Pyrite

The mineral pyrite (/ˈpaɪraɪt/)[5], or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS2 (iron(II) disulfide). Pyrite is considered the most common of the sulfide minerals.

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.[6][7]

The name pyrite is derived from the Greek πυρίτης (pyritēs), "of fire" or "in fire",[8] in turn from πύρ (pyr), "fire".[9] 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.[10]

By Georgius Agricola's time, c. 1550, the term had become a generic term for all of the sulfide minerals.[11]

Pyrite under Normal and Polarized light
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.[12] 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% gold by weight.[13]

Pyrite
2780M-pyrite1
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)
General
CategorySulfide mineral
Formula
(repeating unit)
FeS2
Strunz classification2.EB.05a
Dana classification2.12.1.1
Crystal systemIsometric
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 pyritohedron. 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[1][2][3][4]

Uses

Stolna pri Perneku
An abandoned pyrite mine near Pernek in Slovakia

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

Pyrite has been used since classical times to manufacture copperas (iron(II) sulfate). Iron pyrite was heaped up and allowed to weather (an example of an early form of heap leaching). 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. By the 19th century, it had become the dominant method.[14]

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 540 °C (1,004 °F); at around 700 °C (1,292 °F), pS2 is about 1 atm.[15]

A newer commercial use for pyrite is as the cathode material in Energizer brand non-rechargeable lithium batteries.[16]

Pyrite is a semiconductor material with a band gap of 0.95 eV.[17] 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.[18]

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 germanium diode detector.[19][20]

Pyrite has been proposed as an abundant, non-toxic, inexpensive material in low-cost photovoltaic solar panels.[21] Synthetic iron sulfide was used with copper sulfide to create the photovoltaic material.[22] More recent efforts are working toward thin-film solar cells made entirely of pyrite.[23]

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.[24] 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 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, highlights the exploited in Navajún, La Rioja (Spain).[25]

China represents the main importing country with an import of around 376,000 tonnes, which resulted at 45% of total global imports. China is also the fastest growing in terms of the unroasted iron pyrites imports, with a CAGR of +27.8% from 2007 to 2016. In value terms, China ($47 million) constitutes the largest market for imported unroasted iron pyrites worldwide, making up 65% of global imports.[26]

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 disulfide, H2S2. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast, molybdenite, MoS2, features isolated sulfide (S2−) centers and 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−.[27]

Crystallography

FeS2structure
Crystal structure of pyrite. In the center of the cell a S22− 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.[28] It belongs to the crystallographic space group Pa3 and is denoted by the Strukturbericht notation C2. Under thermodynamic standard conditions the lattice constant of stoichiometric iron pyrite FeS2 amounts to 541.87 pm.[29] The unit cell is composed of a Fe face-centered cubic sublattice into which the S ions are embedded. The pyrite structure is also used 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.[30]

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 Mössbauer 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 (​141414) 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[31]). 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 S22− moeties are closed shell entities, explaining the diamagnetic and 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 C3i 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.[32] 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 inadequately accounted for by a strictly ionic treatment.

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 from that of pyrite. Despite its name a chalcopyrite does not contain dianion pairs, but single S2− sulfide anions.

Crystal habit

Pyrite elbe
Dodecahedron-shaped crystals from Italy

Pyrite usually forms cuboid crystals, sometimes forming in close association to form raspberry-shaped masses called framboids. However, under certain circumstances, it can form anastamozing filaments or T-shaped crystals.[33] Pyrite can also form almost perfect dodecahedral shapes known as pyritohedra and this suggests an explanation for the artificial geometrical models found in Europe as early as the 5th century BC.[34]

Varieties

Cattierite (Co S2) and vaesite (Ni S2) 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).[35]

Distinguishing similar minerals

It is distinguishable from native gold by its hardness, brittleness and crystal form. Natural gold tends to be anhedral (irregularly shaped), whereas pyrite comes as either cubes or multifaceted crystals. 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).[36] Arsenopyrite is silver white and does not become more yellow when wet.

Hazards

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

Iron pyrite is unstable at Earth's surface: 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

Sulfate released from decomposing pyrite combines with water, producing sulfuric acid, leading to acid rock drainage. An example of acid rock drainage caused by pyrite is the 2015 Gold King Mine waste water spill.

