Some Comments on Pyrite's Structure
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Modeling the Shape of Ions in Pyrite-Type Crystals
Crystals 2014, 4, 390-403; doi:10.3390/cryst4030390 OPEN ACCESS crystals ISSN 2073-4352 www.mdpi.com/journal/crystals Article Modeling the Shape of Ions in Pyrite-Type Crystals Mario Birkholz IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany; E-Mail: [email protected]; Tel.: +49-335-56250 Received: 13 April 2014; in revised form: 22 August 2014 / Accepted: 26 August 2014 / Published: 3 September 2014 Abstract: The geometrical shape of ions in crystals and the concept of ionic radii are re-considered. The re-investigation is motivated by the fact that a spherical modelling is justified for p valence shell ions on cubic lattice sites only. For the majority of point groups, however, the ionic radius must be assumed to be an anisotropic quantity. An appropriate modelling of p valence ions then has to be performed by ellipsoids. The approach is tested for pyrite-structured dichalcogenides MX2, with chalcogen ions X = O, S, Se and Te. The latter are found to exhibit the shape of ellipsoids being compressed along the <111> symmetry axes, with two radii r|| and describing their spatial extension. Based on this ansatz, accurate interatomic M–X distances can be derived and a consistent geometrical model emerges for pyrite-structured compounds. Remarkably, the volumes of chalcogen ions are found to vary only little in different MX2 compounds, suggesting the ionic volume rather than the ionic radius to behave as a crystal-chemical constant. Keywords: ionic radius; ionic shape; bonding distance; ionic volume; pyrite-type compounds; di-chalcogenides; di-oxides; di-sulfides; di-selenides; di-tellurides 1. -
Pyrite Roasting, an Alternative to Sulphur Burning
The Southern African Institute of Mining and Metallurgy Sulphur and Sulphuric Acid Conference 2009 M Runkel and P Sturm PYRITE ROASTING, AN ALTERNATIVE TO SULPHUR BURNING M Runkel and P Sturm Outotec GmbH, Oberursel GERMANY Abstract The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, while in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600 - 1000° C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed . For over 60 years, Outotec has progressively been developing the principle of fluidised bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidised bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes. Introduction Pyrite roasting and sulphur burning plants are built for the production of sulphuric acid. -
Ultrafast Band-Gap Oscillations in Iron Pyrite
Ultrafast band-gap oscillations in iron pyrite The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Kolb, Brian, and Alexie Kolpak. “Ultrafast Band-Gap Oscillations in Iron Pyrite.” Phys. Rev. B 88, no. 23 (December 2013). © 2013 American Physical Society As Published http://dx.doi.org/10.1103/PhysRevB.88.235208 Publisher American Physical Society Version Final published version Citable link http://hdl.handle.net/1721.1/88761 Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. PHYSICAL REVIEW B 88, 235208 (2013) Ultrafast band-gap oscillations in iron pyrite Brian Kolb and Alexie M. Kolpak Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA (Received 7 August 2013; revised manuscript received 17 October 2013; published 20 December 2013) With its combination of favorable band gap, high absorption coefficient, material abundance, and low cost, iron pyrite, FeS2, has received a great deal of attention over the past decades as a promising material for photovoltaic applications such as solar cells and photoelectrochemical cells. Devices made from pyrite, however, exhibit open circuit voltages significantly lower than predicted, and despite a recent resurgence of interest in the material, there currently exists no widely accepted explanation for this disappointing behavior. In this paper, we show that phonons, which have been largely overlooked in previous efforts, may play a significant role. Using fully self-consistent GW calculations, we demonstrate that a phonon mode related to the oscillation of the sulfur-sulfur bond distance in the pyrite structure is strongly coupled to the energy of the conduction-band minimum, leading to an ultrafast (≈100 fs) oscillation in the band gap. -
