HOME

TheInfoList




The
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
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 compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass ...
with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ...
Fe
Fe
S
S
2 (iron (II) disulfide). Pyrite is the most abundant
sulfide mineral The sulfide minerals are a class of s containing (S2−) or (S22−) as the major . Some sulfide minerals are economically important as metal s. The sulfide class also includes the , the , the , the , the bismuthinides, the s and the s.http://w ...
. Pyrite's metallic
luster Lustre or Luster may refer to: Places * Luster, Norway, a municipality in Vestlandet, Norway ** Luster (village), a village in the municipality of Luster * Lustre, Montana, an unincorporated community in the United States Entertainment * Luste ...
and pale brass-yellow
hue In color theory, hue is one of the main properties (called color appearance parameters) of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''c ...

hue
give it a superficial resemblance to
gold Gold is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numb ...

gold
, 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 stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

coal
. The name ''pyrite'' is derived from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
(''pyritēs lithos''), "stone or mineral which strikes fire", in turn from (''pyr''), "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 An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
;
Pliny the Elder #REDIRECT Pliny the Elder#REDIRECT Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, a naturalist Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, ...

Pliny the Elder
described one of them as being brassy, almost certainly a reference to what we now call pyrite. By
Georgius Agricola Georgius Agricola (; born Georg Pawer or Georg Bauer; 24 March 1494 – 21 November 1555) was a German Humanist scholar, mineralogist Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal struct ...

Georgius Agricola
's time, , the term had become a generic term for all of the
sulfide minerals The sulfide minerals are a class of 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 na ...
. Pyrite is usually found associated with other sulfides or
oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having vol ...
s in
quartz Quartz is a hard, crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together an ...

quartz
veins Veins are blood vessels in humans, and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein, pulmonary and umbilical veins, both of which ca ...
,
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
, and
metamorphic rock , a type of metamorphic rock Metamorphic rocks arise from the transformation of existing rock (geology), rock to new types of rock, in a process called metamorphism upright=1.35, Schematic representation of a metamorphic reaction. Abbreviat ...

metamorphic rock
, as well as in coal beds and as a replacement mineral in
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication used by humans, inc ...

fossil
s, but has also been identified in the
sclerite A sclerite (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately ...
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 (see Carlin-type gold deposit). It has been suggested that the presence of both gold and
arsenic Arsenic is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same num ...

arsenic
is a case of
coupled substitution Coupled substitution is the geological process by which two elements simultaneous substitute into a crystal in order to maintain overall electrical neutrality and keep the charge constant. In forming a solid solution series, ionic size is more ...
but as of 1997 the chemical state of the gold remained controversial.


Uses

Pyrite enjoyed brief popularity in the 16th and 17th centuries as a source of
ignition Ignition may refer to: Science and technology * Firelighting Fire making, fire lighting or fire craft is the process of artificially starting a fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of co ...
in early
firearm A firearm is any type of gun A gun is a ranged weapon designed to use a shooting tube ( gun barrel) to launch typically solid projectiles, but can also project pressurized liquid (e.g. water guns/ cannons, spray guns for painting ...
s, most notably the
wheellock , c. 1580 A wheellock, wheel-lock or wheel lock is a friction-wheel mechanism which creates a spark that causes a firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined furth ...
, 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 is a sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology ...

flint
stone and a form of
tinder Tinder is easily combustible material used to 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 until it bursts into flame. The flaming tinder i ...

tinder
made of
stringybark '' A stringybark can be any of the many ''Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of Flowering plant, flowering trees, shrubs or Mallee (habit), mallees in the Myrtaceae, myrtle Family (biology), family, Myrtaceae. Alo ...
by the
Kaurna people The Kaurna people (, ; also Coorna, Kaura, Gaurna and other variations) are a group of Aboriginal Australians, Aboriginal people whose traditional lands include the Adelaide Plains of South Australia. They were known as the Adelaide tribe by the ...
, people of
South Australia South Australia (abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Austral ...

