Gold is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
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 conc ...
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
Bright may refer to:
Common meanings
*Bright, an adjective meaning giving off or reflecting illumination; see Brightness
*Bright, an adjective meaning someone with intelligence
People
* Bright (surname)
* Bright (given name)
*Bright, the stage na ...
, slightly orange-yellow, dense, soft,
malleable, and
ductile metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
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. It is one of the least reactive chemical elements and is solid under
standard conditions. Gold often occurs in
free elemental (
native state
In biochemistry, the native state of a protein or nucleic acid is its properly folded and/or assembled form, which is operative and functional. The native state of a biomolecule may possess all four levels of biomolecular structure, with the s ...
), as
nuggets
Nuggets may refer to:
Music
* ''Nuggets'' (series), a series of compilation albums by Elektra Records, continued by Rhino
* '' Nuggets: Original Artyfacts from the First Psychedelic Era, 1965–1968''
* '' Nuggets II: Original Artyfacts from ...
or grains, in
rocks
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's ...
,
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 and umbilical veins, both of which carry oxygenated b ...
, and
alluvial deposits. It occurs in a
solid solution 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 Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and
palladium
Palladium is a chemical element with the 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 asteroid Pallas, which was itself na ...
, 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 with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
(
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 ...
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 nitri ...
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 pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
), 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 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 positive by convent ...
. 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
{{Unreferenced, date=December 2009
Refining (also perhaps called by the mathematical term affining) is the process of purification of a (1) substance or a (2) form. The term is usually used of a natural resource that is almost in a usable form, b ...
gold and confirm the presence of gold in metallic substances, giving rise to the term '
acid test
Acid test or acid tests may refer to:
Scientific or metallurgical test
*Acid test (gold), a chemical or metallurgical test that uses acid, now also a general term for ''verified'', ''approved'', or ''tested'' in a large number of fields
*Acid te ...
'. Gold dissolves in
alkaline
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...
solutions of
cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
, which are used in
mining
Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
and
electroplating
Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the reduction of cations of that metal by means of a direct electric current. The part to be ...
. Gold also dissolves in
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
, forming
amalgam
Amalgam most commonly refers to:
* Amalgam (chemistry), mercury alloy
* Amalgam (dentistry), material of silver tooth fillings
** Bonded amalgam, used in dentistry
Amalgam may also refer to:
* Amalgam Comics, a publisher
* Amalgam Digital, an in ...
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 economic value.
Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lustre. ...
that has been used for
coinage,
jewelry
Jewellery ( UK) or jewelry (U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a western ...
, and other
arts 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 the la ...
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 very short-term borrowing (borrowing by banks from each other to meet their short-term needs) or the money supply, often a ...
. 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 sometime ...
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 non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
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 i ...
s and 10% in
industry.
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 visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
shielding, production of
colored glass,
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 karats and shades. The most commonly used gold is 22-kara ...
ing, and
tooth restoration. Certain
gold salts
Gold-containing drugs are pharmaceuticals that contain gold. Sometimes these species are referred to as "gold salts". "Chrysotherapy" and "aurotherapy" are the applications of gold compounds to medicine. Research on the medicinal effects of g ...
are still used as
anti-inflammatories
Anti-inflammatory is the property of a substance or treatment that reduces inflammation or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs remedy pain by reducing inflammation as o ...
in medicine.
Characteristics
![Small gold nugget 5mm dia and corresponding foil surface of half sq meter](https://upload.wikimedia.org/wikipedia/commons/9/91/Small_gold_nugget_5mm_dia_and_corresponding_foil_surface_of_half_sq_meter.jpg)
Gold is the most
malleable 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 sl ...
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, weight or volume and is derived almost unchanged from the , an Ancient Roman unit of measurement.
The avoirdupois ounce (exactly ) is avoirdupois pound; this is the United States customa ...
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 visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
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 and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, ...
s. Gold is a good
conductor of heat and
electricity
Electricity is the set of physical 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 electromagnetism, as described ...
.
Gold has a density of 19.3 g/cm
3, almost identical to that of
tungsten
Tungsten, or wolfram, is a chemical element with the 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 1781 and first isolat ...
at 19.25 g/cm
3; 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 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 produced ...
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 Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
is 11.34 g/cm
3, and that of the densest element,
osmium
Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mos ...
, is .
Color
![Ag-Au-Cu-colours-english](https://upload.wikimedia.org/wikipedia/commons/e/e7/Ag-Au-Cu-colours-english.svg)
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 plasmas or metals in the ultraviolet region. The oscillations can be described as an instability i ...
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 elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example is an explanation for the color of ...
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 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 elemental metals that a ...
.
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 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 asteroid Pallas, which was itself na ...
or
nickel
Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
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
badges. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as
green gold
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 ...
. Blue gold can be made by alloying with
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
, and purple gold can be made by alloying with
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
. Less commonly, addition of
manganese
Manganese is a chemical element with the 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 industrial alloy use ...
,
indium, and other elements can produce more unusual colors of gold for various applications.
Colloidal gold
Colloidal gold is a 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 nm) or blue/purple (for larger spherical particl ...
, 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 numbers) ...
, , which is also its only naturally occurring isotope, so gold is both a
mononuclidic and
monoisotopic element. Thirty-six
radioisotopes 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 (symbol: kg), atomic mass is often expressed in the non-SI unit dalton (symbol: Da) – equivalently, unified atomic mass unit (u). 1&nbs ...
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 with a half-life of 30 µs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of
proton emission,
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 isomers 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, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ha ...
, 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 Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, 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 protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
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
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
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
Gold (79Au) has one stable isotope, 197Au, and 36 radioisotopes, with 195Au being the most stable with a half-life of 186 days. Gold is currently considered the heaviest monoisotopic element. Bismuth formerly held that distinction until alpha-deca ...
produced by it were all
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
. In 1980,
Glenn Seaborg 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
![Gold(III) chloride solution](https://upload.wikimedia.org/wikipedia/commons/d/d9/Gold%28III%29_chloride_solution.jpg)
Although gold is the most noble of the
noble metals, it still forms many diverse compounds. The
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
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 electr ...
s such as
thioethers,
thiolates, and
organophosphine Organophosphines are organophosphorus compounds with the formula PR''n''H3−''n'', where R is an organic substituent. These compounds can be classified according to the value of ''n'': primary phosphines (''n'' = 1), secondary phosphines ...
s. Au(I) compounds are typically linear. A good example is , which is the soluble form of gold encountered in mining. The binary
gold halide
Gold halides are compounds of gold with the halogens.
