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Gold is a
chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical compounds, chemical elements canno ...
with the
symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different ...
Au (from la, aurum) and
atomic number The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft,
malleable Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
, and
ductile Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
in a pure form. Chemically, gold is a
transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
and a
group 11 element Group 11, by modern IUPAC numbering, is a periodic table group, group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au), and roentgenium (Rg), although no chemical experiments have yet been carrie ...
. It is one of the least reactive chemical elements and is solid under
standard conditions Standard temperature and pressure (STP) are Technical standard, standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the I ...
. Gold often occurs in free elemental (
native state In biochemistry, the native state of a protein or nucleic acid is its properly Protein folding, folded and/or assembled form, which is operative and functional. The native state of a biomolecule may possess all four levels of biomolecular struc ...
), as nuggets or grains, in
rocks In geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over tim ...
,
veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein, pulmonary and umbilical veins, both of which ca ...
, and
alluvial deposit Alluvium (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around ...
s. It occurs in a
solid solution A solid solution, a term popularly used for metals, is a homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word ...
series with the native element silver (as
electrum Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and ...
), naturally
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
ed with other metals like
copper Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, thermal and electrical conductivity. A fre ...
and
palladium Palladium is a chemical element with the Symbol (chemistry), symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the 2 Pallas, asteroid ...
, and
mineral inclusion In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. In gemology, an inclusion is a characteristic enclosed within a gemstone, or reaching its surface from the interior. According to James Hutton, ...
s such as within
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
. Less commonly, it occurs in minerals as gold compounds, often with
tellurium Tellurium is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical ...
(
gold telluride Gold chalcogenides are compounds formed between gold and one of the chalcogens, elements from group 16 of the periodic table: oxygen, sulfur, selenium, or tellurium. *Gold(III) oxide, Au2O3. Decomposes into gold and oxygen above 160 °C, and d ...
s). Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
and
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is a component of the gas ...
), forming a soluble
tetrachloroaurate Chloroauric acid is an inorganic compound with the chemical formula . It forms hydrates . Both the trihydrate and tetrahydrate are known. Both are orange-yellow solids consisting of the planar anion. Often chloroauric acid is handled as a solutio ...
anion An ion () is an atom or molecule with a net electric charge, electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be po ...
. Gold is insoluble in nitric acid alone, which dissolves silver and
base metal A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...
s, a property long used to refine gold and confirm the presence of gold in metallic substances, giving rise to the term ' acid test'. Gold dissolves in
alkaline In chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, ...
solutions of
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers th ...
, which are used in
mining Mining is the Extractivism, extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein (geology), vein, coal mining, seam, quartz reef mining, reef, or placer deposit. The exploitation of ...
and
electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...
. Gold also dissolves in mercury, forming amalgam alloys, and as the gold acts simply as a solute, this is not a
chemical reaction A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
. A relatively rare element, gold is a
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high Value (economics), economic value. Chemically, the precious metals tend to be less reactivity (chemistry), reactive than most elements (see noble metal). They ...
that has been used for coinage,
jewelry Jewellery (British English, UK) or jewelry (American English, U.S.) consists of decorative items worn for personal adornment, such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be at ...
, and other
arts The arts are a very wide range of human practices of creativity, creative expression, storytelling and culture, cultural participation. They encompass multiple diverse and plural modes of thinking, doing and being, in an extremely broad ran ...
throughout
recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader World hist ...
. In the past, a
gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from th ...
was often implemented as a
monetary policy Monetary policy is the policy adopted by the monetary authority of a nation to control either the interest rate payable for federal funds, very short-term borrowing (borrowing by banks from each other to meet their short-term needs) or the money s ...
. Gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a
fiat currency Fiat money (from la, fiat, "let it be done") is a type of currency that is not backed by any commodity such as gold or silver. It is typically designated by the issuing government to be legal tender. Throughout history, fiat money was some ...
system after the Nixon shock measures of 1971. In 2020, the world's largest gold producer was China, followed by Russia and Australia. A total of around 201,296
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a International System of Units#Non-SI units accepted for use with SI, non-SI unit accepted for use with SI. It is also referred to as a metric ton to disting ...
s of gold exists above ground, . This is equal to a cube with each side measuring roughly . The world consumption of new gold produced is about 50% in jewelry, 40% in
investment Investment is the dedication of money to purchase of an asset to attain an increase in value over a period of time. Investment requires a sacrifice of some present asset, such as time, money, or effort. In finance, the purpose of investing is ...
s and 10% in
industry Industry may refer to: Economics * Industry (economics), a generally categorized branch of economic activity * Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery * The wider industrial sect ...
. Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity have led to its continued use in corrosion-resistant
electrical connector Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between ...
s in all types of computerized devices (its chief industrial use). Gold is also used in
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
shielding, production of
colored glass Glass coloring and color marking may be obtained in several ways. # by the addition of ''coloring ions'',Bernard H. W. S. De Jong, Ruud G. C. Beerkens, Peter A. van Nijnatten: "Glass", in: "Ullmann's Encyclopedia of Industrial Chemistry"; Wiley-VC ...
,
gold leaf Gold leaf is gold that has been hammered into thin sheets (usually around 0.1 µm thick) by goldbeating and is often used for gilding. Gold leaf is available in a wide variety of carat (purity), karats and shades. The most commonly used g ...
ing, and tooth restoration. Certain gold salts are still used as
anti-inflammatories Anti-inflammatory is the property of a substance or treatment that reduces inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or ...
in medicine.


Characteristics

Gold is the most
malleable Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
of all metals. It can be drawn into a wire of single-atom width, and then stretched considerably before it breaks. Such nanowires distort via formation, reorientation and migration of
dislocation In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to sli ...
s and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of , and an
avoirdupois ounce The ounce () is any of several different units of mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a body. It was traditionally believed to be related to the physical quantity, quantity of matter in a Physical obje ...
into . Gold leaf can be beaten thin enough to become semi-transparent. The transmitted light appears greenish-blue, because gold strongly reflects yellow and red. Such semi-transparent sheets also strongly reflect
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
light, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for
spacesuit A space suit or spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, Vacuum (outer space), vacuum and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of l ...
s. Gold is a good conductor of heat and
electricity Electricity is the set of physics, physical Phenomenon, phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagne ...
. Gold has a density of 19.3 g/cm3, almost identical to that of
tungsten Tungsten, or wolfram, is a chemical element with the Symbol (chemistry), symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1 ...
at 19.25 g/cm3; as such, tungsten has been used in
counterfeiting To counterfeit means to imitate something authentic, with the intent to steal, destroy, or replace the original, for use in illegal transactions, or otherwise to deceive individuals into believing that the fake is of equal or greater value tha ...
of
gold bar A gold bar, also called gold bullion or gold ingot, is a quantity of refining, refined metallic gold of any shape that is made by a bar producer meeting standard conditions of manufacture, labeling, and record keeping. Larger gold bars that are ...
s, such as by plating a tungsten bar with gold, or taking an existing gold bar, drilling holes, and replacing the removed gold with tungsten rods. By comparison, the density of
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
is 11.34 g/cm3, and that of the densest element,
osmium Osmium (from Ancient Greek, Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the Symbol (chemistry), symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is foun ...
, is .


Color

Whereas most metals are gray or silvery white, gold is slightly reddish-yellow. This color is determined by the frequency of
plasma oscillation Plasma oscillations, also known as Langmuir waves (after Irving Langmuir), are rapid oscillations of the electron density in conducting media such as Plasma (physics), plasmas or metals in the ultraviolet region. The oscillations can be described as ...
s among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to
relativistic effects Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to calculate chemical element, elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanatio ...
affecting the orbitals around gold atoms. Similar effects impart a golden hue to metallic
caesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the Symbol (chemistry), symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elem ...
. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing
palladium Palladium is a chemical element with the Symbol (chemistry), symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the 2 Pallas, asteroid ...
or
nickel Nickel is a chemical element with Chemical symbol, symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and Ductility, ductile transition metal. Pure nickel is chemically reactive bu ...
are also important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain
bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...
alloys, and both may be used to produce police and other
badge A badge is a device or accessory, often containing the insignia of an organization, which is presented or displayed to indicate some feat of service, a special accomplishment, a symbol of authority granted by taking an oath (e.g., police and fi ...
s. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...
, and purple gold can be made by alloying with
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substan ...
. Less commonly, addition of
manganese Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...
,
indium Indium is a chemical element with the Symbol (chemistry), symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that ma ...
, and other elements can produce more unusual colors of gold for various applications.
Colloidal gold Colloidal gold is a sol (colloid), sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The colloid is usually either wine-red coloured (for spherical particles less than 100 nanometre, nm) or blue/purple (for l ...
, used by electron-microscopists, is red if the particles are small; larger particles of colloidal gold are blue.


Isotopes

Gold has only one stable
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbe ...
, , which is also its only naturally occurring isotope, so gold is both a mononuclidic and
monoisotopic element A monoisotopic element is an element which has only a single stable isotope (nuclide). There are only 26 elements that have this property. A list is given in a following section. Stability is experimentally defined for chemical elements, as ther ...
. Thirty-six
radioisotopes A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
have been synthesized, ranging in
atomic mass The atomic mass (''m''a or ''m'') is the mass of an atom. Although the SI unit of mass is the kilogram (unit), kilogram (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (unit), dalton (symbol: Da) – equivalently, unif ...
from 169 to 205. The most stable of these is with a
half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
of 186.1 days. The least stable is , which decays by
proton emission Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a atomic nucleus, nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, ...
with a half-life of 30 µs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of
proton emission Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a atomic nucleus, nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, ...
, α decay, and β+ decay. The exceptions are , which decays by electron capture, and , which decays most often by electron capture (93%) with a minor β decay path (7%). All of gold's radioisotopes with atomic masses above 197 decay by β decay. At least 32
nuclear isomer A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...
s have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only , , , , and do not have isomers. Gold's most stable isomer is with a half-life of 2.27 days. Gold's least stable isomer is with a half-life of only 7 ns. has three decay paths: β+ decay,
isomeric transition A nuclear isomer is a metastable state of an atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsde ...
, and alpha decay. No other isomer or isotope of gold has three decay paths.


Synthesis

The possible production of gold from a more common element, such as
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
, has long been a subject of human inquiry, and the ancient and medieval discipline of
alchemy Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscience, protoscientific tradition that was historically practiced in Chinese alchemy, C ...
often focused on it; however, the transmutation of the chemical elements did not become possible until the understanding of
nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...
in the 20th century. The first synthesis of gold was conducted by Japanese physicist Hantaro Nagaoka, who synthesized gold from mercury in 1924 by neutron bombardment. An American team, working without knowledge of Nagaoka's prior study, conducted the same experiment in 1941, achieving the same result and showing that the isotopes of gold produced by it were all
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive Decay chain, disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nucl ...
. In 1980,
Glenn Seaborg Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the Synthetic element, synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Che ...
transmuted several thousand atoms of bismuth into gold at the Lawrence Berkeley Laboratory. Gold can be manufactured in a nuclear reactor, but doing so is highly impractical and would cost far more than the value of the gold that is produced.


Chemistry

Although gold is the most noble of the
noble metal A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its native element, raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium ...
s, it still forms many diverse compounds. The
oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to different atoms were fully Ionic bond, ionic. It describes the degree of oxidation (loss of elec ...
of gold in its compounds ranges from −1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...
s such as
thioether In organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that ...
s,
thiolate In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
s, and organophosphines. Au(I) compounds are typically linear. A good example is , which is the soluble form of gold encountered in mining. The binary gold halides, such as AuCl, form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives. Au(III) (referred to as the auric) is a common oxidation state, and is illustrated by
gold(III) chloride Gold(III) chloride, traditionally called auric chloride, is a inorganic compound, compound of gold and chlorine with the molecular formula . The "III" in the name indicates that the gold has an oxidation state of +3, typical for many gold comp ...
, . The gold atom centers in Au(III) complexes, like other d8 compounds, are typically
square planar The square planar molecular geometry in chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecule ...
, with
chemical bond A chemical bond is a lasting attraction between atoms or ions that enables the formation of Molecule, molecules and crystals. The bond may result from the Coulomb's law, electrostatic force between oppositely charged ions as in Ionic bonding, ...
s that have both
covalent A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
and ionic character. Gold(I,III) chloride is also known, an example of a
mixed-valence complex Mixed valence complexes contain an chemical element, element which is present in more than one oxidation state. Well-known mixed valence compounds include the Creutz–Taube complex, Prussian blue, and molybdenum blue. Many solids are mixed-vale ...
. Gold does not react with oxygen at any temperature and, up to 100 °C, is resistant to attack from ozone. : \mathrm+\mathrm_2 \neq : \mathrm+\mathrm_3 \overset Some free
halogen The halogens () are a group in the periodic table The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and ...
s react with gold. Gold is strongly attacked by fluorine at dull-red heat to form gold(III) fluoride . Powdered gold reacts with chlorine at 180 °C to form
gold(III) chloride Gold(III) chloride, traditionally called auric chloride, is a inorganic compound, compound of gold and chlorine with the molecular formula . The "III" in the name indicates that the gold has an oxidation state of +3, typical for many gold comp ...
. Gold reacts with bromine at 140 °C to form gold(III) bromide , but reacts only very slowly with iodine to form gold(I) iodide AuI. : 2 Au + 3 F2 -> 2 AuF3 : 2 Au + 3 Cl2 -> 2 AuCl3 : 2 Au + 2 Br2 -> AuBr3 + AuBr : 2 Au + I2 -> 2 AuI Gold does not react with sulfur directly, but gold(III) sulfide can be made by passing
hydrogen sulfide Hydrogen sulfide is a chemical compound with the chemical formula, formula . It is a colorless Chalcogen hydride, chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic ...
through a dilute solution of gold(III) chloride or chlorauric acid. Gold readily dissolves in mercury at room temperature to form an amalgam, and forms
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
s with many other metals at higher temperatures. These alloys can be produced to modify the hardness and other metallurgical properties, to control
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase_(matter), phase exist in Thermodynamic equilibr ...
or to create exotic colors. Gold is unaffected by most acids. It does not react with hydrofluoric,
hydrochloric Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is a component of the gas ...
, hydrobromic, hydriodic, sulfuric, or
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
. It does react with selenic acid, and is dissolved by aqua regia, a 1:3 mixture of
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available ni ...
and
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is a component of the gas ...
. Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable in the pure acid because of the chemical equilibrium of the reaction. However, the ions are removed from the equilibrium by hydrochloric acid, forming ions, or chloroauric acid, thereby enabling further oxidation. : 2 Au + 6 H2SeO4 -> 00^\circ CAu2(SeO4)3 + 3 H2SeO3 + 3 H2O : Au + 4HCl + HNO3 -> H uCl4+ NO\uparrow + 2H2O Gold is similarly unaffected by most bases. It does not react with
aqueous An aqueous solution is a solution in which the solvent A solvent (s) (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solutio ...
,
solid Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...
, or molten
sodium Sodium is a chemical element with the Symbol (chemistry), symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the ...
or
potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
. It does however, react with
sodium Sodium is a chemical element with the Symbol (chemistry), symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the ...
or
potassium cyanide Potassium cyanide is a compound with the chemical formula, formula KCN. This colorless crystalline salt, similar in appearance to sugar, is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller a ...
under alkaline conditions when
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...
is present to form soluble complexes. Common
oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to different atoms were fully Ionic bond, ionic. It describes the degree of oxidation (loss of elec ...
s of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Gold ions in solution are readily reduced and precipitated as metal by adding any other metal as the
reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth meta ...
. The added metal is
oxidized Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
and dissolves, allowing the gold to be displaced from solution and be recovered as a solid precipitate.


