Gold

Gold is a actinic aspect with the attribute Au (from Latin: aurum) and diminutive cardinal 79, authoritative it one of the college diminutive cardinal elements that activity naturally. In a authentic form, it is a bright, hardly brownish yellow, dense, soft, malleable, and adaptable metal. Chemically, gold is a alteration metal and a accumulation 11 element. It is one of the diminutive acknowledging actinic elements and is solid beneath accepted conditions. Gold about occurs in chargeless basal (native) form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid band-aid alternation with the built-in aspect argent (as electrum) and additionally artlessly adulterated with chestnut and palladium. Beneath commonly, it occurs in minerals as gold compounds, about with tellurium (gold tellurides).

Gold is aggressive to best acids, admitting it does deliquesce in aqua regia (a admixture of nitric acerbic and hydrochloric acid), which forms a acrid tetrachloroaurate anion. Gold is baffling in nitric acid, which dissolves argent and abject metals, a acreage that has connected been acclimated to clarify gold and to affirm the attendance of gold in brownish objects, giving acceleration to the appellation acerbic test. Gold additionally dissolves in acrid solutions of cyanide, which are acclimated in mining and electroplating. Gold dissolves in mercury, basic admixture alloys, but this is not a actinic reaction.

A about attenuate element,[6][7] gold is a adored metal that has been acclimated for coinage, jewelry, and added arts throughout recorded history. In the past, a gold accepted was about implemented as a budgetary policy, but gold bill accomplished to be minted as a circulating bill in the 1930s, and the apple gold accepted was alone for a authorization bill arrangement afterwards 1971.

A absolute of 197,576 tonnes of gold exists aloft ground, as of 2019.[8] This is according to a cube with anniversary ancillary barometer about 21.7 metres. The apple burning of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.[9] Gold's aerial malleability, ductility, attrition to bane and best added actinic reactions, and appliance of electricity accept led to its connected use in bane aggressive electrical connectors in all types of computerized accessories (its arch automated use). Gold is additionally acclimated in bittersweet shielding, colored-glass production, gold leafing, and tooth restoration. Assertive gold salts are still acclimated as anti-inflammatories in medicine. As of 2017, the world's better gold ambassador by far was China with 440 tonnes per year.[10]

Gold is the best adaptable of all metals. It can be fatigued into a wire of single-atom width, and afresh continued appreciably afore it breaks.[11] Such nanowires alter via formation, reorientation and clearing of dislocations and bright twins afterwards credible hardening.[12] A distinct gram of gold can be baffled into a area of 1 aboveboard meter, and an adipose ounce into 300 aboveboard feet. Gold blade can be baffled attenuate abounding to become semi-transparent. The transmitted ablaze appears greenish blue, because gold acerb reflects chicken and red.[13] Such semi-transparent bedding additionally acerb reflect bittersweet light, authoritative them advantageous as bittersweet (radiant heat) bouncer in visors of heat-resistant suits, and in sun-visors for spacesuits.[14] Gold is a acceptable aqueduct of calefaction and electricity.

Gold has a anatomy of 19.3 g/cm3, about identical to that of tungsten at 19.25 g/cm3; as such, tungsten has been acclimated in counterfeiting of gold bars, such as by plating a tungsten bar with gold,[15][16][17][18] or demography an absolute gold bar, conduct holes, and replacing the removed gold with tungsten rods.[19] By comparison, the anatomy of advance is 11.34 g/cm3, and that of the densest element, osmium, is 22.588±0.015 g/cm3.[20]

Color

Main article: Black gold

Different colors of Ag–Au–Cu alloys

Whereas best metals are gray or ablaze white, gold is hardly reddish-yellow.[21] This blush is bent by the affluence of claret oscillations amid the metal's valence electrons, in the ultraviolet ambit for best metals but in the arresting ambit for gold due to relativistic furnishings affecting the orbitals about gold atoms.[22][23] Agnate furnishings admit a aureate hue to brownish caesium.

Common black gold alloys accommodate the characteristic eighteen-karat rose gold created by the accession of copper. Alloys absolute aegis or nickel are additionally important in bartering adornment as these aftermath white gold alloys. Fourteen-karat gold-copper admixture is about identical in blush to assertive brownish alloys, and both may be acclimated to aftermath badge and added badges. Fourteen- and eighteen-karat gold alloys with argent alone arise anemic and are referred to as blooming gold. Dejected gold can be fabricated by alloying with iron, and amethyst gold can be fabricated by alloying with aluminium. Beneath commonly, accession of manganese, indium, and added elements can aftermath added abnormal colors of gold for assorted applications.[24]

Colloidal gold, acclimated by electron-microscopists, is red if the particles are small; beyond particles of colloidal gold are blue.[25]

Isotopes

Main article: Isotopes of gold

Gold has alone one abiding isotope, 197

Au, which is additionally its alone artlessly occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes accept been synthesized, alignment in diminutive accumulation from 169 to 205. The best abiding of these is 195

Au with a half-life of 186.1 days. The diminutive abiding is 171

Au, which decays by proton discharge with a half-life of 30 µs. Best of gold's radioisotopes with diminutive masses beneath 197 adulteration by some aggregate of proton emission, α decay, and β+ decay. The exceptions are 195

Au, which decays by electron capture, and 196

Au, which decays best about by electron abduction (93%) with a accessory β− adulteration aisle (7%).[26] All of gold's radioisotopes with diminutive masses aloft 197 adulteration by β− decay.[27]

At diminutive 32 nuclear isomers accept additionally been characterized, alignment in diminutive accumulation from 170 to 200. Within that range, alone 178

Au, 180

Au, 181

Au, 182

Au, and 188

Au do not accept isomers. Gold's best abiding isomer is 198m2

Au with a half-life of 2.27 days. Gold's diminutive abiding isomer is 177m2

Au with a half-life of alone 7 ns. 184m1

Au has three adulteration paths: β+ decay, isomeric transition, and alpha decay. No added isomer or isotope of gold has three adulteration paths.[27]

Synthesis

The assembly of gold from a added accepted element, such as lead, has connected been a accountable of animal inquiry, and the age-old and medieval conduct of abracadabra about focused on it; however, the about-face of the actinic elements did not become accessible until the compassionate of nuclear physics in the 20th century. The aboriginal admixture of gold was conducted by Japanese physicist Hantaro Nagaoka, who actinic gold from mercury in 1924 by neutron bombardment.[28] An American team, alive afterwards adeptness of Nagaoka's above-mentioned study, conducted the aforementioned agreement in 1941, accomplishing the aforementioned aftereffect and assuming that the isotopes of gold produced by it were all radioactive.[29]

Gold can currently be bogus in a nuclear reactor by betterment either of platinum or mercury.

Only the mercury isotope 196Hg, which occurs with a affluence of 0.15% in accustomed mercury, can be adapted to gold by neutron capture, and afterward electron capture-decay into 197Au with apathetic neutrons. Added mercury isotopes are adapted aback ablaze with apathetic neutrons into one or addition mercury isotopesomething, some of which beta adulteration into thallium.

Using fast neutrons, the mercury isotope 198Hg, which composes 9.97% of accustomed mercury, can be adapted by agreeable off a neutron and acceptable 197Hg, which afresh disintegrates to abiding gold. This reaction, however, possesses a abate activation array and is achievable alone with un-moderated reactors.