South Australia
, as a traditional method of starting fires. Pyrite has been used since classical times to manufacture ''copperas'' (
ferrous sulfate Iron(II) sulfate (British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and ...
). Iron pyrite was heaped up and allowed to weather (an example of an early form of
heap leaching Heap leaching is an industrial 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. These deposits form a mineralized com ...
). 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 Despite the various English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography English orthogra ...

sulfuric acid
. By the 19th century, it had become the dominant method. Pyrite remains in commercial use for the production of
sulfur dioxide Sulfur dioxide (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering OrganizationsNational Adhering Organizations in chemistry are the organizations that work as the autho ...
, for use in such applications as the
paper industry Image:InternationalPaper6413.jpg, frame, International Paper is the world's largest pulp and paper maker. The pulp and paper industry comprises companies that use wood as raw material and produce Pulp (paper), pulp, paper, paperboard and other cell ...
, 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 chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more th ...
) 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 from which a leaves a polarized electrical device. This definition can be recalled by using the ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in which positive charges move. Electrons ha ...
material in
Energizer Energizer Holdings, Inc. is an American manufacturer and one of the world's largest manufacturers of batteries, headquartered in St. Louis, Missouri Missouri is a U.S. state, state in the Midwestern United States, Midwestern region of the ...
brand non-rechargeable
lithium batteries Lithium batteries are Primary Cell, primary Battery (electricity), batteries that have metallic lithium as an anode. These types of batteries are also referred to as lithium-metal batteries. They stand apart from other batteries in their high c ...

lithium batteries
. Pyrite is a
semiconductor material A semiconductor material has an 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 curre ...
with a
band gap In solid-state physics Solid-state physics is the study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-stat ...

band gap
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 signaling and telecommunication, communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device ...

radio
receivers, and is still used by
crystal radio crystal radio marketed to children. The earphone is on left. The antenna wire, right, has a clip to attach to metal objects such as a bedspring, which serve as an additional antenna to improve reception. A crystal radio receiver, also called a ...
hobbyists. Until the
vacuum tube A vacuum tube, electron tube, 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. The type kn ...
matured, the crystal detector was the most sensitive and dependable
detector In the broadest definition, a sensor is a device, module, machine, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics, frequently a computer processor. A sensor is alway ...
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 Lead is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scienti ...

galena
detectors and the more mechanically complicated
perikon
perikon
mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A
germanium Germanium is a chemical element with the Symbol (chemistry), symbol Ge and atomic number 32. It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbors silicon and tin. Pure germanium i ...

germanium
diode A diode is a two- that conducts primarily in one direction (asymmetric ); it has low (ideally zero) in one direction, and high (ideally infinite) in the other. A diode or thermionic diode is a vacuum tube with two s, a heated and a , in ...

diode
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 commercia ...

photovoltaic
solar panels. Synthetic iron sulfide was used with
copper sulfideCopper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Eart ...
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, made from small faceted pieces of pyrite, often set in silver, was known since ancient times and was popular in the
Victorian era In the history of the United Kingdom The history of the United Kingdom began in the early eighteenth century with the Treaty of Union A treaty is a formal, legally binding written agreement between actors in international l ...
. At the time when the term became common in jewelry making, "marcasite" referred to all iron sulfides including pyrite, and not to the orthorhombic FeS2 mineral
marcasite 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. R ...

marcasite
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 and La Rioja provinces (Spain). In value terms,
China China (), officially the People's Republic of China (PRC; ), is a country in East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere ...

China
($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
CAGRCompound annual growth rate (CAGR) is a business and investing specific term for the geometric progression In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical stru ...
of +27.8% from 2007 to 2016.


Research

In July 2020 scientists reported that they have observed a voltage-induced transformation of normally
diamagnetic Diamagnetic materials are repelled by a magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in t ...
pyrite into a
ferromagnetic Ferromagnetism is the basic mechanism by which certain materials (such as iron Iron () is a with Fe (from la, ) and 26. It is a that belongs to the and of the . It is, on , right in front of (32.1% and 30.1%, respectively), formi ...
material, which may lead to applications in devices such as solar cells or magnetic data storage. Researchers at Trinity College Dublin, Ireland have demonstrated that FeS2 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 FeS2. 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 FeS2. 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 a anode in lithium-ion batteries.


