The
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
pyrite ( ), or iron pyrite, also known as fool's gold, is an
iron sulfide
Iron sulfide or iron sulphide can refer to range of chemical compounds composed of iron and sulfur.
Minerals
By increasing order of stability:
* Iron(II) sulfide, FeS
* Greigite, Fe3S4 (cubic)
* Pyrrhotite, Fe1−xS (where x = 0 to 0.2) (monocli ...
with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
Fe S2 (iron (II) disulfide). Pyrite is the most abundant
sulfide mineral
The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide () as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenide mineral, selenides, the tell ...
.

Pyrite's metallic
luster and pale brass-yellow
hue
In color theory, hue is one of the properties (called color appearance parameters) of a color, defined in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as ...
give it a superficial resemblance to
gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
, hence the well-known nickname of ''fool's gold''. The color has also led to the nicknames ''brass'', ''brazzle'', and ''brazil'', primarily used to refer to pyrite found in
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal i ...
.
The name ''pyrite'' is derived from the
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
(), 'stone or mineral which strikes fire', in turn from (), 'fire'. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against
steel
Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
;
Pliny the Elder
Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...
described one of them as being brassy, almost certainly a reference to what is now called pyrite.
By
Georgius Agricola
Georgius Agricola (; born Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist and metallurgist. Born in the small town of Glauchau, in the Electorate of Saxony of the Holy Roman Empire, he was b ...
's time, , the term had become a generic term for all of the
sulfide minerals
The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide () as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, the ar ...
.

Pyrite is usually found associated with other sulfides or
oxide
An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
s in
quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
veins
Veins () are blood vessels in the circulatory system of 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 those of the pulmonary and fetal c ...
,
sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
, and
metamorphic rock
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...
, as well as in coal beds and as a replacement mineral in
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s, but has also been identified in the
sclerite
A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...
s of
scaly-foot gastropods. Despite being nicknamed "fool's gold", pyrite is sometimes found in association with small quantities of gold. A substantial proportion of the gold is "
invisible gold" incorporated into the pyrite. It has been suggested that the presence of both gold and
arsenic
Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...
is a case of
coupled substitution but as of 1997 the chemical state of the gold remained controversial.
Uses

Pyrite gained a brief popularity in the 16th and 17th centuries as a source of
ignition
Ignition may refer to:
Science and technology
* Firelighting, the human act of creating a fire for warmth, cooking and other uses
* Combustion, an exothermic chemical reaction between a fuel and an oxidant
* Fusion ignition, the point at which a ...
in early
firearm
A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions).
The first firearms originate ...
s, most notably the
wheellock
A wheellock, wheel-lock, or wheel lock is a friction-wheel mechanism which creates a spark that causes a firearm to fire. It was the next major development in firearms technology after the matchlock, and the first self-igniting firearm. Its name ...
, where a sample of pyrite was placed against a circular file to strike the sparks needed to fire the gun.
Pyrite is used with
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. Historically, flint was widely used to make stone tools and start ...
stone and a form of
tinder
Tinder is easily Combustibility and flammability, combustible material used to Firemaking, start a fire. Tinder is a finely divided, open material which will begin to glow under a shower of sparks. Air is gently wafted over the glowing tinder unt ...
made of
stringybark
A stringybark can be any of the many ''Eucalyptus'' species which have thick, fibrous bark. Like all eucalypts, stringybarks belong to the family Myrtaceae. In exceptionally fertile locations some stringybark species (in particular messmate strin ...
by the
Kaurna people
The Kaurna people (, ; also Coorna, Kaura, Gaurna and other variations) are a group of Aboriginal people whose traditional lands include the Adelaide Plains of South Australia. They were known as the Adelaide tribe by the early settlers. Kau ...
of
South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
, as a traditional method of starting fires.
Pyrite has been used since classical times to manufacture ''copperas'' (
ferrous sulfate
Iron(II) sulfate or ferrous sulfate (British English: sulphate instead of sulfate) denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7), but several values for ...
). Iron pyrite was heaped up and allowed to weather (an example of an early form of
heap leaching
Heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and re-separate them after their division from other e ...