Rare oxidation states

Less common oxidation states of gold include −1, +2, and +5. The −1 oxidation state occurs in aurides, compounds containing the
anion An ion () is an atom or molecule with a net electric charge, electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be po ...
. Caesium auride (CsAu), for example, crystallizes in the caesium chloride motif; rubidium, potassium, and
tetramethylammonium Tetramethylammonium (TMA) or (Me4N+) is the simplest quaternary ammonium cation, consisting of four methyl groups attached to a central nitrogen atom, and is isoelectronic with neopentane. It is positively charged and can only be isolated in assoc ...
aurides are also known. Gold has the highest
electron affinity The electron affinity (''E''ea) of an atom Every atom is composed of a atomic nucleus, nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety ...
of any metal, at 222.8 kJ/mol, making a stable species, analogous to the
halide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom Every atom is composed of a atomic nucleus, nucleus and one or more electrons bound to the nucleus. The nucleus is made of o ...
s. Gold also has a –1 oxidation state in covalent complexes with the group 4 transition metals, such as in titanium tetraauride and the analogous zirconium and hafnium compounds. These chemicals are expected to form gold-bridged dimers in a manner similar to titanium(IV) hydride. Gold(II) compounds are usually
diamagnetic Diamagnetic materials are repelled by a magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field expe ...
with Au–Au bonds such as The evaporation of a solution of in concentrated produces red crystals of gold(II) sulfate, . Originally thought to be a mixed-valence compound, it has been shown to contain cations, analogous to the better-known mercury(I) ion, . A gold(II) complex, the tetraxenonogold(II) cation, which contains xenon as a ligand, occurs in . Gold pentafluoride, along with its derivative anion, , and its difluorine complex, gold heptafluoride, is the sole example of gold(V), the highest verified oxidation state. 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. The interaction is estimated to be comparable in strength to that of a
hydrogen bond In chemistry, a hydrogen bond (or H-bond) is a primarily Electrostatics, electrostatic force of attraction between a hydrogen (H) atom which is Covalent bond, covalently bound to a more electronegativity, electronegative "donor" atom or group ( ...
. Well-defined cluster compounds are numerous. In some cases, gold has a fractional oxidation state. A representative example is the octahedral species .


Origin


Gold production in the universe

Gold is thought to have been produced in
supernova nucleosynthesis Supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions. In sufficiently massive stars, the nucleosynthesis by fusion of lighter elements into heavier ones occurs during sequential hydrostatic burning processe ...
, and from the collision of neutron stars, and to have been present in the
dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...
from which the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
formed. Traditionally, gold in the universe is thought to have formed by the
r-process In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reaction In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and in ...
(rapid neutron capture) in
supernova nucleosynthesis Supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions. In sufficiently massive stars, the nucleosynthesis by fusion of lighter elements into heavier ones occurs during sequential hydrostatic burning processe ...
, but more recently it has been suggested that gold and other elements heavier than
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundance ...
may also be produced in quantity by the r-process in the
collision In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scienc ...
of
neutron star A neutron star is the Gravitational collapse, collapsed Stellar structure, core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially Metallicity, metal-rich. Except fo ...
s. In both cases, satellite spectrometers at first only indirectly detected the resulting gold. However, in August 2017, the spectroscopic signatures of heavy elements, including gold, were observed by electromagnetic observatories in the
GW170817 GW 170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo interferometer, Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy . The signal was produced by the last minutes of a binary pair of ...
neutron star merger event, after
gravitational wave Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that Wave propagation, propagate as waves outward from their source at the speed of light. They were first proposed by Oliv ...
detectors confirmed the event as a neutron star merger. Current astrophysical models suggest that this single neutron star merger event generated between 3 and 13
Earth mass An Earth mass (denoted as M_\mathrm or M_\oplus, where ⊕ is the standard astronomical Earth symbol, symbol for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is , with a relativ ...
es of gold. This amount, along with estimations of the rate of occurrence of these neutron star merger events, suggests that such mergers may produce enough gold to account for most of the abundance of this element in the universe.


Asteroid origin theories

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 A planetary core consists of the innermost layers of a planet. Cores may be entirely solid or entirely liquid, or a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core sizes range from about 20% (the Moon ...
. Therefore, most of the gold that is in the Earth's crust and mantle has in one model thought to have been delivered to Earth later, by asteroid impacts during the
Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion years (Ga) ago, at a time corresponding to the Neohadean and Eoarchean eras on Earth. According to the hypothe ...
, about 4 billion years ago. Gold which is reachable by humans has, in one case, been associated with a particular asteroid impact. The asteroid that formed
Vredefort impact structure The Vredefort impact structure is the largest verified impact structure on Earth. The crater, which has since been eroded away, was around across when it was formed. The remaining structure, comprising the deformed underlying bedrock, is loca ...
2.020 billion years ago is often credited with seeding the
Witwatersrand basin The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing scarp in South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bou ...
in
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
with the richest gold deposits on earth. However, this scenario is now questioned. The gold-bearing
Witwatersrand The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing Escarpment, scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfa ...
rocks were laid down between 700 and 950 million years before the Vredefort impact.McCarthy, T., Rubridge, B. (2005). ''The Story of Earth and Life''. Struik Publishers, Cape Town. pp. 89–90, 102–107, 134–136. Norman, N., Whitfield, G. (2006) ''Geological Journeys''. Struik Publishers, Cape Town. pp. 38–49, 60–61. These gold-bearing rocks had furthermore been covered by a thick layer of Ventersdorp lavas and the Transvaal Supergroup of rocks before the meteor struck, and thus the gold did not actually arrive in the asteroid/meteorite. What the Vredefort impact achieved, however, was to distort the
Witwatersrand basin The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing scarp in South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bou ...
in such a way that the gold-bearing rocks were brought to the present
erosion surface In geology and geomorphology, an erosion surface is a surface of rock (geology), rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault (geology), fault displacement. Erosional surfaces ...
in
Johannesburg Johannesburg ( , , ; Zulu language, Zulu and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a Megacity#List of megacities, megacity, and is List of urban areas by p ...
, on the
Witwatersrand The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing Escarpment, scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfa ...
, just inside the rim of the original diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the
Witwatersrand Gold Rush The Witwatersrand Gold Rush was a gold rush in 1886 that led to the establishment of Johannesburg, South Africa. It was a part of the Mineral Revolution. Origins In the modern day province of Mpumalanga, gold miners in the alluvial mining, min ...
. Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks.


Mantle return theories

Notwithstanding the impact above, much of the rest of the gold on Earth is thought to have been incorporated into the planet since its very beginning, as planetesimals formed the planet's mantle, early in Earth's creation. In 2017, an international group of scientists, established that gold "came to the Earth's surface from the deepest regions of our planet", the mantle, evidenced by their findings at Deseado Massif in the Argentinian Patagonia.


Occurrence

On Earth, gold is found in
ore Ore is natural Rock (geology), rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Ret ...
s in rock formed from the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...
time onward. It most often occurs as a
native metal A native metal is any metal that is found pure in its metallic form in nature. Metals that can be found as native element mineral, native deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indiu ...
, typically in a metal
solid solution A solid solution, a term popularly used for metals, is a homogenous mixture of two different kinds of atoms in solid state and have a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word ...
with silver (i.e. as a gold/silver
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
). Such alloys usually have a silver content of 8–10%.
Electrum Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and ...
is elemental gold with more than 20% silver, and is commonly known as
white gold Pure gold is slightly reddish yellow in color, but colored gold in various other colors can be produced by alloying gold with other elements. Colored golds can be classified in three groups: * Alloys with silver and copper in various proportions ...
. Electrum's color runs from golden-silvery to silvery, dependent upon the silver content. The more silver, the lower the
specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...
. Native gold occurs as very small to microscopic particles embedded in rock, often together with
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra ...
or
sulfide mineral The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenide mineral, selenides, th ...
s such as "fool's gold", which is a
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
. These are called
lode In geology, a lode is a deposit of wikt:metalliferous, metalliferous ore that fills or is embedded in a fissure (or crack) in a rock (geology), rock formation or a vein (geology), vein of ore that is deposited or embedded between layers of rock. ...
deposits. The metal in a native state is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in
alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
deposits called
placer deposit In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish language, Spanish word ''placer'', meaning "alluvium ...
s. Such free gold is always richer at the exposed surface of gold-bearing veins, owing to the
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...
of accompanying minerals followed by weathering; and by washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets. Gold sometimes occurs combined with
tellurium Tellurium is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemical ...
as the
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
s calaverite, krennerite, nagyagite, petzite and sylvanite (see
telluride mineral A telluride mineral is a mineral that has the telluride anion as a main component. Tellurides are similar to sulfides and are grouped with them in both the Dana and Strunz mineral classification systems.http://webmineral.com/strunz/II.shtml We ...
s), and as the rare bismuthide maldonite () and antimonide aurostibite (). Gold also occurs in rare alloys with
copper Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, thermal and electrical conductivity. A fre ...
,
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
, and mercury: the minerals auricupride (), novodneprite () and weishanite (). 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. Another recent study has claimed water in faults vaporizes during an earthquake, depositing gold. When an earthquake strikes, it moves along a fault. Water often lubricates faults, filling in fractures and jogs. About below the surface, under very high temperatures and pressures, the water carries high concentrations of carbon dioxide, silica, and gold. During an earthquake, the fault jog suddenly opens wider. 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.


Seawater

The world's
ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distribution on Earth, Earth's water. An ocean can also refer to any of the ...
s contain gold. 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). In general, gold concentrations for south Atlantic and central Pacific samples are the same (~50 femtomol/L) but less certain. Mediterranean deep waters contain slightly higher concentrations of gold (100–150 femtomol/L) attributed to wind-blown dust and/or rivers. At 10 parts per quadrillion the Earth's
oceans The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distribution on Earth, Earth's water. An ocean can also refer to any of the ...
would hold 15,000 tonnes of gold. These figures are three orders of magnitude less than reported in the literature prior to 1988, indicating contamination problems with the earlier data. A number of people have claimed to be able to economically recover gold from
sea water Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approx ...
, but they were either mistaken or acted in an intentional deception. Prescott Jernegan ran a gold-from-seawater swindle in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
in the 1890s, as did an English fraudster in the early 1900s.
Fritz Haber Fritz Haber (; 9 December 186829 January 1934) was a German chemist who received the Nobel Prize in Chemistry in 1918 for his invention of the Haber process, Haber–Bosch process, a method used in industry to synthesize ammonia from nitrogen g ...
did research on the extraction of gold from sea water in an effort to help pay
Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated between ...
's reparations following
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
. Based on the published values of 2 to 64 ppb of gold in seawater a commercially successful extraction seemed possible. After analysis of 4,000 water samples yielding an average of 0.004 ppb it became clear that extraction would not be possible and he ended the project.