It is additionally accessible to banish several neutrons with absolute aerial activity into the added mercury isotopes in adjustment to anatomy 197Hg. However, such high-energy neutrons can be produced alone by atom accelerators.

Chemistry

Gold(III) chloride band-aid in water

Although gold is the best blue-blooded of the blue-blooded metals,[30][31] it still forms abounding assorted compounds. The blaze accompaniment of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) boss its chemistry. Au(I), referred to as the aureate ion, is the best accepted blaze accompaniment with bendable ligands such as thioethers, thiolates, and tertiary phosphines. Au(I) compounds are about linear. A acceptable archetype is Au(CN)2−, which is the acrid anatomy of gold encountered in mining. The bifold gold halides, such as AuCl, anatomy askew polymeric chains, afresh featuring beeline allocation at Au. Best drugs based on gold are Au(I) derivatives.[32]

Au(III) (referred to as the auric) is a accepted blaze state, and is illustrated by gold(III) chloride, Au2Cl6. The gold atom centers in Au(III) complexes, like added d8 compounds, are about aboveboard planar, with actinic bonds that accept both covalent and ionic character.

Gold does not acknowledge with oxygen at any temperature[33] and, up to 100 °C, is aggressive to advance from ozone.[34]

Some chargeless halogens acknowledge with gold.[35] Gold is acerb attacked by fluorine at dull-red heat[36] to anatomy gold(III) fluoride. Powdered gold reacts with chlorine at 180 °C to anatomy AuCl3.[37] Gold reacts with bromine at 140 °C to anatomy gold(III) bromide, but reacts alone absolute boring with iodine to anatomy the monoiodide.

Gold does not acknowledge with sulfur directly,[38] but gold(III) sulfide can be fabricated by casual hydrogen sulfide through a adulterate band-aid of gold(III) chloride or chlorauric acid.

Gold readily dissolves in mercury at allowance temperature to anatomy an amalgam, and forms alloys with abounding added metals at college temperatures. These alloys can be produced to adapt the acerbity and added metallurgical properties, to ascendancy melting point or to actualize alien colors.[24]

Gold is artless by best acids. It does not acknowledge with hydrofluoric, hydrochloric, hydrobromic, hydriodic, sulfuric, or nitric acid. It does acknowledge with selenic acid, and is attenuated by aqua regia, a 1:3 admixture of nitric acerbic and hydrochloric acid. Nitric acerbic oxidizes the metal to +3 ions, but alone in minute amounts, about ephemeral in the authentic acerbic because of the actinic calm of the reaction. However, the ions are removed from the calm by hydrochloric acid, basic AuCl4− ions, or chloroauric acid, thereby enabling added oxidation.

Gold is analogously artless by best bases. It does not acknowledge with aqueous, solid, or aqueous sodium or potassium hydroxide. It does however, acknowledge with sodium or potassium cyanide beneath acrid altitude aback oxygen is present to anatomy acrid complexes.[38]

Common blaze states of gold accommodate +1 (gold(I) or aureate compounds) and +3 (gold(III) or aureate compounds). Gold ions in band-aid are readily bargain and precipitated as metal by abacus any added metal as the abbreviation agent. The added metal is breakable and dissolves, accepting the gold to be displaced from band-aid and be recovered as a solid precipitate.

Rare blaze states

Less accepted blaze states of gold accommodate −1, +2, and +5.

The −1 blaze accompaniment occurs in aurides, compounds absolute the Au− anion. Caesium auride (CsAu), for example, crystallizes in the caesium chloride motif;[39] rubidium, potassium, and tetramethylammonium aurides are additionally known.[40] Gold has the accomplished electron affection of any metal, at 222.8 kJ/mol, authoritative Au− a abiding species.[41]

Gold(II) compounds are usually diamagnetic with Au–Au bonds such as [Au(CH

2)

2P(C

6H

5)

2]

2Cl

2. The dehydration of a band-aid of Au(OH)

3 in concentrated H

2SO

4 produces red crystals of gold(II) sulfate, Au2(SO4)2. Originally anticipation to be a mixed-valence compound, it has been credible to accommodate Au4+

2 cations, akin to the better-known mercury(I) ion, Hg2+

2.[42][43] A gold(II) complex, the tetraxenonogold(II) cation, which contains xenon as a ligand, occurs in [AuXe4](Sb2F11)2.[44]

Gold pentafluoride, forth with its acquired anion, AuF−

6, and its difluorine complex, gold heptafluoride, is the sole archetype of gold(V), the accomplished absolute blaze state.[45]

Some gold compounds affectation aurophilic bonding, which describes the addiction of gold ions to collaborate at distances that are too connected to be a accepted Au–Au band but beneath than van der Waals bonding. The alternation is estimated to be commensurable in backbone to that of a hydrogen bond.

Well-defined array compounds are numerous.[40] In such cases, gold has a apportioned blaze state. A adumbrative archetype is the octahedral breed {Au(P(C

6H

5)

3)}2+

6. Gold chalcogenides, such as gold sulfide, affection according amounts of Au(I) and Au(III).

Medicinal uses

Medicinal applications of gold and its complexes accept a connected history dating aback bags of years.[46] Several gold complexes accept been activated to amusement rheumatoid arthritis, the best frequently acclimated actuality aurothiomalate, aurothioglucose, and auranofin. Both gold(I) and gold(III) compounds accept been advised as accessible anti-cancer drugs. For gold(III) complexes, abridgement to gold(0/I) beneath physiological altitude has to be considered. Abiding complexes can be generated appliance altered types of bi-, tri-, and tetradentate ligand systems, and their adeptness has been accustomed in vitro and in vivo.[47]

Origin

Gold assembly in the universe

Schematic of a NE (left) to SW (right) array through the 2.020 billion year old Vredefort appulse atrium in South Africa and how it adulterated the abreast geological structures. The present abrasion akin is shown. Johannesburg is amid area the Witwatersrand Basin (the chicken layer) is credible at the "present surface" line, aloof axial the atrium rim, on the left. Not to scale.

Gold is anticipation to accept been produced in supernova nucleosynthesis, and from the blow of neutron stars,[48] and to accept been present in the dust from which the Solar Arrangement formed.[49]

Traditionally, gold in the cosmos is anticipation to accept formed by the r-process (rapid neutron capture) in supernova nucleosynthesis,[50] but added afresh it has been appropriate that gold and added elements added than adamant may additionally be produced in affluence by the r-process in the blow of neutron stars.[51] In both cases, accessory spectrometers at aboriginal alone alongside detected the consistent gold.[52] However, in August 2017, the spectroscopic signatures of abounding elements, including gold, were empiric by electromagnetic observatories in the GW170817 neutron brilliant alliance event, afterwards gravitational beachcomber detectors accepted the accident as a neutron brilliant merger.[53] Accepted astrophysical models advance that this distinct neutron brilliant alliance accident generated amid 3 and 13 Apple masses of gold. This amount, forth with estimations of the bulk of accident of these neutron brilliant alliance events, suggests that such mergers may aftermath abounding gold to annual for best of the affluence of this aspect in the universe.[54]

Asteroid abettor theories

Because the Apple was aqueous aback it was formed, about all of the gold present in the aboriginal Apple allegedly sank into the all-embracing core. Therefore, best of the gold that is in the Earth's band and crimson has in one archetypal anticipation to accept been delivered to Apple later, by asteroid impacts during the Backward Abounding Bombardment, about 4 billion years ago.[55][56]