). The acidic runoff from the heap was then boiled with iron to produce iron sulfate. In the 15th century, new methods of such leaching began to replace the burning of sulfur as a source of
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
. By the 19th century, it had become the dominant method.
Pyrite remains in commercial use for the production of
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
, for use in such applications as the
paper industry
The pulp and paper industry comprises companies that use wood, specifically pulpwood, as raw material and produce pulp, paper, paperboard, and other cellulose-based products.
Manufacturing process
In the manufacturing process, pulp is intro ...
, and in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS (
iron(II) sulfide
Iron(II) sulfide or ferrous sulfide (Br.E. sulphide) is one of a family of chemical compounds and minerals with the approximate chemical formula, formula . Iron sulfides are often iron-deficient non-stoichiometric. All are black, water-insoluble ...
) and elemental sulfur starts at ; at around , ''p''
S2 is about .
A newer commercial use for pyrite is as the
cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device such as a lead-acid battery. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. Conventional curren ...
material in
Energizer
Energizer Holdings, Inc. is an American manufacturer and one of the world's largest manufacturers of batteries, headquartered in Clayton, Missouri. It produces batteries under the Energizer, Ray-O-Vac, Varta, and Eveready brand names and fo ...
brand non-rechargeable
lithium metal batteries.
Pyrite is a
semiconductor material
A semiconductor is a material with electrical conductivity between that of a Electrical conductor, conductor and an Insulator (electricity), insulator. Its conductivity can be modified by adding impurities ("doping (semiconductor), doping") to ...
with a
band gap
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to t ...
of 0.95
eV. Pure pyrite is naturally n-type, in both crystal and thin-film forms, potentially due to sulfur vacancies in the pyrite crystal structure acting as n-dopants.
During the early years of the 20th century, pyrite was used as a
mineral detector in
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
receivers, and is still used by
crystal radio hobbyists. Until the
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
matured, the crystal detector was the most sensitive and dependable
detector
A sensor is often defined as a device that receives and responds to a signal or stimulus. The stimulus is the quantity, property, or condition that is sensed and converted into electrical signal.
In the broadest definition, a sensor is a devi ...
available—with considerable variation between mineral types and even individual samples within a particular type of mineral. Pyrite detectors occupied a midway point between
galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It crysta ...
detectors and the more mechanically complicated
perikon mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A
germanium
Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...
diode
A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance ...
detector.
Pyrite has been proposed as an abundant, non-toxic, inexpensive material in low-cost
photovoltaic
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
solar panels. Synthetic iron sulfide was used with
copper sulfide
Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.
Prominent copper sulfide minerals ...
to create the photovoltaic material. More recent efforts are working toward thin-film solar cells made entirely of pyrite.
Pyrite is used to make
marcasite jewelry. Marcasite jewelry, using small faceted pieces of pyrite, often set in
silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...
, has been made since ancient times and was popular in the
Victorian era
In the history of the United Kingdom and the British Empire, the Victorian era was the reign of Queen Victoria, from 20 June 1837 until her death on 22 January 1901. Slightly different definitions are sometimes used. The era followed the ...
. At the time when the term became common in jewelry making, "marcasite" referred to all iron sulfides including pyrite, and not to the orthorhombic FeS
2 mineral
marcasite
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...
which is lighter in color, brittle and chemically unstable, and thus not suitable for jewelry making.
Marcasite jewelry does not actually contain the mineral marcasite. The specimens of pyrite, when it appears as good quality crystals, are used in decoration. They are also very popular in mineral collecting. Among the sites that provide the best specimens are
Soria
Soria () is a municipality and a Spanish city, located on the Douro river in the east of the autonomous community of Castile and León and capital of the province of Soria. Its population is 38,881 ( INE, 2017), 43.7% of the provincial populatio ...
and
La Rioja
La Rioja () is an autonomous communities in Spain, autonomous community and provinces of Spain, province in Spain, in the north of the Iberian Peninsula. Its capital is Logroño. Other List of municipalities in La Rioja, cities and towns in the ...
provinces (Spain).