History

The earliest recorded metal employed by humans appears to be gold, which can be found
free Free may refer to: Concept * Freedom, having the ability to do something, without having to obey anyone/anything * Freethought, a position that beliefs should be formed only on the basis of logic, reason, and empiricism * Emancipate, to procure ...
or " native". Small amounts of natural gold have been found in Spanish caves used during the late
Paleolithic The Paleolithic or Palaeolithic (), also called the Old Stone Age (from Greek: παλαιός ''wikt:παλαιός, palaios'', "old" and λίθος ''wikt:λίθος, lithos'', "stone"), is a period in human prehistory that is distinguished by ...
period, c. 40,000 BC. The oldest gold artifacts in the world are from
Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedon ...
and are dating back to the 5th millennium BC (4,600 BC to 4,200 BC), such as those found in the
Varna Necropolis The Varna Necropolis ( bg, Варненски некропол), or Varna Cemetery, is a burial site in the western industrial zone of Varna, Bulgaria, Varna (approximately half a kilometre from Lake Varna and 4 km from the city centre), in ...
near Lake Varna and the
Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of An ...
coast, thought to be the earliest "well-dated" finding of gold artifacts in history. Several prehistoric Bulgarian finds are considered no less old – the golden treasures of Hotnitsa, Durankulak, artifacts from the Kurgan settlement of Yunatsite near
Pazardzhik Pazardzhik ( bg, Пазарджик ) is List of cities and towns in Bulgaria, a city situated along the banks of the Maritsa river, southern Bulgaria. It is the capital of Pazardzhik Province and centre for the homonymous Pazardzhik Municipality ...
, the golden treasure Sakar, as well as beads and gold jewelry found in the Kurgan settlement of ProvadiaSolnitsata (“salt pit”). However, Varna gold is most often called the oldest since this treasure is the largest and most diverse. Gold artifacts probably made their first appearance in Ancient Egypt at the very beginning of the pre-dynastic period, at the end of the fifth millennium BC and the start of the fourth, and smelting was developed during the course of the 4th millennium; gold artifacts appear in the archeology of Lower Mesopotamia during the early 4th millennium. As of 1990, gold artifacts found at the
Wadi Qana Wadi Qana (, he, נחל קנה, translit=Nahal Qana), is a wadi, with an intermittent stream meandering westwards from Huwara south of Nablus in the West Bank down to Jaljulia in Israel where it flows into the Yarkon River, of which it is a tr ...
cave cemetery of the
4th millennium BC The 4th millennium BC spanned the years 4000 BC to 3001 BC. Some of the major changes in human culture during this time included the beginning of the Bronze Age and the invention of writing, which played a major role in starting recorded history. ...
in
West Bank The West Bank ( ar, الضفة الغربية, translit=aḍ-Ḍiffah al-Ġarbiyyah; he, הגדה המערבית, translit=HaGadah HaMaʽaravit, also referred to by some Israelis as ) is a landlocked territory near the coast of the Mediter ...
were the earliest from the Levant. Gold artifacts such as the golden hats and the Nebra disk appeared in Central Europe from the 2nd millennium BC
Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of ...
. The oldest known map of a gold mine was drawn in the 19th Dynasty of Ancient Egypt (1320–1200 BC), whereas the first written reference to gold was recorded in the 12th Dynasty around 1900 BC.
Egyptian hieroglyph Egyptian hieroglyphs (, ) were the formal writing system used in Ancient Egypt, used for writing the Egyptian language. Hieroglyphs combined logographic, syllabary, syllabic and alphabetic elements, with some 1,000 distinct characters.There were ...
s from as early as 2600 BC describe gold, which King
Tushratta Tushratta (Akkadian language, Akkadian: and ) was a king of Mitanni, c. 1358–1335 BCE, at the end of the reign of Amenhotep III and throughout the reign of Akhenaten. He was the son of Shuttarna II. Tushratta stated that he was the grandson of ...
of the
Mitanni Mitanni (; Hittite cuneiform ; ''Mittani'' '), c. 1550–1260 BC, earlier called Ḫabigalbat in old Babylonian texts, c. 1600 BC; Hanigalbat or Hani-Rabbat (''Hanikalbat'', ''Khanigalbat'', cuneiform ') in Assyria Assyria (Neo-Assyri ...
claimed was "more plentiful than dirt" in Egypt. Egypt and especially
Nubia Nubia () (Nobiin language, Nobiin: Nobīn, ) is a region along the Nile river encompassing the area between the Cataracts of the Nile, first cataract of the Nile (just south of Aswan in southern Egypt) and the confluence of the Blue Nile, Blue ...
had the resources to make them major gold-producing areas for much of history. One of the earliest known maps, known as the Turin Papyrus Map, shows the plan of a gold mine in Nubia together with indications of the local
geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
. The primitive working methods are described by both
Strabo Strabo''Strabo'' (meaning "squinty", as in strabismus) was a term employed by the Romans for anyone whose eyes were distorted or deformed. The father of Pompey was called "Pompeius Strabo". A native of Sicily so clear-sighted that he could see ...
and
Diodorus Siculus Diodorus Siculus, or Diodorus of Sicily ( grc-gre, wikt:Διόδωρος, Διόδωρος ;  1st century BC), was an ancient Greece, ancient Greek historian. He is known for writing the monumental universal history ''Bibliotheca historica' ...
, and included
fire-setting Fire-setting is a method of traditional mining used most commonly from Prehistory, prehistoric times up to the Middle Ages. Fires were set against a rock face to heat the Rock (geology), stone, which was then doused with liquid, causing the sto ...
. Large mines were also present across the
Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic language, Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''P ...
in what is now
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the List of Asian countries by area, fifth-largest country in Asia ...
. Gold is mentioned in the
Amarna letters The Amarna letters (; sometimes referred to as the Amarna correspondence or Amarna tablets, and cited with the abbreviation EA, for "El Amarna") are an archive, written on clay tablets, primarily consisting of diplomatic correspondence between t ...
numbered 19 and 26 from around the 14th century BC. Gold is mentioned frequently in the
Old Testament The Old Testament (often abbreviated OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible The Hebrew Bible or Tanakh (;
, starting with Genesis 2:11 (at
Havilah Havilah ( ''Ḥăwīlāh'') refers to both a land and people in several books of the Bible; the one mentioned in , while the other is mentioned in . Biblical mentions In one case, Havilah is associated with the Garden of Eden, that mentioned in ...
), the story of the
golden calf According to the Bible, the golden calf (עֵגֶל הַזָּהָב '' ‘ēgel hazzāhāv'') was an idol (a cult image) made by the Israelites when Moses went up to Mount Sinai (bible), Mount Sinai. In Hebrew language, Hebrew, the incident is ...
, and many parts of the temple including the Menorah and the golden altar. In the
New Testament The New Testament grc, Ἡ Καινὴ Διαθήκη, Transliteration, transl. ; la, Novum Testamentum. (NT) is the second division of the Christian biblical canon. It discusses the teachings and person of Jesus in Christianity, Jesus, as ...
, it is included with the gifts of the
magi Magi (; singular magus ; from Latin ''wikt:magus#Noun 2, magus'', cf. fa, مغ ) were priests in Zoroastrianism and the earlier religions of the Western Iranian languages, western Iranians. The earliest known use of the word ''magi'' is in the ...
in the first chapters of Matthew. The
Book of Revelation The Book of Revelation is the final book of the New Testament (and consequently the final book of the Bible#Christian Bible, Christian Bible). Its title is derived from the Incipit, first word of the Koine Greek text: , meaning "unveiling" ...
21:21 describes the city of
New Jerusalem In the Book of Ezekiel in the Hebrew Bible, New Jerusalem (, ''YHWH šāmmā'', YHWH sthere") is Ezekiel's Hebrew prophecy, prophetic vision of a city centered on the rebuilt Temple in Jerusalem, Holy Temple, the Third Temple, to be establ ...
as having streets "made of pure gold, clear as crystal". Exploitation of gold in the south-east corner of the
Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of An ...
is said to date from the time of
Midas Midas (; grc-gre, Μίδας) was the name of a king in Phrygia with whom several myths became associated, as well as two later members of the Phrygian royal house. The most famous King Midas is popularly remembered in Greek mythology for his ...
, and this gold was important in the establishment of what is probably the world's earliest coinage in
Lydia Lydia (Lydian language, Lydian: ‎𐤮𐤱𐤠𐤭𐤣𐤠, ''Śfarda''; Aramaic: ''Lydia''; el, Λυδία, ''Lȳdíā''; tr, Lidya) was an Iron Age Monarchy, kingdom of western Asia Minor located generally east of ancient Ionia in the mod ...
around 610 BC. The legend of the
golden fleece In Greek mythology, the Golden Fleece ( el, Χρυσόμαλλον δέρας, ''Chrysómallon déras'') is the wool, fleece of the golden-woolled,, ''Khrusómallos''. winged Sheep, ram, Chrysomallos, that rescued Phrixus and brought him to Colc ...
dating from eighth century BCE may refer to the use of fleeces to trap gold dust from
placer deposit In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish language, Spanish word ''placer'', meaning "alluvium ...
s in the ancient world. From the 6th or 5th century BC, the
Chu (state) Chu, or Ch'u in Wade–Giles romanization, (, Hanyu Pinyin: Chǔ, Old Chinese: ''*s-r̥aʔ'') was a Zhou dynasty ancient Chinese states, vassal state. Their first ruler was King Wu of Chu in the early 8th century BCE. Chu was located in t ...
circulated the Ying Yuan, one kind of square gold coin. In Roman metallurgy, new methods for extracting gold on a large scale were developed by introducing
hydraulic mining Hydraulic mining is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment.Paul W. Thrush, ''A Dictionary of Mining, Mineral, and Related Terms'', US Bureau of Mines, 1968, p.560. In the placer mining of ...
methods, especially in
Hispania Hispania ( la, Hispānia , ; nearly identically pronounced in Spanish language, Spanish, Portuguese language, Portuguese, Catalan language, Catalan, and Italian language, Italian) was the Ancient Rome, Roman name for the Iberian Peninsula and it ...
from 25 BC onwards and in
Dacia Dacia (, ; ) was the land inhabited by the Dacians, its core in Transylvania, stretching to the Danube in the south, the Black Sea in the east, and the Tisza in the west. The Carpathian Mountains were located in the middle of Dacia. It thus ...
from 106 AD onwards. One of their largest mines was at Las Medulas in León, where seven long aqueducts enabled them to sluice most of a large alluvial deposit. The mines at Roşia Montană in
Transylvania Transylvania ( ro, Ardeal or ; hu, Erdély; german: Siebenbürgen) is a historical and cultural region in Central Europe, encompassing central Romania. To the east and south its natural border is the Carpathian Mountains, and to the west the Ap ...
were also very large, and until very recently, still mined by opencast methods. They also exploited smaller deposits in Britain, such as placer and hard-rock deposits at
Dolaucothi The Dolaucothi Gold Mines (; cy, Mwynfeydd Aur Dolaucothi) (), also known as the Ogofau Gold Mine, are ancient Ancient Rome, Roman surface and underground mining, mines located in the valley of the River Cothi, near Pumsaint, Carmarthenshire, ...
. The various methods they used are well described by
Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman Empire, Roman author, Natural history, naturalist and Natural philosophy, natural philosopher, and naval and army commander of the early Roman Empire, and a friend of t ...
in his
encyclopedia An encyclopedia (American English) or encyclopædia (British English) is a reference work or compendium providing summaries of knowledge either general or special to a particular field or discipline. Encyclopedias are divided into article ( ...
''
Naturalis Historia The ''Natural History'' ( la, Naturalis historia) is a work by Pliny the Elder. The largest single work to have survived from the Roman Empire to the modern day, the ''Natural History'' compiles information gleaned from other ancient authors. ...
'' written towards the end of the first century AD. During
Mansa Musa Mansa Musa ( ar, منسا موسى, Mansā Mūsā; ) was the ninth ''Mansa (title), mansa'' of the Mali Empire, which reached its territorial peak during his reign. Musa is known for his wealth and generosity. He has been subject to popular clai ...
's (ruler of the
Mali Empire The Mali Empire (Manding languages, Manding: ''Mandé''Ki-Zerbo, Joseph: ''UNESCO General History of Africa, Vol. IV, Abridged Edition: Africa from the Twelfth to the Sixteenth Century'', p. 57. University of California Press, 1997. or Manden; ...
from 1312 to 1337)
hajj The Hajj (; ar, حَجّ '; sometimes also spelled Hadj, Hadji or Haj in English) is an annual Islamic pilgrimage to Mecca, Saudi Arabia, the Holiest sites in Islam, holiest city for Muslims. Hajj is a Fard, mandatory religious duty for Mu ...
to
Mecca Mecca (; officially Makkah al-Mukarramah, commonly shortened to Makkah ()) is a city and administrative center of the Mecca Province of Saudi Arabia, and the Holiest sites in Islam, holiest city in Islam. It is inland from Jeddah on the Red ...
in 1324, he passed through
Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the capital of Egypt and its largest city, home to 10 million people. It is also part of the largest urban agglomeration in Africa, the Arab world and the Middle East: The Greater Cairo me ...
in July 1324, and was reportedly accompanied by a
camel train A camel train or caravan is a series of camels carrying passengers and goods on a regular or semi-regular service between points. Despite rarely travelling faster than human walking speed, for centuries camels' ability to withstand harsh condi ...
that included thousands of people and nearly a hundred camels where he gave away so much gold that it depressed the price in Egypt for over a decade, causing high
inflation In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reductio ...
. A contemporary Arab historian remarked: The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion by Native American peoples, especially in
Mesoamerica Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. Withi ...
,
Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...
,
Ecuador Ecuador ( ; ; Quechuan languages, Quechua: ''Ikwayur''; Shuar language, Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechuan ...
and
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Cari ...
. The
Aztec The Aztecs () were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. The Aztec people included different Indigenous peoples of Mexico, ethnic groups of central Mexico, particularly those g ...
s regarded gold as the product of the gods, calling it literally "god excrement" (''teocuitlatl'' in
Nahuatl Nahuatl (; ), Aztec, or Mexicano is a language or, by some definitions, a group of languages of the Uto-Aztecan languages, Uto-Aztecan language family. Varieties of Nahuatl are spoken by about Nahuas, Nahua peoples, most of whom live mainly in ...
), and after
Moctezuma II Moctezuma Xocoyotzin ( – 29 June 1520; Help:IPA/Nahuatl, oteːkˈsoːmaḁ ʃoːkoˈjoːt͡sĩn̥), nci-IPA, Motēuczōmah Xōcoyōtzin, moteːkʷˈsoːma ʃoːkoˈjoːtsin variant spellings include Motewksomah, Motecuhzomatzin, Montezuma ...
was killed, most of this gold was shipped to Spain. However, for the
indigenous peoples of North America The Indigenous peoples of the Americas are the inhabitants of the Americas before the arrival of the European colonization of the Americas, European settlers in the 15th century, and the ethnic groups who now identify themselves with those peopl ...
gold was considered useless and they saw much greater value in other
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
which were directly related to their utility, such as
obsidian Obsidian () is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements s ...
,
flint Flint, occasionally flintstone, is a sedimentary rock, sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tool ...
, and
slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock ...
.
El Dorado El Dorado (, ; Spanish language, Spanish for "the golden"), originally ''El Hombre Dorado'' ("The Golden Man") or ''El Rey Dorado'' ("The Golden King"), was the term used by the Spanish in the 16th century to describe a mythical tribal chief (' ...
is applied to a legendary story in which precious stones were found in fabulous abundance along with gold coins. The concept of El Dorado underwent several transformations, and eventually accounts of the previous myth were also combined with those of a legendary lost city. El Dorado, was the term used by the Spanish Empire to describe a mythical tribal chief (zipa) of the Muisca native people in
Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Cari ...
, who, as an initiation rite, covered himself with gold dust and submerged in Lake Guatavita. The legends surrounding El Dorado changed over time, as it went from being a man, to a city, to a kingdom, and then finally to an empire. Beginning in the early modern period, European
exploration Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
and
colonization Colonization, or colonisation, constitutes large-scale population movements wherein migrants maintain strong links with their, or their ancestors', former country – by such links, gain advantage over other inhabitants of the territory. When ...
of
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations geoscheme for Africa#Western Africa, United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, ...
was driven in large part by reports of gold deposits in the region, which was eventually referred to by Europeans as the " Gold Coast". From the late 15th to early 19th centuries, European trade in the region was primarily focused in gold, along with
ivory Ivory is a hard, white material from the tusks (traditionally from elephants) and teeth of animals, that consists mainly of dentine, one of the physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mammals ...
and
slaves Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...
. The gold trade in West Africa was dominated by the
Ashanti Empire The Asante Empire (Asante Twi: ), today commonly called the Ashanti Empire, was an Akan people, Akan state that lasted between 1701 to 1901, in what is now modern-day Ghana. It expanded from the Ashanti Region to include most of Ghana as well a ...
, who initially traded with the Portuguese before branching out and trading with British, French,
Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Cana ...
and Danish merchants. British desires to secure control of West African gold deposits played a role in the
Anglo-Ashanti wars The Anglo-Ashanti wars were a series of five conflicts that took place between 1824 and 1900 between the Ashanti Empire—in the Akan people, Akan interior of the Gold Coast (British colony), Gold Coast—and the British Empire and its African a ...
of the late 19th century, which saw the Ashanti Empire annexed by Britain. Gold played a role in western culture, as a cause for desire and of corruption, as told in children's
fable Fable is a literary genre: a succinct fictional story, in prose or verse (poetry), verse, that features animals, legendary creatures, plants, inanimate objects, or forces of nature that are Anthropomorphism, anthropomorphized, and that illustrat ...
s such as
Rumpelstiltskin "Rumpelstiltskin" ( ; german: Rumpelstilzchen) is a German fairy tale. It was collected by the Brothers Grimm in the 1812 edition of ''Children's and Household Tales''. The story is about a little imp who spins straw into gold in exchange for a g ...
—where Rumpelstiltskin turns hay into gold for the peasant's daughter in return for her child when she becomes a princess—and the stealing of the hen that lays golden eggs in
Jack and the Beanstalk "Jack and the Beanstalk" is an English fairy tale. It appeared as "The Story of Jack Spriggins and the Enchanted Bean" in 1734 4th edition :File:Round about our Coal Fire, or, Christmas Entertainments, 4th edn, 1734.pdf, On Commons and as Benjami ...
. The top prize at the
Olympic Games The modern Olympic Games or Olympics (french: link=no, Jeux olympiques) are the leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a var ...
and many other sports competitions is the
gold medal A gold medal is a medal awarded for highest achievement in a non-military field. Its name derives from the use of at least a fraction of gold in form of plating or alloy An alloy is a mixture of chemical elements of which at least one is a ...
. 75% of the presently accounted for gold has been extracted since 1910, two-thirds since 1950. One main goal of the alchemists was to produce gold from other substances, such as
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...
 — presumably by the interaction with a mythical substance called the
philosopher's stone The philosopher's stone or more properly philosophers' stone (Arabic: حجر الفلاسفة, , la, lapis philosophorum), is a mythic alchemy, alchemical substance capable of turning base metals such as Mercury (element), mercury into gold (, ...
. Trying to produce gold led the alchemists to systematically find out what can be done with substances, and this laid the foundation for today's
chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, structure, properties ...
, which can produce gold (albeit uneconomically) by using
nuclear transmutation Nuclear transmutation is the conversion of one chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only o ...
. Their symbol for gold was the circle with a point at its center (☉), which was also the
astrological Astrology is a range of Divination, divinatory practices, recognized as pseudoscientific since the 18th century, that claim to discern information about human affairs and terrestrial events by studying the apparent positions of Celestial o ...
symbol and the ancient
Chinese character Chinese characters () are logograms developed for the Written Chinese, writing of Chinese. In addition, they have been adapted to write other East Asian languages, and remain a key component of the Japanese writing system where they are k ...
for the
Sun The Sun is the star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other st ...
. The
Dome of the Rock The Dome of the Rock ( ar, قبة الصخرة, Qubbat aṣ-Ṣakhra) is an Islamic shrine located on the Temple Mount in the Old City (Jerusalem), Old City of Jerusalem, a site also known to Muslims as the ''al-Haram al-Sharif'' or the Al-Aqsa ...
is covered with an ultra-thin golden glassier. The
Sikh Sikhs ( or ; pa, ਸਿੱਖ, ' ) are people who adhere to Sikhism (Sikhi), a monotheistic religion that originated in the late 15th century in the Punjab region of the Indian subcontinent, based on the revelation of Guru Nanak. The ter ...
Golden temple, the Harmandir Sahib, is a building covered with gold. Similarly the
Wat Phra Kaew Wat Phra Kaew ( th, วัดพระแก้ว, , ), commonly known in English as the Temple of the Emerald Buddha and officially as Wat Phra Si Rattana Satsadaram, is regarded as the most sacred Wat, Buddhist temple in Thailand. The compl ...
emerald
Buddhist Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha Siddhartha Gautama, most commonly referred to as the Buddha, was a ...
temple A temple (from the Latin ) is a building reserved for spiritual rituals and activities such as prayer and sacrifice. Religions which erect temples include Christianity (whose temples are typically called church (building), churches), Hindui ...
( wat) in
Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Mainland Southeast Asia, Indochinese Peninsula, spanning , with a population of almost 70 mi ...
has ornamental gold-leafed statues and roofs. Some European king and queen's crowns were made of gold, and gold was used for the bridal crown since antiquity. An ancient Talmudic text circa 100 AD describes Rachel, wife of Rabbi Akiva, receiving a "Jerusalem of Gold" (diadem). A Greek burial crown made of gold was found in a grave circa 370 BC. Gold leaf MET DP260372.jpg,
Minoan The Minoan civilization was a Bronze Age Aegean civilization on the island of Crete and other Aegean Islands, whose earliest beginnings were from 3500BC, with the complex urban civilization beginning around 2000BC, and then declining from 1450BC ...
jewellery; 2300–2100 BC; various sizes;
Metropolitan Museum of Art The Metropolitan Museum of Art of New York City, colloquially "the Met", is the List of largest art museums, largest art museum in the Americas. Its permanent collection contains over two million works, divided among 17 curatorial departments. ...
(New York City) Earrings from Shulgi.JPG, Pair of
Sumer Sumer () is the earliest known civilization in the historical region of southern Mesopotamia (south-central Iraq), emerging during the Chalcolithic and Early Bronze Age, early Bronze Ages between the sixth and fifth millennium BC. It is one of ...
ian earrings with
cuneiform Cuneiform is a logo- syllabic script that was used to write several languages of the Ancient Middle East. The script was in active use from the early Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 B ...
inscriptions; 2093–2046 BC;
Sulaymaniyah Museum The Sulaymaniyah Museum (Kurdish: مۆزه‌خانه‌ی سلێمانی; Arabic: متحف السليمانية), or Slemani Museum, is an archeological museum located within heart of Sulaymaniyah in the Kurdistan Region of Iraq. It is the second ...
(
Sulaymaniyah Sulaymaniyah, also spelled as Slemani ( ku, سلێمانی, Silêmanî, ar, السليمانية, as-Sulaymāniyyah), is a city in the east of the Kurdistan Region of Iraq, not far from the Iran–Iraq border. It is surrounded by the Azmar, Go ...
, Iraq) Statuette of Amun MET DT553.jpg,
Ancient Egypt Ancient Egypt was a civilization in Northeast Africa situated in the Nile Valley. Ancient Egyptian civilization followed prehistoric Egypt and coalesced around 3100Anno Domini, BC (according to conventional Egyptian chronology) with the ...
ian statuette of
Amun Amun (; also Amon, Ammon, Amen; egy, wikt:jmn, jmn, reconstructed as (Old Egyptian and early Middle Egyptian) → (later Middle Egyptian) → (Late Egyptian), cop, Ⲁⲙⲟⲩⲛ, Amoun) romanized: ʾmn) was a major ancient Egyptian dei ...
; 945–715 BC; gold; ; Metropolitan Museum of Art Anillo de Sheshonq (46627183381).jpg, Ancient Egyptian signet ring; 664–525 BC; gold; diameter: ;
British Museum The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the list of largest art museums, largest and most comprehens ...
(London) Gold stater MET DP138743.jpg,
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek Dark ...
stater The stater (; grc, , , statḗr, weight) was an ancient coin used in various regions of Ancient Greece, Greece. The term is also used for similar coins, imitating Greek staters, minted elsewhere in ancient Europe. History The stater, as a Gr ...
; 323–315 BC; ; Metropolitan Museum of Art Gold funerary wreath MET DP257471.jpg, Etruscan funerary wreath; 4th–3rd century BC; length: ; Metropolitan Museum of Art Gold aureus of Hadrian MET DP104782b.jpg,
Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...
aureus The ''aureus'' ( ''aurei'', 'golden', used as a noun) was a gold coin of ancient Rome originally valued at 25 pure silver ''denarius, denarii'' (sin. denarius). The ''aureus'' was regularly issued from the 1st century BC to the beginning of th ...
of
Hadrian Hadrian (; la, Caesar Trâiānus Hadriānus ; 24 January 76 – 10 July 138) was Roman emperor from 117 to 138. He was born in Italica (close to modern Santiponce in Spain), a Roman ''municipium'' founded by Italic peoples, Italic settlers ...
; 134–138 AD; 7.4 g; Metropolitan Museum of Art Lime Container (Poporo) MET DT1262.jpg, Quimbaya lime container; 5th–9th century; gold; height: ; Metropolitan Museum of Art Byzantium, 11th century - Scyphate - 2001.25 - Cleveland Museum of Art.tif,
Byzantine The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople. It survi ...
scyphate Scyphate is a term frequently used in numismatics to refer to the wikt:concave, concave or "cup-shaped" Byzantine coins of the 11th–14th centuries. This usage emerged in the 19th century, when the term ''scyphatus'', attested in Southern Italy, s ...
; 1059–1067; diameter: ;
Cleveland Museum of Art The Cleveland Museum of Art (CMA) is an art museum in Cleveland, Ohio, located in the Wade Park District, in the University Circle neighborhood on the city's east side. Internationally renowned for its substantial holdings of Asian art, Asian and ...
(
Cleveland Cleveland ( ), officially the City of Cleveland, is a city in the United States, U.S. U.S. state, state of Ohio and the county seat of Cuyahoga County, Ohio, Cuyahoga County. Located in the northeastern part of the state, it is situated along ...
,
Ohio Ohio () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Of the List of states and territories of the United States, fifty U.S. states, it is the List of U.S. states and territories by area, 34th-l ...
, USA) Double Bat-Head Figure Pendant MET DT935.jpg,
Pre-Columbian In the history of the Americas, the pre-Columbian era spans from the Migration to the New World, original settlement of North and South America in the Upper Paleolithic period through European colonization of the Americas, European colonization, w ...
pendant with two bat-head warriors who carry spears; 11th–16th century; gold; overall: ; from the Chiriqui Province (
Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a List of transcontinental countries#North America and South America, transcontinental country spanning the Central America, southern ...
); Metropolitan Museum of Art Box with scene depicting Roman hero Gaius Mucius Scaevola before the Etruscan king Lars Porsena MET DP170836 (cropped).jpg, English Neoclassical box; 1741; overall: ; Metropolitan Museum of Art France, 18th century - Scent Bottle - 1916.315 - Cleveland Museum of Art.tif, French
Rococo Rococo (, also ), less commonly Roccoco or Late Baroque, is an exceptionally ornamental and theatrical style of architecture, art and decoration which combines asymmetry, scrolling curves, gilding, white and pastel colours, sculpted moulding, ...
glass bottle mounted in gold; circa 1775; overall: ; Cleveland Museum of Art


