Pyrite
A mass of intergrown pyrite crystals
General
Category	Sulfide mineral
Chemical formula	iron disulfide (FeS2)
Strunz classification	02.EB.05a
Dana classification	2.12.1.1
Crystal symmetry	Isometric diploidal Space group: Pa3 H-M symbol: 2/m3
Unit cell	a = 5.417 Å, Z=4
Identification
Color	Pale brass-yellow, tarnishes darker and iridescent
Crystal habit	Cubic, faces may be striated, but also frequently octahedral and pyritohedron. Often inter-grown, massive, radiated, granular, globular and stalactitic.
Crystal system	Isometric
Twinning	Penetration and contact twinning
Cleavage	Indistinct on {001}; partings on {011} and {111}
Fracture	Very uneven, sometimes conchoidal
Tenacity	Brittle
Mohs scale hardness	6–6.5
Luster	Metallic, glistening
Streak	Greenish-black to brownish-black
Diaphaneity	Opaque
Specific gravity	4.95–5.10
Fusibility	2.5–3 to a magnetic globule
Solubility	Insoluble in water
Other characteristics	paramagnetic
References	[1][2][3][4]

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS₂. This mineral's metallic luster and pale brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold. The color has also led to the nicknames brass, brazzle and Brazil, primarily used to refer to pyrite found in coal.^[5][6]

Pyrite is the most common of the sulfide minerals. The name pyrite is derived from the Greek πυρίτης (puritēs), "of fire" or "in fire",^[7] in turn from πύρ (pur), "fire".^[8] In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what we now call pyrite.^[9] By Georgius Agricola's time, the term had become a generic term for all of the sulfide minerals.^[10]

Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds, and as a replacement mineral in fossils. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37 wt% gold.^[11]

Uses[link]

Pyrite from Ampliación a Victoria Mine, Navajún, La Rioja, Spain

Pyrite enjoyed brief popularity in the 16th and 17th centuries as a source of ignition in early firearms, most notably the wheellock, where the cock held a lump of pyrite against a circular file to strike the sparks needed to fire the gun.

Pyrite has been used since classical times to manufacture copperas, that is, iron(II) sulfate. Iron pyrite was heaped up and allowed to weather as described above (an early form of heap leaching). The acidic runoff from the heap was then boiled with iron to produce iron sulfate. In the 15^th century, such leaching began to replace the burning of sulfur as a source of sulfuric acid. By the 19th century, it had become the dominant method. ^[12]

Pyrite remains in commercial use for the production of sulfur dioxide, for use in such applications as the paper industry, and in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS (iron(II) sulfide) and elemental sulfur starts at 550 °C; at around 700 °C p_S2 is about 1 atm.^[13]

Pyrite is a semiconductor material with band gap of 0.95 eV.^[14]

During the early years of the 20th century, pyrite was used as a mineral detector in radio receivers, and is still used by 'crystal radio' hobbyists. Until the vacuum tube matured, the crystal detector was the most sensitive and dependable detector 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 detectors and the more mechanically complicated perikon mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A diode detector.^[15][16]

Pyrite has been proposed as an abundant, inexpensive material in low cost photovoltaic solar panels.^[17] Synthetic iron sulfide is used with copper sulfide to create the experimental photovoltaic material.^[18]

Pyrite is used to make marcasite jewelry (incorrectly termed marcasite). Marcasite jewelry, made from small faceted pieces of pyrite, often set in silver, was popular in the Victorian era.^[19]

Formal oxidation states for pyrite, marcasite, and arsenopyrite[link]

From the perspective of classical inorganic chemistry, 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, H₂S₂. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast, molybdenite, MoS₂, features isolated sulfide (S²⁻) centers. Consequently, the oxidation state of molybdenum is Mo⁴⁺. The mineral arsenopyrite has the formula FeAsS. Whereas pyrite has S₂ subunits, arsenopyrite has AsS units, formally derived from deprotonation of H₂AsSH. Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe³⁺(AsS)³⁻.^[20]

Crystallography[link]

Crystal structure of pyrite. In the center of the cell a S₂^2- pair is seen in yellow.

