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An insight into the inverse transformation of realgar altered by light

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Published/Copyright: May 12, 2015
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American Mineralogist
From the journal American Mineralogist Volume 100 Issue 5-6

Abstract

The light-induced alteration of realgar and β-As4S4 is a well-known phenomenon but still displays interesting aspects not completely explained. In the transformation from realgar to pararealgar the molecule As4S4 undergoes a structural modification, and ever since the initial studies two important issues have been highlighted: the influence of the oxygen and the reversibility of the process. The previous study on the reversibility of the altered β-As4S4 points out that this polymorph exhibits a dual behavior. When the light-induced alteration occurs with the presence of the air, pararealgar and arsenolite, along with amorphous material, are the products, while if the air is not present β-As4S4 turns completely into pararealgar. Moreover, when annealing the altered material in the realgar stability fields (220 °C), in the first case pararealgar and amorphous material turn into stoichiometric alacranite, while in the second case the alteration is completely reversible. Similarly, the present study focuses the attention on the question if realgar, when altered by means of the light and when annealed, might behave as β-As4S4 does. These results display that the phenomenon is more complex. The alteration of realgar with the presence of the air yields pararealgar along with arsenolite, a small quantity of uzonite and amorphous material, and when the air is not present pararealgar is the only product. In the first case, when annealing the products of alteration at 220 °C, alacranite, β-As4S4, realgar, and little amorphous material occur along with arsenolite. In the second case at first β-As4S4 crystallizes, then it turns into realgar, but this process yields orpiment and amorphous material as it moves forward, showing that from the products of alteration of realgar it is not possible to obtain the starting material. Examination of the stoichiometry of the products let to infer that the amorphous material occurring in the two cases has very different content of arsenic and sulfur.

Keywords: Realgar; light; heat; pararealgar; alacranite; uzonite; Rietveld
Received: 2014-5-9
Accepted: 2014-11-30
Published Online: 2015-5-12
Published in Print: 2015-5-1

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am-2015-5045
Keywords for this article
Realgar; light; heat; pararealgar; alacranite; uzonite; Rietveld

Articles in the same Issue

  1. Highlights and Breakthroughs. Reaction pathways toward the formation of dolomite
  2. Highlights and Breakthroughs. Zircon dissolution and growth during metamorphism
  3. Review Paper. Linear partitioning in binary solutions: A review with a novel partitioning array
  4. Presidential Address. The many facets of apatite
  5. Thermal expansion of F-Cl apatite crystalline solutions
  6. Pieczkaite, ideally Mn5(PO4)3Cl, a new apatite-supergroup mineral from Cross Lake, Manitoba, Canada: Description and crystal structure
  7. First-principles prediction of pressure-enhanced defect segregation and migration at MgO grain boundaries
  8. Optical properties of siderite (FeCO3) across the spin transition: Crossover to iron-rich carbonates in the lower mantle
  9. Calculation of the energetics of water incorporation in majorite garnet
  10. Influence of hydration on 23Na, 27Al, and 29Si MAS-NMR spectra of sodium saponites and sodium micas
  11. Quantification of water in majoritic garnet
  12. How to make a planet: An introduction
  13. Modeling siderophile elements during core formation and accretion, and the role of the deep mantle and volatiles
  14. Optical constants of synthetic potassium, sodium, and hydronium jarosite
  15. A photoluminescence study of REE3+ emissions in radiation-damaged zircon
  16. Hydrothermal chloritization processes from biotite in the Toki granite, Central Japan: Temporal variations of of the compositions of hydrothermal fluids associated with chloritization
  17. Fayalite oxidation processes in Obsidian Cliffs rhyolite flow, Oregon
  18. Effect of pores and grain size on the elastic and piezoelectric properties of quartz-based materials
  19. A route for the direct crystallization of dolomite
  20. Very large differences in intramolecular D-H partitioning in hydrated silicate melts synthesized at upper mantle pressures and temperatures
  21. Temperature dependence of crystal structure of CaGeO3 high-pressure perovskite phase and experimental determination of its Debye temperatures studied by low- and hightemperature single-crystal X-ray diffraction
  22. Insights into the structure of mixed CO2/CH4 in gas hydrates
  23. Hydrous species in feldspars: A reassessment based on FTIR and SIMS
  24. An insight into the inverse transformation of realgar altered by light
  25. First evidence of CaCO3-III and CaCO3-IIIb high-pressure polymorphs of calcite: Authigenically formed in near surface sediments
  26. Surface transformations of platinum grains from Fifield, New South Wales, Australia
  27. Cation exchange capacity and water content of opal in sedimentary basins: Example from the Monterey Formation, California
  28. Impact of preparation method and chemical composition on physicochemical and photocatalytic properties of nano-dimensional magnetite-type materials
  29. Transition metal cation site preferences in forsterite (Mg2SiO4) determined from paramagnetically shifted NMR resonances
  30. Review. Routine characterization and interpretation of complex alkali feldspar intergrowths
  31. Letter. Experimental confirmation of high-temperature silicate liquid immiscibility in multicomponent ferrobasaltic systems
  32. Letter. Discovery of stishovite in Apollo 15299 sample
  33. Presentation of the 2014 Roebling Medal of the Mineralogical Society of America to Bernard J. Wood
  34. Acceptance of the 2014 Roebling Medal of the Mineralogical Society of America
  35. Presentation of the Dana Medal of the Mineralogical Society of America for 2015 to Marc Hirschmann
  36. Acceptance of the Dana Medal of the Mineralogical Society of America for 2015
  37. Presentation of the Mineralogical Society of America Award for 2014 to Fang-Zhen Teng
  38. Acceptance of the Mineralogical Society of America Award for 2014
  39. New Mineral Names
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