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Encyclopedia > Pyrite
Pyrite

A mass of intergrown, striated pyrite crystals
General
Category Mineral
Chemical formula iron persulfide (FeS2)
Identification
Color Pale, dull gold
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; bar 3 2/m
Cleavage Poor
Fracture Very uneven, sometimes conchoidal
Mohs Scale hardness 6–6.5
Luster Metallic, glistening
Refractive index Opaque
Streak Greenish-black to brownish-black; smells of sulfur
Specific gravity 4.95–5.10
Melting point 1,177–1,188°C [1]
Fusibility 2.5–3
Solubility insoluble in water
Other Characteristics paramagnetic

The mineral pyrite, or iron pyrite, is iron sulfide, FeS2. It has 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. It is brittle, meaning it breaks or powders easily. It can be identified in the field by the sulfur smell of the powdered mineral. Its metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold due to many miners mistaking it for the real thing, though small quantities of actual gold are sometimes found in pyrite. In fact, such auriferous pyrite is a valuable ore of gold. Download high resolution version (800x614, 121 KB)Pyrite or foolsgold Taken by User:Fir0002 File links The following pages link to this file: Pyrite Categories: GFDL images ... A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. ... This article or section does not cite any references or sources. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ... A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups. ... In crystallography, the cubic crystal system (or isometric crystal system) is the most symmetric of the 7 crystal systems. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... For fractures in geologic formations, see Rock fracture. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... The streak (also called powder color) of a mineral is the color of the powder produced when it is dragged across a unweathered surface. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fusibility is the ease with which a material will melt. ... Solubility refers to the ability for a given substance, the solute, to dissolve in a solvent. ... A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties. ... In crystallography, the cubic crystal system (or isometric crystal system) is the most symmetric of the 7 crystal systems. ... Quartz crystal Synthetic bismuth hopper crystal Insulin crystals Gallium, a metal that easily forms large single crystals A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain for the megajoule laser of CEA. In chemistry and mineralogy, a crystal is a solid in which the constituent atoms... A pyritohedron is an irregular dodecahedron. ... An octahedron (plural: octahedra) is a polyhedron with eight faces. ... This article or section does not cite any references or sources. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... For other uses, see Brass (disambiguation). ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Standard atomic weight 196. ... Iron ore (Banded iron formation) Manganese ore Lead ore Gold ore An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining. ...


Pyrite is the most common of the sulfide minerals. It 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 the replacement mineral in fossils. Strictly, a mineral that is a sulfide. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... Quartz (from German Quarz[1]) is the second most common mineral in the Earths continental crust. ... In geology, a vein is a finite volume within a rock, having a distinct shape, filled with crystals of one or more minerals, which were precipitated from an (aqueous) fluid. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... FOSSIL is a standard for allowing serial communication for telecommunications programs under DOS. FOSSIL is an acronym for Fido Opus Seadog Standard Interface Layer. ...

Euhedral parabolic pyrite crystals
Euhedral parabolic pyrite crystals

The name pyrite is from the Greek word πυρά (pura) meaning "fire". This is likely due to the sparks that result when pyrite is struck against steel. This capacity made it popular for use in early firearms such as the wheellock. Image File history File links Download high resolution version (2167x2049, 686 KB) Summary cubic pyrite crystals Licensing I, the creator of this work, hereby release it into the public domain. ... Image File history File links Download high resolution version (2167x2049, 686 KB) Summary cubic pyrite crystals Licensing I, the creator of this work, hereby release it into the public domain. ... Euhedral refers to well formed crystals with sharp easily recognised faces. ... The steel cable of a colliery winding tower. ... A Glock 22 hand-held firearm with internal laser sight and mounted flashlight, surrounded by hollowpoint ammunition. ... Wheellock, Wheel-Lock or Wheel lock, is a mechanism for firing a firearm. ...

Contents

Weathering and release of sulfuric acid

Pyrite exposed to the environment during mining and excavation reacts with oxygen and water to form sulfuric acid, resulting in acid mine drainage. This drainage results from the action of Thiobacillus bacteria, which generate their energy by using oxygen to oxidize ferrous iron (Fe2+) to ferric iron (Fe3+). The ferric iron in turn reacts with pyrite to produce ferrous iron and sulfuric acid. The ferrous iron is then available for oxidation by the bacteria; this cycle can continue until the pyrite is exhausted. Chuquicamata, the largest open pit copper mine in the world, Chile. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Sulfuric (or sulphuric) acid, H2SO4, is a strong mineral acid. ... Acid mine drainage (AMD), or acid rock drainage (ARD), refers to the outflow of acidic water from (usually) abandoned metal mines or coal mines. ... Genera Hydrogenophilus Thiobacillus The Hydrogenophilaceae are a small family of Proteobacteria, with two genera. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ...