The Electrical Resistivity of Galena, Pyrite, and Chalcopyrite
American Mineralogist, Volume61, pages248-259, 1976 The electricalresistivity of galena,pyrite, and chalcopyrite Doneln F. PnlorrronreNn RnlpH T. Suurv Departmentof Geologyand Geophysics,Uniuersity of Utah Salt Lake Cily, Utah 84112 Abstract. The sulfidesgalena, chalcopyrite, and pyrite are semiconductorswhose electrical resistivity and type are controlled by deviationsfrom stoichiometryand impurity content,and henceby their geochemicalenvironment. We measuredelectrical resistivity,type, and the impurity content (emissionspectrograph and microprobe) on small volumesof sample.Our results, together with those obtained from a comprehensiveliterature analysis, are usedto construct histogramsof the natural variability in carrier density and resistivity. Sulfur deficiency is the dominant defect in chalcopyrite and hence almost all natural samplesare n-type. lt appearsthat the copper/iron ratio is also important electrically,the copper-richsamples being the more resistive. lmportant donor deiectsin galena(z-type samples)are antimony and bismuth impurities, and sulfur vacancies;acceptor defects(p-type samples) include silver impurities and lead 'Mississippi vacancies.P-type samplesappear to be restrictedto Valley' and argentiferous deposits. In pyrite, electricallyactive impurities include cobalt, nickel, and copper as donors, and arsenicas an acceptor.Deviations from stoichiometry,in the same senseas galena,may be important. Pyritesfrom sedimentaryand epithermaldeposits are usuallyp-type if cupriferous sulfidesare not present.Samples from hypothermaldeposits -
Banded Iron Formations
Banded Iron Formations Cover Slide 1 What are Banded Iron Formations (BIFs)? • Large sedimentary structures Kalmina gorge banded iron (Gypsy Denise 2013, Creative Commons) BIFs were deposited in shallow marine troughs or basins. Deposits are tens of km long, several km wide and 150 – 600 m thick. Photo is of Kalmina gorge in the Pilbara (Karijini National Park, Hamersley Ranges) 2 What are Banded Iron Formations (BIFs)? • Large sedimentary structures • Bands of iron rich and iron poor rock Iron rich bands: hematite (Fe2O3), magnetite (Fe3O4), siderite (FeCO3) or pyrite (FeS2). Iron poor bands: chert (fine‐grained quartz) and low iron oxide levels Rock sample from a BIF (Woudloper 2009, Creative Commons 1.0) Iron rich bands are composed of hematitie (Fe2O3), magnetite (Fe3O4), siderite (FeCO3) or pyrite (FeS2). The iron poor bands contain chert (fine‐grained quartz) with lesser amounts of iron oxide. 3 What are Banded Iron Formations (BIFs)? • Large sedimentary structures • Bands of iron rich and iron poor rock • Archaean and Proterozoic in age BIF formation through time (KG Budge 2020, public domain) BIFs were deposited for 2 billion years during the Archaean and Proterozoic. There was another short time of deposition during a Snowball Earth event. 4 Why are BIFs important? • Iron ore exports are Australia’s top earner, worth $61 billion in 2017‐2018 • Iron ore comes from enriched BIF deposits Rio Tinto iron ore shiploader in the Pilbara (C Hargrave, CSIRO Science Image) Australia is consistently the leading iron ore exporter in the world. We have large deposits where the iron‐poor chert bands have been leached away, leaving 40%‐60% iron. -
A Sulfur Isotope Study of Pyrite Genesis: the Mid-Proterozoic Newland Formation, Belt Supergroup, Montana