Monohalides
AuCl, AuBr, and AuI are all crystalline solids with a structure containing alternating linear chains: ..-X-Au-X-Au-X-Au-X-... The X-Au-X angle is less than 180°.
The monomer ...
s, 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 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 compounds. Gold(III) c ...
, . The gold atom centers in Au(III) complexes, like other d
8 compounds, are typically
square planar
The square planar molecular geometry in chemistry describes the stereochemistry (spatial arrangement of atoms) that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corne ...
, with
chemical bonds 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
ion
An ion () is an atom or molecule with a net 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 positive by conven ...
ic character.
Gold(I,III) chloride
Gold(I,III) chloride is a black solid with the chemical formula Au4 Cl8. It is an example of a mixed valence compound as it contains gold in two different oxidation states; square-planar gold(III) and almost linear gold(I). The compound is photo ...
is also known, an example of a
mixed-valence complex
Mixed valence complexes contain an 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-valency including in ...
.
Gold does not react with oxygen at any temperature and, up to 100 °C, is resistant to attack from ozone.
:
:
Some free
halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
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 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 compounds. Gold(III) c ...
. Gold reacts with bromine at 140 °C to form
gold(III) bromide
Gold(III) bromide is a dark-red to black crystalline solid.Macintyre, J. E. (ed.) ''Dictionary of Inorganic Compounds''; Chapman & Hall: London, 1992; vol. 1, pp. 121Greenwood, N.N.; Earnshaw, A. ''Chemistry of the Elements''; Butterworth-Heineman ...
, but reacts only very slowly with iodine to form
gold(I) iodide
Gold monoiodide is the inorganic compound of gold and iodine with the formula AuI. It can be synthesized by dissolving gold powder in an aqueous solution of iodine and potassium iodide
Potassium iodide is a chemical compound, medication, a ...
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
Gold(III) sulfide or auric sulfide is an inorganic compound with the formula .Auric sulfide has been described as a black and amorphous. Little evidence has been published supporting the existence of macroscopic quantities of this material.
Clai ...
can be made by passing
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
through a dilute solution of gold(III) chloride or
chlorauric acid
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 ...
.
Gold readily dissolves in
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
at room temperature to form an
amalgam
Amalgam most commonly refers to:
* Amalgam (chemistry), mercury alloy
* Amalgam (dentistry), material of silver tooth fillings
** Bonded amalgam, used in dentistry
Amalgam may also refer to:
* Amalgam Comics, a publisher
* Amalgam Digital, an in ...
, 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 from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
or to create exotic colors.
Gold is unaffected by most acids. It does not react with
hydrofluoric,
hydrochloric,
hydrobromic,
hydriodic,
sulfuric
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
, 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 nitri ...
. It does react with
selenic acid
Selenic acid is the inorganic compound with the formula . It is an oxoacid of selenium, and its structure is more accurately described as . It is a colorless compound. Although it has few uses, its derivative sodium selenate is used in the prod ...
, 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 nitri ...
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 pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
. 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
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 ...
, thereby enabling further oxidation.
:
2 Au + 6 H2SeO4 -> 00^\circ CAu2(SeO4)3 + 3 H2SeO3 + 3 H2O
:
Au + 4HCl + HNO3 -> HuCl4
Uranium tetrachloride is an inorganic compound, a salt of uranium and chlorine, with the formula UCl4. It is a hygroscopic olive-green solid. It was used in the electromagnetic isotope separation (EMIS) process of uranium enrichment. It is one o ...
+ NO\uparrow + 2H2O
Gold is similarly unaffected by most bases. It does not react with
aqueous,
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
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...
sodium
Sodium is a chemical element with the 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 of the periodic table. Its only stable iso ...
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 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 of the periodic table. Its only stable iso ...
or
potassium cyanide
Potassium cyanide is a compound with the 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 applications includ ...
under alkaline conditions when
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
is present to form soluble complexes.
Common
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
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
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
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 change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
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 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 positive by convent ...
.
Caesium auride
Caesium auride is the inorganic compound with the formula CsAu. It is the Cs+ salt of the unusual Au− anion.
Preparation and reactions
CsAu is obtained by heating a Stoichiometry, stoichiometric mixture of caesium and gold. The two metallic-yel ...
(CsAu), for example, crystallizes in the
caesium chloride
Caesium chloride or cesium chloride is the inorganic compound with the formula Cs Cl. This colorless salt is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each ...
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 asso ...
aurides are also known.
Gold has the highest
electron affinity
The electron affinity (''E''ea) of an atom or molecule is defined as the amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion.
::X(g) + e− → X−(g) + energy
Note that this is ...
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 and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
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
dimer
Dimer may refer to:
* Dimer (chemistry), a chemical structure formed from two similar sub-units
** Protein dimer, a protein quaternary structure
** d-dimer
* Dimer model, an item in statistical mechanics, based on ''domino tiling''
* Julius Dimer ( ...
s in a manner similar to
titanium(IV) hydride
Titanium(IV) hydride (systematically named titanium tetrahydride) is an inorganic compound with the empirical chemical formula . It has not yet been obtained in bulk, hence its bulk properties remain unknown. However, molecular titanium(IV) hyd ...
.
Gold(II) compounds are usually
diamagnetic 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
Gold heptafluoride is a gold(V) compound with the empirical formula AuF7. The synthesis of this compound was first reported in 1986. However, current calculations suggest that the structure of the synthesized molecule was actually a difluorine lig ...
, 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
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and th ...
. 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 electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...
.
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
![Vredefort crater cross section 2](https://upload.wikimedia.org/wikipedia/commons/2/22/Vredefort_crater_cross_section_2.png)
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 homes ...
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 reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", ...
(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 Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
may also be produced in quantity by the r-process in the
collision of
neutron star
A neutron star is the collapsed 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 metal-rich. Except for black holes and some hypothetical objects (e.g. white ...
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 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 stars' inspir ...
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 propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1 ...
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 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 relative uncertainty ...
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
The early Earth is loosely defined as Earth in its first one billion years, or gigayear (Ga, 109y). The “early Earth” encompasses approximately the first gigayear in the evolution of our planet, from its initial formation in the young Solar Sy ...
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
A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that.
Mantle may refer to:
*Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear
**Mantle (vesture), an Eastern Orthodox ve ...
has in one model thought to have been delivered to Earth later, by
asteroid impacts during the
Late Heavy Bombardment, 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. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
in
South Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
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 scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
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
The Transvaal Supergroup is a stratigraphic unit in northern South Africa and southern Botswana, situated on the Kaapvaal Craton, roughly between 23 and 29 degrees southern latitude and 22 to 30 degrees eastern longitude. It is dated to the boun ...