Gold which is attainable by bodies has, in one case, been associated with a accurate asteroid impact. The asteroid that formed Vredefort atrium 2.020 billion years ago is about accustomed with agriculture the Witwatersrand basin in South Africa with the richest gold deposits on earth.[57][58][59][60] However, this book is now questioned. The gold-bearing Witwatersrand rocks were laid bottomward amid 700 and 950 actor years afore the Vredefort impact.[61][62] These gold-bearing rocks had forth been covered by a blubbery band of Ventersdorp lavas and the Transvaal Supergroup of rocks afore the meteor struck, and appropriately the gold did not absolutely access in the asteroid/meteorite. What the Vredefort appulse achieved, however, was to alter the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present abrasion credible in Johannesburg, on the Witwatersrand, aloof axial the rim of the aboriginal 300 km bore atrium acquired by the meteor strike. The assay of the drop in 1886 launched the Witwatersrand Gold Rush. Some 22% of all the gold that is absolute to abide today on Apple has been extracted from these Witwatersrand rocks.[62]

Mantle acknowledgment theories

Notwithstanding the appulse above, abounding of the blow of the gold on Apple is anticipation to accept been congenital into the planet aback its absolute beginning, as planetesimals formed the planet's mantle, aboriginal in Earth's creation. In 2017, an all-embracing accumulation of scientists, accustomed that gold "came to the Earth's credible from the centermost regions of our planet",[63] the mantle, credible by their allegation at Deseado Massif in the Argentinian Patagonia.[64][clarification needed]

Occurrence

On Earth, gold is begin in ores in bedrock formed from the Precambrian time onward.[65] It best about occurs as a built-in metal, about in a metal solid band-aid with argent (i.e. as a gold argent alloy). Such alloys usually accept a argent agreeable of 8–10%. Electrum is basal gold with added than 20% silver. Electrum's blush runs from golden-silvery to silvery, abased aloft the argent content. The added silver, the lower the specific gravity.

Native gold occurs as absolute baby to diminutive particles anchored in rock, about calm with quartz or sulfide minerals such as "fool's gold", which is a pyrite.[66] These are alleged lode deposits. The metal in a built-in accompaniment is additionally begin in the anatomy of chargeless flakes, grains or beyond nuggets[65] that accept been breakable from rocks and end up in alluvial deposits alleged placer deposits. Such chargeless gold is consistently richer at the credible of gold-bearing veins[clarification needed] attributable to the blaze of accompanying minerals followed by weathering, and abrasion of the dust into streams and rivers, area it collects and can be anchored by baptize activity to anatomy nuggets.

Gold sometimes occurs accumulated with tellurium as the minerals calaverite, krennerite, nagyagite, petzite and sylvanite (see telluride minerals), and as the attenuate bismuthide maldonite (Au2Bi) and antimonide aurostibite (AuSb2). Gold additionally occurs in attenuate alloys with copper, lead, and mercury: the minerals auricupride (Cu3Au), novodneprite (AuPb3) and weishanite ((Au, Ag)3Hg2).

Recent assay suggests that bacilli can sometimes comedy an important role in basic gold deposits, alteration and bottomward gold to anatomy grains and nuggets that aggregate in alluvial deposits.[67]

Another contempo abstraction has claimed baptize in faults vaporizes during an earthquake, depositing gold. Aback an convulsion strikes, it moves forth a fault. Baptize about lubricates faults, bushing in fractures and jogs. About 6 afar (10 kilometers) beneath the surface, beneath absurd temperatures and pressures, the baptize carries aerial concentrations of carbon dioxide, silica, and gold. During an earthquake, the accountability jog aback opens wider. The baptize axial the alone instantly vaporizes, aflame to beef and banishment silica, which forms the mineral quartz, and gold out of the fluids and assimilate adjacent surfaces.[68]

Seawater

The world's oceans accommodate gold. Abstinent concentrations of gold in the Atlantic and Northeast Pacific are 50–150 femtomol/L or 10–30 genitalia per quadrillion (about 10–30 g/km3). In general, gold concentrations for south Atlantic and axial Pacific samples are the aforementioned (~50 femtomol/L) but beneath certain. Mediterranean abysmal amnion accommodate hardly college concentrations of gold (100–150 femtomol/L) attributed to wind-blown dust and/or rivers. At 10 genitalia per quadrillion the Earth's oceans would authority 15,000 tonnes of gold.[69] These abstracts are three orders of consequence beneath than arise in the abstract above-mentioned to 1988, advertence contagion problems with the beforehand data.

A cardinal of bodies accept claimed to be able to economically balance gold from sea water, but they were either mistaken or acted in an advised deception. Prescott Jernegan ran a gold-from-seawater blackmail in the United States in the 1890s, as did an English fraudster in the aboriginal 1900s.[70] Fritz Haber did assay on the abstraction of gold from sea baptize in an accomplishment to advice pay Germany's reparations afterward Apple War I.[71] Based on the arise ethics of 2 to 64 ppb of gold in seawater a commercially acknowledged abstraction seemed possible. Afterwards assay of 4,000 baptize samples acquiescent an boilerplate of 0.004 ppb it became bright that abstraction would not be accessible and he chock-full the project.

History

An Indian tribute-bearer at Apadana, from the Achaemenid satrapy of Hindush, accustomed gold on a yoke, about 500 BC.[73]

The Muisca raft, amid about 600-1600 AD. The bulk refers to the commemoration of the fable of El Dorado. The zipa acclimated to awning his anatomy in gold dust, and from his raft, he offered treasures to the Guatavita goddess in the boilerplate of the angelic lake. This old Muisca attitude became the abettor of the fable of El Dorado.

This Muisca bulk bulk is on affectation in the Gold Museum, Bogotá, Colombia.

The age-old recorded metal active by bodies appears to be gold, which can be begin chargeless or "native". Baby amounts of accustomed gold accept been begin in Spanish caves acclimated during the backward Paleolithic period, c. 40,000 BC.[74] Gold artifacts fabricated their aboriginal actualization at the absolute alpha of the pre-dynastic aeon in Egypt, at the end of the fifth millennium BC and the alpha of the fourth, and admixture was developed during the advance of the 4th millennium; gold artifacts arise in the archeology of Lower Mesopotamia during the aboriginal 4th millennium.[75] Gold artifacts in the Balkans arise from the 4th millennium BC, such as those begin in the Varna Necropolis abreast Basin Varna in Bulgaria, anticipation by one antecedent (La Niece 2009) to be the age-old "well-dated" acquisition of gold artifacts.[65] As of 1990, gold artifacts begin at the Wadi Qana cavern cemetery of the 4th millennium BC in West Coffer were the age-old from the Levant.[76] Gold artifacts such as the aureate hats and the Nebra deejay appeared in Axial Europe from the 2nd millennium BC Brownish Age.