Etymology

"Gold" is
cognate In historical linguistics, cognates or lexical cognates are sets of words in different languages that have been inherited in direct descent from an etymological ancestor in a common parent language. Because language change can have radical ...
with similar words in many
Germanic languages The Germanic languages are a branch of the Indo-European languages, Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania and Southern Africa. The most widely spoken ...
, deriving via
Proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the linguistic reconstruction, reconstructed proto-language of the Germanic languages, Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from ...
*''gulþą'' from
Proto-Indo-European Proto-Indo-European (PIE) is the reconstructed common ancestor of the Indo-European language family. Its proposed features have been derived by linguistic reconstruction from documented Indo-European languages. No direct record of Proto-Indo-E ...
*''ǵʰelh₃-'' ("to shine, to gleam; to be yellow or green"). The symbol ''Au'' is from the la, aurum, the Latin word for "gold". The Proto-Indo-European ancestor of ''aurum'' was ''*h₂é-h₂us-o-'', meaning "glow". This word is derived from the same
root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often b ...
(Proto-Indo-European ''*h₂u̯es-'' "to dawn") as ''*h₂éu̯sōs'', the ancestor of the Latin word
Aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in polar regions of Earth, high-latitude regions (around the Arctic and Antarctic). Auroras display ...
, "dawn". This etymological relationship is presumably behind the frequent claim in scientific publications that ''aurum'' meant "shining dawn".Christie, A and Brathwaite, R. (Last updated 2 November 2011
Mineral Commodity Report 14 — Gold
Institute of geological and Nuclear sciences Ltd – Retrieved 7 June 2012