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. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
in such a way that the gold-bearing rocks were brought to the present
erosion surface in
Johannesburg
Johannesburg ( , , ; 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, and is one of the 100 largest urban areas in the world. According to Demo ...
, on the
Witwatersrand
The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
, 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. 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
Planetesimals are solid objects thought to exist in protoplanetary disks and debris disks. Per the Chamberlin–Moulton planetesimal hypothesis, they are believed to form out of cosmic dust grains. Believed to have formed in the Solar System a ...
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
A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that.
Mantle may refer to:
*Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear
**Mantle (vesture), an Eastern Orthodox ve ...
, evidenced by their findings at
Deseado Massif
The Deseado Massif (Spanish: ''Macizo del Deseado'') is a massif in southern Patagonia located in the Argentine province of Santa Cruz. On surface the massif is made up of Middle to Late Jurassic-aged felsic volcanic rocks. Analysis of mantle xeno ...
in the
Argentinian Patagonia
Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...
.
Occurrence
On Earth, gold is found in
ore
Ore is natural 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. Retrieved 7 April 2 ...
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 the ...
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 deposits singly or in alloys include aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, indium, iron, manganese, m ...
, typically in a metal
solid solution 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 tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...
or
sulfide minerals 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 deposits. The metal in a native state is also found in the form of free flakes, grains or larger
nuggets
Nuggets may refer to:
Music
* ''Nuggets'' (series), a series of compilation albums by Elektra Records, continued by Rhino
* '' Nuggets: Original Artyfacts from the First Psychedelic Era, 1965–1968''
* '' Nuggets II: Original Artyfacts from ...
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 deposits. 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 change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
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 with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally fou ...
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. ( ...
s
calaverite
Calaverite, or gold telluride, is an uncommon telluride of gold, a metallic mineral with the chemical formula AuTe2, with approximately 3% of the gold replaced by silver. It was first discovered in Calaveras County, California in 1861, and was ...
,
krennerite,
nagyagite,
petzite and
sylvanite
Sylvanite or silver gold telluride, chemical formula , is the most common telluride of gold.
Properties
The gold:silver ratio varies from 3:1 to 1:1. It is a metallic mineral with a color that ranges from a steely gray to almost white. It is c ...
(see
telluride minerals), and as the rare bismuthide maldonite () and antimonide
aurostibite
Aurostibite is an isometric gold antimonide mineral which is a member of the pyrite group. Aurostibite was discovered in 1952 and can be found in hydrothermal gold-quartz veins, in sulfur-deficient environments that contain other antimony mineral ...
(). Gold also occurs in rare alloys with
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
,
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
, and
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
: the minerals
auricupride
Auricupride is a natural alloy that combines copper and gold. Its chemical formula is Cu3Au. The alloy crystallizes in the cubic crystal system in the L12 structure type and occurs as malleable grains or platey masses. It is an opaque yellow wit ...
(), 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 salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
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/km
3). 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 salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the worl ...
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 primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
in the 1890s, as did an English fraudster in the early 1900s.
Fritz Haber 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 betwe ...
's reparations following
World War I
World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
. 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
![Gold Museum, Bogota (36145671394)](https://upload.wikimedia.org/wikipedia/commons/9/99/Gold_Museum%2C_Bogota_%2836145671394%29.jpg)
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 procur ...
or "
native
Native may refer to:
People
* Jus soli, citizenship by right of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Native Americans (disambiguation)
In arts and entert ...
". 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 ''palaios'', "old" and λίθος ''lithos'', "stone"), is a period in human prehistory that is distinguished by the original development of stone too ...
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 (approximately half a kilometre from Lake Varna and 4 km from the city centre), internationally co ...
near Lake Varna and the
Black Sea
The Black Sea is a marginal 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 Anatolia. It is bounded by Bulgaria, Georgia, Roma ...
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
Durankulak ( bg, Дуранкулак ) is a village in northeastern Bulgaria, part of Shabla Municipality, Dobrich Province. Located in the historical region of Southern Dobruja, Durankulak is the north-easternmost inhabited place in Bulgaria a ...
, artifacts from the Kurgan settlement of Yunatsite near
Pazardzhik, the golden treasure Sakar, as well as beads and gold jewelry found in the Kurgan settlement of
Provadia –
Solnitsata
Solnitsata ( bg, Солницата, "The Saltworks") was a prehistoric town located in present-day Bulgaria, near the modern city of Provadia. Believed by archaeologists to be the oldest town in Europe, Solnitsata was a fortified stone settlement ...
(“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
Golden hats (or gold hats) (german: Goldhüte, singular: ) are a very specific and rare type of archaeological artifact from Bronze Age Europe. So far, four such objects ("cone-shaped gold hats of the Schifferstadt type") are known. The objects ...
and the
Nebra disk
The Nebra sky disc (german: Himmelsscheibe von Nebra) is a bronze disc of around diameter and a weight of , having a blue-green patina and inlaid with gold symbols. These symbols are interpreted generally as the Sun or full moon, a lunar crescen ...
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, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...
.
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, syllabic and alphabetic elements, with some 1,000 distinct characters.There were about 1,00 ...
s from as early as 2600 BC describe gold, which King
Tushratta
Tushratta (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 Artatama I. His si ...
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 Assyrian records, or ''Naharin'' in ...
claimed was "more plentiful than dirt" in Egypt. Egypt and especially
Nubia
Nubia () (Nobiin: Nobīn, ) is a region along the Nile river encompassing the area between the first cataract of the Nile (just south of Aswan in southern Egypt) and the confluence of the Blue and White Niles (in Khartoum in central Sudan), or ...
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
The Turin Papyrus Map is an ancient Egyptian map, generally considered the oldest surviving map of topographical interest from the ancient world. It is drawn on a papyrus reportedly discovered at Deir el-Medina in Thebes, collected by Bernardino ...
, 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 objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...
. 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, Διόδωρος ; 1st century BC), was an ancient Greek historian. He is known for writing the monumental universal history ''Bibliotheca historica'', in forty books, fifteen of which su ...
, and included
fire-setting. 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: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...
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 fifth-largest country in Asia, the second-largest in the A ...
.
![Golden crown Armento Staatliche Antikensammlungen 01](https://upload.wikimedia.org/wikipedia/commons/f/f0/Golden_crown_Armento_Staatliche_Antikensammlungen_01.jpg)
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 or Tanakh, a collection of ancient religious Hebrew writings by the Israelites. The ...
