William N. Sharp J.W. Adams Eugene E. Foord 1984 <p><span>A Zn- and Y-group-bearing senaite, formulated as&nbsp;</span><i><span class="italic">AM</span></i>_{<span class="sub">21</span>}<span>O</span>_{<span class="sub">38</span>}<span>&nbsp;(Pb</span>_{<span class="sub">0.63</span>}<span>Na</span>_{<span class="sub">0.46</span>}<span>Ba</span>_{<span class="sub">0.11</span>}<span>)</span><span class="sub">Σ1.20</span><span>(Ti</span>_{<span class="sub">14.64</span>}<img src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline01.png?pub-status=live" alt="" data-mce-src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline01.png?pub-status=live"><span>Zn</span>_{<span class="sub">1.74</span>}<img src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline04.png?pub-status=live" alt="" data-mce-src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline04.png?pub-status=live"><span>Y‒group REE</span>_{<span class="sub">0.70</span>}<span>Mn</span>_{<span class="sub">0.38</span>}<span>Nb</span>_{<span class="sub">0.20</span>}<span>Sn</span>_{<span class="sub">0.03</span>}<span>Zr</span>_{<span class="sub">0.03</span>}<span>Th</span>_{<span class="sub">0.02</span>}<span>)</span>_{<span class="sub">Σ20.9</span>}<span>O</span>_{<span class="sub">38</span>}<span>, a member of the crichtonite group, is a newly characterized phase associated with murataite at the St Peters Dome area, Colorado. The Zn- and Y-group-bearing senaite is uranium-free and nonmetamict, but otherwise is comparable to known senaites and davidites in X-ray diffraction pattern, symmetry, and structure. The&nbsp;</span><span class="italic">REE</span><span>&nbsp;distribution shows a strong dominance of Y and the Y-group&nbsp;</span><span class="italic">REE</span><span>&nbsp;which are present in&nbsp;</span><i><span class="italic">M</span></i><span>(1). Megascopically, the mineral is black, submetallic, and opaque; in polished section it appears to be white and moderately bright compared with murataite. Cleavage is absent but twinning on {52</span><img src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline07.png?pub-status=live" alt="" data-mce-src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline07.png?pub-status=live"><span>0} is present.</span></p><p><span>Senaite and hitherto unreported zinc-bearing senaite from Dattas, Diamantina, Minas Gerais, Brazil, have the following respective structural formulas as determined by electron microprobe:</span></p><p>(Pb_{<span class="sub">0.76</span>}Sr_{<span class="sub">0.20</span>}La_{<span class="sub">0.08</span>}Ce_{<span class="sub">0.07</span>}Ba_{<span class="sub">0.04</span>})_{<span class="sub">Σ1.15</span>}(Ti_{<span class="sub">12.89</span>}<img src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline03.png?pub-status=live" alt="" data-mce-src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline03.png?pub-status=live">Mn_{<span class="sub">0.88</span>}Y_{<span class="sub">0.59</span>}Zn_{<span class="sub">0.12</span>}Mg_{<span class="sub">0.07</span>}Nb_{<span class="sub">0.03</span>}Cr_{<span class="sub">0.02</span>}Th_{<span class="sub">0.02</span>})_{<span class="sub">Σ20.61</span>}O_{<span class="sub">38</span>}</p><p>and</p><p>(Pb_{<span class="sub">0.89</span>}Ba_{<span class="sub">0.15</span>}Ce_{<span class="sub">0.02</span>}Sr_{<span class="sub">0.02</span>})_{<span class="sub">Σ1.08</span>}(Ti_{<span class="sub">14.57</span>}<img src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline05.png?pub-status=live" alt="" data-mce-src="https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20210202014135270-0938:S0026461X00023380:S0026461X00023380_inline05.png?pub-status=live">Zn_{<span class="sub">1.76</span>}Na_{<span class="sub">0.63</span>}Mn_{<span class="sub">0.50</span>}Y_{<span class="sub">0.28</span>}Nb_{<span class="sub">0.14</span>}Mg_{<span class="sub">0.04</span>}Cr_{<span class="sub">0.02</span>})_{<span class="sub">Σ20.83</span>}O_{<span class="sub">38</span>}</p><p><span><br data-mce-bogus="1"></span></p> application/pdf 10.1180/minmag.1984.048.346.13 en Cambridge University Press Zinc- and Y-group-bearing senaite from St Peters Dome, and new data on senaite from Dattas, Minas Gerais, Brazil article