<?xml version='1.0' encoding='utf-8'?>
<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>J. J. Papike</dc:contributor>
  <dc:creator>J. R. Clark</dc:creator>
  <dc:date>1966</dc:date>
  <dc:description>&lt;p&gt;&lt;span id="_mce_caret" data-mce-bogus="1" data-mce-type="format-caret"&gt;&lt;span&gt;X-ray diffraction crystal-structure analysis of omphacite from eclogite, Tiburon Peninsula, Marin County, California, shows that this clinopyroxene has&amp;nbsp;&lt;/span&gt;&lt;i&gt;P&lt;/i&gt;&lt;span&gt;2 symmetry with a nearly ordered distribution of the multiple cation content defined by its approximate formula: (Na&lt;/span&gt;&lt;sub&gt;0.5&lt;/sub&gt;&lt;span&gt;Ca&lt;/span&gt;&lt;sub&gt;0.5&lt;/sub&gt;&lt;span&gt;) (Mg&lt;/span&gt;&lt;sub&gt;0.4&lt;/sub&gt;&lt;span&gt;Fe&lt;/span&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;span&gt;+&lt;/span&gt;&lt;sub&gt;0.1&lt;/sub&gt;&lt;span&gt;Al&lt;/span&gt;&lt;sub&gt;0.4&lt;/sub&gt;&lt;span&gt;Fe&lt;/span&gt;&lt;sup&gt;3&lt;/sup&gt;&lt;span&gt;+&lt;/span&gt;&lt;sub&gt;0.1&lt;/sub&gt;&lt;span&gt;)Si&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O&lt;/span&gt;&lt;sub&gt;6&lt;/sub&gt;&lt;span&gt;. Na+ and Ca&lt;/span&gt;&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;tend to assume alternate locations in the structure, and (Mg,Fe&lt;/span&gt;&lt;sup&gt;2+&lt;/sup&gt;&lt;span&gt;) octahedra alternate with Al&lt;/span&gt;&lt;sup&gt;3+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;or (Al,F&lt;/span&gt;&lt;sup&gt;3+&lt;/sup&gt;&lt;span&gt;) octahedra in chains along&amp;nbsp;&lt;/span&gt;&lt;i&gt;c&lt;/i&gt;&lt;span&gt;.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1126/science.154.3752.1003</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>American Association for the Advancement of Science</dc:publisher>
  <dc:title>Eclogitic pyroxenes, ordered with P2 symmetry</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>