, starting with
Genesis
Genesis may refer to:
Bible
* Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of mankind
* Genesis creation narrative, the first several chapters of the Book of ...
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. In Hebrew, the incident is known as ''ḥēṭə’ hā‘ēgel'' ...
, and many parts of the temple including the
Menorah and the golden altar. In the
New Testament
The New Testament grc, Ἡ Καινὴ Διαθήκη, transl. ; la, Novum Testamentum. (NT) is the second division of the Christian biblical canon. It discusses the teachings and person of Jesus, as well as events in first-century Christ ...
, it is included with the gifts of the
magi
Magi (; singular magus ; from Latin ''magus'', cf. fa, مغ ) were priests in Zoroastrianism and the earlier religions of the western Iranians. The earliest known use of the word ''magi'' is in the trilingual inscription written by Darius th ...
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 Christian Bible). Its title is derived from the first word of the Koine Greek text: , meaning "unveiling" or "revelation". The Book of R ...
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 prophetic vision of a city centered on the rebuilt Holy Temple, the Third Temple, to be established in Jerusalem, which would be the c ...
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 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 Anatolia. It is bounded by Bulgaria, Georgia, Roma ...
is said to date from the time of
Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in
Lydia
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 dating from eighth century BCE may refer to the use of fleeces to trap gold dust from
placer deposits 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 vassal state. Their first ruler was King Wu of Chu in the early 8th century BCE. Chu was located in the south of the Zhou he ...
circulated the
Ying Yuan
Ying Yuan () were stamped blocks of gold bullion. This was an early form of currency that could be considered a precursor to gold coins. They were issued by the ancient Chinese state of Chu during the Warring States period between the 400s and lat ...
, 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, Portuguese, Catalan, and Italian) was the Roman name for the Iberian Peninsula and its provinces. Under the Roman Republic, Hispania was divided into two provinces: Hispania ...
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 r ...
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 various methods they used are well described by
Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
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 articles ...
''
Naturalis Historia'' written towards the end of the first century AD.
During
Mansa Musa
Mansa Musa ( ar, منسا موسى, Mansā Mūsā; ) was the ninth ''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 claims that he is ...
's (ruler of the
Mali Empire
The Mali Empire ( 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; ar, مالي, Māl ...
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 city for Muslims. Hajj is a mandatory religious duty for Muslims that must be carried ...
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 metro ...
in July 1324, and was reportedly accompanied by a
camel train 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:
![Monnaie de Bactriane, Eucratide I, 2 faces](https://upload.wikimedia.org/wikipedia/commons/e/e6/Monnaie_de_Bactriane%2C_Eucratide_I%2C_2_faces.jpg)
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. W ...
,
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 ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...
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 Car ...
. 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 language family. Varieties of Nahuatl are spoken by about Nahua peoples, most of whom live mainly in Central Mexico and have smaller ...
), and after
Moctezuma II
Moctezuma Xocoyotzin ( – 29 June 1520; oteːkˈsoːmaḁ ʃoːkoˈjoːt͡sĩn̥), nci-IPA, Motēuczōmah Xōcoyōtzin, moteːkʷˈsoːma ʃoːkoˈjoːtsin variant spellings include Motewksomah, Motecuhzomatzin, Montezuma, Moteuczoma, Motecu ...
was killed, most of this gold was shipped to Spain. However, for the
indigenous peoples of North America 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 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 tools and start fir ...
, 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 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 (''zipa'') or king o ...
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 Car ...
, who, as an initiation rite, covered himself with gold dust and submerged in
Lake Guatavita
Lake Guatavita (Spanish: ''Laguna Guatavita'') is located in the Cordillera Oriental of the Colombian Andes in the municipality of Sesquilé in the Almeidas Province, Cundinamarca department of Colombia, northeast of Bogotá, the capital of ...
. 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 defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Maurit ...
was driven in large part by reports of gold deposits in the region, which was eventually referred to by Europeans as the "
Gold Coast
Gold Coast may refer to:
Places Africa
* Gold Coast (region), in West Africa, which was made up of the following colonies, before being established as the independent nation of Ghana:
** Portuguese Gold Coast (Portuguese, 1482–1642)
** Dutch G ...
". From the late 15th to early 19th centuries, European trade in the region was primarily focused in gold, along with
ivory 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, who initially traded with the
Portuguese before branching out and trading with
British,
French
French (french: français(e), link=no) may refer to:
* Something of, from, or related to France
** French language, which originated in France, and its various dialects and accents
** French people, a nation and ethnic group identified with Franc ...
,
Spanish and
Danish
Danish may refer to:
* Something of, from, or related to the country of Denmark
People
* A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark
* Culture of Denmark
* Danish people or Danes, people with a Danish ance ...
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 interior of the Gold Coast—and the British Empire and its African allies. Though the Ashanti emerged victorio ...
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, that features animals, legendary creatures, plants, inanimate objects, or forces of nature that are anthropomorphized, and that illustrates or leads to a particular mo ...
s such as
Rumpelstiltskin—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 On Commons and as Benjamin Tabart's moralized "The History of Jack and the Bean-Stalk" in 1807. Henry Cole ...
.
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 alloying in its manufacture.
Since the eighteenth century, gold medals have bee ...
.
75% of the presently accounted for gold has been extracted since 1910, two-thirds since 1950.
One main goal of the
alchemists
Alchemy (from Arabic: ''al-kīmiyā''; from Ancient Greek: χυμεία, ''khumeía'') is an ancient branch of natural philosophy, a philosophical and protoscientific tradition that was historically practiced in China, India, the Muslim world, ...
was to produce gold from other substances, such as
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
— presumably by the interaction with a mythical substance called the
philosopher's stone. 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 science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, which can produce gold (albeit uneconomically) by using
nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed.
A transmutatio ...
. Their symbol for gold was the circle with a point at its center (☉), which was also the
astrological 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
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 of Jerusalem, a site also known to Muslims as the ''al-Haram al-Sharif'' or the Al-Aqsa Compound. Its initial ...
is covered with an ultra-thin golden glassier. The
Sikh
Sikhs ( or ; pa, ਸਿੱਖ, ' ) are people who adhere to Sikhism, Sikhism (Sikhi), a Monotheism, monotheistic religion that originated in the late 15th century in the Punjab region of the Indian subcontinent, based on the revelation of Gu ...
