Nannoniite, Al<sub>2</sub>(OH)<sub>5</sub>F, a new mineral from the Cetine di Cotorniano mine (Tuscany, Italy)
<p>The new mineral nannoniite, Al<span class="inline-formula"><sub>2</sub></span>(OH)<span class="inline-formula"><sub>5</sub></span>F (<span class="inline-formula"><i>Z</i>=4</span>), has bee...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-12-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/36/1011/2024/ejm-36-1011-2024.pdf |
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| Summary: | <p>The new mineral nannoniite, Al<span class="inline-formula"><sub>2</sub></span>(OH)<span class="inline-formula"><sub>5</sub></span>F (<span class="inline-formula"><i>Z</i>=4</span>), has been discovered in the Cetine di Cotorniano mine, Chiusdino, Siena, Tuscany, Italy. It occurs as spherical aggregates formed by micrometre-sized crystals, colourless to white in colour, with a white streak and a vitreous to earthy lustre. Fluorescence is bluish-yellow and yellowish-white under short- and longwave UV radiation, respectively. Electron microprobe analysis gave (in wt %) SO<span class="inline-formula"><sub>3</sub></span> 0.49, Al<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>3</sub></span> 63.97, MgO 0.51, CaO 0.22, K<span class="inline-formula"><sub>2</sub></span>O 0.07, F 11.72, H<span class="inline-formula"><sub>2</sub></span>O<span class="inline-formula"><sub>(calc)</sub></span> 28.54, and <span class="inline-formula">−</span>O <span class="inline-formula">=</span> F <span class="inline-formula">−4.94</span>, with a total of 100.58. Nannoniite is monoclinic, with space group <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>P</mi><msub><mn mathvariant="normal">2</mn><mn mathvariant="normal">1</mn></msub><mo>/</mo><mi>n</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="34pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f46ec57be4c405f29b4061d652d98bf3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-36-1011-2024-ie00001.svg" width="34pt" height="14pt" src="ejm-36-1011-2024-ie00001.png"/></svg:svg></span></span> and with <span class="inline-formula"><i>a</i>=8.68</span>8(3), <span class="inline-formula"><i>b</i>=5.024</span>(2), <span class="inline-formula"><i>c</i>=9.734</span>(4) Å, <span class="inline-formula"><i>β</i>=90.77</span>(2)°, and <span class="inline-formula"><i>V</i>=424.9</span>(3) Å<span class="inline-formula"><sup>3</sup></span>. The crystal structure was solved using three-dimensional electron diffraction and refined to <span class="inline-formula"><i>R</i><sub>(obs)</sub>=0.1524</span> for 2141 unique reflections with <span class="inline-formula"><i>I</i>>3<i>σ</i>(<i>I</i>)</span>. Nannoniite is homeotypic with gibbsite. In type material, nannoniite is associated with quartz, baryte, gypsum, and alunite in vugs of a silicified limestone. Its origin is probably related to the late-stage circulation of (Al,F)-rich fluids within the Sb ore deposit formerly exploited at the Cetine di Cotorniano mine.</p> |
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| ISSN: | 0935-1221 1617-4011 |