A sulfur isotope study of pyrite genesis: The Mid-Proterozoic Newland Formation, Belt Supergroup, Montana HARALD STRAUSS' and JORGEN SCHIEBER 2 'Ruhr-Universitat Bochum, Institut fur Geologie, Postfach 102148, 4630 Bochum 1, FRG 2University of Texas at Arlington, Department of Geology, Arlington, TX 76019, USA Abstract-Different generations of sedimentary pyrite from the Mid-Proterozoic Newland Formation, USA, have been analysed for their sulfur isotopic compositions. The results indicate bacterial sulfate reduction as the pyrite forming process. The V'S values for early diagenetic pyrite, around -14%o, are in contrast to dominantly more positive values for many other Middle Proterozoic units. A progressive reduction of sulfate availability during diagenesis can be recognized by an increase in 34S content (Rayleigh Distillation) as well as through detailed petrographic observations. Contemporaneous seawater had a sulfur isotopic ratio between +14 and +18%o as measured from sedimentary barite within the unit. INTRODUCTION deposited between 1450 and 850 Ma ago (HARRISON, 1972), and the Newland Formation accumulated early in basin history. OBRADOVICH and PETERMAN THE MID-PROTEROZOIC Newland Formation (Belt Supergroup) contains (1968) defined a 1325 Ma Rb-Sr isochron in Belt rocks (including the Newland horizons of pyritic shale. These and surrounding sediments have been Formation) of the Big Belt and Little Belt Mountains. Because the whole Lower investigated in detail by SCHIEBER (1985) and a continuous spectrum of pyrite Beltian sequence shows the 1325 Ma age, it is likely that this age represents the types from early diagenetic fine crystalline to late diagenetic eudedral and approximate time of diagenetic smectite-illite trans concretionary pyrite has been distinguished. -
Geochemistry, Mineralogy and Microbiology of Cobalt in Mining-Affected Environments
minerals Article Geochemistry, Mineralogy and Microbiology of Cobalt in Mining-Affected Environments Gabriel Ziwa 1,2,*, Rich Crane 1,2 and Karen A. Hudson-Edwards 1,2 1 Environment and Sustainability Institute, University of Exeter, Penryn TR10 9FE, UK; [email protected] (R.C.); [email protected] (K.A.H.-E.) 2 Camborne School of Mines, University of Exeter, Penryn TR10 9FE, UK * Correspondence: [email protected] Abstract: Cobalt is recognised by the European Commission as a “Critical Raw Material” due to its irreplaceable functionality in many types of modern technology, combined with its current high-risk status associated with its supply. Despite such importance, there remain major knowledge gaps with regard to the geochemistry, mineralogy, and microbiology of cobalt-bearing environments, particu- larly those associated with ore deposits and subsequent mining operations. In such environments, high concentrations of Co (up to 34,400 mg/L in mine water, 14,165 mg/kg in tailings, 21,134 mg/kg in soils, and 18,434 mg/kg in stream sediments) have been documented. Co is contained in ore and mine waste in a wide variety of primary (e.g., cobaltite, carrolite, and erythrite) and secondary (e.g., erythrite, heterogenite) minerals. When exposed to low pH conditions, a number of such minerals are 2+ known to undergo dissolution, typically forming Co (aq). At circumneutral pH, such aqueous Co can then become immobilised by co-precipitation and/or sorption onto Fe and Mn(oxyhydr)oxides. This paper brings together contemporary knowledge on such Co cycling across different mining environments. -
Using the High-Temperature Phase Transition of Iron Sulfide Minerals As
www.nature.com/scientificreports OPEN Using the high-temperature phase transition of iron sulfde minerals as an indicator of fault Received: 9 November 2018 Accepted: 15 May 2019 slip temperature Published: xx xx xxxx Yan-Hong Chen1, Yen-Hua Chen1, Wen-Dung Hsu2, Yin-Chia Chang2, Hwo-Shuenn Sheu3, Jey-Jau Lee3 & Shih-Kang Lin2 The transformation of pyrite into pyrrhotite above 500 °C was observed in the Chelungpu fault zone, which formed as a result of the 1999 Chi-Chi earthquake in Taiwan. Similarly, pyrite transformation to pyrrhotite at approximately 640 °C was observed during the Tohoku earthquake in Japan. In this study, we investigated the high-temperature phase-transition of iron sulfde minerals (greigite) under anaerobic conditions. We simulated mineral phase transformations during fault movement with the aim of determining the temperature of fault slip. The techniques used in this study included