In value terms,
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
($47 million) constitutes the largest market for imported unroasted iron pyrites worldwide, making up 65% of global imports. China is also the fastest growing in terms of the unroasted iron pyrites imports, with a
CAGR
Compound annual growth rate (CAGR) is a business, economics and investing term representing the mean annualized growth rate for compounding values over a given time period. CAGR smoothes the effect of volatility of periodic values that can render ...
of +27.8% from 2007 to 2016.
Research
In July 2020 scientists reported that they have observed a voltage-induced transformation of normally
diamagnetic
Diamagnetism is the property of materials that are repelled by a magnetic field; an applied magnetic field creates an induced magnetic field in them in the opposite direction, causing a repulsive force. In contrast, paramagnetic and ferromagn ...
pyrite into a
ferromagnetic
Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...
material, which may lead to applications in devices such as solar cells or magnetic data storage.
Researchers at
Trinity College Dublin
Trinity College Dublin (), officially titled The College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin, and legally incorporated as Trinity College, the University of Dublin (TCD), is the sole constituent college of the Unive ...
, Ireland have demonstrated that FeS
2 can be exfoliated into few-layers just like other two-dimensional layered materials such as graphene by a simple liquid-phase exfoliation route. This is the first study to demonstrate the production of non-layered 2D-platelets from 3D bulk FeS
2. Furthermore, they have used these 2D-platelets with 20% single walled carbon-nanotube as an anode material in lithium-ion batteries, reaching a capacity of 1000 mAh/g close to the theoretical capacity of FeS
2.
In 2021, a natural pyrite stone has been crushed and pre-treated followed by liquid-phase exfoliation into two-dimensional nanosheets, which has shown capacities of 1200 mAh/g as an anode in lithium-ion batteries.
Formal oxidation states for pyrite, marcasite, molybdenite and arsenopyrite
From the perspective of classical
inorganic chemistry
Inorganic chemistry deals with chemical synthesis, synthesis and behavior of inorganic compound, inorganic and organometallic chemistry, organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subj ...
, which assigns formal oxidation states to each atom, pyrite and marcasite are probably best described as Fe
2+ 2">2sup>2−. This formalism recognizes that the sulfur atoms in pyrite occur in pairs with clear S–S bonds. These
persulfide
In chemistry, persulfide refers to the functional group R-S-S-H. Persulfides are intermediates in the biosynthesis of iron-sulfur proteins and are invoked as precursors to hydrogen sulfide, a signaling molecule.
Nomenclature
The nomenclature use ...
−S–S−">sup>−S–S−units can be viewed as derived from
hydrogen disulfide
Hydrogen disulfide is the inorganic compound with the formula . This hydrogen chalcogenide is a pale yellow volatile liquid with a camphor-like odor. It decomposes readily to hydrogen sulfide () and elemental sulfur.
Structure
The connection of ...
, H
2S
2. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast,
molybdenite
Molybdenite is a mineral of molybdenum disulfide, Mo S2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum at ...
,
MoS
2, features isolated sulfide S
2− centers and the oxidation state of molybdenum is Mo
4+. The mineral
arsenopyrite
Arsenopyrite ( IMA symbol: Apy) is an iron arsenic sulfide (FeAsS). It is a hard ( Mohs 5.5–6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1.
When dissolved in nitric acid, it releases el ...
has the formula Fe
AsS. Whereas pyrite has
2">2sup>2− units, arsenopyrite has
sSsup>3− units, formally derived from
deprotonation
Deprotonation (or dehydronation) is the removal (transfer) of a proton (or hydron, or hydrogen cation), (H+) from a Brønsted–Lowry acid in an acid–base reaction.Henry Jakubowski, Biochemistry Online Chapter 2A3, https://employees.csbsju.ed ...
of arsenothiol (H
2AsSH). Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe
3+ sSsup>3−.
Crystallography
Iron-pyrite FeS
2 represents the prototype compound of the
crystallographic
Crystallography is the branch of science devoted to the study of molecular and crystalline structure and properties. The word ''crystallography'' is derived from the Ancient Greek word (; "clear ice, rock-crystal"), and (; "to write"). In J ...
pyrite structure. The structure is
cubic
Cubic may refer to:
Science and mathematics
* Cube (algebra), "cubic" measurement
* Cube, a three-dimensional solid object bounded by six square faces, facets or sides, with three meeting at each vertex
** Cubic crystal system, a crystal system w ...
and was among the first
crystal structures
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat a ...
solved by
X-ray diffraction
X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. ...