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 Buddhist temple in Thailand. The complex co ...
emerald
Buddhist
Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and ...
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 churches), Hinduism (whose temples ...
(
wat
A wat ( km, វត្ត, ; lo, ວັດ, ; th, วัด, ; khb, 「ᩅᨯ᩠ᨰ」(waD+Dha); nod, 「ᩅ᩠ᨯ᩶」 (w+Da2)) is a type of Buddhist temple and Hindu temple in Cambodia, Laos, East Shan State, Yunnan, the Southern Provi ...
) 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 Indochinese Peninsula, spanning , with a population of almost 70 million. The country is bo ...
has ornamental gold-leafed statues and roofs. Some European king and queen's
crowns
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
were made of gold, and gold was used for the
bridal crown
Traditionally a bridal crown (german: Brautkrone or, in the Black Forest, ''Schäppel'') is a headdress that, in Central and Northern Europe, single women wear on certain holidays, at festivals and, finally, at their wedding. Bridal crowns today ...
since antiquity. An ancient Talmudic text circa 100 AD describes
Rachel, wife of Rabbi Akiva
The wife of Rabbi Akiva ( he, אשת רבי עקיבא) was a late 1st-century CE Jewish resident of Judea who is cited by the Talmud and Aggadah as a paragon of the Jewish wife who encourages her husband to pursue Torah study and is willing to mak ...
, 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 1450B ...
jewellery; 2300–2100 BC; various sizes; Metropolitan Museum of Art
The Metropolitan Museum of Art of New York City, colloquially "the Met", is the largest art museum in the Americas. Its permanent collection contains over two million works, divided among 17 curatorial departments. The main building at 1000 ...
(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 Ages between the sixth and fifth millennium BC. It is one of the cradles of c ...
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 until the beginning of the Common Era. It is named for the characteristic wedge-sha ...
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, Iraq)
Statuette of Amun MET DT553.jpg, Ancient Egyptian statuette of Amun
Amun (; also ''Amon'', ''Ammon'', ''Amen''; egy, jmn, reconstructed as (Old Egyptian and early Middle Egyptian) → (later Middle Egyptian) → (Late Egyptian), cop, Ⲁⲙⲟⲩⲛ, Amoun) romanized: ʾmn) was a major ancient Egyptian ...
; 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 largest and most comprehensive in existence. It docum ...
(London)
Gold stater MET DP138743.jpg, Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
stater; 323–315 BC; ; Metropolitan Museum of Art
Gold funerary wreath MET DP257471.jpg, Etruscan __NOTOC__
Etruscan may refer to:
Ancient civilization
*The Etruscan language, an extinct language in ancient Italy
*Something derived from or related to the Etruscan civilization
**Etruscan architecture
**Etruscan art
**Etruscan cities
**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 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 settlers in Hispania B ...
; 134–138 AD; 7.4 g; Metropolitan Museum of Art
Lime Container (Poporo) MET DT1262.jpg, Quimbaya
The Quimbaya (/kɪmbaɪa/) were a small indigenous group in present-day Colombia noted for their gold work characterized by technical accuracy and detailed designs. The majority of the gold work is made in ''tumbaga'' alloy, with 30% copper, ...
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 primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...
scyphate; 1059–1067; diameter: ; Cleveland Museum of Art (Cleveland
Cleveland ( ), officially the City of Cleveland, is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located in the northeastern part of the state, it is situated along the southern shore of Lake Erie, across the U.S. ...
, Ohio
Ohio () is a state in the Midwestern region of the United States. Of the fifty U.S. states, it is the 34th-largest by area, and with a population of nearly 11.8 million, is the seventh-most populous and tenth-most densely populated. The sta ...
, USA)
Double Bat-Head Figure Pendant MET DT935.jpg, Pre-Columbian
In the history of the Americas, the pre-Columbian era spans from the original settlement of North and South America in the Upper Paleolithic period through European colonization, which began with Christopher Columbus's voyage of 1492. Usually, th ...
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 transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Cos ...
); 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
![Beowulf - gold](https://upload.wikimedia.org/wikipedia/commons/d/d5/Beowulf_-_gold.jpg)
"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 etymology, etymological ancestor in a proto-language, common parent language. Because language c ...
with similar words in many
Germanic languages
The Germanic languages are a branch of the 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 Germanic language, Engli ...
, deriving via
Proto-Germanic
Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the reconstructed proto-language of the Germanic branch of the Indo-European languages.
Proto-Germanic eventually developed from pre-Proto-Germanic into three Germanic branc ...
*''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
Aurum may refer to:
*''Aurum'', the Latin word for gold and the source of its chemical symbol, "Au"
*''Aurum'' means "Ananya".
*Aurum (liqueur), an Italian liqueur
*Aurum Geyser, in the Upper Geyser Basin of Yellowstone
*Aurum, Nevada, a ghost to ...
, 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 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 below the sur ...
(Proto-Indo-European ''*h₂u̯es-'' "to dawn") as
''*h₂éu̯sōs'', the ancestor of the Latin word
Aurora, "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
![Jewelry and clothing ornaments](https://upload.wikimedia.org/wikipedia/commons/e/e0/Jewelry_and_clothing_ornaments.jpg)
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 alloying in its manufacture.
Since the eighteenth century, gold medals have bee ...
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 medals (or, in ...
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's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...
are made from gold as well. Other award statues and prizes are depicted in gold or are
gold plated
Gold plating is a method of depositing a thin layer of gold onto the surface of another metal, most often copper or silver (to make silver-gilt), by chemical or electrochemical plating. This article covers plating methods used in the modern elec ...
(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, 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 period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of phil ...
in his
ethics
Ethics or moral philosophy is a branch of philosophy that "involves systematizing, defending, and recommending concepts of right and wrong behavior".''Internet Encyclopedia of Philosophy'' The field of ethics, along with aesthetics, concerns m ...
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 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 of the date a wedding took place. Couples may take the occasion to celebrate their relationship, either privately or with a larger party. Special celebrations and gifts are often given for particular an ...
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 t ...
, 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. In Hebrew, the incident is known as ''ḥēṭə’ hā‘ēgel'' ...
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 A ...
, 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 Hebrew patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father of the special relationship between the Jew ...
was said to be rich in gold and silver, and Moses was instructed to cover the
Mercy Seat
According to the Hebrew Bible, the ''kaporet'' ( ''kapōreṯ'') or mercy seat was the gold lid placed on the Ark of the Covenant, with two cherubim beaten out of the ends to cover and create the space into which Yahweh was said to appear. This ...
of
the Ark of the Covenant
The Ark of the Covenant,; Ge'ez: also known as the Ark of the Testimony or the Ark of God, is an alleged artifact believed to be the most sacred relic of the Israelites, which is described as a wooden chest, covered in pure gold, with an e ...