thermogravimetry and diferential thermal analysis (TG/DTA) and in situ X-ray difraction (XRD). We found diversifcation between 520 °C and 630 °C in the TG/DTA curves that signifes the transformation of pyrite into pyrrhotite. Furthermore, the in situ XRD results confrmed the sequence in which greigite underwent phase transitions to gradually transform into pyrite and pyrrhotite at approximately 320 °C. Greigite completely changed into pyrite and pyrrhotite at 450 °C. Finally, pyrite was completely transformed into pyrrhotite at 580 °C. Our results reveal the temperature and sequence in which the phase transitions of greigite occur, and indicate that this may be used to constrain the temperature of fault-slip. This conclusion is supported by feld observations made following the Tohoku and Chi-Chi earthquakes. -
The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn
minerals Article The Gersdorffite-Bismuthinite-Native Gold Association and the Skarn-Porphyry Mineralization in the Kamariza Mining District, Lavrion, Greece † Panagiotis Voudouris 1,* , Constantinos Mavrogonatos 1 , Branko Rieck 2, Uwe Kolitsch 2,3, Paul G. Spry 4 , Christophe Scheffer 5, Alexandre Tarantola 6 , Olivier Vanderhaeghe 7, Emmanouil Galanos 1, Vasilios Melfos 8 , Stefanos Zaimis 9, Konstantinos Soukis 1 and Adonis Photiades 10 1 Department of Geology & Geoenvironment, National and Kapodistrian University of Athens, 15784 Athens, Greece; [email protected] (C.M.); [email protected] (E.G.); [email protected] (K.S.) 2 Institut für Mineralogie und Kristallographie, Universität Wien, 1090 Wien, Austria; [email protected] 3 Mineralogisch-Petrographische Abteilung, Naturhistorisches Museum, 1010 Wien, Austria; [email protected] 4 Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011, USA; [email protected] 5 Département de Géologie et de Génie Géologique, Université Laval, Québec, QC G1V 0A6, Canada; [email protected] 6 Université de Lorraine, CNRS, GeoRessources UMR 7359, Faculté des Sciences et Technologies, F-54506 Vandoeuvre-lès-Nancy, France; [email protected] 7 Université de Toulouse, Géosciences Environnement Toulouse (GET), UMR 5563 CNRS, F-31400 Toulouse, France; [email protected] 8 Department of Mineralogy-Petrology-Economic Geology, Faculty of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; [email protected] 9 Institut für Mineralogie, TU Bergakademie Freiberg, 09599 Freiberg, Germany; [email protected] 10 Institute of Geology and Mineral Exploration (I.G.M.E.), 13677 Acharnae, Greece; [email protected] * Correspondence: [email protected]; Tel.: +30-210-7274129 † The paper is an extended version of our paper published in 1st International Electronic Conference on Mineral Science. -
Cobalt Mineral Ecology
American Mineralogist, Volume 102, pages 108–116, 2017 Cobalt mineral ecology ROBERT M. HAZEN1,*, GRETHE HYSTAD2, JOSHUA J. GOLDEN3, DANIEL R. HUMMER1, CHAO LIU1, ROBERT T. DOWNS3, SHAUNNA M. MORRISON3, JOLYON RALPH4, AND EDWARD S. GREW5 1Geophysical Laboratory, Carnegie Institution, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A. 2Department of Mathematics, Computer Science, and Statistics, Purdue University Northwest, Hammond, Indiana 46323, U.S.A. 3Department of Geosciences, University of Arizona, 1040 East 4th Street, Tucson, Arizona 85721-0077, U.S.A. 4Mindat.org, 128 Mullards Close, Mitcham, Surrey CR4 4FD, U.K. 5School of Earth and Climate Sciences, University of Maine, Orono, Maine 04469, U.S.A. ABSTRACT Minerals containing cobalt as an essential element display systematic trends in their diversity and distribution. We employ data for 66 approved Co mineral species (as tabulated by the official mineral list of the International Mineralogical Association, http://rruff.info/ima, as of 1 March 2016), represent- ing 3554 mineral species-locality pairs (www.mindat.org and other sources, as of 1 March 2016). We find that cobalt-containing mineral species, for which 20% are known at only one locality and more than half are known from five or fewer localities, conform to a Large Number of Rare Events (LNRE) distribution. Our model predicts that at least 81 Co minerals exist in Earth’s crust today, indicating that at least 15 species have yet to be discovered—a minimum estimate because it assumes that new minerals will be found only using the same methods as in the past. Numerous additional cobalt miner- als likely await discovery using micro-analytical methods. -