Dust explosions

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.

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.[38]

Weakened building materials

Building stone containing pyrite tends to stain brown as the pyrite oxidizes. This problem appears to be significantly worse if any marcasite is present.[39] The presence of pyrite in the aggregate used to make concrete can lead to severe deterioration as the pyrite oxidizes.[40] In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to oxidation of pyrite, which releases hydrogen sulfide gas. These problems included a foul odor and corrosion of copper wiring.[41] In the United States, in Canada,[42] and more recently in Ireland,[43][44][45] where it was used as underfloor infill, pyrite contamination has caused major structural damage. Modern tests for aggregate materials[46] certify such materials as free of pyrite.

Pyritised fossils

Pyrite and marcasite commonly occur as replacement pseudomorphs after fossils in black shale and other sedimentary rocks formed under reducing environmental conditions.[47] However, pyrite dollars or pyrite suns which have an appearance similar to sand dollars are pseudofossils and lack the pentagonal symmetry of the animal.

Images

Bullypyrite2

As a replacement mineral in an ammonite from France

Pyrite from Ampliación a Victoria Mine, Navajún, La Rioja, Spain 2

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

Pyrite-Tetrahedrite-Quartz-184642

Pyrite from the Sweet Home Mine, with golden striated cubes intergrown with minor tetrahedrite, on a bed of transparent quartz needles

Pyrite-200582

Radiating form of pyrite

Fluorite-Pyrite-tmu38b

Pink fluorite perched between pyrite on one side and metallic galena on the other side