Uses

Pyrite is used commercially for the production of sulfur dioxide, for use in such applications as the paper industry, and in the manufacture of sulfuric acid, though such applications are declining in importance. It is also used for costume jewelry. Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ...


Pyrites can show negative resistance and have experimentally been used in oscillator circuits as radio detectors [2]. A VI curve with a negative differential resistance region Negative resistance or negative differential resistance (NDR) is a property of electrical circuit elements composed of certain materials in which, over certain voltage ranges, current is a decreasing function of voltage. ...


Pyrite and marcasite

Pyrite is often confused with the mineral marcasite, a name derived from the Arabic word for pyrite, due to their similar characteristics. Marcasite is a polymorph of pyrite, which means it has the same formula as pyrite but a different structure and, therefore, different symmetry and crystal shapes. The formal oxidation states are, however, the same as in pyrite because again the sulfur atoms occur in persulfide-like pairs. Marcasite/pyrite is probably the most famous polymorph pair next to the diamond/graphite pair. Appearance is slightly more silver. Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 1. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution (2272 × 1704 pixel, file size: 1. ... The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2). ... Arabic ( or just ) is the largest living member of the Semitic language family in terms of speakers. ... Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. ... This article is about the gemstone. ... Graphite (named by Abraham Gottlob Werner in 1789 from the Greek γραφειν (graphein): to draw/write, for its use in pencils) is one of the allotropes of carbon. ...


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. Pb is the abbreviation for the element lead. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ...


Pyrite is often used in jewellery such as necklaces and bracelets, but although the two are similar, marcasite cannot be used in jewelery as it has a tendency 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 are actually pyrite. Amber jewellery in the form of pendants Jewellery (also spelled jewelry, see spelling differences) is a personal ornament, such as a necklace, ring, or bracelet, made from jewels, precious metals or other substance. ... Facets are flat faces on geometric shapes. ... Sterling silver is an alloy of silver containing 92. ...


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+, or Mo(IV). 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-. Of course these formalisms ignore covalency, which is strongly implied by the semi-conducting behavior of this family of inorganic solids. Molybdenite is a mineral of molybdenum disulfide, MoS2. ... Deprotonation is a chemistry term that refers to the removal of a proton (hydrogen ion H+) from a molecule, forming the conjugate base. ... Covalent bonding is a description of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. ... A semiconductor is a fuckin solid whose electrical conductivity is in between that of a metal and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...


Varieties

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)[3].


References

Wikimedia Commons has media related to:
  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York, p 285-286, ISBN 0-471-80580-7
  • American Geological Institute, 2003, Dictionary of Mining, Mineral, and Related Terms, 2nd ed., Springer, New York, ISBN 978-3540012719
  • Mineral galleries
  • Webmineral
  • Pyrite on Mindat.org
  • Bravoite on Mindat.org

Image File history File links Commons-logo. ... The Wikimedia Commons (also called Wikicommons) is a repository of free content images, sound and other multimedia files. ...

External links


  Results from FactBites:
 
PYRITE (Iron Sulfide) (542 words)
Pyrite is difficult to distinguish from marcasite when a lack of clear indicators exists.
Pyrite's structure is analogous to galena's structure with a formula of PbS.
Pyrite is not as ecomonical as these ores possibly due to their tendency to form larger concentrations of more easily mined material.
Pyrites - LoveToKnow 1911 (1418 words)
As pyrites, from its brass-yellow colour, is sometimes mistaken for gold, it has been vulgarly called "fool's gold." Traces of thallium, which are present in some pyrites, may be detected in the flues of the furnaces where the metal is roasted.
Pyrites low in sulphur is incapable of sustaining its own combustion without the aid of an external source of heat, and 45% of sulphur is, for economic reasons, usually regarded as the lowest admissible for sulphuric acid manufacture.
From Indiana and Ohio a quantity of pyrites is obtained as a by-product in coalmining.
  More results at FactBites »

 
 

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