.
It belongs to the crystallographic
space group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
''Pa'' and is denoted by the
Strukturbericht notation C2. Under thermodynamic standard conditions the
lattice constant
A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. A simple cubic crystal has ...
of stoichiometric iron pyrite FeS
2 amounts to .
The
unit cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector
In mathematics, a unit vector i ...
is composed of a Fe
face-centered cubic sublattice into which the ions are embedded. (Note though that the iron atoms in the faces are not equivalent by translation alone to the iron atoms at the corners.) The pyrite structure is also seen in other ''MX''
2 compounds of
transition metals
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. The lanthanide and actinid ...
''M'' and
chalcogen
The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the rad ...
s ''X'' =
O,
S,
Se and
Te. Certain
dipnictides with ''X'' standing for
P,
As and
Sb etc. are also known to adopt the pyrite structure.
The Fe atoms are bonded to six S atoms, giving a distorted octahedron. The material is a
semiconductor
A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...
. The Fe ions are usually considered to be ''
low spin
Spin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. For several oxidation states, metals can adopt high-spin and low-spin configurations. The ambiguity ...
''
divalent
In chemistry, the valence (US spelling) or valency (British spelling) of an atom is a measure of its combining capacity with other atoms when it forms chemical compounds or molecules. Valence is generally understood to be the number of chemica ...
state (as shown by
Mössbauer spectroscopy
Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer (sometimes written "Moessbauer", German: "Mößbauer") in 1958, consists of the nearly recoil-free emission and a ...
as well as XPS). The material as a whole behaves as a Van Vleck
paramagnet
Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, d ...
, despite its low-spin divalency.
The sulfur centers occur in pairs, described as S
22−. Reduction of pyrite with potassium gives
potassium dithioferrate, KFeS
2. This material features ferric ions and isolated sulfide (S
2−) centers.
The S atoms are tetrahedral, being bonded to three Fe centers and one other S atom. The site symmetry at Fe and S positions is accounted for by
point symmetry groups ''C''
3''i'' and ''C''
3, respectively. The missing
center of inversion at S lattice sites has important consequences for the crystallographic and physical properties of iron pyrite. These consequences derive from the crystal electric field active at the sulfur lattice site, which causes a
polarization
Polarization or polarisation may refer to:
Mathematics
*Polarization of an Abelian variety, in the mathematics of complex manifolds
*Polarization of an algebraic form, a technique for expressing a homogeneous polynomial in a simpler fashion by ...
of S ions in the pyrite lattice.
The polarisation can be calculated on the basis of higher-order
Madelung constant
The Madelung constant is used in determining the electrostatic potential of a single ion in a crystal by approximating the ions by point charges. It is named after Erwin Madelung, a German physicist.
Because the anions and cations in an ioni ...
s and has to be included in the calculation of the
lattice energy
In chemistry, the lattice energy is the energy change (released) upon formation of one mole of a crystalline compound from its infinitely separated constituents, which are assumed to initially be in the gaseous state at 0 K. It is a measure of ...
by using a generalised
Born–Haber cycle. This reflects the fact that the covalent bond in the sulfur pair is inadequately accounted for by a strictly ionic treatment.
Arsenopyrite has a related structure with heteroatomic As–S pairs rather than S-S pairs. Marcasite also possesses homoatomic anion pairs, but the arrangement of the metal and diatomic anions differs from that of pyrite. Despite its name, chalcopyrite () does not contain dianion pairs, but single S
2− sulfide anions.
Crystal habit

Pyrite usually forms cuboid crystals, sometimes forming in close association to form raspberry-shaped masses called
framboid A framboid is a micromorphological feature common to certain sedimentary minerals, particularly pyrite (FeS2). The first known use of the term is ascribed to Rust in 1935 and is derived from the French 'framboise', meaning 'raspberry', reflecting th ...
s. However, under certain circumstances, it can form
anastomosing filaments or T-shaped crystals.