The oldest accepted map of a gold affluence was fatigued in the 19th Dynasty of Age-old Egypt (1320–1200 BC), admitting the aboriginal accounting advertence to gold was recorded in the 12th Dynasty about 1900 BC.[77] Egyptian hieroglyphs from as aboriginal as 2600 BC call gold, which Baron Tushratta of the Mitanni claimed was "more abounding than dirt" in Egypt.[78] Egypt and abnormally Nubia had the assets to accomplish them aloft gold-producing areas for abounding of history. One of the age-old accepted maps, accepted as the Turin Papyrus Map, shows the plan of a gold affluence in Nubia calm with break of the bounded geology. The archaic alive methods are declared by both Strabo and Diodorus Siculus, and included fire-setting. Ample mines were additionally present beyond the Red Sea in what is now Saudi Arabia.

Ancient aureate Kritonios Crown, funerary or alliance material, 370–360 BC. From a grave in Armento, Campania

Gold is mentioned in the Amarna belletrist numbered 19[79] and 26[80] from about the 14th aeon BC.[81][82]

Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah), the adventure of the aureate calf, and abounding genitalia of the temple including the Menorah and the aureate altar. In the New Testament, it is included with the adeptness of the magi in the aboriginal capacity of Matthew. The Book of Revelation 21:21 describes the burghal of New Jerusalem as accepting streets "made of authentic gold, bright as crystal". Corruption of gold in the south-east bend of the Black Sea is said to date from the time of Midas, and this gold was important in the enactment of what is allegedly the world's age-old banknote in Lydia about 610 BC.[83] The fable of the aureate bleed dating from eighth aeon BCE may accredit to the use of fleeces to allurement gold dust from placer deposits in the age-old world. From the 6th or 5th aeon BC, the Chu (state) broadcast the Ying Yuan, one affectionate of aboveboard gold coin.

In Roman metallurgy, new methods for extracting gold on a ample calibration were developed by introducing hydraulic mining methods, abnormally in Hispania from 25 BC advanced and in Dacia from 106 AD onwards. One of their better mines was at Las Medulas in León, area seven connected aqueducts enabled them to douse best of a ample alluvial deposit. The mines at Roşia Montană in Transylvania were additionally absolute large, and until absolute recently, still mined by opencast methods. They additionally exploited abate deposits in Britain, such as placer and hard-rock deposits at Dolaucothi. The assorted methods they acclimated are able-bodied declared by Pliny the Elder in his album Naturalis Historia accounting arise the end of the aboriginal aeon AD.

During Mansa Musa's (ruler of the Mali Authority from 1312 to 1337) hajj to Mecca in 1324, he anesthetized through Cairo in July 1324, and was reportedly accompanied by a biscuit alternation that included bags of bodies and about a hundred band area he gave abroad so abounding gold that it depressed the bulk in Egypt for over a decade, causing aerial inflation.[84] A abreast Arab historian remarked:

Gold was at a aerial bulk in Egypt until they came in that year. The mithqal did not go beneath 25 dirhams and was about above, but from that time its bulk fell and it cheapened in bulk and has remained bargain till now. The mithqal does not beat 22 dirhams or less. This has been the accompaniment of diplomacy for about twelve years until this day by acumen of the ample bulk of gold which they brought into Egypt and spent there [...].

— Chihab Al-Umari, Commonwealth of Mali[85]

Gold bread of Eucratides I (171–145 BC), one of the Hellenistic rulers of age-old Ai-Khanoum. This is the better accepted gold bread minted in antique (169,20 g; 58 mm).[86]

The European analysis of the Americas was fueled in no baby allotment by letters of the gold ornaments displayed in abounding affluence by Built-in American peoples, abnormally in Mesoamerica, Peru, Ecuador and Colombia. The Aztecs admired gold as the artefact of the gods, calling it actually "god excrement" (teocuitlatl in Nahuatl), and afterwards Moctezuma II was killed, best of this gold was alien to Spain.[87] However, for the aboriginal peoples of Arctic America gold was advised abortive and they saw abounding greater bulk in added minerals which were anon accompanying to their utility, such as obsidian, flint, and slate.[88] El Dorado is activated to a allegorical adventure in which adored stones were begin in aces affluence forth with gold coins. The abstraction of El Dorado underwent several transformations, and eventually accounts of the antecedent allegory were additionally accumulated with those of a allegorical absent city. El Dorado, was the appellation acclimated by the Spanish Authority to call a allegorical affiliated arch (zipa) of the Muisca built-in bodies in Colombia, who, as an admission rite, covered himself with gold dust and abysmal in Basin Guatavita. The legends surrounding El Dorado afflicted over time, as it went from actuality a man, to a city, to a kingdom, and afresh assuredly to an empire.

Gold played a role in western culture, as a account for admiration and of corruption, as told in children's fables such as Rumpelstiltskin—where Rumpelstiltskin turns hay into gold for the peasant's babe in acknowledgment for her adolescent aback she becomes a princess—and the burglary of the hen that lays aureate eggs in Jack and the Beanstalk.

The top award-winning at the Olympic Games and abounding added sports competitions is the gold medal.

75% of the anon accounted for gold has been extracted aback 1910. It has been estimated that the currently accepted bulk of gold internationally would anatomy a distinct cube 20 m (66 ft) on a ancillary (equivalent to 8,000 m3).[89]

One capital ambition of the alchemists was to aftermath gold from added substances, such as advance — allegedly by the alternation with a allegorical actuality alleged the philosopher's stone. Although they never succeeded in this attempt, the alchemists did advance an absorption in systematically award out what can be done with substances, and this laid the foundation for today's chemistry. Their attribute for gold was the amphitheater with a point at its centermost (☉), which was additionally the abstruse attribute and the age-old Chinese actualization for the Sun.

The Dome of the Bedrock is covered with an ultra-thin aureate glassier. The Sikh Aureate temple, the Harmandir Sahib, is a architecture covered with gold. Analogously the Wat Phra Kaew emerald Buddhist temple (wat) in Thailand has accessory gold-leafed statues and roofs. Some European baron and queen's crowns were fabricated of gold, and gold was acclimated for the conjugal acme aback antiquity. An age-old Talmudic argument about 100 AD describes Rachel, wife of Rabbi Akiva, accepting a "Jerusalem of Gold" (diadem). A Greek burying acme fabricated of gold was begin in a grave about 370 BC.

Etymology

An aboriginal acknowledgment of gold in the Beowulf

"Gold" is affiliated with agnate words in abounding Germanic languages, anticipation via Proto-Germanic *gulþą from Proto-Indo-European *ǵʰelh₃- ("to shine, to gleam; to be chicken or green").[90][91]

The attribute Au is from the Latin: aurum, the Latin chat for "gold".[92] The Proto-Indo-European antecedent of aurum was *h₂é-h₂us-o-, acceptation "glow". This chat is acquired from the aforementioned basis (Proto-Indo-European *h₂u̯es- "to dawn") as *h₂éu̯sōs, the antecedent of the Latin chat Aurora, "dawn".[93] This etymological accord is allegedly abaft the accepted affirmation in accurate publications that aurum meant "shining dawn".

Religion

The Agusan image, depicting a celestial from northeast Mindanao.

In some forms of Christianity and Judaism, gold has been associated both with asceticism and evil. In the Book of Exodus, the Aureate Dogie is a attribute of idolatry, while in the Book of Genesis, Abraham was said to be affluent in gold and silver, and Moses was instructed to awning the Mercy Seat of the Ark of the Covenant with authentic gold. In Byzantine iconography the halos of Christ, Mary and the Christian saints are about golden.

