Through the ages men and women have cherished gold, and many have had a compelling desire to amass great quantities of it. Gold was one of the first metals to be mined because it commonly occurs in its native form, that is, not combined with other elements, because it is beautiful and imperishable and because exquisite objects can be made from it.
Until recent times, gold was considered essentially a monetary metal, and most of the bullion produced each year went into the vaults of government treasuries or central banks. Nations of the world today continue to use gold as a medium of exchange in monetary transactions, but because it is the most malleable and ductile of all metals, has no oxides, is the only metal not affected by the oxygen in the atmosphere and because of its superior electrical conductivity and resistance to corrosion and other desirable combinations of physical and chemical properties; today gold has become an essential industrial metal. Gold is used in allied wares, electrical-electronic applications, dentistry, the aircraft-aerospace industry, the arts and medical and chemical fields; however, jewellery fabrication is the crucial cornerstone of the gold market, annually consuming all gold that is newly mined. In the industrial countries gold jewellery is primarily a fashion item, but in the Middle East and much of Asia gold jewellery is seen equally as an investment.
After gold was deregulated in 1971, the price increased markedly, briefly reaching more than US$800 per troy ounce. Since 1980, the price has remained in the range of US$252 to US$460 per troy ounce.
Of the 112 elements that make up the earth's crust, the eight most common elements account for more than 98%; in order of abundance gold ranks 80th. Gold is relatively scarce in the earth, but it occurs in many different kinds of rock and in many different geological environments. Though scarce, gold is concentrated by geological processes to form commercial deposits of two principal types: primary (lode and disseminated) deposits and secondary (placer) deposits.
Primary deposits are the targets of prospectors seeking metals at their source in '"hardrock". Geologists have proposed various hypotheses to explain how primary deposits are formed but most generally agree that primary deposits are formed when water under intense heat and pressure containing a solution of dissolved metals is carried upward to the surface of the earth through fractures in the earth's crust precipitating ore materials as pressures and temperatures decrease thereby forming deposits.
In lode deposits the metals have been concentrated in rock in the form of high grade veins. In disseminated deposits the metals have been widely distributed throughout a large volume of rock. Improvements during the last several decades in exploration techniques, extraction methods and mineral processing engineering have made it possible to work lower grade deposits at a profit, as a result, low grade disseminated deposits have become increasingly important.
Placer gold deposits represent concentrations of gold weathered and eroded from primary deposits. Gold is extremely resistant to weathering and when freed from enclosing rocks, is carried downstream as metallic particles consisting of dust, flakes, grains or nuggets. Prospectors look for concentrations of metal particles, that is, placer deposits, where coarse sands and gravel have accumulated.
World gold production is dominated by South Africa, the United States, Australia, Canada and Indonesia. These nations produce approximately 55% of annual global output. Total historical world production is thought to be around 3.4 billion troy ounces, of which about three-quarters has been produced since the colonisation of the Americas by Europeans and two-thirds produced in the last 50 years. Of this total, about 64% is privately held as bullion, coin and jewellery, about 21% lies in the vaults of central banks and other institutions and about 15% is thought to have been lost or otherwise unrecoverable or unaccounted for. About 45% of the world's historical gold production has been from the Witwatersrand district in South Africa.