Culture

In popular culture gold is a high standard of excellence, often used in awards. Great achievements are frequently rewarded with gold, in the form of
gold medal A gold medal is a medal awarded for highest achievement in a non-military field. Its name derives from the use of at least a fraction of gold in form of plating or alloy An alloy is a mixture of chemical elements of which at least one is a ...
s, gold
trophies A trophy is a tangible, durable reminder of a specific achievement, and serves as a recognition or evidence of merit. Trophies are often awarded for sporting events, from youth sports to professional level athletics. In many sports medal A ...
and other decorations. Winners of athletic events and other graded competitions are usually awarded a gold medal. Many awards such as the
Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel#Nobel Prize, Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest ben ...
are made from gold as well. Other award statues and prizes are depicted in gold or are gold plated (such as the
Academy Awards The Academy Awards, better known as the Oscars, are awards for artistic and technical merit for the American and international film industry. The awards are regarded by many as the most prestigious, significant awards in the entertainment ind ...
, the
Golden Globe Awards The Golden Globe Awards are accolades bestowed by the Hollywood Foreign Press Association beginning in January 1944, recognizing excellence in both American and international film and television. Beginning in 2022, there are 105 members of t ...
, the
Emmy Awards The Emmy Awards, or Emmys, are an extensive range of awards for artistic and technical merit for the American and international television industry. A number of annual Emmy Award ceremonies are held throughout the calendar year, each with the ...
, the
Palme d'Or The Palme d'Or (; en, Golden Palm) is the highest prize awarded at the Cannes Film Festival. It was introduced in 1955 by the festival's organizing committee. Previously, from 1939 to 1954, the festival's highest prize was the Grand Prix du Fe ...
, and the
British Academy Film Awards The British Academy Film Awards, more commonly known as the BAFTA Film Awards is an annual award show hosted by the British Academy of Film and Television Arts (BAFTA) to honour the best British and international contributions to film. The cere ...
).
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical Greece, Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatet ...
in his
ethics Ethics or moral philosophy is a branch of philosophy that "involves systematizing, defending, and recommending concepts of morality, right and wrong action (philosophy), behavior".''Internet Encyclopedia of Philosophy'' The field of ethics, alo ...
used gold symbolism when referring to what is now known as the golden mean. Similarly, gold is associated with perfect or divine principles, such as in the case of the
golden ratio In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their summation, sum to the larger of the two quantities. Expressed algebraically, for quantities a and b with a > b > 0, where the Greek let ...
and the golden rule. Gold is further associated with the wisdom of aging and fruition. The fiftieth
wedding anniversary A wedding anniversary is the anniversary An anniversary is the date on which an event took place or an institution Institutions are humanly devised structures of rules and norms that shape and constrain individual behavior. All defi ...
is golden. A person's most valued or most successful latter years are sometimes considered "golden years". The height of a civilization is referred to as a
golden age The term Golden Age comes from Greek mythology, particularly the ''Works and Days'' of Hesiod, and is part of the description of temporal decline of the state of peoples through five Ages of Man, Ages, Gold being the first and the one during ...
.


Religion

In some forms of Christianity and Judaism, gold has been associated both with the sacred and evil. In the
Book of Exodus The Book of Exodus (from grc, Ἔξοδος, translit=Éxodos; he, שְׁמוֹת ''Šəmōṯ'', "Names") is the second book of the Bible. It narrates the story of the Exodus, in which the Israelites leave slavery in Biblical Egypt through th ...
, the
Golden Calf According to the Bible, the golden calf (עֵגֶל הַזָּהָב '' ‘ēgel hazzāhāv'') was an idol (a cult image) made by the Israelites when Moses went up to Mount Sinai (bible), Mount Sinai. In Hebrew language, Hebrew, the incident is ...
is a symbol of
idolatry Idolatry is the worship of a cult image or "idol" as though it were God. In Abrahamic religions (namely Judaism, Samaritanism, Christianity, the Baháʼí Faith, and Islam) idolatry connotes the worship of something or someone other than the Go ...
, while in the
Book of Genesis The Book of Genesis (from Greek ; Hebrew: בְּרֵאשִׁית ''Bəreʾšīt'', "In hebeginning") is the first book of the Hebrew Bible and the Christian Old Testament. Its Hebrew name is the same as its first word, ( "In the beginning") ...
,
Abraham Abraham, ; ar, , , name=, group= (originally Abram) is the common Hebrews, Hebrew patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father of the Covenant (biblical), special ...
was said to be rich in gold and silver, and Moses was instructed to cover the Mercy Seat of the Ark of the Covenant with pure gold. In
Byzantine The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople. It survi ...
icon An icon () is a religious work of art, most commonly a painting, in the cultures of the Eastern Orthodox, Oriental Orthodox, and Catholic Church, Catholic churches. They are not simply artworks; "an icon is a sacred image used in religious devo ...
ography the halos of Christ,
Virgin Mary Mary; arc, ܡܪܝܡ, translit=Mariam; ar, مريم, translit=Maryam; grc, Μαρία, translit=María; la, Maria; cop, Ⲙⲁⲣⲓⲁ, translit=Maria was a first-century Jews, Jewish woman of Nazareth, the wife of Saint Joseph, Jose ...
and the saints are often golden. In
Islam Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ''Allah'') as it was revealed to Muh ...
, gold (along with
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoon (silk), cocoons. The be ...
) is often cited as being forbidden for men to wear. Abu Bakr al-Jazaeri, quoting a
hadith Ḥadīth ( or ; ar, حديث, , , , , , , literally "talk" or "discourse") or Athar ( ar, أثر, , literally "remnant"/"effect") refers to what the majority of Muslims believe to be a record of the words, actions, and the silent approva ...
, said that " e wearing of silk and gold are forbidden on the males of my nation, and they are lawful to their women". This, however, has not been enforced consistently throughout history, e.g. in the Ottoman Empire. Further, small gold accents on clothing, such as in
embroidery Embroidery is the craft of decorating Textile, fabric or other materials using a sewing needle, needle to apply yarn, thread or yarn. Embroidery may also incorporate other materials such as pearls, beads, quills, and sequins. In modern days, emb ...
, may be permitted. In
ancient Greek religion Religious practices in ancient Greece encompassed a collection of beliefs, Ritual, rituals, and Greek mythology, mythology, in the form of both popular public religion and Cult (religious practice), cult practices. The application of the modern ...
and
mythology Myth is a folklore genre consisting of narratives that play a fundamental role in a society, such as foundational tales or origin myths. Since "myth" is widely used to imply that a story is not objectively true, the identification of a narra ...
,
Theia In Greek mythology, Theia (; grc, Θεία, Theía, divine, also rendered Thea or Thia), also called Euryphaessa ( grc, Εὐρυφάεσσα) "wide-shining", is one of the twelve Titans, the children of the earth goddess Gaia and the Sky deity ...
was seen as the goddess of gold, silver and other gems. According to
Christopher Columbus Christopher Columbus * lij, Cristoffa C(or)ombo * es, link=no, Cristóbal Colón * pt, Cristóvão Colombo * ca, Cristòfor (or ) * la, Christophorus Columbus. (; born between 25 August and 31 October 1451, died 20 May 1506) was a ...
, those who had something of gold were in possession of something of great value on Earth and a substance to even help souls to paradise.
Wedding ring A wedding ring or wedding band is a finger ring that indicates that its wearer is marriage, married. It is usually forged from metal, traditionally gold or another precious metal. Rings were used in ancient Rome during marriage, though the mo ...
s are typically made of gold. It is long lasting and unaffected by the passage of time and may aid in the ring symbolism of eternal vows before God and the perfection the marriage signifies. In Orthodox Christian wedding ceremonies, the wedded couple is adorned with a golden crown (though some opt for wreaths, instead) during the ceremony, an amalgamation of symbolic rites. On 24 August 2020,
Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
i archaeologists discovered a trove of early
Islam Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ''Allah'') as it was revealed to Muh ...
ic gold coins near the central city of Yavne. Analysis of the extremely rare collection of 425 gold coins indicated that they were from the late 9th century. Dating to around 1,100 years back, the gold coins were from the
Abbasid Caliphate The Abbasid Caliphate ( or ; ar, الْخِلَافَةُ الْعَبَّاسِيَّة, ') was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abdul-Muttalib ...
.


Production

According to the
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the USGS study th ...
in 2016, about of gold has been accounted for, of which 85% remains in active use.


Mining and prospecting

Since the 1880s, South Africa has been the source of a large proportion of the world's gold supply, and about 22% of the gold presently accounted is from
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...
. Production in 1970 accounted for 79% of the world supply, about 1,480 tonnes. In 2007
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
(with 276 tonnes) overtook South Africa as the world's largest gold producer, the first time since 1905 that South Africa had not been the largest. In 2020,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
was the world's leading gold-mining country, followed in order by Russia, Australia, the United States, Canada, and Ghana. In South America, the controversial project Pascua Lama aims at exploitation of rich fields in the high mountains of
Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific Ocean, Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar ...
, at the border between
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
and
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...
. It has been estimated that up to one-quarter of the yearly global gold production originates from artisanal or small scale mining. The city of
Johannesburg Johannesburg ( , , ; Zulu language, Zulu and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a Megacity#List of megacities, megacity, and is List of urban areas by p ...
located in South Africa was founded as a result of the
Witwatersrand Gold Rush The Witwatersrand Gold Rush was a gold rush in 1886 that led to the establishment of Johannesburg, South Africa. It was a part of the Mineral Revolution. Origins In the modern day province of Mpumalanga, gold miners in the alluvial mining, min ...
which resulted in the discovery of some of the largest natural gold deposits in recorded history. The gold fields are confined to the northern and north-western edges of the
Witwatersrand basin The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing scarp in South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bou ...
, which is a thick layer of
archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Ear ...
rocks located, in most places, deep under the Free State,
Gauteng Gauteng ( ) is one of the nine provinces of South Africa. The name in Sotho-Tswana, Sotho-Tswana languages means 'place of gold'. Situated on the Highveld, Gauteng is the smallest provinces of South Africa, province by land area in South Afric ...
and surrounding provinces.Truswell, J.F. (1977). ''The Geological Evolution of South Africa''. pp. 21–28. Purnell, Cape Town. These Witwatersrand rocks are exposed at the surface on the
Witwatersrand The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing Escarpment, scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfa ...
, in and around Johannesburg, but also in isolated patches to the south-east and south-west of Johannesburg, as well as in an arc around the Vredefort Dome which lies close to the center of the Witwatersrand basin. From these surface exposures the basin dips extensively, requiring some of the mining to occur at depths of nearly , making them, especially the Savuka and TauTona mines to the south-west of Johannesburg, the deepest mines on earth. The gold is found only in six areas where
archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Ear ...
rivers from the north and north-west formed extensive pebbly
Braided river A braided river, or braided channel, consists of a network of river channel (geography), channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers ...
deltas before draining into the "Witwatersrand sea" where the rest of the Witwatersrand sediments were deposited. The
Second Boer War The Second Boer War ( af, Tweede Vryheidsoorlog, , 11 October 189931 May 1902), also known as the Boer War, the Anglo–Boer War, or the South African War, was a conflict fought between the British Empire and the two Boer Republics (the South ...
of 1899–1901 between the
British Empire The British Empire was composed of the dominions, Crown colony, colonies, protectorates, League of Nations mandate, mandates, and other Dependent territory, territories ruled or administered by the United Kingdom and its predecessor states. I ...
and the
Afrikaner Afrikaners () are a South African ethnic group descended from Free Burghers, predominantly Dutch settlers first arriving at the Cape of Good Hope in the 17th and 18th centuries.Entry: Cape Colony. ''Encyclopædia Britannica Volume 4 Part 2: ...
Boer Boers ( ; af, Boere ()) are the descendants of the Dutch-speaking Free Burghers of the eastern Cape Colony, Cape frontier in Southern Africa during the 17th, 18th, and 19th centuries. From 1652 to 1795, the Dutch East India Company controll ...
s was at least partly over the rights of miners and possession of the gold wealth in South Africa. During the 19th century,
gold rush A gold rush or gold fever is a discovery of gold—sometimes accompanied by other precious metals and rare-earth minerals—that brings an onrush of miners seeking their fortune. Major gold rushes took place in the 19th century in Australia, New Ze ...
es occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at the Reed Gold Mine near Georgeville, North Carolina in 1803. The first major gold strike in the United States occurred in a small north Georgia town called Dahlonega. Further gold rushes occurred in
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
,
Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...
, the
Black Hills The Black Hills ( lkt, Ȟe Sápa; chy, Moʼȯhta-voʼhonáaeva; hid, awaxaawi shiibisha) is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black Elk P ...
,
Otago Otago (, ; mi, Ōtākou ) is a region of New Zealand located in the southern half of the South Island administered by the Otago Regional Council. It has an area of approximately , making it the country's second largest local government re ...
in New Zealand, a number of locations across
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
,
Witwatersrand The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing Escarpment, scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfa ...
in South Africa, and the Klondike in Canada. Grasberg mine located in Papua,
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. It consists of over List of islands of Indonesia, 17,000 islands, including Sumatr ...
is the largest gold mine in the world.