Iron-pyrite FeS₂ represents the prototype compound of the crystallographic pyrite structure. The structure is simple cubic and was among the first crystal structures solved by X-ray diffraction.^[21] It belongs to the crystallographic space group Pa3 and is denoted by the Strukturbericht notation C2. Under thermodynamic standard conditions the lattice constant Failed to parse (Missing texvc executable; please see math/README to configure.): a

of stoichiometric iron pyrite FeS2 amounts to 541.87 pm.[22] The unit cell is composed of a Fe face-centered cubic sublattice into which the S ions are embedded. The pyrite structure is also taken by other compounds MX2 of transition metals M and chalcogens X = O, S, Se and Te. Also certain dipnictides with X standing for P, As and Sb etc. are known to adopt the pyrite structure.[23] 

In the first bonding sphere, the Fe atoms are surrounded by six S nearest neighbours, in a distorted octahedral arrangement. The material is a diamagnetic semiconductor and the Fe ions should be considered to be in a low spin divalent state (as shown by Mösbauer spectroscopy as well as XPS), rather than a tetravalent state as the stoichiometry would suggest.

The positions of X ions in the pyrite structure may be derived from the fluorite structure, starting from a hypothetical Fe²⁺(S^-)₂ structure. Whereas F^- ions in CaF₂ occupy the centre positions of the eight subcubes of the cubic unit cell (¼ ¼ ¼) etc., the S^- ions in FeS₂ are shifted from these high symmetry positions along <111> axes to reside on (uuu) and symmetry-equivalent positions. Here, the parameter u should be regarded as a free atomic parameter that takes different values in different pyrite-structure compounds (iron pyrite FeS₂: u(S) = 0.385 ^[24]). The shift from fluorite u=0.25 to pyrite u=0.385 is rather large and creates a S-S distance that is clearly a binding one. This is not surprising as in contrast to F^- an ion S^- is not a closed shell species. It is isoelectronic with a chlorine atom, also undergoing pairing to form Cl₂ molecules. Both low spin Fe²⁺ and the disulfide S₂^2- moeties are closed shell entities, explaining the diamagnetic en semiconducting properties.

The S atoms have bonds with three Fe and one other S atom. The site symmetry at Fe and S positions is accounted for by point symmetry groups C_3i and C₃, 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.^[25] The polarisation can be calculated on the basis of higher-order Madelung constants and has to be included in the calculation of the lattice energy by using a generalised Born-Haber cycle. This reflects the fact that the covalent bond in the sulfur pair is ill accounted for in the strictly ionic treatment of Madelung theory.

Arsenopyrite has a related structure with heteroatomic As-S pairs rather than homoatomic ones. Marcasite also possesses homoatomic anion pairs, but the arrangement of the metal and diatomic anions is different than in a pyrite. Despite its name a chalcopyrite does not contain dianion pairs, but single S^2- sulfide anions.

Varieties[link]

Cattierite (CoS₂) and Vaesite (NiS₂) 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 Ni²⁺ for Fe²⁺ within pyrite. Bravoite is not a formally recognised mineral, and is named after Peruvian scientist Jose J. Bravo (1874–1928).^[26]

Synthetically, materials MX₂ with a pyrite structure can be made in the lab with for M a whole series of elements from the Mn column of the d block all the way to the Zn column and for X the chalcogenides S, Se or Te. For most of these systems it is also possible to make continuous solid solution series, so that the Bravo's geological findings are hardly surprising. From a chemical point of view the mineral is therefore likely to vary considerably in composition, depending on which elements were available during its formation.

Distinguishing similar minerals[link]

Chalcopyrite is brighter yellow with a greenish hue when wet and is softer (3.5–4 on Mohs' scale).^[27]

Arsenopyrite is silver white and does not become more yellow when wet.

Hazards[link]

A pyrite cube (center) has dissolved away from a host rock, leaving behind trace gold.

Iron pyrite is unstable in the natural environment: in nature it is always in the process of being created or being destroyed. Iron pyrite exposed to air and water decomposes into iron oxides and sulfate. This process is hastened by the action of Acidithiobacillus bacteria which oxidize the pyrite to produce ferrous iron and sulfate. These reactions occur more rapidly when the pyrite is in fine crystals and dust, which is the form it takes in most mining operations.