Eg9601814 Supergene Alteration of Magnetite And
EG9601814 SUPERGENE ALTERATION OF MAGNETITE AND PYRITE AND THE ROLE OF THEIR ALTERATION PRODUCTS IN THE FIXATION OF URANIUM FROM THE CIRCULATING MEDIA. BY MA EL GEMMIZI Nuclear Materials A uthority Cairo- Egypt. ABSTRACT. In most of the Egyptian altered radioactive granites, highly magnetic heavy particles were found to be radioactive. They are a mixture of several iron oxide minerals which are products of supergene alteration of the pre-existing hypogene iron-bearing minerals especially magnetite and pyrite. The end products of this supergene alteration are mainly hydrated iron oxide minerals limonite hematite and geothite. During the alteration, deformation and defects in the minerals structure took place , thereby promoting diffusion of the substitutional and interstitial ions (uranium) to words these sites The mechanism of the alteration of the hypogene iron-bearing minerals; magnetite and pyrite to form the secondary minerals hematite, limonite and geothite; the role of these minerals in fixing uranium from the ciculating media as well as the applicability of these minerals as indicators to the radioactivity of the host rocks were discussed. INTRODUCTION It is quite common that in all the altered rocks magnetite and to some extent pyrite which are present as accessories are suffering from some degrees of alteration. Magnetite and pyrite in the altered granite of Wadi Nugrus, El Missikat and £1 Aradyia, Eastern Desert was found by (1 & 2) to possess several degrees of alteration and crystal deformation. This means that both minerals are sensitive to postdepositional environmental changes. The granites of the present study were described as altered granites overlained by metasediments and underlained by magmatic bodies which invaded the granites itself by sills. -
Pyrite's Evil Twin Marcasite and Pyrite Are Two Common Minerals. Both Fes2 Chemically, Making Them Polymorphs. Polym
Marcasite - Pyrite's Evil Twin Marcasite and pyrite are two common minerals. Both FeS2 chemically, making them polymorphs. Polymorphs are minerals with the same chemical composition but different crystal structures. Diamond and graphite are polymorphs, both minerals being pure carbon. In diamond and graphite the different arrangement of carbon atoms gives these two minerals of very different physical properties. Pyrite and marcasite, on the other hand, have almost identical physical properties, making them tough to tell from each other. Let's go through their properties. Both are metallic and pale yellow to brassy yellow. Both can tarnish and be iridescent. Both are 6-6.5 on the Mohs' hardness scale. Neither have a particularly prominent cleavage, although marcasite does have one that occasionally shows up. Both have densities of about 5 grams per cubic centimeter (pyrite is a bit denser, but not enough to be detectible without delicate measurements). They can even be found together in the same rock. Fortunately these minerals often show good outer crystal shapes that are quite different. Pyrite crystals are generally equant, and dominated by cubes, octahedrons and 12-sided pyritohedrons. Marcasite crystals are usually rectangular (tabular) with wedge-shaped ends and tend to form in star shaped, radiating or cockscomb groups. Marcasite is also much more restricted in occurrence than pyrite, forming only in low temperature, near surface, very acidic environments. It is found in some ore deposits, in sediments formed under somewhat stagnant conditions and as ground water precipitates in rocks such as in limestone and shale. Although pyrite can also be found in many of these same environments, the crystal shapes are diagnostic.