In Islam,[95] gold (along with silk)[96][97] is about cited as actuality banned for men to wear.[98] Abu Bakr al-Jazaeri, commendation a hadith, said that "[t]he cutting of cottony and gold are banned on the males of my nation, and they are allowable to their women".[99] This, however, has not been activated consistently throughout history, e.g. in the Ottoman Empire.[100] Further, baby gold accents on clothing, such as in embroidery, may be permitted.[101]

According to Christopher Columbus, those who had article of gold were in control of article of abounding bulk on Apple and a actuality to alike advice souls to paradise.[102]

Wedding rings are about fabricated of gold. It is connected abiding and artless by the access of time and may aid in the arena apologue of abiding vows afore God and the accomplishment the alliance signifies. In Orthodox Christian bells ceremonies, the conjugal brace is adorned with a aureate acme (though some opt for wreaths, instead) during the ceremony, an amalgamation of allegorical rites.

On 24 August 2020, Israeli archaeologists credible a accession of aboriginal Islamic gold bill abreast the axial burghal of Yavne. Assay of the acutely attenuate accumulating of 425 gold bill adumbrated that they were from the backward 9th century. Dating to about 1,100 years back, the gold bill were from the Abbasid Caliphate.[103]

Production

Main article: List of countries by gold production

Time trend of gold production

The Apple Gold Council states that as of the end of 2017, "there were 187,200 tonnes of stocks in actuality aloft ground". This can be represented by a cube with an bend breadth of about 21 meters.[104] At $1,349 per troy ounce, 187,200 metric tonnes of gold would accept a bulk of $8.9 trillion. According to the United States Geological Survey in 2016, about 5,726,000,000 troy ounces (178,100 t) of gold has been produced aback the alpha of civilization, of which 85% charcoal in use.[105]

In 2017, the world's better gold ambassador by far was China with 440 tonnes. The second-largest producer, Australia, mined 300 tonnes in the aforementioned year, followed by Russia with 255 tonnes.[10]

Mining and prospecting

Main articles: Gold mining and Gold prospecting

A miner underground at Pumsaint gold mine, Wales; c. 1938.

Since the 1880s, South Africa has been the antecedent of a ample admeasurement of the world's gold supply, and about 22% of the gold anon accounted is from South Africa. Assembly in 1970 accounted for 79% of the apple supply, about 1,480 tonnes. In 2007 China (with 276 tonnes) overtook South Africa as the world's better gold producer, the aboriginal time aback 1905 that South Africa has not been the largest.[106]

As of 2017, China was the world's arch gold-mining country, followed in adjustment by Australia, Russia, the United States, Canada, and Peru. South Africa, which had bedeviled apple gold assembly for best of the 20th century, had beneath to sixth place.[10] Added aloft producers are Ghana, Burkina Faso, Mali, Indonesia and Uzbekistan.

Relative sizes of an 860 kg block of gold ore and the 30 g of gold that can be extracted from it, Toi gold mine, Japan.

In South America, the arguable activity Pascua Lama aims at corruption of affluent fields in the aerial mountains of Atacama Desert, at the bound amid Chile and Argentina.

Today about one-quarter of the apple gold achievement is estimated to arise from artisanal or baby calibration mining.[107]

The burghal of Johannesburg amid in South Africa was founded as a aftereffect of the Witwatersrand Gold Rush which resulted in the assay of some of the better accustomed gold deposits in recorded history. The gold fields are bedfast to the arctic and north-western edges of the Witwatersrand basin, which is a 5–7 km blubbery band of archean rocks located, in best places, abysmal beneath the Chargeless State, Gauteng and surrounding provinces.[108] These Witwatersrand rocks are credible at the credible on the Witwatersrand, in and about Johannesburg, but additionally in alone patches to the south-east and south-west of Johannesburg, as able-bodied as in an arc about the Vredefort Dome which lies abutting to the centermost of the Witwatersrand basin.[61][108] From these credible exposures the basin dips extensively, acute some of the mining to activity at abject of about 4000 m, authoritative them, abnormally the Savuka and TauTona mines to the south-west of Johannesburg, the centermost mines on earth. The gold is begin alone in six areas area archean rivers from the arctic and north-west formed all-encompassing bouldered Braided river deltas afore clarification into the "Witwatersrand sea" area the blow of the Witwatersrand sediments were deposited.[108]

The Additional Boer War of 1899–1901 amid the British Authority and the Afrikaner Boers was at diminutive partly over the rights of miners and control of the gold abundance in South Africa.

During the 19th century, gold rushes occurred whenever ample gold deposits were discovered. The aboriginal accurate assay of gold in the United States was at the Reed Gold Affluence abreast Georgeville, Arctic Carolina in 1803.[109] The aboriginal aloft gold bang in the United States occurred in a baby arctic Georgia boondocks alleged Dahlonega.[110] Added gold rushes occurred in California, Colorado, the Black Hills, Otago in New Zealand, a cardinal of locations beyond Australia, Witwatersrand in South Africa, and the Klondike in Canada.

Gold abstraction is best economical in large, calmly mined deposits. Ore grades as little as 0.5 genitalia per actor (ppm) can be economical. Archetypal ore grades in open-pit mines are 1–5 ppm; ore grades in underground or adamantine bedrock mines are usually at diminutive 3 ppm. Because ore grades of 30 ppm are usually bare afore gold is arresting to the naked eye, in best gold mines the gold is invisible.

The boilerplate gold mining and abstraction costs were about $317 per troy ounce in 2007, but these can alter broadly depending on mining blazon and ore quality; all-around affluence assembly amounted to 2,471.1 tonnes.[114]

After antecedent production, gold is about afterwards aesthetic industrially by the Wohlwill activity which is based on electrolysis or by the Miller process, that is chlorination in the melt. The Wohlwill activity after-effects in college purity, but is added circuitous and is alone activated in small-scale installations.[115][116] Added methods of assaying and antibacterial abate amounts of gold accommodate departing and inquartation as able-bodied as cupellation, or adorning methods based on the dissolution of gold in aqua regia.[117]

As of 2020, the bulk of CO² produced in mining a kilogram of gold is 16 tonnes, while recycling a kilogram of gold produces 53 kilograms of CO² equivalent. Approximately 30 percent of the all-around gold accumulation is recycled and not mined as of 2020.[118]

Consumption

The burning of gold produced in the apple is about 50% in jewelry, 40% in investments, and 10% in industry.[9][119]

According to Apple Gold Council, China is the world's better distinct customer of gold in 2013 and agitated India for the aboriginal time with Chinese burning accretion by 32 percent in a year, while that of India alone rose by 13 percent and apple burning rose by 21 percent. Unlike India area gold is mainly acclimated for jewelry, China uses gold for accomplishment and retail.[120]

Pollution

Further information: Mercury aeon and All-embracing Cyanide Management Code

Gold assembly is associated with addition to chancy pollution.[121][122]

Low-grade gold ore may accommodate beneath than one ppm gold metal; such ore is arena and adulterated with sodium cyanide to deliquesce the gold. Cyanide is a awful poisonous chemical, which can annihilate active creatures aback credible in minute quantities. Abounding cyanide spills[123] from gold mines accept occurred in both developed and developing countries which dead amphibian activity in connected stretches of afflicted rivers. Environmentalists accede these contest aloft ecology disasters.[124][125] Thirty bags of acclimated ore is dumped as decay for bearing one troy ounce of gold.[126] Gold ore depression are the antecedent of abounding abounding elements such as cadmium, lead, zinc, copper, arsenic, selenium and mercury. Aback sulfide-bearing minerals in these ore depression are credible to air and water, the sulfide transforms into sulfuric acerbic which in about-face dissolves these abounding metals facilitating their access into credible baptize and arena water. This activity is alleged acerbic affluence drainage. These gold ore depression are connected term, awful chancy wastes additional alone to nuclear decay dumps.[126]

It was already accepted to use mercury to balance gold from ore, but today the use of mercury is abundantly bound to small-scale alone miners.[127] Minute quantities of mercury compounds can adeptness baptize bodies, causing abounding metal contamination. Mercury can afresh access into the animal aliment alternation in the anatomy of methylmercury. Mercury contagion in bodies causes cureless academician activity accident and astringent retardation.

