<?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:contributor>M. Ross</dc:contributor>
  <dc:creator>C.T. Prewitt</dc:creator>
  <dc:date>1970</dc:date>
  <dc:description>&lt;div id="abstracts" class="Abstracts u-font-serif"&gt;&lt;div id="ab1" class="abstract author" lang="en"&gt;&lt;div id="aep-abstract-sec-id6"&gt;&lt;p id="SP0005"&gt;Cummingtonite from the Gouverneur, New York, talc district (Sample No. U.S.N.M. 115046) with the composition, (Ca&lt;sub&gt;0.36&lt;/sub&gt;Na&lt;sub&gt;0.06&lt;/sub&gt;Mn&lt;sub&gt;0.96&lt;/sub&gt;Mg&lt;sub&gt;0.57&lt;/sub&gt;) Mg&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;8&lt;/sub&gt;O&lt;sub&gt;22&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;(OH)&lt;sub&gt;2&lt;/sub&gt;, unit cell parametersa = 9.550 ± 0.001, b = 18.007 ± 0.003, c = 5.298 ± 0.001Å, β = 102°39′ ± 1′, and space groupP2&lt;sub&gt;1&lt;/sub&gt;/m, has been used in a high-temperature, single-crystal, X-ray diffraction study. When diffraction patterns are taken of the crystals heated in a sealed silica capillary to 45°C or higher, these reflections disappear, indicating a transition toC2/m symmetry. The transition appears to be analogous to theP2&lt;sub&gt;1&lt;/sub&gt;/ctoC2/c transition between 700° and 800°C discovered recently in (Mg&lt;sub&gt;0.30&lt;/sub&gt;Fe&lt;sub&gt;0.70&lt;/sub&gt;) SiO&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;clinopyroxene.&lt;/p&gt;&lt;p id="SP0010"&gt;In addition to the cummingtonite transition, we have also found a transition in pigeonite at higher temperatures. The transition occurs in this pigeonite (Gunflint Iron Formation, Minnesota, (Ca&lt;sub&gt;0.04&lt;/sub&gt;Fe&lt;sub&gt;0.78&lt;/sub&gt;Mg&lt;sub&gt;0.18&lt;/sub&gt;)SiO&lt;sub&gt;3&lt;/sub&gt;) at about 670°C. This is a significantly lower temperature than was found for the Ca-poor clinopyroxene.&lt;/p&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/0012-821X(70)90150-0</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>Cummingtonite: A reversible, nonquenchable transition from P21/m to C2/m symmetry</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>