References

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  16. ^ "Cylindrical Primary Lithium [battery]". Lithium-Iron Disulfide (Li-FeS2) (PDF). Handbook and Application Manual. Energizer Corporation. 2017-09-19. Retrieved 2018-04-20.
  17. ^ Ellmer, K. & Tributsch, H. (2000-03-11). "Iron Disulfide (Pyrite) as Photovoltaic Material: Problems and Opportunities". Proceedings of the 12th Workshop on Quantum Solar Energy Conversion – (QUANTSOL 2000). Archived from the original on 2010-01-15.
  18. ^ Xin Zhang & Mengquin Li (2017-06-19). "Potential resolution to the doping puzzle in iron pyrite: Carrier type determination by Hall effect and thermopower". Physical Review Materials. Archived from the original on 2017-06-19.
  19. ^ The Principles Underlying Radio Communication. U.S. Army Signal Corps. Radio Pamphlet. 40. 1918. section 179, pp 302–305 – via Google Books.
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  21. ^ Wadia, Cyrus; Alivisatos, A. Paul; Kammen, Daniel M. (2009). "Materials availability expands the opportunity for large-scale photovoltaics deployment". Environmental Science & Technology. 43 (6): 2072–7. Bibcode:2009EnST...43.2072W. doi:10.1021/es8019534. PMID 19368216.
  22. ^ Sanders, Robert (17 February 2009). "Cheaper materials could be key to low-cost solar cells". Berkeley, CA: University of California – Berkeley.
  23. ^ Xin Zhang & Mengquin Li (2017-06-19). "Potential resolution to the doping puzzle in iron pyrite: Carrier type determination by Hall effect and thermopower". Physical Review Materials. Archived from the original on 2017-06-19.
  24. ^ Hesse, Rayner W. (2007). Jewelrymaking Through History: An Encyclopedia. Greenwood Publishing Group. p. 15. ISBN 978-0-313-33507-5.
  25. ^ Calvo, Miguel and Sevillano, Emilia (1998). "Pyrite crystals from Soria and La Rioja provinces, Spain". The Mineralogical Record. 20: 451–456.CS1 maint: multiple names: authors list (link)
  26. ^ "Which Country Imports the Most Unroasted Iron Pyrites in the World? – IndexBox". www.indexbox.io. Retrieved 2018-09-11.
  27. ^ Vaughan, D. J.; Craig, J. R. (1978). Mineral Chemistry of Metal Sulfides. Cambridge, UK: Cambridge University Press. ISBN 978-0-521-21489-6.
  28. ^ Bragg, W. L. (1913). "The structure of some crystals as indicated by their diffraction of X-rays". Proceedings of the Royal Society A. 89 (610): 248–277. Bibcode:1913RSPSA..89..248B. doi:10.1098/rspa.1913.0083. JSTOR 93488.
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  30. ^ Brese, Nathaniel E.; von Schnering, Hans Georg (1994). "Bonding Trends in Pyrites and a Reinvestigation of the Structure of PdAs2, PdSb2, PtSb2 and PtBi2". Z. Anorg. Allg. Chem. 620 (3): 393–404. doi:10.1002/zaac.19946200302.
  31. ^ Stevens, E. D.; Delucia, M. L.; Coppens, P. (1980). "Experimental observation of the Effect of Crystal Field Splitting on the Electron Density Distribution of Iron Pyrite". Inorg. Chem. 19 (4): 813–820. doi:10.1021/ic50206a006.
  32. ^ Birkholz, M. (1992). "The crystal energy of pyrite". J. Phys.: Condens. Matter. 4 (29): 6227–6240. Bibcode:1992JPCM....4.6227B. doi:10.1088/0953-8984/4/29/007.
  33. ^ Bonev, I. K.; Garcia-Ruiz, J. M.; Atanassova, R.; Otalora, F.; Petrussenko, S. (2005). "Genesis of filamentary pyrite associated with calcite crystals". European Journal of Mineralogy. 17 (6): 905–913. Bibcode:2005EJMin..17..905B. CiteSeerX 10.1.1.378.3304. doi:10.1127/0935-1221/2005/0017-0905.
  34. ^ The pyritohedral form is described as a dodecahedron with pyritohedral symmetry; Dana J. et al., (1944), System of mineralogy, New York, p 282
  35. ^ Mindat – bravoite. Mindat.org (2011-05-18). Retrieved on 2011-05-25.
  36. ^ Pyrite on. Minerals.net (2011-02-23). Retrieved on 2011-05-25.
  37. ^ Andrew Roy, Coal Mining in Iowa, Coal Trade Journal, quoted in History of Lucas County Iowa, State Historical Company, Des Moines (1881) pp. 613–615.
  38. ^ Zodrow, E (2005). "Colliery and surface hazards through coal-pyrite oxidation (Pennsylvanian Sydney Coalfield, Nova Scotia, Canada)". International Journal of Coal Geology. 64: 145–155. doi:10.1016/j.coal.2005.03.013.
  39. ^ Bowles, Oliver (1918) The Structural and Ornamental Stones of Minnesota. Bulletin 663, United States Geological Survey, Washington. p. 25.
  40. ^ Tagnithamou, A; Sariccoric, M; Rivard, P (2005). "Internal deterioration of concrete by the oxidation of pyrrhotitic aggregates". Cement and Concrete Research. 35: 99–107. doi:10.1016/j.cemconres.2004.06.030.
  41. ^ Angelo, William (28 January 2009) A Material Odor Mystery Over Foul-Smelling Drywall. Engineering News-Record.
  42. ^ "PYRITE and Your House, What Home-Owners Should Know Archived 2012-01-06 at the Wayback Machine" – ISBN 2-922677-01-X – Legal deposit – National Library of Canada, May 2000
  43. ^ Shrimer, F. and Bromley, AV (2012) "Pyritic Heave in Ireland". Proceedings of the Euroseminar on Building Materials. International Cement Microscopy Association (Halle Germany)
  44. ^ Homeowners in protest over pyrite damage to houses. The Irish Times (11 June 2011
  45. ^ Brennan, Michael (22 February 2010) Devastating 'pyrite epidemic' hits 20,000 newly built houses. Irish Independent
  46. ^ I.S. EN 13242:2002 Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction
  47. ^ Briggs, D. E. G.; Raiswell, R.; Bottrell, S. H.; Hatfield, D.; Bartels, C. (1996-06-01). "Controls on the pyritization of exceptionally preserved fossils; an analysis of the Lower Devonian Hunsrueck Slate of Germany". American Journal of Science. 296 (6): 633–663. Bibcode:1996AmJS..296..633B. doi:10.2475/ajs.296.6.633. ISSN 0002-9599.

Further reading

  • American Geological Institute, 2003, Dictionary of Mining, Mineral, and Related Terms, 2nd ed., Springer, New York, ISBN 978-3-540-01271-9.
  • David Rickard, Pyrite: A Natural History of Fool's Gold, Oxford, New York, 2015, ISBN 978-0-19-020367-2.

