• journal_title：Mineralogical Magazine
• Contributor：F. Demartin ; I. Campostrini ; C. Castellano ; C. M. Gramaccioli ; M. Russo
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-12-01
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.7.10
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：7
• firstpage：2773
• section：Articles

d="p-1">The new minerals d'ansite-(Mn), Na<sub>21sub>Mn<sup>2+sup> (SO<sub>4sub>)<sub>10sub>Cl<sub>3sub>, and d'ansite-(Fe), Na<sub>21sub>Fe<sup>2+sup> (SO<sub>4sub>)<sub>10sub>Cl<sub>3sub>, occur as encrustations in fumaroles at Vesuvius, Naples, Italy and La Fossa crater, Vulcano, Aeolian Islands, Italy, respectively. Both minerals are cubic and crystallize in space group I4İ3d. D'ansite-(Mn) forms colourless translucent tristetrahedral crystals up to 0.2 mm on edge; d'ansite-(Fe) forms aggregates of colourless to white complex isometric crystals of about the same size. Chemical analyses obtained by energy-dispersive spectrometry on an electron microprobe gave the following mean compositions: d'ansite-(Mn), Na<sub>2sub>O 39.37, MnO 3.46, MgO 0.13, SO<sub>3sub> 49.99, Cl 6.36, O=Cl −1.44, total 97.87 wt.%, corresponding to an empirical formula, on the basis of 43 anions, of Na (<span class="inline-formula" id="inline-formula-1">ss="math mml" alt="Formula" src="2773/embed/mml-math-1.gif" /> span>Mg<sub>0.05sub>)<sub>Σ0.84sub>S<sub>10.13sub>O<sub>40.09sub>Cl<sub>2.91sub>; and d'ansite-(Fe), Na<sub>2sub>O 39.12, FeO 4.18, MgO 0.12, SO<sub>3sub> 49.91, Cl 6.81, O=Cl −1.54, total 98.60 wt.%, corresponding to an empirical formula of Na<sub>20.42sub>(<span class="inline-formula" id="inline-formula-2">ss="math mml" alt="Formula" src="2773/embed/mml-math-2.gif" /> span>Mg<sub>0.05sub>)<sub>Σ0.99sub>S<sub>10.08sub>O<sub>39.89sub>Cl<sub>3.11sub>. The six strongest reflections in the X-ray powder diffraction pattern of d'ansite-(Fe) [listed as d<sub>obssub>(Å) (I) (hkl)] are as follows: 2.807(100)(044), 2.570(37)(235), 1.714(29)(129), 3.384(27)(233), 3.113(26)(134), 2.108(15)(237). The unit-cell parameters obtained from single-crystal data are 15.9291(9) and 15.882(3) Å for d'ansite-(Mn) and d'ansite-(Fe), respectively. The structure of both minerals was refined, using single-crystal diffraction data, to final R parameters of 0.0309 and 0.0336 on reflections with I > 2σ(I). The structure contains three independent Na sites, one of which is partially occupied by Mn<sup>2+sup> or Fe<sup>2+sup>, two independent sulfate anions and one chlorine site.