Formal oxidation states for pyrite, marcasite, and arsenopyrite

From the perspective of classical
inorganic chemistry#REDIRECT Inorganic chemistry features unusual bonding B: Caesium chloride Caesium chloride or cesium chloride is the inorganic compound with the formula Caesium, CsChloride, Cl. This colorless salt is an important source of caesium ions in a var ...
, which assigns formal oxidation states to each atom, pyrite is probably best described as Fe2+S22−. This formalism recognizes that the sulfur atoms in pyrite occur in pairs with clear S–S bonds. These persulfide units can be viewed as derived from
hydrogen disulfide Hydrogen disulfide is the inorganic compound In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, ...

hydrogen disulfide
, H2S2. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast,
molybdenite Molybdenite is a 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 f ...

molybdenite
, S2, features isolated sulfide (S2−) centers and the oxidation state of molybdenum is Mo4+. The mineral
arsenopyrite Arsenopyrite 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 Relative density, or specific gravity, is the ratio In mathematics, a r ...

arsenopyrite
has the formula FeS. Whereas pyrite has S2 subunits, arsenopyrite has units, formally derived from
deprotonation Deprotonation (or dehydronation) is the removal (transfer) of a proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutr ...

deprotonation
of arsenothiol (H2AsSH). Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe3+sup>3−.


Crystallography

Iron-pyrite FeS2 represents the prototype compound of the
crystallographic Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen drop", with its mean ...

crystallographic
pyrite structure. The structure is simple
cubic Cubic may refer to: Science and mathematics * Cube (algebra) In arithmetic and algebra Algebra (from ar, الجبر, lit=reunion of broken parts, bonesetting, translit=al-jabr) is one of the areas of mathematics, broad areas of mathema ...
and was among the first crystal structures solved by
X-ray diffraction X-ray crystallography (XRC) is the experimental science determining the atomic and molecular structure of a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a ...
. It belongs to the crystallographic
space group In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities and ...
''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 cell In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, ...
a of stoichiometric iron pyrite FeS2 amounts to . The
unit cell In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space t ...

unit cell
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, the term transition metal (or transition element) has three possible definitions: * The IUPAC definition defines a transition metal as "an chemical element, element whose atom has a partially filled Electron shell, ''d'' sub-shel ...
''M'' and
chalcogen The chalcogens () are the chemical elements in group (periodic table), group 16 of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the Radioa ...
s ''X'' = , , and . Certain dipnictides with ''X'' standing for , and 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 material has an 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 curre ...
. The Fe ions is usually considered to be ''
low spinSpin states when describing transition metal coordination complexes refers to the potential spin configurations of the central metal's d electrons. In many these spin states vary between high-spin and low-spin configurations. These configurations ca ...
''
divalent In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they und ...
state (as shown by
Mössbauer spectroscopy Mössbauer spectroscopy is a spectroscopic Spectroscopy is the study of the interaction between matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday ob ...
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, Magnetization, induced magnetic fields in the direction of the applied magnetic field. In contrast with th ...
, despite its low-spin divalency. The sulfur centers occur in pairs, described as S22−. Reduction of pyrite with potassium gives potassium dithioferrate, KFeS2. This material features ferric ions and isolated sulfide (S2-) 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 polarisation 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 The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is the amount of work energy needed to move a unit of ele ...
s and has to be included in the calculation of the
lattice energy The lattice energy is the energy change on formation of one mole of an ionic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: ...
by using a generalised
Born–Haber cycle The Born–Haber cycle is an approach to analyze reaction energies. It was named after the two German scientists Max Born and Fritz Haber Fritz Haber (; 9 December 1868 – 29 January 1934) was a German chemist who received the Nobel Prize ...
. 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 differ from that of pyrite. Despite its name, chalcopyrite () does not contain dianion pairs, but single S2− sulfide anions.