Extraction and refining

Gold extraction Gold extraction refers to the processes required to extract gold from its ores. The great majority of gold is extracted from dilute ores using a combination of chemical processes. About 2000 tons are obtained from the earth annually, plus anothe ...
is most economical in large, easily mined deposits. Ore grades as little as 0.5 parts per million (ppm) can be economical. Typical ore grades in
open-pit Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique of extracting rock (geology), rock or minerals from the earth from an open-air pit, sometimes known as a Borrow pit, b ...
mines are 1–5 ppm; ore grades in underground or
hard rock Hard rock or heavy rock is a loosely defined subgenre of rock music typified by aggressive vocals and Distortion (music), distorted Electric guitar, electric guitars. Hard rock began in the mid-1960s with the Garage rock, garage, Psychedelic roc ...
mines are usually at least 3 ppm. Because ore grades of 30 ppm are usually needed before gold is visible to the naked eye, in most gold mines the gold is invisible. The average gold mining and extraction costs were about $317 per troy ounce in 2007, but these can vary widely depending on mining type and ore quality; global mine production amounted to 2,471.1 tonnes. After initial production, gold is often subsequently refined industrially by the Wohlwill process which is based on
electrolysis In chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers the elements that make up matter to the compounds made of atoms, molecules and ions: their composition, str ...
or by the Miller process, that is chlorination in the melt. The Wohlwill process results in higher purity, but is more complex and is only applied in small-scale installations. Other methods of assaying and purifying smaller amounts of gold include parting and inquartation as well as
cupellation Cupellation is a refining process in metallurgy Metallurgy is a domain of Materials science, materials science and engineering that studies the physical and chemical behavior of metallic Chemical element, elements, their Inter-metallic alloy, ...
, or refining methods based on the dissolution of gold in aqua regia. As of 2020, the amount of
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetraval ...
produced in mining a kilogram of gold is 16 tonnes, while recycling a kilogram of gold produces 53 kilograms of equivalent. Approximately 30 percent of the global gold supply is recycled and not mined as of 2020. Corporations are starting to adopt gold recycling including jewelry companies such as Generation Collection and computer companies including
Dell Dell is an American based technology company. It develops, sells, repairs, and supports computers and related products and services. Dell is owned by its parent company, Dell Technologies. Dell sells personal computers (PCs), Server (computin ...
.


Consumption

The consumption of gold produced in the world is about 50% in jewelry, 40% in investments, and 10% in industry. According to the
World Gold Council The World Gold Council is the market development organisation for the gold industry. It works across all parts of the industry, from gold mining to investment, with the aim of stimulating and sustaining demand for gold. They frequently publish ...
, China was the world's largest single consumer of gold in 2013, overtaking India.


Pollution

Gold production is associated with contribution to hazardous pollution. Low-grade gold ore may contain less than one ppm gold metal; such ore is ground and mixed with
sodium cyanide Sodium cyanide is a Poison, poisonous compound with the chemical formula, formula sodium, Nacarbon, Cnitrogen, N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main ap ...
to dissolve the gold. Cyanide is a highly poisonous chemical, which can kill living creatures when exposed in minute quantities. Many cyanide spills from gold mines have occurred in both developed and developing countries which killed aquatic life in long stretches of affected rivers. Environmentalists consider these events major environmental disasters. Up to thirty tons of used ore can dumped as waste for producing one troy ounce of gold.Behind gold's glitter, torn lands and pointed questions
, ''The New York Times'', 24 October 2005
Gold ore dumps are the source of many heavy elements such as cadmium, lead, zinc, copper,
arsenic Arsenic is a chemical element with the Symbol (chemistry), symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has vario ...
,
selenium Selenium is a chemical element with the Symbol (chemistry), symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, su ...
and mercury. When sulfide-bearing minerals in these ore dumps are exposed to air and water, the sulfide transforms into
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen ...
which in turn dissolves these heavy metals facilitating their passage into surface water and ground water. This process is called
acid mine drainage Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mining, mines or Coal mining, coal mines. Acid rock drainage occurs naturally within some environments as part of ...
. These gold ore dumps are long-term, highly hazardous wastes second only to
nuclear waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, Rare-earth element, rare-earth mining, an ...
dumps. It was once common to use mercury to recover gold from ore, but today the use of mercury is largely limited to small-scale individual miners. Minute quantities of mercury compounds can reach water bodies, causing heavy metal contamination. Mercury can then enter into the human food chain in the form of
methylmercury Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a ...
.
Mercury poisoning Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rash ...
in humans causes incurable brain function damage and severe retardation. Gold extraction is also a highly energy-intensive industry, extracting ore from deep mines and grinding the large quantity of ore for further chemical extraction requires nearly 25 kWh of electricity per gram of gold produced.


Monetary use

Gold has been widely used throughout the world as
money Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are as ...
, for efficient indirect exchange (versus
barter In trade, barter (derived from ''baretor'') is a system of exchange in which participants in a transaction directly exchange goods or services for other goods or services without using a medium of exchange, such as money. Economists d ...
), and to store wealth in
hoard A hoard or "wealth deposit" is an archaeological Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of artifacts, architecture, ...
s. For exchange purposes, mints produce standardized gold bullion
coins A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint (facility), ...
, bars and other units of fixed weight and purity. The first known coins containing gold were struck in Lydia, Asia Minor, around 600 BC. The '' talent'' coin of gold in use during the periods of Grecian history both before and during the time of the life of Homer weighed between 8.42 and 8.75 grams. From an earlier preference in using silver, European economies re-established the minting of gold as coinage during the thirteenth and fourteenth centuries. Bills (that mature into gold coin) and gold certificates (convertible into gold coin at the issuing bank) added to the circulating stock of
gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from th ...
money in most 19th century industrial economies. In preparation for
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was List of wars and anthropogenic disasters by death toll, one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, ...
the warring nations moved to fractional gold standards, inflating their currencies to finance the war effort. 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. After
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
gold was replaced by a system of nominally convertible currencies related by fixed exchange rates following the
Bretton Woods system The Bretton Woods system of Monetary system, monetary management established the rules for commercial and financial relations among the United States, Canada, Western European countries, Australia, and Japan after the 1944 Bretton Woods Agree ...
.
Gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from th ...
s and the direct convertibility of currencies to gold have been abandoned by world governments, led in 1971 by the United States' refusal to redeem its dollars in gold.
Fiat currency Fiat money (from la, fiat, "let it be done") is a type of currency that is not backed by any commodity such as gold or silver. It is typically designated by the issuing government to be legal tender. Throughout history, fiat money was some ...
now fills most monetary roles.
Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel, St. Gall ...
was the last country to tie its currency to gold; this was ended by a referendum in 1999. Central banks continue to keep a portion of their liquid reserves as gold in some form, and metals exchanges such as the London Bullion Market Association still clear transactions denominated in gold, including future delivery contracts. Today,
gold mining Gold mining is the resource extraction, extraction of gold resources by mining. Historically, mining gold from Alluvium, alluvial deposits used manual separation processes, such as gold panning. However, with the expansion of gold mining to Ore ...
output is declining. With the sharp growth of economies in the 20th century, and increasing foreign exchange, the world's
gold reserve A gold reserve is the gold held by a national central bank, intended mainly as a guarantee to redeem promises to pay depositors, note holders (e.g. paper money), or trading peers, during the eras of the gold standard, and also as a store of v ...
s and their trading market have become a small fraction of all markets and fixed exchange rates of currencies to gold have been replaced by floating prices for gold and gold future contract. Though the gold stock grows by only 1% or 2% per year, very little metal is irretrievably consumed. Inventory above ground would satisfy many decades of industrial and even artisan uses at current prices. The gold proportion (fineness) of alloys is measured by
karat The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of ''fine metal'' therein, in proportion to the total weight which includes alloying base metals and any impurity, impurities. Alloy metals are added to incre ...
(k). Pure gold (commercially termed ''fine'' gold) is designated as 24 karat, abbreviated 24k. English gold coins intended for circulation from 1526 into the 1930s were typically a standard 22k alloy called
crown gold Crown gold is a 22 Carat (purity), karat (kt) gold alloy used in the Crown (English coin), crown coin introduced in England in 1526 (by Henry VIII of England, Henry VIII). In this alloy, the proportion of gold is 22 parts out of 24 (91.667% gold) ...
, for hardness (American gold coins for circulation after 1837 contain an alloy of 0.900 fine gold, or 21.6 kt). Although the prices of some
platinum Platinum is a chemical element with the Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
group metals can be much higher, gold has long been considered the most desirable of
precious metal Precious metals are rare, naturally occurring metallic chemical elements of high Value (economics), economic value. Chemically, the precious metals tend to be less reactivity (chemistry), reactive than most elements (see noble metal). They ...
s, and its value has been used as the standard for many
currencies A currency, "in circulation", from la, Wikt:currens, currens, -entis, literally meaning "running" or "traversing" is a standardization of money in any form, in use or currency in circulation, circulation as a medium of exchange, for example ba ...
. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties. Gold as a sign of wealth and prestige was ridiculed by
Thomas More Sir Thomas More (7 February 1478 – 6 July 1535), veneration, venerated in the Catholic Church as Saint Thomas More, was an English lawyer, judge, social philosopher, author, statesman, and noted Renaissance humanist. He also served Henry VII ...
in his treatise ''
Utopia A utopia ( ) typically describes an imaginary community or society that possesses highly desirable or nearly perfect qualities for its members. It was coined by Sir Thomas More for his 1516 book '' Utopia'', describing a fictional island soc ...
''. On that imaginary island, gold is so abundant that it is used to make chains for slaves, tableware, and lavatory seats. When ambassadors from other countries arrive, dressed in ostentatious gold jewels and badges, the Utopians mistake them for menial servants, paying homage instead to the most modestly dressed of their party. The
ISO 4217 ISO 4217 is a Standardization, standard published by the International Organization for Standardization (ISO) that defines alpha codes and numeric codes for the representation of Currency, currencies and provides information about the relation ...
currency code of gold is XAU. Many holders of gold store it in form of
bullion Bullion is non-ferrous metal that has been refined to a high standard of chemical element, elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. ...
coins or bars as a hedge against
inflation In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reductio ...
or other economic disruptions, though its efficacy as such has been questioned; historically, it has not proven itself reliable as a hedging instrument. Modern
bullion coin Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes from ...
s for investment or collector purposes do not require good mechanical wear properties; they are typically fine gold at 24k, although the
American Gold Eagle The American Gold Eagle is an official gold bullion coin of the United States. Authorized under the Gold Bullion Coin Act of 1985, it was first released by the United States Mint in 1986. Because the term "Eagle (United States coin), eagle" a ...
and the British gold sovereign continue to be minted in 22k (0.92) metal in historical tradition, and the South African
Krugerrand The Krugerrand (; ) is a South African coin, first minted on 3 July 1967 to help market South African gold and produced by Rand Refinery and the South African Mint. The name is a compound of ''Paul Kruger'', the former President of the South Af ...
, first released in 1967, is also 22k (0.92). The ''special issue''
Canadian Gold Maple Leaf The Canadian Gold Maple Leaf (GML) is a gold coin, gold bullion coin that is issued annually by the Government of Canada. It is produced by the Royal Canadian Mint. The Gold Maple Leaf is legal tender with a face value of 50 Canadian dollars. Th ...
coin contains the highest purity gold of any
bullion coin Bullion is non-ferrous metal that has been refined to a high standard of elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. It comes from ...
, at 99.999% or 0.99999, while the ''popular issue'' Canadian Gold Maple Leaf coin has a purity of 99.99%. In 2006, the
United States Mint The United States Mint is a bureau of the United States Department of the Treasury, Department of the Treasury responsible for producing currency, coinage for the United States to conduct its trade and commerce, as well as controlling the movemen ...
began producing the American Buffalo gold bullion coin with a purity of 99.99%. The
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
n Gold Kangaroos were first coined in 1986 as the Australian Gold Nugget but changed the reverse design in 1989. Other modern coins include the
Austria The Republic of Austria, commonly just Austria, , bar, Östareich is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine States of Austria, states, one of which is the capital, Vienna, ...
n
Vienna Philharmonic The Vienna Philharmonic (VPO; german: Wiener Philharmoniker, links=no) is an orchestra that was founded in 1842 and is considered to be one of the finest in the world. The Vienna Philharmonic is based at the Musikverein in Vienna, Austria. Its ...
bullion coin and the
Chinese Gold Panda The Chinese Gold Panda () is a series of gold coin, gold bullion coins issued by the China, People's Republic of China. The Official Mint of the China, People's Republic of China introduced the panda gold bullion coins in 1982. The panda design c ...
.


Price

, gold is valued at around $42 per gram ($1,300 per troy ounce). Like other precious metals, gold is measured by
troy weight Troy weight is a system of Physical unit, units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The troy weight units are the Grain (unit), grain, the pennyweight (24 grains), the troy oun ...
and by grams. The proportion of gold in the alloy is measured by ''
karat The fineness of a precious metal object (coin, bar, jewelry, etc.) represents the weight of ''fine metal'' therein, in proportion to the total weight which includes alloying base metals and any impurity, impurities. Alloy metals are added to incre ...
'' (k), with 24 karat (24k) being pure gold (100%), and lower karat numbers proportionally less (18k = 75%). The purity of a
gold bar A gold bar, also called gold bullion or gold ingot, is a quantity of refining, refined metallic gold of any shape that is made by a bar producer meeting standard conditions of manufacture, labeling, and record keeping. Larger gold bars that are ...
or coin can also be expressed as a decimal figure ranging from 0 to 1, known as the
millesimal fineness The fineness of a precious metal Precious metals are rare, naturally occurring metallic chemical elements of high Value (economics), economic value. Chemically, the precious metals tend to be less reactivity (chemistry), reactive than mos ...
, such as 0.995 being nearly pure. The price of gold is determined through trading in the gold and derivatives markets, but a procedure known as the Gold Fixing in
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
, originating in September 1919, provides a daily benchmark price to the industry. The afternoon fixing was introduced in 1968 to provide a price when US markets are open.