Pyrite can also form shapes almost the same as a regular
dodecahedron
In geometry, a dodecahedron (; ) or duodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagons as faces, which is a Platonic solid. There are also three Kepler–Po ...
, known as pyritohedra, and this suggests an explanation for the artificial geometrical models found in Europe as early as the 5th century BC.
Varieties
Cattierite
Cattierite (CoS2) is a cobalt sulfide mineral found in the Democratic Republic of Congo. It was discovered together with the nickel sulfide vaesite by Johannes F. Vaes, a Belgian mineralogist and named after Felicien Cattier, who was chairman of ...
(
Co S2),
vaesite
Vaesite ( Ni S2) is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralogist. It is part of the pyrite group
The pyrite group of minerals is a set of cubic crystal s ...
(
Ni S2) and
hauerite (
Mn S2), as well as
sperrylite
Sperrylite is a platinum arsenide mineral with the chemical formula and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in ...
(
Pt As2) are similar in their structure and belong also to the pyrite group.
is a nickel-cobalt bearing variety of pyrite, with > 50% substitution of
Ni2+ for Fe
2+ within pyrite. Bravoite is not a formally recognised mineral, and is named after the Peruvian scientist Jose J. Bravo (1874–1928).
Distinguishing similar minerals
Pyrite is distinguishable from
native gold by its hardness, brittleness and crystal form. Pyrite fractures are very
uneven, sometimes
conchoidal
A conchoidal fracture is a break or fracture of a brittle material that does not follow any natural planes of separation. Mindat.org defines ''conchoidal fracture'' as follows: "a fracture with smooth, curved surfaces, typically slightly concave, ...
because it does not cleave along a preferential plane. Native
gold nugget
A gold nugget is a naturally occurring piece of Native metal, native gold. Watercourses often concentrate nuggets and finer gold in placer deposit, placers. Nuggets are recovered by placer mining, but they are also found in residual deposits wher ...
s, or glitters, do not break but deform in a
ductile
Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...
way. Pyrite is brittle, gold is malleable.
Natural gold tends to be
anhedral (irregularly shaped without well defined faces), whereas pyrite comes as either cubes or multifaceted crystals with well developed and sharp faces easy to recognise. Well crystallised pyrite crystals are
euhedral
Euhedral and anhedral are terms used to describe opposite properties in the formation of crystals. Euhedral (also known as idiomorphic or automorphic) crystals
are those that are well-formed, with sharp, easily recognised faces. The opposite i ...
(''i.e.'', with nice faces). Pyrite can often be distinguished by the striations which, in many cases, can be seen on its surface.
Chalcopyrite
Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a Mohs scale, hardness of 3.5 to 4 ...
() is brighter yellow with a greenish hue when wet and is softer (3.5–4 on Mohs' scale).
Arsenopyrite
Arsenopyrite ( IMA symbol: Apy) is an iron arsenic sulfide (FeAsS). It is a hard ( Mohs 5.5–6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1.
When dissolved in nitric acid, it releases el ...
(FeAsS) is silver white and does not become more yellow when wet.
Hazards

Iron pyrite is unstable when exposed to the
oxidizing
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
conditions prevailing at the Earth's surface: iron pyrite in contact with atmospheric
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
and water, or damp, ultimately decomposes into
iron oxyhydroxides (
ferrihydrite
Ferrihydrite (Fh) is a widespread hydrous ferric oxyhydroxide mineral at the Earth's surface, and a likely constituent in extraterrestrial materials. It forms in several types of environments, from freshwater to marine systems, aquifers to hydro ...
, FeO(OH)) and
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
(). This process is accelerated by the action of ''
Acidithiobacillus
''Acidithiobacillus'' is a genus of the '' Acidithiobacillia'' in the phylum "'' Pseudomonadota''". This genus includes ten species of acidophilic microorganisms capable of sulfur and/or iron oxidation: ''Acidithiobacillus albertensis, Acidithiob ...
