AskDefine | Define pyrite

Dictionary Definition

pyrite n : a common mineral (iron disulfide) that has a pale yellow color [syn: iron pyrite, fool's gold]

User Contributed Dictionary

English

Etymology

From πυρίτης < πῦρ

Noun

  1. A common mineral of a pale brass-yellow color and brilliant metallic luster, crystallizing in the isometric system; iron pyrites; iron disulfide.
  2. In the context of "solid state|_|chemistry": any metal dichalcogenide that is isostructural to the common mineral
    Copper diselenide can occur both as a marcassite and a pyrite.

Translations

Thryduulf/trans2 (talk contribs)

See also

Extensive Definition

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold due to its resemblance to gold. Pyrite is the most common of the sulfide minerals. The name pyrite is derived from the Greek πυρίτης (puritēs), “of fire” or "in fire”, from πύρ (pur), “fire”. This name is likely due to the sparks that result when pyrite is struck against steel or flint. This property made pyrite popular for use in early firearms such as the wheellock.

Mineralogy

This mineral occurs as isometric crystals that usually appear as cubes. The cube faces may be striated (parallel lines on crystal surface or cleavage face) as a result of alternation of the cube and pyritohedron faces. Pyrite also frequently occurs as octahedral crystals and as pyritohedra (a dodecahedron with pentagonal faces). It has a slightly uneven and conchoidal fracture, a hardness of 6–6.5, and a specific gravity of 4.95–5.10. Marcasite/pyrite is probably the most famous polymorph pair next to the diamond/graphite pair. Appearance is slightly more silver.
Marcasite is metastable relative to pyrite and will slowly be changed to pyrite if heated or given enough time. Marcasite is relatively rare, but may be locally abundant in some types of ore deposits, such as Mississippi Valley-type Pb-Zn deposits. Marcasite appears to form only from aqueous solutions.
Pyrite is often used in jewellery such as necklaces and bracelets, but although the two are similar, marcasite cannot be used in jewellery as it tends to crumble into powder. Adding to the confusion between marcasite and pyrite is the use of the word marcasite as a jewellery trade name. The term is applied to small polished and faceted stones that are inlaid in sterling silver, but even though they are called marcasite, they actually contain pyrite.

Formal oxidation states for pyrite, marcasite, and arsenopyrite

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 persulfide, 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+AsS3-.

References

  • American Geological Institute, 2003, Dictionary of Mining, Mineral, and Related Terms, 2nd ed., Springer, New York, ISBN 978-3540012719
  • Mineral galleries

External links

pyrite in Catalan: Pirita
pyrite in Czech: Pyrit
pyrite in Danish: Pyrit
pyrite in German: Pyrit
pyrite in Estonian: Püriit
pyrite in Spanish: Pirita
pyrite in Esperanto: Pirito
pyrite in Basque: Pirita
pyrite in French: Pyrite
pyrite in Galician: Pirita
pyrite in Italian: Pirite
pyrite in Hebrew: פיריט
pyrite in Lithuanian: Piritas
pyrite in Hungarian: Pirit
pyrite in Dutch: Pyriet
pyrite in Japanese: 黄鉄鉱
pyrite in Norwegian: Svovelkis
pyrite in Norwegian Nynorsk: Svovelkis
pyrite in Polish: Piryt
pyrite in Portuguese: Pirita
pyrite in Romanian: Pirită
pyrite in Russian: Пирит
pyrite in Sicilian: Petra fucali
pyrite in Slovak: Pyrit
pyrite in Slovenian: Pirit
pyrite in Finnish: Rikkikiisu
pyrite in Swedish: Pyrit
pyrite in Turkish: Pirit
pyrite in Ukrainian: Пірит
pyrite in Chinese: 黄铁矿
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