History

Historically gold coinage was widely used as currency; when
paper money A banknote—also called a bill ( North American English), paper money, or simply a note—is a type of negotiable promissory note, made by a bank A bank is a financial institution that accepts deposits from the public and creates ...
was introduced, it typically was a
receipt A receipt (also known as a packing list, packing slip, packaging slip, (delivery) docket, shipping list, delivery list, bill of the parcel, Manifest (transportation), manifest, or customer receipt) is a document acknowledging that a person ha ...
redeemable for gold coin or
bullion Bullion is non-ferrous metal that has been refined to a high standard of chemical element, elemental purity. The term is ordinarily applied to bulk metal used in the production of coins and especially to precious metals such as gold and silver. ...
. In a
monetary Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are as ...
system known as the
gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from th ...
, a certain
weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weigh ...
of gold was given the name of a unit of currency. For a long period, the United States government set the value of the US dollar so that one
troy ounce Troy weight is a system of Physical unit, units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The troy weight units are the Grain (unit), grain, the pennyweight (24 grains), the troy oun ...
was equal to $20.67 ($0.665 per gram), but in 1934 the dollar was devalued to $35.00 per troy ounce ($0.889/g). 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 In macroeconomics and modern monetary policy, a devaluation is an official lowering of the value of a country's currency within a fixed exchange-rate system, in which a monetary authority formally sets a lower exchange rate of the national curren ...
against increased gold demand. 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.
Central bank A central bank, reserve bank, or monetary authority is an institution that manages the currency and monetary policy of a country or monetary union, and oversees their commercial bank, commercial banking system. In contrast to a commercial ba ...
s still hold historical gold reserves as a
store of value A store of value is any commodity or asset that would normally retain purchasing power into the future and is the function of the asset that can be saved, retrieved and exchanged at a later time, and be predictably useful when retrieved. The most ...
although the level has generally been declining. The largest gold depository in the world is that of the U.S. Federal Reserve Bank in New York, which holds about 3% of the gold known to exist and accounted for today, as does the similarly laden U.S. Bullion Depository at
Fort Knox Fort Knox is a United States Army installation in Kentucky, south of Louisville, Kentucky, Louisville and north of Elizabethtown, Kentucky, Elizabethtown. It is adjacent to the United States Bullion Depository, which is used to house a large po ...
. In 2005 the
World Gold Council The World Gold Council is the market development organisation for the gold industry. It works across all parts of the industry, from gold mining to investment, with the aim of stimulating and sustaining demand for gold. They frequently publish ...
estimated total global gold supply to be 3,859 tonnes and demand to be 3,754 tonnes, giving a surplus of 105 tonnes. After 15 August 1971 Nixon shock, the price began to greatly increase, and between 1968 and 2000 the price of gold ranged widely, from a high 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). Prices increased rapidly from 2001, but the 1980 high was not exceeded until 3 January 2008, when a new maximum of $865.35 per
troy ounce Troy weight is a system of Physical unit, units of mass that originated in 15th-century England, and is primarily used in the precious metals industry. The troy weight units are the Grain (unit), grain, the pennyweight (24 grains), the troy oun ...
was set. Another record price was set on 17 March 2008, at $1023.50 per troy ounce ($32.91/g). In late 2009, gold markets experienced renewed momentum upwards due to increased demand and a weakening US dollar. On 2 December 2009, gold reached a new high closing at $1,217.23. Gold further rallied hitting new highs in May 2010 after the European Union debt crisis prompted further purchase of gold as a safe asset. On 1 March 2011, gold hit a new all-time high of $1432.57, based on
investor An investor is a person who allocates financial capital with the expectation of a future Return on capital, return (profit) or to gain an advantage (interest). Through this allocated capital most of the time the investor purchases some specie ...
concerns regarding ongoing unrest in
North Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in t ...
as well as in the
Middle East The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabian Peninsula, Arabia (including the Arabian Peninsula and Bahrain), Anatolia, Asia Minor (Asian part of Turkey except Hatay Pro ...
. From April 2001 to August 2011, spot gold prices more than quintupled in value against the US dollar, hitting a new all-time high of $1,913.50 on 23 August 2011, prompting speculation that the long secular bear market had ended and a
bull market A market trend is a perceived tendency of financial markets to move in a particular direction over time. Analysts classify these trends as ''secular'' for long time-frames, ''primary'' for medium time-frames, and ''secondary'' for short time-fram ...
had returned. However, the price then began a slow decline towards $1200 per troy ounce in late 2014 and 2015. In August 2020, the gold price picked up to US$2060 per ounce after a complexive growth of 59% from August 2018 to October 2020, a period during which it outplaced the Nasdaq total return of 54%. Gold futures are traded on the COMEX exchange. These contacts are priced in USD per troy ounce (1 troy ounce = 31.1034768 grams). Below are the CQG contract specifications outlining the futures contracts:


Medicinal uses

Medicinal applications of gold and its complexes have a long history dating back thousands of years. Several gold complexes have been applied to treat
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and ...
, the most frequently used being aurothiomalate, aurothioglucose, and auranofin. Both gold(I) and gold(III) compounds have been investigated as possible anti-cancer drugs. For gold(III) complexes, reduction to gold(0/I) under physiological conditions has to be considered. Stable complexes can be generated using different types of bi-, tri-, and tetradentate ligand systems, and their efficacy has been demonstrated in vitro and in vivo.


Other applications


Jewelry

Because of the softness of pure (24k) gold, it is usually
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...
ed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower karat rating, typically 22k, 18k, 14k or 10k, contain higher percentages of copper or other base metals or silver or palladium in the alloy.Jewellery Alloys
World Gold Council
Nickel is toxic, and its release from nickel white gold is controlled by legislation in Europe. Palladium-gold alloys are more expensive than those using nickel. High-karat white gold alloys are more resistant to corrosion than are either pure silver or
sterling silver Sterling silver is an alloy of silver containing 92.5% by weight of silver and 7.5% by weight of other metals, usually copper. The sterling silver Silver standards, standard has a minimum millesimal fineness of 925. ''Fineness, Fine silver'', whic ...
. The Japanese craft of
Mokume-gane is a Japanese metalworking procedure which produces a mixed-metal laminate with distinctive layered patterns; the term is also used to refer to the resulting laminate itself. The term translates closely to "wood grain metal" or "wood eye metal" ...
exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects. By 2014, the gold jewelry industry was escalating despite a dip in gold prices. Demand in the first quarter of 2014 pushed turnover to $23.7 billion according to a
World Gold Council The World Gold Council is the market development organisation for the gold industry. It works across all parts of the industry, from gold mining to investment, with the aim of stimulating and sustaining demand for gold. They frequently publish ...
report. Gold
solder Solder (; North American English, NA: ) is a fusible alloy, fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces afte ...
is used for joining the components of gold jewelry by high-temperature hard soldering or
brazing Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...
. If the work is to be of
hallmark A hallmark is an official mark or series of marks struck on items made of metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, s ...
ing quality, the gold solder alloy must match the
fineness The fineness of a precious metal Precious metals are rare, naturally occurring metallic chemical elements of high Value (economics), economic value. Chemically, the precious metals tend to be less reactivity (chemistry), reactive than mos ...
(purity) of the work, and alloy formulas are manufactured to color-match yellow and white gold. Gold solder is usually made in at least three melting-point ranges referred to as Easy, Medium and Hard. By using the hard, high-melting point solder first, followed by solders with progressively lower melting points, goldsmiths can assemble complex items with several separate soldered joints. Gold can also be made into thread and used in
embroidery Embroidery is the craft of decorating Textile, fabric or other materials using a sewing needle, needle to apply yarn, thread or yarn. Embroidery may also incorporate other materials such as pearls, beads, quills, and sequins. In modern days, emb ...
.


Electronics

Only 10% of the world consumption of new gold produced goes to industry, but by far the most important industrial use for new gold is in fabrication of corrosion-free
electrical connectors Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between ...
in computers and other electrical devices. For example, according to the World Gold Council, a typical cell phone may contain 50 mg of gold, worth about 2 dollars 82 cents. But since nearly one billion cell phones are produced each year, a gold value of US$2.82 in each phone adds to US$2.82 billion in gold from just this application. (Prices updated to November 2022) Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments (including resistance to non-chlorinated acids) has led to its widespread industrial use in the electronic era as a thin-layer coating on
electrical connector Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between ...
s, thereby ensuring good connection. For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and
USB Universal Serial Bus (USB) is an technical standard, industry standard that establishes specifications for cables, connectors and communication protocol, protocols for connection, communication and power supply (Interface (computing), interfa ...
cables. The benefit of using gold over other connector metals such as
tin Tin is a chemical element with the Chemical symbol, symbol Sn (from la, :la:Stannum, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand wit ...
in these applications has been debated; gold connectors are often criticized by audio-visual experts as unnecessary for most consumers and seen as simply a marketing ploy. However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as Computer program, pr ...
s, communications equipment,
spacecraft A spacecraft is a vehicle or machine designed to spaceflight, fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth ...
,
jet aircraft A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines. Whereas the engines in Propeller (aircraft), propeller-powered aircraft generally achieve their maximum efficiency at much lower speed ...
engines) remains very common. Besides sliding electrical contacts, gold is also used in
electrical contacts An electrical contact is an electrical circuit component found in electrical switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the ...
because of its resistance to
corrosion Corrosion is a Erosion, natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosio ...
,
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
,
ductility Ductility is a List of materials properties, mechanical property commonly described as a material's amenability to Drawing (manufacturing), drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a materia ...
and lack of
toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect ...
. Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts. Fine gold wires are used to connect
semiconductor device A semiconductor device is an electronic component that relies on the electronics, electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its co ...
s to their packages through a process known as
wire bonding Wire bonding is the method of making interconnections between an integrated circuit (IC) or other semiconductor device and its integrated circuit packaging, packaging during Fabrication (semiconductor), semiconductor device fabrication. Altho ...
. The concentration of free electrons in gold metal is 5.91×1022 cm−3. Gold is highly
conductive In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...
to electricity, and has been used for
electrical wiring Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets, and light fittings in a structure. Wiring is subject to safety standards for design and installation. Allowable ...
in some high-energy applications (only silver and copper are more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the
Manhattan Project The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
's atomic experiments, but large high-current silver wires were used in the
calutron A calutron is a mass spectrometer originally designed and used for isotope separation, separating the isotopes of uranium. It was developed by Ernest Lawrence during the Manhattan Project and was based on his earlier invention, the cyclotron. I ...
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 silver is contained in electronic technology in Japan.


Medicine

Metallic and gold compounds have long been used for medicinal purposes. Gold, usually as the metal, is perhaps the most anciently administered medicine (apparently by shamanic practitioners) and known to
Dioscorides Pedanius Dioscorides ( grc-gre, Πεδάνιος Διοσκουρίδης, ; 40–90 AD), “the father of pharmacognosy”, was a Greek physician, pharmacologist, botanist, and author of ''De materia medica'' (, On Medical Material) —a 5-vol ...
. In medieval times, gold was often seen as beneficial for the health, in the belief that something so rare and beautiful could not be anything but healthy. Even some modern esotericists and forms of
alternative medicine Alternative medicine is any practice that aims to achieve the healing effects of medicine despite lacking biological plausibility, testability, repeatability, or evidence from clinical trials. Complementary medicine (CM), complementary and alte ...
assign metallic gold a healing power. In the 19th century gold had a reputation as an
anxiolytic An anxiolytic (; also antipanic or antianxiety agent) is a medication or other intervention that reduces anxiety (mood), anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the tre ...
, a therapy for nervous disorders. Depression,
epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent Seizure, epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal el ...
,
migraine Migraine (, ) is a common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...
, and glandular problems such as
amenorrhea Amenorrhea is the absence of a Menstrual cycle, menstrual period in a woman of reproductive age. Physiological states of amenorrhoea are seen, most commonly, during pregnancy and lactation (breastfeeding). Outside the reproductive years, there is ...
and
impotence Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the Human penis, penis fails to become or stay Erection, erect during Human sexual activity, sexual activity. It is the most common sexual problem in ...
were treated, and most notably
alcoholism Alcoholism is, broadly, any drinking of alcohol (drug), alcohol that results in significant Mental health, mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognize ...
(Keeley, 1897). The apparent paradox of the actual toxicology of the substance suggests the possibility of serious gaps in the understanding of the action of gold in physiology. Only salts and radioisotopes of gold are of pharmacological value, since elemental (metallic) gold is inert to all chemicals it encounters inside the body (e.g., ingested gold cannot be attacked by stomach acid). Some gold salts do have
anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or ...
properties and at present two are still used as pharmaceuticals in the treatment of arthritis and other similar conditions in the US ( sodium aurothiomalate and auranofin). These drugs have been explored as a means to help to reduce the pain and swelling of
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and ...
, and also (historically) against
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
and some parasites. Gold alloys are used in
restorative dentistry Restorative dentistry is the study, diagnosis and integrated management of diseases of the teeth and their supporting structures and the rehabilitation of the dentition to functional and aesthetic requirements of the individual. Restorative dentis ...
, especially in tooth restorations, such as crowns and permanent
bridges A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...
. The gold alloys' slight malleability facilitates the creation of a superior molar mating surface with other teeth and produces results that are generally more satisfactory than those produced by the creation of porcelain crowns. The use of gold crowns in more prominent teeth such as incisors is favored in some cultures and discouraged in others.
Colloidal gold Colloidal gold is a sol (colloid), sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The colloid is usually either wine-red coloured (for spherical particles less than 100 nanometre, nm) or blue/purple (for l ...
preparations (suspensions of
gold nanoparticle Colloidal gold is a sol (colloid), sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The colloid is usually either wine-red coloured (for spherical particles less than 100 nanometre, nm) or blue/purple (for l ...
s) in water are intensely red-
color Color (American English) or colour (British English) is the visual perception, visual perceptual Physical property, property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physica ...
ed, and can be made with tightly controlled particle sizes up to a few tens of nanometers across by reduction of gold chloride with
citrate Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a Transparency and translucency, colorless Weak acid, weak organic acid. It occurs naturally in Citrus, citrus fruits. In biochemistry, it is an intermedi ...
or ascorbate ions. Colloidal gold is used in research applications in medicine, biology and
materials science Materials science is an interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of multiple academic disciplines into one activity (e.g., a research project). It draws knowledge from several other field ...
. The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells. In ultrathin sections of tissues viewed by
electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
, the immunogold labels appear as extremely dense round spots at the position of the
antigen In immunology, an antigen (Ag) is a molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. ...
. Gold, or alloys of gold and
palladium Palladium is a chemical element with the Symbol (chemistry), symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the 2 Pallas, asteroid ...
, 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. The coating, which is usually applied by
sputtering In physics, sputtering is a phenomenon in which microscopic particles of a solid material are ejected from its surface, after the material is itself bombarded by energetic particles of a plasma or gas. It occurs naturally in outer space, and ...
with an
argon Argon is a chemical element with the Symbol (chemistry), symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 Parts-per notatio ...
plasma Plasma or plasm may refer to: Science * Plasma (physics) Plasma () 1, where \nu_ is the electron gyrofrequency and \nu_ is the electron collision rate. It is often the case that the electrons are magnetized while the ions are not. Magnetized ...
, has a triple role in this application. Gold's very high electrical conductivity drains
electrical charge Electricity is the set of physics, physical Phenomenon, phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagne ...
to earth, and its very high density provides stopping power for electrons in the
electron beam Cathode rays or electron beam (e-beam) are streams of electrons observed in vacuum tube, discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glo ...
, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases the
spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolution ...
of the image. Gold also produces a high output of
secondary electrons Secondary electrons are electrons generated as ionization products. They are called 'secondary' because they are generated by other radiation (the ''primary'' radiation). This radiation can be in the form of ions, electrons, or photons with suffici ...
when irradiated by an electron beam, and these low-energy electrons are the most commonly used signal source used in the scanning electron microscope. The isotope gold-198 (
half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
2.7 days) is used in
nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease A disease is a particular abnormal condition that negatively affects the structure or ...
, in some
cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Poss ...
treatments and for treating other diseases.