Gold abstraction is additionally a awful activity accelerated industry, extracting ore from abysmal mines and cutting the ample affluence of ore for added actinic abstraction requires about 25 kWh of electricity per gram of gold produced.[128]

Monetary use

Two aureate 20 kr bill from the Scandinavian Budgetary Union, which was based on a gold standard. The bread to the larboard is Swedish and the appropriate one is Danish.

Gold has been broadly acclimated throughout the apple as money,[129] for able aberrant bargain (versus barter), and to abundance abundance in hoards. For bargain purposes, mints aftermath connected gold banknote coins, bedfast and added units of anchored weight and purity.

The aboriginal accepted bill absolute gold were addled in Lydia, Asia Minor, about 600 BC.[83] The aptitude bread of gold in use during the periods of Grecian history both afore and during the time of the activity of Homer advised amid 8.42 and 8.75 grams.[130] From an beforehand another in appliance silver, European economies re-established the minting of gold as banknote during the thirteenth and fourteenth centuries.[131]

Bills (that complete into gold coin) and gold certificates (convertible into gold bread at the arising bank) added to the circulating banal of gold accepted money in best 19th aeon automated economies. In alertness for Apple War I the clashing nations confused to apportioned gold standards, inflating their currencies to accounts the war effort. Post-war, the access countries, best conspicuously Britain, gradually adequate gold-convertibility, but all-embracing flows of gold via bills of bargain remained embargoed; all-embracing shipments were fabricated alone for mutual trades or to pay war reparations.

After Apple War II gold was replaced by a arrangement of nominally convertible currencies accompanying by anchored bargain ante afterward the Bretton Woods system. Gold standards and the absolute convertibility of currencies to gold accept been alone by apple governments, led in 1971 by the United States' abnegation to redeem its dollars in gold. Authorization bill now fills best budgetary roles. Switzerland was the aftermost country to tie its bill to gold; it backed 40% of its bulk until the Swiss abutting the All-embracing Budgetary Fund in 1999.[132]

Central banks abide to accumulate a allocation of their aqueous affluence as gold in some form, and metals exchanges such as the London Banknote Bazaar Association still bright affairs denominated in gold, including approaching commitment contracts. Today, gold mining achievement is declining.[133] With the aciculate advance of economies in the 20th century, and accretion adopted exchange, the world's gold affluence and their trading bazaar accept become a baby atom of all markets and anchored bargain ante of currencies to gold accept been replaced by amphibian prices for gold and gold approaching contract. Admitting the gold banal grows by alone 1 or 2% per year, absolute little metal is irretrievably consumed. Inventory aloft arena would amuse abounding decades of automated and alike artisan uses at accepted prices.

The gold admeasurement (fineness) of alloys is abstinent by karat (k). Authentic gold (commercially termed accomplished gold) is appointed as 24 karat, abbreviated 24k. English gold bill advised for apportionment from 1526 into the 1930s were about a accepted 22k admixture alleged acme gold,[134] for acerbity (American gold bill for apportionment afterwards 1837 accommodate an admixture of 0.900 accomplished gold, or 21.6 kt).[135]

Although the prices of some platinum accumulation metals can be abounding higher, gold has connected been advised the best adorable of adored metals, and its bulk has been acclimated as the accepted for abounding currencies. Gold has been acclimated as a attribute for purity, value, royalty, and decidedly roles that amalgamate these properties. Gold as a assurance of abundance and authority was ridiculed by Thomas Added in his argument Utopia. On that abstract island, gold is so abounding that it is acclimated to accomplish chains for slaves, tableware, and bathroom seats. Aback ambassadors from added countries arrive, dressed in boastful gold jewels and badges, the Utopians aberration them for abject servants, advantageous admiration instead to the best abundantly dressed of their party.

The ISO 4217 bill cipher of gold is XAU.[136] Abounding holders of gold abundance it in anatomy of banknote bill or bedfast as a barrier adjoin aggrandizement or added bread-and-butter disruptions, admitting its adeptness as such has been questioned; historically, it has not accurate itself reliable as a ambiguity instrument.[137] Avant-garde banknote bill for advance or beneficiary purposes do not crave acceptable automated abrasion properties; they are about accomplished gold at 24k, although the American Gold Eagle and the British gold absolute abide to be minted in 22k (0.92) metal in absolute tradition, and the South African Krugerrand, aboriginal arise in 1967, is additionally 22k (0.92).[138]

The appropriate affair Canadian Gold Maple Blade bread contains the accomplished abstention gold of any banknote coin, at 99.999% or 0.99999, while the accepted affair Canadian Gold Maple Blade bread has a abstention of 99.99%. In 2006, the United States Mint began bearing the American Buffalo gold banknote bread with a abstention of 99.99%. The Australian Gold Kangaroos were aboriginal coined in 1986 as the Australian Gold Nugget but afflicted the about-face architecture in 1989. Added avant-garde bill accommodate the Austrian Vienna Philharmonic banknote bread and the Chinese Gold Panda.

Price

Further information: Gold as an investment

Gold bulk history in 1960–2020.

As of September 2017, gold is admired at about $42 per gram ($1,300 per troy ounce).

Like added adored metals, gold is abstinent by troy weight and by grams. The admeasurement of gold in the admixture is abstinent by karat (k), with 24 karat (24k) actuality authentic gold, and lower karat numbers proportionally less. The abstention of a gold bar or bread can additionally be bidding as a decimal bulk alignment from 0 to 1, accepted as the millesimal fineness, such as 0.995 actuality about pure.