External links

Biogeology

Biogeology is the study of the interactions between the Earth's biosphere and the lithosphere.

Biogeology examines biotic, hydrologic, and terrestrial systems in relation to each other, to help understand the Earth's climate, oceans, and other effects on geologic systems.For example, bacteria are responsible for the formation of some minerals such as pyrite, and can concentrate economically important metals such as tin and uranium. Bacteria are also responsible for the chemical composition of the atmosphere, which affects weathering rates of rocks.

Prior to the late Devonian period, there was little plant life beyond lichens, and bryophytes. At this time large vascular plants evolved, growing up to 30 meters (98 ft 5.1 in) in height. These large plants changed the atmosphere, and altered the composition of the soil by increasing the amount of organic carbon. This helped prevent the soil being washed away through erosion.

Preston Cloud biogeologist and professor at the University of California, Santa Barbara received a research grant from NASA to examine the lunar rocks returned from the Apollo missions.

Chalcopyrite

Chalcopyrite ( KAL-ko-PY-ryt) is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical formula CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.

On exposure to air, chalcopyrite oxidises to a variety of oxides, hydroxides and sulfates. Associated copper minerals include the sulfides bornite (Cu5FeS4), chalcocite (Cu2S), covellite (CuS), digenite (Cu9S5); carbonates such as malachite and azurite, and rarely oxides such as cuprite (Cu2O). Chalcopyrite is rarely found in association with native copper.

Crystal habit

In mineralogy, crystal habit is the characteristic external shape of an individual crystal or crystal group. A single crystal's habit is a description of its general shape and its crystallographic forms, plus how well developed each form is.

Recognizing the habit may help in identifying a mineral. When the faces are well-developed due to uncrowded growth a crystal is called euhedral, one with partially developed faces is subhedral, and one with undeveloped crystal faces is called anhedral. The long axis of a euhedral quartz crystal typically has a six-sided prismatic habit with parallel opposite faces. Aggregates can be formed of individual crystals with euhedral to anhedral grains. The arrangement of crystals within the aggregate can be characteristic of certain minerals. For example, minerals used for asbestos insulation often grow in a fibrous habit, a mass of very fine fibers.The terms used by mineralogists to report crystal habits describe the typical appearance of an ideal mineral. Recognizing the habit can aid in identification as some habits are characteristic. Most minerals, however, do not display ideal habits due to conditions during crystallization. Euhedral crystals formed in uncrowded conditions with no adjacent crystal grains are not common; more often faces are poorly formed or unformed against adjacent grains and the mineral's habit may not be easily recognized.

Factors influencing habit include: a combination of two or more crystal forms; trace impurities present during growth; crystal twinning and growth conditions (i.e., heat, pressure, space); and specific growth tendencies such as growth striations. Minerals belonging to the same crystal system do not necessarily exhibit the same habit. Some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum.

Some minerals may replace other existing minerals while preserving the original's habit: this process is called pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos replaced by silica. While quartz typically forms prismatic (elongate, prism-like) crystals, in tiger's eye the original fibrous habit of crocidolite is preserved.

The names of crystal habits are derived from:

Predominant crystal faces (prism – prismatic, pyramid – pyramidal and pinacoid – platy)

Crystal forms (cubic, octahedral, dodecahedral)

Aggregation of crystals or aggregates (fibrous, botryoidal, radiating, massive)

Crystal appearance (foliated/lamellar (layered), dendritic, bladed, acicular, lenticular, tabular (tablet shaped))

Declezville, California

Declezville is an unincorporated community in southwestern San Bernardino County, in the Inland Empire region of southern California.It is named for William Declez, a naturalized U.S. citizen, born in France, well known for his marble business on Los Angeles Street. He opened granite quarries in Southern California in the 1860s in the Jurupa Hills on Pyrite Street, and built several Mexican public buildings. He died at age 73 on February 7, 1921 in the Southern Alps. When the Southern Pacific Railroad built a spur to the large granite quarries, it named the junction Declez and the terminal Declezville, for William Declez, owner of the granite works. Declez is a community in south Fontana.

Dodecahedron

In geometry, a dodecahedron (Greek δωδεκάεδρον, from δώδεκα dōdeka "twelve" + ἕδρα hédra "base", "seat" or "face") is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron, which is a Platonic solid. There are also three regular star dodecahedra, which are constructed as stellations of the convex form. All of these have icosahedral symmetry, order 120.

