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<front>
<journal-meta>
<journal-id journal-id-type="archive">gsminmag</journal-id>
<journal-title>Mineralogical Magazine</journal-title>
<abbrev-journal-title abbrev-type="full">Mineralogical Magazine</abbrev-journal-title>
<issn pub-type="ppub">0026-461X</issn>
<publisher>
<publisher-name>Mineralogical Society</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1180/minmag.1965.034.268.19</article-id>
<title-group>
<article-title>A Second Occurrence of Lyndochite</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Horne</surname>
<given-names>J. E. T.</given-names>
</name>
<xref ref-type="author-notes" rid="FN1">1</xref>
<aff>Atomic Energy Division, Geological Survey of Great Britain</aff></contrib>
<contrib contrib-type="author">
<name>
<surname>Butler</surname>
<given-names>J. R.</given-names>
</name>
<aff>Pure Geochemistry Section, Department of Geology, Imperial College of Science and Technology, University of London</aff></contrib></contrib-group>
<author-notes>
<fn fn-type="com" id="FN1"><label>1</label><p>Communicated by permission of the Director of the Geological Survey of Great Britain.</p></fn></author-notes>
<pub-date pub-type="ppub">
<year>1965</year>
</pub-date>
<volume>34</volume>
<issue>268</issue>
<fpage>237</fpage>
<lpage>248</lpage>
<copyright-statement>Copyright &#x00A9; 1965, The Mineralogical Society</copyright-statement>
<copyright-year>1965</copyright-year>
<abstract>
<title>Summary</title>
<p>Lyndochite from Tura dukas, 35 miles north of Nanyuki, Kenya, agrees closely with the type material from Canada in its chemical analysis, in the distribution of the rare earths, and in X-ray diffraction data for powder after heat treatment. The mineral is compared and contrasted with aeschynite. Uranium-poor euxenite is intimately associated with lyndochite at the type locality.</p>
<p>Since its discovery over thirty-five years ago, lyndochite has remained unrecorded outside its type locality of Lyndoch Township in Ontario, Canada. Its distinetive chemical composition sets it apart from almost all other Ti-rich metamiet niobates and, despite the many analyses that have been made on rare-earth niobate-tantalates, specimens that could have been regarded as similar to or approximating to lyndochite have rarely been mentioned. Its unusual characteristics include high ThO<sub>2</sub> (about 10%) and appreciable rare-earth oxides (about 20%) with a lanthanon assemblage showing a peak concentration of Nd (and Ce), rather than any of the heavy lanthanons. The proportions of TiO<sub>2</sub> (about 20%) and (Nb,Ta)<sub>2</sub>O<sub>5</sub> (about 40%) are comparable to those in numerous niobate-tantalates, but are only associated with the percentages of ThO<sub>2</sub> and Re<sub>2</sub>O<sub>3</sub> mentioned above in some members of the aesehynite-priorite series. The lyndochite now described is chemi-cally very close indeed to the Canadian lyndochite, and both specimens give closely similar X-ray diffraction patterns (after suitable heat treatment) which are distinct from those of any other metamict mineral.</p></abstract>
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