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 primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...
icon
An icon () is a religious work of art, most commonly a painting, in the cultures of the Eastern Orthodox, Oriental Orthodox, and Catholic churches. They are not simply artworks; "an icon is a sacred image used in religious devotion". The most ...
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 Jewish woman of Nazareth, the wife of Joseph and the mother o ...
and the saints are often golden.
In
Islam
Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic religions, Abrahamic Monotheism#Islam, monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ...
,
gold (along with
silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the coc ...
)
is often cited as being forbidden for men to wear.
Abu Bakr al-Jazaeri Abu Bakr Jabir bin Musa bin Abdul Qadir ibn Jaber, better known as Abu Bakr al-Jazairi (1921 – 15 August 2018), was an Algerian Sunni Islamic scholar.
Biography
Al-Jazairi was born in 1921 in the village of Lioua, close to Tolga, which is loc ...
, 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 approval ...
, 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 fabric or other materials using a needle to apply thread or yarn. Embroidery may also incorporate other materials such as pearls, beads, quills, and sequins. In modern days, embroidery is usually seen on c ...
, may be permitted.
[ ]
In
ancient Greek religion
Religious practices in ancient Greece encompassed a collection of beliefs, rituals, and mythology, in the form of both popular public religion and cult practices. The application of the modern concept of "religion" to ancient cultures has been ...
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 narrat ...
,
Theia 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 rings 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
Orthodoxy (from Greek: ) is adherence to correct or accepted creeds, especially in religion.
Orthodoxy within Christianity refers to acceptance of the doctrines defined by various creeds and ecumenical councils in Antiquity, but different Churche ...
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 religions, Abrahamic Monotheism#Islam, monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ...
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
![Gold - world production trend](https://upload.wikimedia.org/wikipedia/commons/a/aa/Gold_-_world_production_trend.svg)
According to the
United States Geological Survey
The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
in 2016, about of gold has been accounted for, of which 85% remains in active use.
Mining and prospecting
![Grasberg mine](https://upload.wikimedia.org/wikipedia/commons/0/05/Grasberg_mine.jpg)
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 southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
. 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 most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
(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 most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
was the world's leading gold-mining country, followed in order by Russia, Australia, the United States, Canada, and Ghana.
![Gold 30g for a 860kg rock](https://upload.wikimedia.org/wikipedia/commons/f/f9/Gold_30g_for_a_860kg_rock.jpg)
In South America, the controversial project
Pascua Lama
''Pascua'' is a genus of gobies native to the Pacific Ocean. The origin of the name ''"Pascua"'' is from the Spanish for "Easter" in recognition of the Easter Island
Easter Island ( rap, Rapa Nui; es, Isla de Pascua) is an island and s ...
aims at exploitation of rich fields in the high mountains of
Atacama Desert, 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 second-largest country in South America after Brazil, th ...
.
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 and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a megacity, and is one of the 100 largest urban areas in the world. According to Demo ...
located in South Africa was founded as a result of the
Witwatersrand Gold Rush 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. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
, 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
Earth ...
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 languages means 'place of gold'.
Situated on the Highveld, Gauteng is the smallest province by land area in South Africa. Although Gauteng accounts for only ...
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 scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
, 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
Savuka, occasionally referred to as Johnny Clegg & Savuka, was a multi-racial South African band formed in 1986 by Johnny Clegg after the disbanding of Juluka. Savuka's music blended traditional Zulu musical influences with Celtic music and ro ...
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
Earth ...
rivers from the north and north-west formed extensive pebbly
Braided river
A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''.
Braided streams tend to occur in rivers with high sediment l ...
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 Sout ...
of 1899–1901 between the
British Empire
The British Empire was composed of the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom and its predecessor states. It began with the overseas possessions and trading posts esta ...
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: ...
Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa.
![Kullanhuuhdontaa Ivalossa](https://upload.wikimedia.org/wikipedia/commons/3/3f/Kullanhuuhdontaa_Ivalossa.jpg)
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 Z ...
es occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at the
Reed Gold Mine
The Reed Gold Mine is located in Midland, Cabarrus County, North Carolina, and is the site of the first documented commercial gold find in the United States. It has been designated a National Historic Landmark because of its importance and li ...
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 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 western edge of t ...
, 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 reg ...
in New Zealand, a number of locations across
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
,
Witwatersrand
The Witwatersrand () (locally the Rand or, less commonly, the Reef) is a , north-facing scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which ...
in South Africa, and the
Klondike in Canada.
Grasberg mine
The Grasberg mine has one of the largest reserves of gold and copper in the world. It is located in Mimika Regency, Central Papua, Indonesia near Puncak Jaya. It is operated by PT Freeport Indonesia (PTFI, ''see below''), a joint venture be ...
located in
Papua,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
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 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 distorted electric guitars. Hard rock began in the mid-1960s with the garage, psychedelic and blues rock movements. Some of the earliest hard ...
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
The Wohlwill process is an industrial-scale chemical procedure used to refine gold to the highest degree of purity (99.999%). The process was invented in 1874 by Emil Wohlwill. This electrochemical process involves using a cast gold ingot, often c ...
which is based on
electrolysis
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
or by the
Miller process
The Miller process is an industrial-scale chemical procedure used to refine gold to a high degree of purity (99.5%). It was patented by Francis Bowyer Miller in 1867. This chemical process involves blowing chlorine gas through molten, but (slightly ...
, 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, 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 atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
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
A generation refers to all of the people born and living at about the same time, regarded collectively. It can also be described as, "the average period, generally considered to be about 20–30 years, during which children are born and gr ...
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), servers, data ...
.
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, 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
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
and mixed with
sodium cyanide 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](_blank)
, ''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 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 various allotropes, but ...
,
selenium 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 ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
which in turn dissolves these heavy metals facilitating their passage into surface water and ground water. This process is called
acid mine drainage. These gold ore dumps are long-term, highly hazardous wastes second only to
nuclear waste 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 rashe ...
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
A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a unit of energy: one kilowatt of power for one hour. In terms of SI derived units with special names, it equals 3.6 megajoules (MJ). Kilowatt-hours are a common bil ...
of electricity per gram of gold produced.