The pyritohedron, a common crystal form in pyrite, is an irregular pentagonal dodecahedron, having the same topology as the regular one but pyritohedral symmetry while the tetartoid has tetrahedral symmetry. The rhombic dodecahedron, seen as a limiting case of the pyritohedron, has octahedral symmetry. The elongated dodecahedron and trapezo-rhombic dodecahedron variations, along with the rhombic dodecahedra, are space-filling. There are numerous other dodecahedra.

Hauerite

Hauerite is a manganese sulfide mineral with the chemical formula MnS2. It forms reddish brown or black octahedral crystals with the pyrite structure and it is usually found associated with the sulfides of other transition metals such as rambergite. It occurs in low temperature, sulfur rich environments associated with solfataras and salt deposits in association with native sulfur, realgar, gypsum and calcite.It was discovered in Austro-Hungarian Monarchy in Kalinka (now Vígľašská Huta-Kalinka village) sulfur desposit near Detva in what is now Slovakia in 1846 and named after the Austrian geologists, Joseph Ritter von Hauer (1778–1863) and Franz Ritter von Hauer (1822–1899).Under high pressure conditions (P>11 GPa), Hauerite undergoes a large collapse in unit cell volume (22 %) driven by a spin-state transition.

List of mining areas in Colombia

This is a list of mining areas in Colombia. The mineral industry of Colombia is large and diverse; the country occupies the first place in mining areas per surface area in the world. In pre-Columbian times, mining of gold, silver, copper, emeralds, salt, coal and other minerals was already widespread. Precious metals as gold, and silver, platinum, nickel and coltan are located in different areas throughout the country. Colombia is the first producer of emeralds and as per February 2017 occupied a ninth position in the production of coal, produced in almost all of the departments of the country. Platinum is mostly found in the Western and Central Ranges of the Colombian Andes. Copper said to have been produced during colonial and later times apparently came from small shoots which may have been worked primarily for their gold content. The largest gold mine in Colombia is scheduled to start operations in Buriticá, Antioquia.Frequently, there are conflicts between the potential mining activities and the indigenous communities in the country, especially in the eastern, sparsely populated departments of Vichada, Guanía, Guaviare and Vaupés.

Lousal mine

Lousal mine was a pyrite mine in Portugal. The mine was opened in 1900 and closed in 1988.

Manganese diselenide

Manganese(II) diselenide is the inorganic compound with the formula MnSe2. This rarely encountered solid is structurally similar to that of iron pyrite (FeS2). Analogous to the description of iron pyrite, manganese diselenide is sometimes viewed as being composed of Mn2+ and Se22− ions, although being a semiconductor, MnSe2 is not appropriately described in formal oxidation states. The high‐resolution Mn 2p spectra of the MnSe2 has two distinct peaks at 642.2 and 653.9 eV correspond to the Mn 2p3/2 and Mn 2p1/2 spin–orbit components, respectively. The energy difference (Δ 2p) of 11.7 eV confirms the presence of Mn4+ ions in the sample. A good correlation was observed with the literature value for the Mn4+ state.[1], No peaks for Mn2+ ions were observed at 640–641 eV, which confirmed the formation of only the Mn4+ oxidation state with a d3 electronic configuration.The Se 3d spectra were deconvoluted into two well‐defined peaks (3d5/2 and 3d3/2) at a binding energy of 54.46 and 55.31 eV, respectively. These two peaks confirmed the presence of Se2− ions in MnSe2.[2].

Marcasite

The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures do have in common that they contain the disulfide S22− ion having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe2+ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.

On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called "cockscombs."

In marcasite jewellery, pyrite used as a gemstone is termed "marcasite" – that is, marcasite jewellery is made from pyrite, not from the mineral marcasite. In the late medieval and early modern eras the word "marcasite" meant both pyrite and the mineral marcasite (and iron sulfides in general). The narrower, modern scientific definition for marcasite as orthorhombic iron sulfide dates from 1845. The jewellery sense for the word pre-dates this 1845 scientific redefinition. Marcasite in the scientific sense is not used as a gem due to its brittleness.

