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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>E. E. Inan</dc:contributor>
  <dc:contributor>Bruce S. Hemingway</dc:contributor>
  <dc:creator>Robert R. Seal, II</dc:creator>
  <dc:date>2001</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;The Gibbs free energy of formation of nukundamite (Cu&lt;/span&gt;&lt;sub&gt;3.38&lt;/sub&gt;&lt;span&gt;Fe&lt;/span&gt;&lt;sub&gt;0.62&lt;/sub&gt;&lt;span&gt;S&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;) was calculated from published experimental studies of the reaction 3.25 Cu&lt;/span&gt;&lt;sub&gt;3.38&lt;/sub&gt;&lt;span&gt;Fe&lt;/span&gt;&lt;sub&gt;0.62&lt;/sub&gt;&lt;span&gt;S&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;+ S&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;= 11 CuS + 2 FeS&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;in order to correct an erroneous expression in the published record. The correct expression describing the Gibbs free energy of formation (kJ·mol&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;) of nukundamite relative to the elements and ideal S&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;gas is Δ&lt;/span&gt;&lt;sub&gt;f&lt;/sub&gt;&lt;span&gt;G°&lt;/span&gt;&lt;sub&gt;nukundamite, T(K)&lt;/sub&gt;&lt;span&gt;&amp;nbsp;= −549.75 + 0.23242 T + 3.1284 T&lt;/span&gt;&lt;sup&gt;0.5&lt;/sup&gt;&lt;span&gt;, with an uncertainty of 0.6%. An evaluation of the phase equilibria of nukundamite with associated phases in the system Cu–Fe–S as a function of temperature and sulfur fugacity indicates that nukundamite is stable from 224 to 501°C at high sulfidation states. At its greatest extent, at 434°C, the stability field of nukundamite is only 0.4 log&amp;nbsp;&lt;/span&gt;&lt;i&gt;f&lt;/i&gt;&lt;span&gt;(S&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;) units wide, which explains its rarity. Equilibria between nukundamite and bornite, which limit the stability of both phases, involve bornite compositions that deviate significantly from stoichiometric Cu&lt;/span&gt;&lt;sub&gt;5&lt;/sub&gt;&lt;span&gt;FeS&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;. Under equilibrium conditions in the system Cu–Fe–S, nukundamite + chalcopyrite is not a stable assemblage at any temperature.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.2113/gscanmin.39.6.1635</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Mineralogical Association of Canada</dc:publisher>
  <dc:title>The Gibbs free energy of nukundamite (Cu3.38Fe0.62S4): A correction and implications for phase equilibria</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>