'' bacteria which oxidize pyrite to first produce
ferrous ion
In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ''ferrous'' or the prefix ''ferro-'' is often used to specify such compounds, as in ''ferrous chloride'' for iron(II) chloride (). The adjective ''ferr ...
s (),
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
ions (), and release protons (, or ). In a second step, the ferrous ions () are oxidized by into
ferric ions () which
hydrolyze
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
also releasing ions and producing FeO(OH). These oxidation reactions occur more rapidly when pyrite is finely dispersed (framboidal crystals initially formed by
sulfate reducing bacteria
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate () as termina ...
(SRB) in argillaceous sediments or dust from mining operations).
Pyrite oxidation and acid mine drainage
Pyrite oxidation by atmospheric in the presence of moisture () initially produces ferrous ions () and
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
which dissociates into
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
ions and
protons
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' ( elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an electron (the pro ...
, leading to
acid mine drainage
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) is the outflow of acidic water from metal mines and coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weatherin ...
(AMD). An example of acid rock drainage caused by pyrite is the
2015 Gold King Mine waste water spill
The 2015 Gold King Mine waste water spill was an environmental disaster that began at the Gold King Mine near Silverton, Colorado, when Environmental Protection Agency (EPA) personnel, along with workers for Environmental Restoration LLC (a Mis ...
.
:
Dust explosions
Pyrite oxidation is sufficiently
exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...
that underground
coal mine
Coal mining is the process of resource extraction, extracting coal from the ground or from a mine. Coal is valued for its Energy value of coal, energy content and since the 1880s has been widely used to Electricity generation, generate electr ...
s in high-sulfur coal seams have occasionally had serious problems with
spontaneous combustion
Spontaneous combustion or spontaneous ignition is a type of combustion which occurs by self-heating (increase in temperature due to exothermic internal reactions), followed by thermal runaway (self heating which rapidly accelerates to high tem ...
. The solution is the use of buffer blasting and the use of various sealing or cladding agents to
hermetically seal the mined-out areas to exclude oxygen.
In modern coal mines,
limestone
Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
dust is sprayed onto the exposed coal surfaces to reduce the hazard of
dust explosion
A dust explosion is the rapid combustion of fine particles suspended in the air within an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high-enough concentrations in the atmosphere ...
s. This has the secondary benefit of neutralizing the acid released by pyrite oxidation and therefore slowing the oxidation cycle described above, thus reducing the likelihood of spontaneous combustion. In the long term, however, oxidation continues, and the
hydrated
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
sulfate
The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ...
s formed may exert crystallization pressure that can expand cracks in the rock and lead eventually to
roof fall.
Weakened building materials
Building stone containing pyrite tends to stain brown as pyrite oxidizes. This problem appears to be significantly worse if any
marcasite
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...
is present. The presence of pyrite in the
aggregate used to make
concrete
Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
can lead to severe deterioration as pyrite oxidizes. In early 2009, problems with
Chinese drywall
"Chinese drywall" refers to an environmental health issue involving defective drywall manufactured in China, imported to the United States and used in residential construction between 2001 and 2009 affecting "an estimated 100,000 homes in more tha ...
imported into the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
after
Hurricane Katrina
Hurricane Katrina was a powerful, devastating and historic tropical cyclone that caused 1,392 fatalities and damages estimated at $125 billion in late August 2005, particularly in the city of New Orleans and its surrounding area. ...
were attributed to pyrite oxidation, followed by microbial sulfate reduction which released
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
gas (). These problems included a foul odor and
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 ...
of
copper
Copper is a chemical element; it has symbol Cu (from Latin ) 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 pinkish-orang ...
wiring. In the United States, in Canada, and more recently in Ireland, where it was used as underfloor infill, pyrite contamination has caused major structural damage.
Concrete
Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
exposed to sulfate ions, or sulfuric acid, degrades by
sulfate attack: the formation of expansive mineral phases, such as
ettringite
Ettringite is a hydrous calcium aluminium sulfate mineral with formula: . It is a colorless to yellow mineral crystallizing in the trigonal crystal system, system. The prismatic crystals are typically colorless, turning white on partial dehydratio ...