Acid drainage[link]

Sulfate released from decomposing pyrite combines with water, producing sulfuric acid, leading to acid rock drainage and potentially acid rain.

Dust explosions[link]

Iron pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion in the mined-out areas of the mine. The solution is to hermetically seal the mined-out areas to exclude oxygen.^[28]

Weakened building materials[link]

Building stone containing pyrite tends to stain brown as the pyrite oxidizes. This problem appears to be significantly worse if any marcasite is also present.^[29] The presence of pyrite in the aggregate used to make concrete can lead to severe deterioration as the pyrite oxidizes.^[30] In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to oxidation of pyrite.^[31] In the United States, in Canada,^[32] and more recently in Ireland,^[33] pyrite contamination has caused major structural damage. Modern tests for aggregate materials^[34] certify such materials as free of pyrite.

Prevention in mines[link]

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 roof fall.^[35]

Gallery[link]

The following images show other pyrite forms:

• 

  Disc or "pyrite dollar" from south of Tucson, Arizona; diameter 10 cm

• 

  Cubes in rock

• 

  Crystal cluster from Elba, Italy

• 

  As a replacement mineral in an ammonite from France

See also[link]

• Chalcopyrite (Copper Pyrite)
• List of minerals

References[link]

Further reading[link]

• American Geological Institute, 2003, Dictionary of Mining, Mineral, and Related Terms, 2nd ed., Springer, New York, ISBN 978-3-540-01271-9
• Mineral galleries

External links[link]

Wikimedia Commons has media related to: Pyrite

• How Minerals Form and Change "Pyrite oxidation under room conditions".

Frank Ocean
Frank Ocean performing at the Coachella Valley Music and Arts Festival in 2012
Background information
Birth name	Christopher Breaux
Also known as	Christopher Francis Ocean, Lonny Breaux, Frank Ocean
Born	(1987-10-28) October 28, 1987 (age 24)[1] New Orleans, Louisiana
Genres	jazz R&B, Neo Soul, Alternative hip hop, hip hop soul[2]
Occupations	Singer-songwriter, rapper, musician, entertainer, vocalist
Instruments	Vocals, Keyboards,
Years active	2007–present
Labels	Odd Future Records, Island Def Jam
Associated acts	OFWGKTA, James Fauntleroy II, Jay-Z, Kanye West, Justin Bieber, Beyonce
Website	frankocean.com

Christopher Francis Ocean (born Christopher Breaux; October 28, 1987), better known by his stage name Frank Ocean, is an American singer-songwriter from New Orleans, Louisiana. Breaux made an early career as a ghost-writer for artists such as Justin Bieber, Bridget Kelly, Aramide Makinde and John Legend. In mid 2010 he became a member of OFWGKTA premiering on Domo Genesis' track, "SteamRoller". In February 2011, he released his debut mixtape Nostalgia, Ultra to critical acclaim. He released two singles; "Novacane" and "Swim Good". Both singles achieved chart success. Ocean went on a 7 show tour through North America and Europe promoting the mixtape. He is currently located in New York City.

The mixtape caught the interest of recording artists such as Kanye West, Beyoncé Knowles and Jay-Z, and he appeared on Watch the Throne. He co-wrote the popular track "Thinking About You" for Bridget Kelly. On January 5, 2012, the BBC announced that he had finished in second place in the BBC's Sound of 2012 poll.^[3] Ocean is currently working on his debut studio album, set to be released in the first half of 2012, while the same year he appeared at Coachella and he is scheduled to appear at Lollapalooza.