Crystal habit

Pyrite usually forms cuboid crystals, sometimes forming in close association to form raspberry-shaped masses called
framboidThe term framboid describes a micromorphological feature common to certain sedimentary minerals, particularly pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula A chemical fo ...
s. However, under certain circumstances, it can form Anastomosis, anastomosing filaments or T-shaped crystals. Pyrite can also form shapes almost the same as a regular dodecahedron, dodecahedral, 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 (Cobalt, Co2) and vaesite (Nickel, Ni2) are similar in their structure and belong also to the pyrite group. Bravoite is a nickel-cobalt bearing variety of pyrite, with > 50% substitution of nickel, Ni2+ for Fe2+ 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 Gold#Occurrence, native gold by its hardness, brittleness and crystal form. Pyrite fractures are very Fracture (mineralogy)#Uneven fracture, uneven, sometimes conchoidal fracture, conchoidal because it does not cleave along a preferential plane. Native gold nuggets, or glitters, do not break but deform in a ductility, ductile way. Pyrite is brittle, gold is malleable. Natural gold tends to be Euhedral and anhedral, 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 (''i.e.'', with nice faces). Pyrite can often be distinguished by the striations which, in many cases, can be seen on its surface. Chalcopyrite () is brighter yellow with a greenish hue when wet and is softer (3.5–4 on Mohs' scale). Arsenopyrite (FeAsS) is silver white and does not become more yellow when wet.


Hazards

Iron pyrite is unstable at Earth's surface: iron pyrite exposed to atmospheric oxygen and water decomposes into iron oxides and sulfate. This process is accelerated by the action of ''Acidithiobacillus'' bacteria which oxidize pyrite to produce ferrous iron, sulfate, and protons (). These reactions occur more rapidly when pyrite is finely dispersed (framboidal crystals initially formed by Sulfate-reducing microorganisms, sulfate reducing bacteria (SRB) in argillaceous sediments or dust from mining operations).


Pyrite oxidation and acid mine drainage

Sulfate released from decomposing pyrite combines with water, producing
sulfuric acid Sulfuric acid (American spelling Despite the various English dialects spoken from country to country and within different regions of the same country, there are only slight regional variations in English orthography English orthogra ...

sulfuric acid
, leading to acid mine drainage. An example of acid rock drainage caused by pyrite is the 2015 Gold King Mine waste water spill. :2FeS2 + 7O2 + 2H2O -> 2Fe^ + 4SO4^ + 4H+.


Dust explosions

Pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion. The solution is the use of buffer blasting and the use of various sealing or cladding agents to Hermetic seal, hermetically seal the mined-out areas to exclude oxygen. In modern coal mines, limestone dust is sprayed onto the exposed coal surfaces to reduce the hazard of dust explosions. 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 sulfates formed may exert crystallization pressure that can expand cracks in the rock and lead eventually to cave-in, 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 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. R ...

marcasite
is present. The presence of pyrite in the Construction aggregate, aggregate used to make concrete can lead to severe deterioration as pyrite oxidizes. In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to pyrite oxidation, followed by microbial sulfate reduction which released hydrogen sulfide gas. These problems included a foul odor and corrosion of copper 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. Normalized tests for aggregate materials certify such materials as free of pyrite.


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 Miscibility, immiscible sulfide phase in the original magma. It is found in metamorphic rocks as a product of contact metamorphism. It also forms as a high-temperature hydrothermal mineralization, 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. Pyrite and
marcasite 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. R ...

marcasite
commonly occur as replacement pseudomorphs after fossils in black shale and other sedimentary rocks formed under Redox, 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.


Belief

In the beliefs of Thai people (especially the southerner), pyrite is known by many names ''Khao tok Phra Ruang'', ''Khao khon bat Phra Ruang'' (ข้าวตอกพระร่วง, ข้าวก้นบาตรพระร่วง) or ''Phet na tang'', ''Hin na tang'' (เพชรหน้าทั่ง, หินหน้าทั่ง), believed to be a amulet, sacred item that has the power to prevent evil, black magic or demons.


Images

File:Bullypyrite2.jpg, As a replacement mineral in an ammonite 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, 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)


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


Educational article about the famous pyrite crystals from the Navajun Mine


"Pyrite oxidation under room conditions". * {{Authority control Disulfides Firelighting Pyrite group Iron(II) minerals Cubic minerals Minerals in space group 205 Sulfide minerals Alchemical substances Semiconductor materials Transition metal dichalcogenides