Pyrite

Not to be confused with Synthetic gold.
"Fool's Gold" redirects here. For other uses, see Fool's Gold (disambiguation).
This article is about iron pyrite. For other pyrite minerals, see Pyrite group.
Pyrite
Intergrowth of lustrous, cubic crystals of pyrite, with some surfaces showing characteristic striations, from Huanzala mine, Ancash, Peru. Specimen size: 7.0 × 5.0 × 2.5 cm
General
CategorySulfide mineral
Formula
(repeating unit)		FeS2
IMA symbolPy[1]
Strunz classification2.EB.05a
Dana classification2.12.1.1
Crystal systemCubic
Crystal classDiploidal (m3)
H-M symbol: (2/m 3)
Space groupPa3
Unit cella = 5.417 Å, Z = 4
Identification
Formula mass119.98 g/mol
ColorPale brass-yellow reflective; tarnishes darker and iridescent
Crystal habitCubic, faces may be striated, but also frequently octahedral and pyritohedral. Often inter-grown, massive, radiated, granular, globular, and stalactitic.
TwinningPenetration and contact twinning
CleavageIndistinct on {001}; partings on {011} and {111}
FractureVery uneven, sometimes conchoidal
TenacityBrittle
Mohs scale hardness6–6.5
LusterMetallic, glistening
StreakGreenish-black to brownish-black
DiaphaneityOpaque
Specific gravity4.95–5.10
Density4.8–5 g/cm3
Fusibility2.5–3 to a magnetic globule
SolubilityInsoluble in water
Other characteristicsparamagnetic
References[2][3][4][5]

The mineral pyrite (/ˈpaɪraɪt/ PY-ryte),[6] or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.[7]

Pyrite cubic crystals on marl from Navajún, La Rioja, Spain (size: 95 by 78 millimetres [3.7 by 3.1 in], 512 grams [18.1 oz]; main crystal: 31 millimetres [1.2 in] on edge)

Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to 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.[8][9]

The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), 'stone or mineral which strikes fire',[10] in turn from πῦρ (pŷr), 'fire'.[11] 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 is now called pyrite.[12]

By Georgius Agricola's time, c. 1550, the term had become a generic term for all of the sulfide minerals.[13]

Pyrite under normal and polarized light

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, but has also been identified in the sclerites of scaly-foot gastropods.[14] 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 is a case of coupled substitution but as of 1997 the chemical state of the gold remained controversial.[15]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Hurlbut, Cornelius S.; Klein, Cornelis (1985). Manual of Mineralogy (20th ed.). New York, NY: John Wiley and Sons. pp. 285–286. ISBN 978-0-471-80580-9.
  3. ^ "Pyrite". Webmineral.com. Retrieved 2011-05-25.
  4. ^ "Pyrite". Mindat.org. Retrieved 2011-05-25.
  5. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1990). "Pyrite" (PDF). Handbook of Mineralogy. Vol. I (Elements, Sulfides, Sulfosalts). Chantilly, Virginia, US: Mineralogical Society of America. ISBN 978-0962209734.
  6. ^ "Pyrite | meaning in the Cambridge English Dictionary". dictionary.cambridge.org.
  7. ^ Vernon J. Hurst; Thomas J. Crawford (1970). Sulfide Deposits in the Coosa Valley Area, Georgia. Economic Development Administration, Technical Assistance Project, U. S. Department of Commerce. p. 137.
  8. ^ Jackson, Julia A.; Mehl, James; Neuendorf, Klaus (2005). Glossary of Geology. American Geological Institute. p. 82. ISBN 9780922152766 – via Google Books.
  9. ^ Fay, Albert H. (1920). A Glossary of the Mining and Mineral Industry. United States Bureau of Mines. pp. 103–104 – via Google Books.
  10. ^ πυρίτης. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  11. ^ πῦρ in Liddell and Scott.
  12. ^ Dana, James Dwight; Dana, Edward Salisbury (1911). Descriptive Mineralogy (6th ed.). New York: Wiley. p. 86.
  13. ^ "De re metallica". The Mining Magazine. Translated by Hoover, H.C.; Hoover, L.H. London: Dover. 1950 [1912]. see footnote on p 112.
  14. ^ "Armor-plated snail discovered in deep sea". news.nationalgeographic.com. Washington, DC: National Geographic Society. Archived from the original on November 10, 2003. Retrieved 2016-08-29.
  15. ^ Fleet, M. E.; Mumin, A. Hamid (1997). "Gold-bearing arsenian pyrite and marcasite and arsenopyrite from Carlin Trend gold deposits and laboratory synthesis" (PDF). American Mineralogist. 82 (1–2): 182–193. Bibcode:1997AmMin..82..182F. doi:10.2138/am-1997-1-220. S2CID 55899431.