Marcasite jewellery

Marcasite jewelry is jewelry made from pyrite (fool's gold), not, as the name suggests, from marcasite. Pyrite is slightly similar to marcasite, but more stable and less brittle. It is frequently made by setting small pieces of pyrite into silver. Cheaper costume jewelry is made by glueing pieces of pyrite rather than setting. A similar-looking type of jewelry can be made from small pieces of cut steel.

Nodule (geology)

In sedimentology and geology, a nodule is small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition, such as a pyrite nodule in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale, from the enclosing sediment or sedimentary rock. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to concretions and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.In sedimentology and geology, nodular is used to describe a sediment or sedimentary rock composed of scattered to loosely packed nodules in matrix of like or unlike character. It is also used to describe mineral aggregates that occur in the form of nodules, e.g. colloform mineral aggregate with a bulbed surface.Nodule is also used for widely scattered concretionary lumps of manganese, cobalt, iron, and nickel found on the floors of the world's oceans. This is especially true of manganese nodules. Manganese and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are concretions instead of nodules.Chert and flint nodules are often found in beds of limestone and chalk. They form from the redeposition of amorphous silica arising from the dissolution of siliceous spicules of sponges, or debris from radiolaria and the postdepositional replacement of either the enclosing limestone or chalk by this silica.

Northland Pyrite Mine

The Northland Pyrite Mine, also known as James Lake Mine, Rib Lake Mine, Harris Mine or simply Northland Mine, is an abandoned underground mine in Northeastern Ontario, Canada, located on the southwestern shore of James Lake in Best Township of Temagami. It was operated by the Northland Mining Company during the early 1900s with the construction of a 91 m (299 ft) shaft and many open-cuts north of the shaft. Minerals present at the mine include chalcopyrite, pyrite and pyrrhotite, deposited in Precambrian volcanic rock of the Canadian Shield.

Pyrrhotite

Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite.

Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is weakly magnetic. The magnetism decreases as the iron content increases, and troilite is non-magnetic.

Quantico Creek

Quantico Creek is a 13.7-mile-long (22.0 km) partially tidal tributary of the Potomac River in eastern Prince William County, Virginia. Quantico Creek rises southeast of Independent Hill, flows through Prince William Forest Park and Dumfries and empties into the Potomac at Possum Point.

Shamva District

Shamva is one of seven districts in the Mashonaland Central province of Zimbabwe. The district capital is the village of Shamva.

One of the noted gold mines in Zimbabwe is the Shamva Mine, located 70 km northeast of Harare, which had produced 52 tonnes of gold by 1982. Gold deposits are found within volcaniclastics, associated with pyrite.Schools in Shamva include Chindunduma, madziva Wadzanai secondary schools. DAPP Humana People to People head office is In Shamva.

Sperrylite

Sperrylite is a platinum arsenide mineral with formula PtAs2 and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in addition to massive and reniform habits. It has a Mohs hardness of 6 - 7 and a very high specific gravity of 10.6.

It was discovered by Francis Louis Sperry, an American chemist, in 1889 at Sudbury.

The most important occurrence of sperrylite is in the nickel ore deposit of Sudbury Basin in Ontario, Canada. It also occurs in the layered igneous complex of the Bushveld region of South Africa and the Oktyabr'skoye copper-nickel deposit of the Eastern-Siberian Region, Russia.

Sphalerite

Sphalerite ((Zn, Fe)S) is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides along with calcite, dolomite, and fluorite. Miners have also been known to refer to sphalerite as zinc blende, black-jack and ruby jack.

Wolframite

Wolframite, (Fe,Mn)WO4, is an iron manganese tungstate mineral that is the intermediate between ferberite (Fe2+ rich) and hübnerite (Mn2+ rich). Along with scheelite, the wolframite series are the most important tungsten ore minerals. Wolframite is found in quartz veins and pegmatites associated with granitic intrusives. Associated minerals include cassiterite, scheelite, bismuth, quartz, pyrite, galena, sphalerite, and arsenopyrite.

This mineral was historically found in Europe in Bohemia, Saxony, and Cornwall. China reportedly has the world's largest supply of tungsten ore with about 60%. Other producers are Canada, Portugal, Russia, Australia, Thailand, South Korea, Rwanda, Bolivia, the United States, and the Democratic Republic of the Congo.

Sulfur compounds

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