Monetary use
![Two 20kr gold coins](https://upload.wikimedia.org/wikipedia/commons/a/a2/Two_20kr_gold_coins.png)
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), and to store wealth in
hoard
A hoard or "wealth deposit" is an archaeological term for a collection of valuable objects or artifacts, sometimes purposely buried in the ground, in which case it is sometimes also known as a cache. This would usually be with the intention of ...
s. For exchange purposes,
mints produce standardized
gold bullion
A gold bar, also called gold bullion or gold ingot, is a quantity of 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 produced ...
coins,
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 the la ...
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 one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
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 vast majority of the world's countries—including all of the great powers—forming two opposin ...
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 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 Agreement. The Bretto ...
.
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 the la ...
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 sometime ...
now fills most monetary roles.
Switzerland
). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...
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
The London Bullion Market Association (now known simply as LBMA), established in 1987, is the international trade association representing the global Over The Counter (OTC) bullion market, and defines itself as "the global authority on precious ...
still clear transactions denominated in gold, including future delivery contracts. Today,
gold mining 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
In finance, a futures contract (sometimes called a futures) is a standardized legal contract to buy or sell something at a predetermined price for delivery at a specified time in the future, between parties not yet known to each other. The asset ...
. 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 (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, 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 Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
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 economic value.
Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lustre. ...
s, and its value has been used as the standard for many
currencies. 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 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 (book), Utopia'', describing a fictional ...
''. 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 standard published by the International Organization for Standardization (ISO) that defines alpha codes and numeric codes for the representation of currencies and provides information about the relationships between individual cu ...
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 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 t ...
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 coins for investment or collector purposes do not require good mechanical wear properties; they are typically fine gold at 24k, although the
American Gold Eagle and the British
gold sovereign continue to be minted in 22k (0.92) metal in historical tradition, and the South African
Krugerrand, first released in 1967, is also 22k (0.92).
The ''special issue''
Canadian Gold Maple Leaf coin contains the highest purity gold of any
bullion coin, 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 began producing the
American Buffalo
American Buffalo may refer to:
*American Buffalo (play), ''American Buffalo'' (play), a play by David Mamet
*American Buffalo (film), ''American Buffalo'' (film), a 1996 film of Mamet's play directed by Michael Corrente
*American Buffalo (coin), a ...
gold bullion coin with a purity of 99.99%. The
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
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
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
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. It ...
bullion coin and the
Chinese Gold Panda.
Price
![Gold price in USD](https://upload.wikimedia.org/wikipedia/commons/e/e3/Gold_price_in_USD.png)
, 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'' (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 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 produced ...
or coin can also be expressed as a decimal figure ranging from 0 to 1, known as the
millesimal fineness, such as 0.995 being nearly pure.
The price of gold is determined through trading in the gold and
derivatives
The derivative of a function is the rate of change of the function's output relative to its input value.
Derivative may also refer to:
In mathematics and economics
* Brzozowski derivative in the theory of formal languages
* Formal derivative, an ...
markets, but a procedure known as the
Gold Fixing in
London
London is the capital and 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 down to the North Sea, and has been a majo ...
, 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 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, or customer receipt) is a document acknowledging that a person has received money or propert ...
redeemable for gold coin or
bullion
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 t ...
. 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 the la ...
, 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 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 banking system. In contrast to a commercial bank, a central ba ...
s still hold historical
gold reserves
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 ...
as a
store of value although the level has generally been declining. The largest gold depository in the world is that of the
U.S. Federal Reserve Bank
The Federal Reserve System (often shortened to the Federal Reserve, or simply the Fed) is the central banking system of the United States of America. It was created on December 23, 1913, with the enactment of the Federal Reserve Act, after a ...
in
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
, 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 and north of Elizabethtown. It is adjacent to the United States Bullion Depository, which is used to house a large portion of the United States' official gold res ...
.
In 2005 the
World Gold Council 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 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 concerns regarding ongoing
unrest
Unrest, also called disaffection, is a sociological phenomenon, including:
* Civil unrest
* Civil disorder
* Domestic terrorism
* Industrial unrest
* Labor unrest
* Rebellion
* Riot
* Strike action
* State of emergency
Notable historical instance ...
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 ...
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
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 ended and a
bull market 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
CQG is a US-based company creating financial software for market technical analysis, charting, and electronic trading. CQG specializes mostly in the futures market but provides both real-time and historical data from more than 100 exchanges from ...
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 joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involv ...
, the most frequently used being
aurothiomalate
Sodium aurothiomalate (INN, known in the United States as gold sodium thiomalate) is a gold compound that is used for its immunosuppressive anti-rheumatic effects. Along with an orally-administered gold salt, auranofin, it is one of only two go ...
,
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
![Boule de Genève, ca](https://upload.wikimedia.org/wikipedia/commons/2/25/Boule_de_Gen%C3%A8ve%2C_ca._1890.jpeg/1200px-Boule_de_Gen%C3%A8ve%2C_ca._1890.jpeg)
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](_blank)
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. The Japanese craft of
Mokume-gane 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 report.
Gold
solder 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
hallmarking quality, the gold solder alloy must match the
fineness
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 impurities. Alloy metals are added to increase hardne ...
(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
Thread may refer to:
Objects
* Thread (yarn), a kind of thin yarn used for sewing
** Thread (unit of measurement), a cotton yarn measure
* Screw thread, a helical ridge on a cylindrical fastener
Arts and entertainment
* ''Thread'' (film), 2016 ...
and used in
embroidery
Embroidery is the craft of decorating fabric or other materials using a needle to apply thread or yarn. Embroidery may also incorporate other materials such as pearls, beads, quills, and sequins. In modern days, embroidery is usually seen on c ...
.
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 betwee ...
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 industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad v ...
cables. The benefit of using gold over other connector metals such as
tin
Tin is a chemical element with the symbol Sn (from la, 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 with little effort. When bent, t ...
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 Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
s, communications equipment,
spacecraft
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...
,
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-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...
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 switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, typically metal. When a pair of contacts touch, they ca ...
because of its resistance to
corrosion
Corrosion is a 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. Corrosion engine ...
,
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 allow ...
,
ductility
Ductility is a mechanical property commonly described as a material's amenability to drawing (e.g. into wire). In materials science, ductility is defined by the degree to which a material can sustain plastic deformation under tensile stres ...
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, bacterium, or plant, as well as the effect on a subst ...
. 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 electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivity li ...
s to their packages through a process known as
wire bonding.
The concentration of free electrons in gold metal is 5.91×10
22 cm
−3. Gold is highly
conductive 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 separating the isotopes of uranium. It was developed by Ernest Lawrence during the Manhattan Project and was based on his earlier invention, the cyclotron. Its name was derived ...
