Whiteite-(CaMnFe), a new jahnsite-group mineral from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria
<p>Whiteite-(CaMnFe), CaMn<span class="inline-formula"><sup>2+</sup></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dsp...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-02-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/95/2023/ejm-35-95-2023.pdf |
| Summary: | <p>Whiteite-(CaMnFe),
CaMn<span class="inline-formula"><sup>2+</sup></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">2</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="12pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="d4d25c079dd3abd10641323026d872bc"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-95-2023-ie00001.svg" width="12pt" height="16pt" src="ejm-35-95-2023-ie00001.png"/></svg:svg></span></span>Al<span class="inline-formula"><sub>2</sub></span>(PO<span class="inline-formula"><sub>4</sub></span>)<span class="inline-formula"><sub>4</sub></span>(OH)<span class="inline-formula"><sub>2</sub></span> <span class="inline-formula">⋅</span> 8H<span class="inline-formula"><sub>2</sub></span>O, is a new whiteite-subgroup member of the jahnsite group from the
Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in
vugs in an altered feldspar area of a specimen composed predominantly of
rockbridgeite, with hureaulite and relic triphylite. Other associated
minerals in small vugs in the specimen were strengite and laueite.
Whiteite-(CaMnFe) occurs as sprays and clusters of colourless to pale
yellow, rod-like crystals, with diameters of typically 10 to 50 <span class="inline-formula">µ</span>m
and lengths up to <span class="inline-formula">∼</span> 500 <span class="inline-formula">µ</span>m. The crystals are flattened
on {001} and elongated along [010]. The measured
density is 2.80(2) g cm<span class="inline-formula"><sup>−3</sup></span>. Optically, whiteite-(CaMnFe)
crystals are biaxial (<span class="inline-formula">+</span>), with <span class="inline-formula"><i>α</i>=1.608(3)</span>, <span class="inline-formula"><i>β</i>=1.612(3)</span>, <span class="inline-formula"><i>γ</i>=1.624(3)</span> and 2<span class="inline-formula"><i>V</i></span>(meas.) <span class="inline-formula">=</span> 59(1)<span class="inline-formula"><sup>∘</sup></span>. The
empirical formula from electron microprobe analyses and structure refinement
is
(Ca<span class="inline-formula"><sub>0.70</sub></span>Mn<span class="inline-formula"><sub>0.30</sub></span>)Mn(Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">1.23</mn><mrow><mn mathvariant="normal">2</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="c3536c245242a69d83af5e6ae6673104"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-95-2023-ie00002.svg" width="18pt" height="17pt" src="ejm-35-95-2023-ie00002.png"/></svg:svg></span></span>Mn<span class="inline-formula"><sub>0.49</sub></span>Mg<span class="inline-formula"><sub>0.29</sub></span>Zn<span class="inline-formula"><sub>0.06</sub>)</span>(Al<span class="inline-formula"><sub>1.88</sub></span>Fe<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M27" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">0.12</mn><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="18pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="52ae71ce42731e2fbe7ffaabbf49c6b6"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-95-2023-ie00003.svg" width="18pt" height="17pt" src="ejm-35-95-2023-ie00003.png"/></svg:svg></span></span>)(PO<span class="inline-formula"><sub>4</sub></span>)<span class="inline-formula"><sub>3.96</sub></span>(OH)<span class="inline-formula"><sub>2</sub></span>(H<span class="inline-formula"><sub>2</sub></span>O)<span class="inline-formula"><sub>8</sub></span>.
Whiteite-(CaMnFe) is monoclinic, P2 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M33" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>/</mo><mi>a</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="15pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9fa8492de05c7f0837a0c278f8848864"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-95-2023-ie00004.svg" width="15pt" height="14pt" src="ejm-35-95-2023-ie00004.png"/></svg:svg></span></span>, <span class="inline-formula"><i>a</i>=14.925(5)</span>, <span class="inline-formula"><i>b</i>=7.0100(14)</span>, <span class="inline-formula"><i>c</i>=10.053(2)</span> Å, <span class="inline-formula"><i>β</i>=111.31(2)</span><span class="inline-formula"><sup>∘</sup></span>, <span class="inline-formula"><i>V</i>=979.9(4)</span> Å<span class="inline-formula"><sup>3</sup></span> and <span class="inline-formula"><i>Z</i>=2</span>. The crystal structure was refined using
single-crystal data to <span class="inline-formula"><i>w</i><i>R</i><sub>obs</sub>=0.052</span> for 1613 reflections with <span class="inline-formula"><i>I</i><i>></i>3<i>σ</i>(<i>I</i>)</span>. Site occupancy refinements confirm the ordering
of dominant Ca, Mn and Fe<span class="inline-formula"><sup>2+</sup></span> in the <span class="inline-formula"><i>X</i></span>, <span class="inline-formula"><i>M</i></span>1 and <span class="inline-formula"><i>M</i></span>2 sites, respectively, of
the general jahnsite-group formula
<span class="inline-formula"><i>X</i><i>M</i></span>1<span class="inline-formula"><i>M</i></span>2<span class="inline-formula"><sub>2</sub></span><span class="inline-formula"><i>M</i></span>3<span class="inline-formula"><sub>2</sub></span>(H<span class="inline-formula"><sub>2</sub></span>O)<span class="inline-formula"><sub>8</sub></span>(OH)<span class="inline-formula"><sub>2</sub></span>(PO<span class="inline-formula"><sub>4</sub></span>)<span class="inline-formula"><sub>4</sub></span>.</p> |
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| ISSN: | 0935-1221 1617-4011 |