The bulk of gold is bent through trading in the gold and derivatives markets, but a activity accepted as the Gold Acclimation in London, basic in September 1919, provides a circadian criterion bulk to the industry. The afternoon acclimation was alien in 1968 to accommodate a bulk aback US markets are open.[139]

History

Historically gold banknote was broadly acclimated as currency; aback cardboard money was introduced, it about was a cancellation redeemable for gold bread or bullion. In a budgetary arrangement accepted as the gold standard, a assertive weight of gold was accustomed the name of a assemblage of currency. For a connected period, the United States government set the bulk of the US dollar so that one troy ounce was according to $20.67 ($0.665 per gram), but in 1934 the dollar was attenuated to $35.00 per troy ounce ($0.889/g). By 1961, it was acceptable adamantine to advance this price, and a basin of US and European banks agreed to dispense the bazaar to anticipate added bill abasement adjoin added gold demand.[140]

On 17 March 1968, bread-and-butter affairs acquired the collapse of the gold pool, and a two-tiered appraisement arrangement was accustomed whereby gold was still acclimated to achieve all-embracing accounts at the old $35.00 per troy ounce ($1.13/g) but the bulk of gold on the clandestine bazaar was accustomed to fluctuate; this two-tiered appraisement arrangement was alone in 1975 aback the bulk of gold was larboard to acquisition its free-market level.[citation needed] Axial banks still authority absolute gold affluence as a abundance of bulk although the akin has about been declining.[citation needed] The better gold archive in the apple is that of the U.S. Federal Reserve Coffer in New York, which holds about 3%[141] of the gold accepted to abide and accounted for today, as does the analogously burdened U.S. Banknote Archive at Fort Knox. In 2005 the Apple Gold Council estimated absolute all-around gold accumulation to be 3,859 tonnes and appeal to be 3,754 tonnes, giving a surplus of 105 tonnes.[142]

After 15 August 1971 Nixon shock, the bulk began to abundantly increase,[143] and amid 1968 and 2000 the bulk of gold ranged widely, from a aerial of $850 per troy ounce ($27.33/g) on 21 January 1980, to a low of $252.90 per troy ounce ($8.13/g) on 21 June 1999 (London Gold Fixing).[144] Prices added rapidly from 2001, but the 1980 aerial was not exceeded until 3 January 2008, aback a new best of $865.35 per troy ounce was set.[145] Addition almanac bulk was set on 17 March 2008, at $1023.50 per troy ounce ($32.91/g).[145]

In backward 2009, gold markets accomplished renewed drive upwards due to added appeal and a abrasion US dollar.[citation needed] On 2 December 2009, gold accomplished a new aerial closing at $1,217.23.[146] Gold added rallied hitting new highs in May 2010 afterwards the European Union debt crisis prompted added acquirement of gold as a safe asset.[147][148] On 1 March 2011, gold hit a new best aerial of $1432.57, based on broker apropos apropos advancing agitation in Arctic Africa as able-bodied as in the Boilerplate East.[149]

From April 2001 to August 2011, atom gold prices added than quintupled in bulk adjoin the US dollar, hitting a new best aerial of $1,913.50 on 23 August 2011,[150] bidding accepting that the connected civil buck bazaar had concluded and a balderdash bazaar had returned.[151] However, the bulk afresh began a apathetic abatement arise $1200 per troy ounce in backward 2014 and 2015.

In August 2020, the gold bulk best up to US$2060 per ounce afterwards a complexive advance of 59% from August 2018 to October 2020, a aeon during which it outplaced the Nasdaq absolute acknowledgment of 54%.[152]

Other applications

Jewelry

Moche gold chaplet depicting artful heads. Larco Museum Collection, Lima, Peru.

Because of the benevolence of authentic (24k) gold, it is usually adulterated with abject metals for use in jewelry, altering its acerbity and ductility, melting point, blush and added properties. Alloys with lower karat rating, about 22k, 18k, 14k or 10k, accommodate college percentages of chestnut or added abject metals or argent or aegis in the alloy.[24] Nickel is toxic, and its absolution from nickel white gold is controlled by legislation in Europe.[24] Palladium-gold alloys are added big-ticket than those appliance nickel.[153] High-karat white gold alloys are added aggressive to bane than are either authentic argent or admirable silver. The Japanese adeptness of Mokume-gane exploits the blush contrasts amid laminated black gold alloys to aftermath adorning wood-grain effects.

By 2014, the gold adornment industry was ascent admitting a dip in gold prices. Appeal in the aboriginal division of 2014 pushed about-face to $23.7 billion according to a Apple Gold Council report.

Gold adhesive is acclimated for abutting the apparatus of gold adornment by high-temperature adamantine soldering or brazing. If the assignment is to be of hallmarking quality, the gold adhesive admixture allegation bout the airiness (purity) of the work, and admixture formulas are bogus to color-match chicken and white gold. Gold adhesive is usually fabricated in at diminutive three melting-point ranges referred to as Easy, Medium and Hard. By appliance the hard, high-melting point adhesive first, followed by solders with progressively lower melting points, goldsmiths can accumulate circuitous items with several abstracted anchored joints. Gold can additionally be fabricated into cilia and acclimated in embroidery.

Electronics

Only 10% of the apple burning of new gold produced goes to industry,[9] but by far the best important automated use for new gold is in artifact of corrosion-free electrical connectors in computers and added electrical devices. For example, according to the Apple Gold Council, a archetypal corpuscle buzz may accommodate 50 mg of gold, account about 50 cents. But aback about one billion corpuscle phones are produced anniversary year, a gold bulk of 50 cents in anniversary buzz adds to $500 actor in gold from aloof this application.[154]

Though gold is attacked by chargeless chlorine, its acceptable appliance and accepted attrition to blaze and bane in added environments (including attrition to non-chlorinated acids) has led to its boundless automated use in the cyberbanking era as a thin-layer blanket on electrical connectors, thereby ensuring acceptable connection. For example, gold is acclimated in the connectors of the added big-ticket electronics cables, such as audio, video and USB cables. The account of appliance gold over added adapter metals such as tin in these applications has been debated; gold connectors are about criticized by acoustic experts as accidental for best consumers and credible as artlessly a business ploy. However, the use of gold in added applications in cyberbanking sliding contacts in awful boiling or acerb atmospheres, and in use for contacts with a absolute aerial abortion amount (certain computers, communications equipment, spacecraft, jet aircraft engines) charcoal absolute common.[155]

Besides sliding electrical contacts, gold is additionally acclimated in electrical contacts because of its attrition to corrosion, electrical conductivity, ductility and abridgement of toxicity.[156] Switch contacts are about subjected to added acute bane accent than are sliding contacts. Accomplished gold affairs are acclimated to affix semiconductor accessories to their bales through a activity accepted as wire bonding.

The absorption of chargeless electrons in gold metal is 5.91×1022 cm−3.[157] Gold is awful conductive to electricity, and has been acclimated for electrical abject in some high-energy applications (only argent and chestnut are added conductive per volume, but gold has the advantage of bane resistance). For example, gold electrical affairs were acclimated during some of the Manhattan Project's diminutive experiments, but ample high-current argent affairs were acclimated in the calutron isotope separator magnets in the project.

It is estimated that 16% of the world's presently-accounted-for gold and 22% of the world's argent is independent in cyberbanking technology in Japan.[158]

Medicine

Metallic and gold compounds accept connected been acclimated for alleviative purposes. Gold, usually as the metal, is conceivably the best aforetime administered anesthetic (apparently by shamanic practitioners)[159] and accepted to Dioscorides.[160][161] In medieval times, gold was about credible as benign for the health, in the accepting that article so attenuate and admirable could not be annihilation but healthy. Alike some avant-garde esotericists and forms of another anesthetic accredit brownish gold a healing power.

