to be true. Look at these Gold Prices:

It is amazing but 50% of all gold ever mined has been produced since 1960. Demand for Gold continues to rise despite the price and most people predict a bright future for Gold. As of 2009 the top 8 Gold Producing countries were:

1. China: 313.98 metric tons
2. Australia: 227.00 metric tons
3. United States: 216.00 metric tons
4. South Africa: 204.92 metric tons
5. Russia: 205.00 metric tons
6. Peru: 180metric tons (estimate)
7. Indonesia: 90.00 metric tons
8. Canada: 95.00 metric tons (estimate)

With Prices Like these more gold is being discovered produced all the time.

(Au), chemical element, a dense, lustrous, yellow precious metal of Group Ib, Period 6, of the periodic table. Gold has several qualities that have made it exceptionally valuable throughout history. It is attractive in color 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 value in the minds of men from earliest times.

Gold is one of the heaviest of all metals. It is a good conductor of heat and electricity. It is also soft and the most malleable and ductile of metals; an ounce (28 g) can be beaten out to 187 square feet (about 17 square m) in extremely thin sheets called gold leaf. Note that mining industry standards refer to troy ounces (1 troy ounce = 31.12035g).

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 has continued to be a highly favored material out of which to craft jewelry and other decorative objects.

Owing to 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 has generally been the standard medium of payments in the world's trading 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 is widespread in low concentrations in all igneous rocks. Its abundance in the Earth's crust is estimated at about 0.005 parts per million. It occurs mostly in the native state, remaining chemically uncombined except with tellurium, selenium, and possibly bismuth. The element's only naturally occurring isotope is gold-197. 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 byproduct 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.

The origin of enriched veins is not fully known, but it is believed that the gold was carried up from great depths with other minerals, at least in partial solid 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.

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 (now 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 exploitation of mines by slave labor and the looting of Indian 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' 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.

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 color 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.

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. 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.

The characteristic oxidation states of gold are +1 (aurous compounds) and +3 (auric compounds). Gold is more easily displaced from solution by reduction than any other metal; even platinum will reduce Au3+ ions to metallic gold.

Among the relatively few gold compounds of practical importance are gold(I) chloride, AuCl; gold(III) chloride, or gold trichloride, AuCl3; and chlorauric acid, HAuCl4. All three are involved in the electrolytic refining of gold. Potassium cyanoaurate, K[Au(CN)2], is the basis for most gold-plating baths (the solution employed when gold is plated). The soluble salt sodium aurichloride, NaAuCl42H2O, is used in the treatment of rheumatoid arthritis. Several organic compounds of gold have industrial applications. For example, gold mercaptides, which are obtained from sulfurized terpenes, are dissolved in certain organic solutions and used for decorating china and glass articles.

atomic number 79 atomic weight 196.967 melting point 1,063 C (1,945 F) boiling point 2,966 C (5,371 F) specific gravity 19.3 (20 C) valence 1, 3 electronic config. 2-8-18-32-18-1

Refining

Gold extracted by amalgamation or cyanidation contains a variety of impurities, including zinc, copper, silver, and iron. Two methods are commonly employed for purification: the Miller process and the Wohlwill process. The Miller process is based on the fact that virtually all the impurities present in gold combine with gaseous chlorine more readily than gold does at temperatures equal to or greater than the melting point of gold. The impure gold is therefore melted and gaseous chlorine is blown into the resulting liquid. The impurities form chloride compounds that separate into a layer on the surface of the molten gold.

The Miller process is rapid and simple, but it produces gold of only about 99.5 percent purity. The Wohlwill process increases purity to about 99.99 percent by electrolysis. In this process, a casting of impure gold is lowered into an electrolyte solution of hydrochloric acid and gold chloride. Under the influence of an electric current, the casting functions as a positively charged electrode, or anode. The anode dissolves, and the impurities either pass into solution or report to the bottom of the electrorefining tank as an insoluble slime. The gold migrates under the influence of the electric field to a negatively charged electrode called the cathode, where it is restored to a highly pure metallic state.

Although the Wohlwill process produces gold of high purity, it requires the producer to keep on hand a substantial inventory of gold (mainly for the electrolyte), and this is very costly. Processes based on direct chemical purification and recovery from solution as elemental gold can greatly speed gold processing and virtually eliminate expensive in-process inventories.

Assaying

Fire assay is considered the most reliable method for accurately determining the content of gold, silver, and platinum-group metals (except osmium and ruthenium) in ores or concentrates. This process involves melting a gold-bearing sample in a clay crucible with a mixture of fluxes (such as silica and borax), lead oxide (called litharge), and a reducing agent (frequently flour). The fluxes lower the melting point of the oxidic materials, allowing them to fuse, and the molten litharge is reduced by the flour to extremely fine drops of lead dispersed throughout the charge. The drops of lead dissolve the gold, silver, and platinum-group metals, then coalesce and gradually descend through the sample to form a metallic layer at the bottom of the crucible. After cooling, the lead "button" is separated from the slag layer and heated under oxidizing conditions to oxidize and eliminate the lead. The shiny metallic bead that is left contains the precious metals. The bead is boiled in nitric acid to dissolve the silver (a process called parting), and the gold residue is weighed. If platinum metals are present, they will alter the appearance of the bead, and their concentration can sometimes be determined by use of an arc spectrograph.

In the jewelry industry, gold content is specified by karat. Pure gold is designated 24 karats; therefore, each karat is equal to 4.167 percent gold content, so that, for example, 18 karats equals 18 4.167, or 75 percent gold. "Fineness" refers to parts per thousand of gold in an alloy; e.g., three-nines fine would correspond to gold of 99.9 percent purity.


 

 

 

 

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