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 alt ...
assign metallic gold a healing power.
In the 19th century gold had a reputation as an
anxiolytic, a therapy for nervous disorders.
Depression,
epilepsy
Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...
,
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 and
impotence 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 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 joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are involv ...
, 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, especially in tooth restorations, such as
crowns
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...
and permanent
bridges
A bridge is a structure built to Span (engineering), 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, whic ...
. 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 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 nm) or blue/purple (for larger spherical particl ...
preparations (suspensions of
gold nanoparticles) in water are intensely red-
color
Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
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 or
ascorbate
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) and ...
ions. Colloidal gold is used in research applications in medicine, biology and
materials science. The technique of
immunogold labeling
Immunogold labeling or Immunogold staining (IGS) is a staining technique used in electron microscopy. This staining technique is an equivalent of the indirect immunofluorescence technique for visible light. Colloidal gold particles are most ofte ...
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 or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
.
Gold, or alloys of gold and
palladium
Palladium is a chemical element with the 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 asteroid Pallas, which was itself na ...
, 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 with an
argon
Argon is a chemical element with the 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 ppmv). It is more than twice as abu ...
plasma
Plasma or plasm may refer to:
Science
* Plasma (physics), one of the four fundamental states of matter
* Plasma (mineral), a green translucent silica mineral
* Quark–gluon plasma, a state of matter in quantum chromodynamics
Biology
* Blood pla ...
, has a triple role in this application. Gold's very high electrical conductivity drains
electrical charge 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 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 glow, due to ele ...
, 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 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
Gold-198 (198Au) is a radioactive isotope of gold. It undergoes beta decay to stable 198 Hg with a half-life of 2.697 days.
The decay properties of 198Au have led to widespread interest in its potential use in radiotherapy for cancer treatments ...
(
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. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emitting ...
, in some
cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
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 ...
175.
In 2016, the
European Food Safety Authority 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 of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with Mutagen, mutagenicity, all mutagens are genotoxic, but some geno ...
in mammalian cells
in vitro
''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology an ...
.
*
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 karats and shades. The most commonly used gold is 22-kara ...
, 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 period of global history. It began with the fall of the Western Roman Empire a ...
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
Goldwasser ("Gold water from Gdańsk"), pol. Wódka Gdańska, with Goldwasser as the registered tradename, is a strong (40% ABV) root and herbal liqueur which was produced from 1598 to 2009 in Gdańsk. Production now takes place in Germany.
Th ...
( en, Goldwater) is a traditional German herbal
liqueur
A liqueur (; ; ) is an alcoholic drink composed of 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 beyond ...
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, covering an area of . Poland has a population of over 38 million and is the fifth-most populous ...
, and
Schwabach, 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 is a
foil composed of a pure metal that is sometimes gold, and is used for
garnishing sweets in South Asian cuisine.
Miscellanea
![Kamakshi Amman Temple with golden roof, Kanchipuram](https://upload.wikimedia.org/wikipedia/commons/d/da/Kamakshi_Amman_Temple_with_golden_roof%2C_Kanchipuram.jpg)
* 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 sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. A ...
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 visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
and
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
, as well as
radio waves. 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 radioisotope ...
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 to control the spectrum, attack an enemy, or impede enemy assaults. The purpose of electronic warfare is to deny the opponen ...
planes such as the
EA-6B Prowler
The Northrop Grumman (formerly Grumman) EA-6B Prowler is a twin-engine, four-seat, mid-wing electronic-warfare aircraft derived from the A-6 Intruder airframe. The EA-6A was the initial electronic warfare version of the A-6 used by the United S ...
.
* 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 motor racing team based at the McLaren Technology Centre in Woking, Surrey, England. McLaren is best known as a Formula One constructor, the second oldest active team, and the second most successful Formul ...
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 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, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
, to form the salt gold cyanide—a technique that has been used in extracting metallic gold from ores in the
cyanide process. 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 electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...
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 reduction of cations of that metal by means of a direct electric current. The part to be ...
of gold onto base metals and
electroforming.
* Gold chloride (
chloroauric acid
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 ...
) solutions are used to make colloidal gold by reduction with
citrate or
ascorbate
Vitamin C (also known as ascorbic acid and ascorbate) is a water-soluble vitamin found in citrus and other fruits and vegetables, also sold as a dietary supplement and as a topical 'serum' ingredient to treat melasma (dark pigment spots) and ...
ions. 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 extend ...
al gold suspensions, contains evenly sized spherical
gold nanoparticles.
* Gold, when dispersed in nanoparticles, can act as a
heterogeneous catalyst
In chemistry, heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reactants or products. The process contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. Ph ...
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 karats and shades. The most commonly used gold is 22-kara ...
. Metallic gold is also a component of the alcoholic drinks
Goldschläger
''Goldschläger'' is a Swiss cinnamon schnapps (43.5% alcohol by volume or 87 proof; originally it was 53.5% alcohol or 107 proof), a liqueur with very thin, yet visible flakes of gold floating in it. The actual amount of gold has been measured ...
,
Gold Strike, and
Goldwasser
Goldwasser ("Gold water from Gdańsk"), pol. Wódka Gdańska, with Goldwasser as the registered tradename, is a strong (40% ABV) root and herbal liqueur which was produced from 1598 to 2009 in Gdańsk. Production now takes place in Germany.
Th ...
. Metallic gold is approved as a
food additive
Food additives are substances added to food to preserve 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), salt (salt ...
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
Gold-containing drugs are pharmaceuticals that contain gold. Sometimes these species are referred to as "gold salts". "Chrysotherapy" and "aurotherapy" are the applications of gold compounds to medicine. Research on the medicinal effects of g ...
) such as
gold chloride 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, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
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 reduction of cations of that metal by means of a direct electric current. The part to be ...
, are toxic by virtue of both their cyanide and gold content. There are rare cases of lethal gold poisoning from
potassium gold cyanide
Potassium dicyanoaurate is an inorganic compound with formula Ku(CN)2
U or u, is the twenty-first and sixth-to-last letter and fifth vowel letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''u'' (pro ...
It is a colorless to white solid that is soluble in water and slightly soluble in alcohol. The salt itself is often not isolated, but solutions of the dicyanoaurate ion ( . Gold toxicity can be ameliorated with
u( ...
. Gold toxicity can be ameliorated with chelation therapy with an agent such as dimercaprol">chelation therapy">u( ...