Biography[link]

2005–2010: Career beginnings[link]

Frank Ocean began his career with the producer duo The MIDI Mafia. Ocean joined Los Angeles-based hip hop collective OFWGKTA, whom he met through his connections, at the end of 2009.^[4][5] In late 2009, he met Tricky Stewart, who helped Ocean sign a contract with Def Jam Recordings as a solo artist, however, he was initially unable to build a relationship with the company.^[5][6][7] In 2010, he changed his name from Christopher Breaux to Christopher Francis William Ocean via a legal website.^[5]

[edit] 2011–present: Nostalgia, Ultra and debut album

Ocean has written songs for Justin Bieber, John Legend, Brandy,^[5] and Beyoncé Knowles ("I Miss You" from the album 4),^[8][9] Ocean has also worked with Nas^[10] (on whose 10th studio album Ocean is expected to feature, along with fellow Odd Future members Tyler, the Creator and Hodgy Beats)^[11] and Pharrell Williams.^[12] On February 18, 2011, Ocean released his first mixtape, Nostalgia, Ultra, to critical acclaim.^[5][7] His music mostly focuses on interpersonal relationships, personal reflection and social commentary.^[5] NPR's Andrew Noz calls Ocean's songwriting "smart and subtle...setting him apart from the pack."^[13] Rolling Stone magazine's Jonah Weiner calls Ocean a "gifted avant-R&B smoothie".^[14] In an April 2011 interview, Ocean stated that his relationship with Def Jam has strengthened since the release of his mixtape.^[4]

Ocean appeared in Tyler, the Creator's music video for the single "She", from Tyler's second studio album Goblin (2011).^[15][16] Ocean first performed with Odd Future at the Coachella Music & Arts Festival in April 2011, then later joined his OFWGKTA bandmates for the first time on tour from May 12 to May 19, 2011. They toured the eastern seaboard of the United States.^[17] On May 19, 2011 Ocean's record label Def Jam announced its plans to re-release Nostalgia, Ultra as an EP.^[18] The single "Novacane" was released to iTunes on May 31, 2011, and the EP originally was set to be released on July 26, 2011, but through his Tumblr blog on July 24, he stated that it would not be released on that date.^[19][20] In June 2011, Ocean revealed on his Tumblr that he would be working on the upcoming Kanye West and Jay-Z collaborative album, Watch the Throne.^[21] Ocean was ultimately a writer and featured artist on the tracks "No Church in the Wild" and "Made in America".^[22][23] On July 28, 2011 a song titled "Thinking About You"^[24] was leaked on the internet. It was later revealed the song was a reference track and written for Roc Nation artist Bridget Kelly for her debut studio album.^[25] Kelly who has performed an acoustic version of the song, retitled the song "Thinking About Forever".^[26] However, on September 15, 2011, a music video directed by High5Collective for Ocean's version was released, yet the song appeared on Bridget Kelly's debut EP Every Girl.^[27] His debut album is set for a release on Def Jam Records in Spring 2012.^[28] On March 8, 2012, a re-mastered version of "Thinking About You" leaked, intended to be a single.^[29] On April 5, Ocean released the cover art for his upcoming debut studio album's lead single "Thinkin' Bout You", revealing the song would be released to digital retailers on April 10.^[30] "It succinctly defines me as an artist for where I am right now and that was the aim," he said of the follow-up to the acclaimed Nostalgia, Ultra. "It’s about the stories. If I write 14 stories that I love, then the next step is to get the environment of music around it to best envelop the story and all kinds of sonic goodness."^[30]

Ocean used the entire melody and chords of The Eagles' song "Hotel California", without permission, on his own song, “American Wedding.” When asked about it, Ocean stated that Eagles band member "Don Henley is apparently intimidated by my rendition of 'Hotel California'. He threatened to sue if I perform it again." In response to Ocean's comments, The Eagles released a statement: “Frank Ocean did not merely 'sample' a portion of the Eagles’ 'Hotel California,' he took the whole master track, plus the song’s existing melody, and replaced the lyrics with his own. This is not creative, let alone 'intimidating.' It’s illegal. For the record, Don Henley has not threatened or instituted any legal action against Frank Ocean, although the Eagles are now considering whether they should.”^[31] In early 2012, a suit was filed against Frank Ocean for the use of Hotel California.

In March 2012, Coldplay announced that Ocean would perform as an opening act for a number of shows on their European tour in July and August 2012.^[32]

Discography[link]

Collaborative albums[link]

• The OF Tape Vol. 2 (2012)

Mixtapes[link]

• Nostalgia, Ultra (2011)

Awards and nominations[link]

References[link]