as a gold silver alloy).
This means that 58.3% of this alloy is gold (14/24 x 100).  Further gold rushes occurred in California, Colorado, the Black Hills, Otago in New Zealand, a number of locations across Australia, Witwatersrand in South Africa, and the Klondike in Canada.
 Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts.
These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors.. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 femtomol/L or 10–30 parts per quadrillion (about 10–30 g/km3).
Analysis of the extremely rare collection of 425 gold coins indicated that they were from the late 9th century.
On 24 August 2020, Israeli archaeologists discovered a trove of early Islamic gold coins near the central city of Yavne.
In Roman metallurgy, new methods for extracting gold on a large scale were developed by introducing hydraulic mining methods, especially in Hispania from 25 BC onwards and in Dacia from 106 AD onwards. When sulfide-bearing minerals in these ore dumps are exposed to air and water, the sulfide transforms into sulfuric acid which in turn dissolves these heavy metals facilitating their passage into surface water and ground water. Both gold(I) and gold(III) compounds have been investigated as possible anti-cancer drugs.
Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test.
, Because the Earth was molten when it was formed, almost all of the gold present in the early Earth probably sank into the planetary core. Typical ore grades in open-pit mines are 1–5 ppm; ore grades in underground or hard rock mines are usually at least 3 ppm. Within that range, only 178Au, 180Au, 181Au, 182Au, and 188Au do not have isomers. , Gold is thought to have been produced in supernova nucleosynthesis, and from the collision of neutron stars, and to have been present in the dust from which the Solar System formed.
, After initial production, gold is often subsequently refined industrially by the Wohlwill process which is based on electrolysis or by the Miller process, that is chlorination in the melt. As of September 2017[update], gold is valued at around $42 per gram ($1,300 per troy ounce).
It does not react with aqueous, solid, or molten sodium or potassium hydroxide. Some free halogens react with gold.  Great human achievements are frequently rewarded with gold, in the form of gold medals, gold trophies and other decorations. The world's oceans contain gold.
The water inside the void instantly vaporizes, flashing to steam and forcing silica, which forms the mineral quartz, and gold out of the fluids and onto nearby surfaces.. , Historically gold coinage was widely used as currency; when paper money was introduced, it typically was a receipt redeemable for gold coin or bullion. The gold-bearing Witwatersrand rocks were laid down between 700 and 950 million years before the Vredefort impact. , On 17 March 1968, economic circumstances caused the collapse of the gold pool, and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. However, such high-energy neutrons can be produced only by particle accelerators.
Gold sometimes occurs combined with tellurium as the minerals calaverite, krennerite, nagyagite, petzite and sylvanite (see telluride minerals), and as the rare bismuthide maldonite (Au2Bi) and antimonide aurostibite (AuSb2).
A number of people have claimed to be able to economically recover gold from sea water, but they were either mistaken or acted in an intentional deception. Exploitation of gold in the south-east corner of the Black Sea is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC.  Gold artifacts in the Balkans appear from the 4th millennium BC, such as those found in the Varna Necropolis near Lake Varna in Bulgaria, thought by one source (La Niece 2009) to be the earliest "well-dated" find of gold artifacts.  The legend of the golden fleece dating from eighth century BCE may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. Approximately 30 percent of the global gold supply is recycled and not mined as of 2020.
"Furthermore the second member of Delegation XVIII is carrying four small but evidently heavy jars on a yoke, probably containing the gold dust which was the tribute paid by the Indians." Using fast neutrons, the mercury isotope 198Hg, which composes 9.97% of natural mercury, can be converted by splitting off a neutron and becoming 197Hg, which then disintegrates to stable gold. Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah), the story of the golden calf, and many parts of the temple including the Menorah and the golden altar. An ancient Talmudic text circa 100 AD describes Rachel, wife of Rabbi Akiva, receiving a "Jerusalem of Gold" (diadem).
Gold also produces a high output of secondary electrons when irradiated by an electron beam, and these low-energy electrons are the most commonly used signal source used in the scanning electron microscope. Gold is a soft metal that is not durable unless mixed with other alloys.
 Similar effects impart a golden hue to metallic caesium. Post-war, the victorious countries, most notably Britain, gradually restored gold-convertibility, but international flows of gold via bills of exchange remained embargoed; international shipments were made exclusively for bilateral trades or to pay war reparations. Like other precious metals, gold is measured by troy weight and by grams. Gold as a sign of wealth and prestige was ridiculed by Thomas More in his treatise Utopia.
As of 2017[update], China was the world's leading gold-mining country, followed in order by Australia, Russia, the United States, Canada, and Peru. Other modern coins include the Austrian Vienna Philharmonic bullion coin and the Chinese Gold Panda. After World War II gold was replaced by a system of nominally convertible currencies related by fixed exchange rates following the Bretton Woods system. This improves definition of the position and topography of the specimen surface and increases the spatial resolution of the image.  This, however, has not been enforced consistently throughout history, e.g.
 Several gold complexes have been applied to treat rheumatoid arthritis, the most frequently used being aurothiomalate, aurothioglucose, and auranofin. In the past, a gold standard was often implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after 1971. [clarification needed]. Au(III) (referred to as the auric) is a common oxidation state, and is illustrated by gold(III) chloride, Au2Cl6.
 Gold is strongly attacked by fluorine at dull-red heat to form gold(III) fluoride. 14 karat gold watch chain with small diamond in slide lg 48 chrysoberyll kette 48 karat chrysoberylle aus inn edelsteinketten roberto coin princess 48 carat total weight diamond bangle in 18 14kt gold 48 ct morganite 10 ctw diamond byp ring 18 karat gold bananabell kristalltropfen synthetischer opal 2010 canada maple leaf 48 gram 14 karat gold proof set. By 1961, it was becoming hard to maintain this price, and a pool of US and European banks agreed to manipulate the market to prevent further currency devaluation against increased gold demand.
, Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties.  Nickel is toxic, and its release from nickel white gold is controlled by legislation in Europe. Unlike India where gold is mainly used for jewelry, China uses gold for manufacturing and retail.
If the work is to be of hallmarking quality, the gold solder alloy must match the fineness (purity) of the work, and alloy formulas are manufactured to color-match yellow and white gold. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. , Colloidal gold, used by electron-microscopists, is red if the particles are small; larger particles of colloidal gold are blue. Although the prices of some platinum group metals can be much higher, gold has long been considered the most desirable of precious metals, and its value has been used as the standard for many currencies.
Recent research suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits. Some gold compounds exhibit aurophilic bonding, which describes the tendency of gold ions to interact at distances that are too long to be a conventional Au–Au bond but shorter than van der Waals bonding. A Greek burial crown made of gold was found in a grave circa 370 BC.
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