Cuisine

* Gold can be used in food and has the
E number E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly f ...
175. In 2016, the
European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union, agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was ...
published an opinion on the re-evaluation of gold as a food additive. Concerns included the possible presence of minute amounts of gold nanoparticles in the food additive, and that gold nanoparticles have been shown to be
genotoxic Genotoxicity is the property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right ...
in mammalian cells
in vitro ''In vitro'' (meaning in glass, or ''in the glass'') Research, studies are performed with microorganisms, Cell (biology), cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", thes ...
. *
Gold leaf Gold leaf is gold that has been hammered into thin sheets (usually around 0.1 µm thick) by goldbeating and is often used for gilding. Gold leaf is available in a wide variety of carat (purity), karats and shades. The most commonly used g ...
, flake or dust is used on and in some gourmet foods, notably sweets and drinks as decorative ingredient. Gold flake was used by the nobility in
medieval Europe In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...
as a decoration in food and drinks, in the form of leaf, flakes or dust, either to demonstrate the host's wealth or in the belief that something that valuable and rare must be beneficial for one's health. * Danziger Goldwasser (German: Gold water of Danzig) or Goldwasser ( en, Goldwater) is a traditional German herbal
liqueur A liqueur (; ; ) is an alcoholic drink composed of Liquor, spirits (often rectified spirit) and additional flavorings such as sugar, fruits, herbs, and spices. Often served with or after dessert, they are typically heavily sweetened and un-aged ...
produced in what is today
Gdańsk Gdańsk ( , also ; ; csb, Gduńsk;Stefan Ramułt, ''Słownik języka pomorskiego, czyli kaszubskiego'', Kraków 1893, Gdańsk 2003, ISBN 83-87408-64-6. , Johann Georg Theodor Grässe, ''Orbis latinus oder Verzeichniss der lateinischen Benen ...
,
Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called Voivodeships of Poland, voivodeships, covering an area of . Poland has a population of over 38 million and is ...
, and
Schwabach Schwabach () is a German Town#Germany, city of about 40,000 inhabitants near Nuremberg in the centre of the region of Franconia in the north of Bavaria. The city is an autonomous administrative district (''kreisfreie Stadt''). Schwabach is also ...
, Germany, and contains flakes of gold leaf. There are also some expensive (c. $1000) cocktails which contain flakes of gold leaf. However, since metallic gold is inert to all body chemistry, it has no taste, it provides no nutrition, and it leaves the body unaltered. *
Vark Vark (also varak or warq) is a fine filigree Filigree (also less commonly spelled ''filagree'', and formerly written ''filigrann'' or ''filigrene'') is a form of intricate metalwork used in jewellery and other small forms of metalwork. In ...
is a foil composed of a pure metal that is sometimes gold, and is used for garnishing sweets in South Asian cuisine.


Miscellanea

* Gold produces a deep, intense red color when used as a coloring agent in cranberry glass. * In photography, gold toners are used to shift the color of
silver bromide Silver bromide (AgBr) is a soft, pale-yellow, water-insoluble salt well known (along with other silver halides) for its unusual photosensitive, sensitivity to light. This property has allowed silver halides to become the basis of modern photograph ...
black-and-white prints towards brown or blue tones, or to increase their stability. Used on sepia-toned prints, gold toners produce red tones. Kodak published formulas for several types of gold toners, which use gold as the chloride. * Gold is a good reflector of
electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
such as
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
and
visible light Light or visible light is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequency, fr ...
, as well as
radio waves Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...
. It is used for the protective coatings on many artificial
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radiois ...
s, in infrared protective faceplates in thermal-protection suits and astronauts' helmets, and in
electronic warfare Electronic warfare (EW) is any action involving the use of the electromagnetic spectrum (EM spectrum) or Directed-energy weapon, directed energy to control the spectrum, attack an enemy, or impede enemy assaults. The purpose of electronic warfare ...
planes such as the
EA-6B Prowler The Northrop Grumman (formerly Grumman) EA-6B Prowler is a Twinjet, twin-engine, four-seat, mid-wing electronic-warfare aircraft derived from the Grumman A-6 Intruder, A-6 Intruder airframe. The EA-6A was the initial electronic warfare version ...
. * Gold is used as the reflective layer on some high-end CDs. * Automobiles may use gold for heat shielding.
McLaren McLaren Racing Limited is a British auto racing, motor racing team based at the McLaren Technology Centre in Woking, Surrey, England. McLaren is best known as a Formula One List of Formula One constructors, constructor, the second oldest activ ...
uses gold foil in the engine compartment of its F1 model. * Gold can be manufactured so thin that it appears semi-transparent. It is used in some aircraft cockpit windows for
de-icing Deicing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only deice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or preve ...
or anti-icing by passing electricity through it. The heat produced by the resistance of the gold is enough to prevent ice from forming. * Gold is attacked by and dissolves in alkaline solutions of potassium or sodium
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers th ...
, to form the salt gold cyanide—a technique that has been used in extracting metallic gold from ores in the
cyanide process Gold cyanidation (also known as the cyanide process or the MacArthur-Forrest process) is a Hydrometallurgy, hydrometallurgical technique for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex. It is t ...
. Gold cyanide is the
electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electron The electron ( or ) is a subatomic particle with a negative one elementary charge, elementary electr ...
used in commercial
electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...
of gold onto base metals and
electroforming Electroforming is a metal forming process in which parts are fabricated through Electrophoretic deposition, electrodeposition on a model, known in the industry as a mandrel. Conductive (metallic) mandrels are treated to create a mechanical parting ...
. * Gold chloride ( chloroauric acid) solutions are used to make colloidal gold by reduction with
citrate Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a Transparency and translucency, colorless Weak acid, weak organic acid. It occurs naturally in Citrus, citrus fruits. In biochemistry, it is an intermedi ...
or ascorbate
ions An ion () is an atom or molecule with a net electric charge, electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be po ...
. Gold chloride and gold oxide are used to make cranberry or red-colored glass, which, like
colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others ext ...
al gold suspensions, contains evenly sized spherical
gold nanoparticle Colloidal gold is a sol (colloid), sol or colloidal suspension of nanoparticles of gold in a fluid, usually water. The colloid is usually either wine-red coloured (for spherical particles less than 100 nanometre, nm) or blue/purple (for l ...
s. * Gold, when dispersed in nanoparticles, can act as a
heterogeneous catalyst In chemistry, heterogeneous catalysis is catalysis where the Phase (matter), phase of catalysts differs from that of the reactants or product (chemistry), products. The process contrasts with homogeneous catalysis where the reactants, products and ...
of chemical reactions.


Toxicity

Pure metallic (elemental) gold is non-toxic and non-irritating when ingested and is sometimes used as a food decoration in the form of
gold leaf Gold leaf is gold that has been hammered into thin sheets (usually around 0.1 µm thick) by goldbeating and is often used for gilding. Gold leaf is available in a wide variety of carat (purity), karats and shades. The most commonly used g ...
. Metallic gold is also a component of the alcoholic drinks Goldschläger, Gold Strike, and Goldwasser. Metallic gold is approved as a
food additive Food additives are substances added to food to preserve Taste, flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), sal ...
in the EU ( E175 in the
Codex Alimentarius The Codex Alimentarius () is a collection of internationally recognized standards, codes of practice, guidelines, and other recommendations published by the Food and Agriculture Organization of the United Nations relating to food, food production ...
). Although the gold ion is toxic, the acceptance of metallic gold as a food additive is due to its relative chemical inertness, and resistance to being corroded or transformed into soluble salts (gold compounds) by any known chemical process which would be encountered in the human body. Soluble compounds ( gold salts) such as
gold chloride Gold chloride can refer to: * Gold(I) chloride (gold monochloride), AuCl * Gold(I,III) chloride (gold dichloride, tetragold octachloride), Au4Cl8 * Gold(III) chloride (gold trichloride, digold hexachloride), Au2Cl6 * Chloroauric acid, HAuCl4 (brown ...
are toxic to the liver and kidneys. Common
cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a natural science that covers th ...
salts of gold such as potassium gold cyanide, used in gold
electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...
, are toxic by virtue of both their cyanide and gold content. There are rare cases of lethal gold poisoning from potassium gold cyanide. Gold toxicity can be ameliorated with
chelation therapy Chelation therapy is a medical procedure that involves the administration of Chelation, chelating agents to remove heavy metals from the body. Chelation therapy has a long history of use in clinical toxicology and remains in use for some very sp ...
with an agent such as
dimercaprol Dimercaprol, also called British anti-Lewisite (BAL), is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preve ...
. Gold metal was voted
Allergen of the Year Allergen of the Year is an annual award voted upon by the American Contact Dermatitis Society. This is "designed to draw attention to allergen An allergen is a type of antigen that produces an abnormally vigorous immune response in which the imm ...
in 2001 by the American Contact Dermatitis Society; gold contact allergies affect mostly women. Despite this, gold is a relatively non-potent contact allergen, in comparison with metals like
nickel Nickel is a chemical element with Chemical symbol, symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and Ductility, ductile transition metal. Pure nickel is chemically reactive bu ...
. A sample of the fungus ''
Aspergillus niger ''Aspergillus niger'' is a mold classified within the ''Nigri'' section of the '' Aspergillus'' genus. The ''Aspergillus'' genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on d ...
'' was found growing from gold mining solution; and was found to contain cyano metal complexes, such as gold, silver, copper, iron and zinc. The fungus also plays a role in the solubilization of heavy metal sulfides.


See also

* Bulk leach extractable gold, for sampling ores * Chrysiasis (dermatological condition) * Digital gold currency, form of electronic currency * GFMS business consultancy * Gold fingerprinting, use impurities to identify an alloy *
Gold standard A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from th ...
in banking * List of countries by gold production * Tumbaga, alloy of gold and copper *
Iron pyrite The mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John ...
, fool's gold * Nordic gold, non-gold copper alloy


References


Further reading

* Bachmann, H. G. ''The lure of gold : an artistic and cultural history'' (2006
online
* Bernstein, Peter L. ''The Power of Gold: The History of an Obsession'' (2000
online
* Brands, H.W. ''The Age of Gold: The California Gold Rush and the New American Dream'' (2003
excerpt
* Buranelli, Vincent. ''Gold : an illustrated history'' (1979
online
wide-ranging popular history * Cassel, Gustav. "The restoration of the gold standard." ''Economica'' 9 (1923): 171–185
online
* Eichengreen, Barry. ''Golden Fetters: The Gold Standard and the Great Depression, 1919–1939'' (Oxford UP, 1992). * Ferguson, Niall. ''The Ascent of Money - Financial History of the World'' (2009
online
* Hart, Matthew
Gold: The Race for the World's Most Seductive Metal
''Gold : the race for the world's most seductive metal"], New York: Simon & Schuster, 2013. '' * Johnson, Harry G. "The gold rush of 1968 in retrospect and prospect." ''American Economic Review'' 59.2 (1969): 344–348
online
* Kwarteng, Kwasi. ''War and Gold: A Five-Hundred-Year History of Empires, Adventures, and Debt'' (2014
online
* Vilar, Pierre. '' A History of Gold and Money, 1450 to 1920'' (1960)
online
* Vilches, Elvira. ''New World Gold: Cultural Anxiety and Monetary Disorder in Early Modern Spain'' (2010).


External links

*
Chemistry in its element podcast
(MP3) from the
Royal Society of Chemistry The Royal Society of Chemistry (RSC) is a learned society (professional association) in the United Kingdom with the goal of "advancing the chemistry, chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Ro ...
's Chemistry World
Gold
www.rsc.org

at ''
The Periodic Table of Videos ''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
''Getting Gold'' 1898 book
www.lateralscience.co.uk * , www.epa.gov
Gold element information
- rsc.org {{Authority control Chemical elements Transition metals Noble metals Precious metals Cubic minerals Minerals in space group 225 Dental materials Electrical conductors Native element minerals E-number additives Symbols of Alaska Symbols of California Chemical elements with face-centered cubic structure