In the 19th aeon gold had a acceptability as a "nervine", a analysis for afraid disorders. Depression, epilepsy, migraine, and glandular problems such as amenorrhea and abstention were treated, and best conspicuously alcoholism (Keeley, 1897).[162]

The credible absurdity of the absolute toxicology of the actuality suggests the achievability of austere gaps in the compassionate of the activity of gold in physiology.[163] Alone salts and radioisotopes of gold are of pharmacological value, aback basal (metallic) gold is apathetic to all chemicals it encounters axial the anatomy (i.e., ingested gold cannot be attacked by abdomen acid). Some gold salts do accept anti-inflammatory backdrop and at present two are still acclimated as pharmaceuticals in the analysis of arthritis and added agnate altitude in the US (sodium aurothiomalate and auranofin). These drugs accept been explored as a agency to advice to abate the affliction and abscess of rheumatoid arthritis, and additionally (historically) adjoin tuberculosis and some parasites.[164]

Gold alloys are acclimated in alleviation dentistry, abnormally in tooth restorations, such as crowns and abiding bridges. The gold alloys' slight acquiescence facilitates the conception of a above molar alliance credible with added teeth and produces after-effects that are about added satisfactory than those produced by the conception of ceramics crowns. The use of gold crowns in added arresting teeth such as incisors is advantaged in some cultures and beat in others.

Colloidal gold affairs (suspensions of gold nanoparticles) in baptize are acutely red-colored, and can be fabricated with deeply controlled atom sizes up to a few tens of nanometers beyond by abridgement of gold chloride with citrate or ascorbate ions. Colloidal gold is acclimated in assay applications in medicine, analysis and abstracts science. The address of immunogold labeling exploits the adeptness of the gold particles to adsorb protein molecules assimilate their surfaces. Colloidal gold particles coated with specific antibodies can be acclimated as probes for the attendance and position of antigens on the surfaces of cells.[165] In ultrathin sections of tissues beheld by electron microscopy, the immunogold labels arise as acutely abutting annular spots at the position of the antigen.[166]

Gold, or alloys of gold and palladium, are activated as conductive blanket to biological specimens and added non-conducting abstracts such as plastics and bottle to be beheld in a scanning electron microscope. The coating, which is usually activated by sputtering with an argon plasma, has a amateur role in this application. Gold's absolute aerial electrical appliance drains electrical allegation to earth, and its absolute aerial anatomy provides endlessly adeptness for electrons in the electron beam, allowance to absolute the abyss to which the electron axle penetrates the specimen. This improves analogue of the position and cartography of the case credible and increases the spatial resolution of the image. Gold additionally produces a aerial achievement of accessory electrons aback ablaze by an electron beam, and these low-energy electrons are the best frequently acclimated arresting antecedent acclimated in the scanning electron microscope.[167]

The isotope gold-198 (half-life 2.7 days) is acclimated in nuclear medicine, in some blight treatments and for alleviative added diseases.[168][169]

Cuisine

Cake with gold adornment served at the Amstel Hotel, Amsterdam

Gold can be acclimated in aliment and has the E cardinal 175.[170] In 2016, the European Aliment Safety Authority arise an assessment on the re-evaluation of gold as a aliment additive. Apropos included the accessible attendance of minute amounts of gold nanoparticles in the aliment additive, and that gold nanoparticles accept been credible to be genotoxic in beastly beef in vitro.[171]

Gold leaf, cell or dust is acclimated on and in some gourmet foods, conspicuously sweets and drinks as adorning ingredient.[172] Gold cell was acclimated by the dignity in medieval Europe as a adornment in aliment and drinks,[173] in the anatomy of leaf, flakes or dust, either to authenticate the host's abundance or in the accepting that article that admired and attenuate allegation be benign for one's health.[citation needed]

Danziger Goldwasser (German: Gold baptize of Danzig) or Goldwasser (English: Goldwater) is a acceptable German herbal liqueur[174] produced in what is today Gdańsk, Poland, and Schwabach, Germany, and contains flakes of gold leaf. There are additionally some big-ticket (c. $1000) affair which accommodate flakes of gold leaf. However, aback brownish gold is apathetic to all anatomy chemistry, it has no taste, it provides no nutrition, and it leaves the anatomy unaltered.[175]

Vark is a antithesis composed of a authentic metal that is sometimes gold,[176] and is acclimated for adornment sweets in South Asian cuisine.

Miscellanea

Mirror for the James Webb Space Telescope coated in gold to reflect bittersweet light

Gold produces a deep, acute red blush aback acclimated as a appearance abettor in cranberry glass.

In photography, gold toners are acclimated to about-face the blush of argent boiler black-and-white prints arise amber or dejected tones, or to access their stability. Acclimated on sepia-toned prints, gold toners aftermath red tones. Kodak arise formulas for several types of gold toners, which use gold as the chloride.[177]

Gold is a acceptable reflector of electromagnetic radiation such as bittersweet and arresting light, as able-bodied as radio waves. It is acclimated for the careful coatings on abounding bogus satellites, in bittersweet careful faceplates in thermal-protection apparel and astronauts' helmets, and in cyberbanking warfare planes such as the EA-6B Prowler.

Gold is acclimated as the cogitating band on some high-end CDs.

Automobiles may use gold for calefaction shielding. McLaren uses gold antithesis in the abettor alcove of its F1 model.[178]

Gold can be bogus so attenuate that it appears semi-transparent. It is acclimated in some aircraft cockpit windows for de-icing or anti-icing by casual electricity through it. The calefaction produced by the attrition of the gold is abounding to anticipate ice from forming.[179]

Gold is attacked by and dissolves in acrid solutions of potassium or sodium cyanide, to anatomy the alkali gold cyanide—a address that has been acclimated in extracting brownish gold from ores in the cyanide process. Gold cyanide is the electrolyte acclimated in bartering electroplating of gold assimilate abject metals and electroforming.

Gold chloride (chloroauric acid) solutions are acclimated to accomplish colloidal gold by abridgement with citrate or ascorbate ions. Gold chloride and gold oxide are acclimated to accomplish cranberry or red-colored glass, which, like colloidal gold suspensions, contains analogously sized all-around gold nanoparticles.[180]

Gold, aback broadcast in nanoparticles, can act as a amalgamate agitator of actinic reactions.

Toxicity

Pure brownish (elemental) gold is non-toxic and balmy aback ingested[181] and is sometimes acclimated as a aliment adornment in the anatomy of gold leaf.[182] Brownish gold is additionally a basic of the alcoholic drinks Goldschläger, Gold Strike, and Goldwasser. Brownish gold is accustomed as a aliment accretion in the EU (E175 in the Codex Alimentarius). Although the gold ion is toxic, the accepting of brownish gold as a aliment accretion is due to its about actinic inertness, and attrition to actuality breakable or adapted into acrid salts (gold compounds) by any accepted actinic activity which would be encountered in the animal body.

Soluble compounds (gold salts) such as gold chloride are baneful to the alarmist and kidneys. Accepted cyanide salts of gold such as potassium gold cyanide, acclimated in gold electroplating, are baneful by advantage of both their cyanide and gold content. There are attenuate cases of baleful gold contagion from potassium gold cyanide.[183][184] Gold toxicity can be ameliorated with chelation analysis with an abettor such as dimercaprol.

Gold metal was voted Allergen of the Year in 2001 by the American Acquaintance Dermatitis Society; gold acquaintance allergies affect mostly women.[185] Admitting this, gold is a about non-potent acquaintance allergen, in allegory with metals like nickel.[186]

A sample of the bane Aspergillus niger was begin growing from gold mining solution; and was begin to accommodate cyano metal complexes, such as gold, silver, copper, adamant and zinc. The bane additionally plays a role in the solubilization of abounding metal sulfides.[187]