(small needle crystals exerting a huge crystallization pressure inside the concrete pores) and
gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...
creates inner
tensile forces in the concrete matrix which destroy the hardened
cement
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...
paste, form cracks and fissures in concrete, and can lead to the ultimate ruin of the structure. Normalized tests for
construction aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, crushed stone. As with other types of ag ...
certify such materials as free of pyrite or marcasite.
Occurrence
Pyrite is the most common of sulfide minerals and is widespread in igneous, metamorphic, and sedimentary rocks. It is a common accessory mineral in igneous rocks, where it also occasionally occurs as larger masses arising from an
immiscible
Miscibility () is the property of two chemical substance, substances to mix in all mixing ratio, proportions (that is, to fully dissolution (chemistry), dissolve in each other at any concentration), forming a homogeneity and heterogeneity, homoge ...
sulfide phase in the original magma. It is found in metamorphic rocks as a product of
contact metamorphism
Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of c ...
. It also forms as a high-temperature
hydrothermal mineral, though it occasionally forms at lower temperatures.
Pyrite occurs both as a primary mineral, present in the original sediments, and as a secondary mineral, deposited during
diagenesis
Diagenesis () is the process of physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sedi ...
.
Pyrite and
marcasite
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...
commonly occur as replacement
pseudomorph
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced b ...
s after
fossils
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
in
black shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
and other
sedimentary rocks
Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedim ...
formed under
reducing environmental conditions. Pyrite is common as an accessory mineral in shale, where it is formed by precipitation from anoxic seawater, and coal beds often contain significant pyrite.
Notable deposits are found as lenticular masses in Virginia, U.S., and in smaller quantities in many other locations. Large deposits are mined at Rio Tinto in Spain and elsewhere in the Iberian Peninsula.
Cultural beliefs
In the beliefs of the Thai people (especially those in the south), pyrite is known as ''Khao tok
Phra Ruang'', ''Khao khon bat Phra Ruang'' (ข้าวตอกพระร่วง, ข้าวก้นบาตรพระร่วง) or ''Phet na tang'', ''Hin na tang'' (เพชรหน้าทั่ง, หินหน้าทั่ง). It is believed to be a
sacred item that has the power to prevent evil,
black magic
Black magic (Middle English: ''nigromancy''), sometimes dark magic, traditionally refers to the use of Magic (paranormal), magic or supernatural powers for evil and selfish purposes.
The links and interaction between black magic and religi ...
or demons.
Images
File:Bullypyrite2.jpg, As a replacement mineral in an ammonite
Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
from France
File:Pyrite from Ampliación a Victoria Mine, Navajún, La Rioja, Spain 2.jpg, Pyrite from Ampliación a Victoria Mine, Navajún, La Rioja, Spain
File:Pyrite-Tetrahedrite-Quartz-184642.jpg, Pyrite from the Sweet Home Mine, with golden striated cubes intergrown with minor tetrahedrite, on a bed of transparent quartz needles
File:Pyrite-200582.jpg, Radiating form of pyrite
File:Paraspirifer bownockeri.fond.jpg, '' Paraspirifer bownockeri'' in pyrite
File:Fluorite-Pyrite-tmu38b.jpg, Pink fluorite perched between pyrite on one side and metallic galena on the other side
File:Pyrite in pyrrhotite SEM image.png, SEM image of intergrowth of pyrite cuboctahedral crystals (yellow) and pyrrhotite (pinkish yellow)
See also
*
Iron–sulfur world hypothesis
*
Sulfur isotope biogeochemistry
References
Further reading
* American Geological Institute, 2003, ''Dictionary of Mining, Mineral, and Related Terms'', 2nd ed., Springer, New York, .
* David Rickard, ''Pyrite: A Natural History of Fool's Gold'', Oxford, New York, 2015, .
External links
Pyrite.Virtual Museum of Mineralogy. Universidad de Zaragoza, SpainEducational article about the famous pyrite crystals from the Navajun Mine"Pyrite oxidation under room conditions".
*
{{Authority control
Disulfides
Fire making
Pyrite group
Iron(II) minerals
Cubic minerals
Minerals in space group 205
Sulfide minerals
Alchemical substances
Semiconductor materials
Transition metal dichalcogenides
Blendes