• journal_title：The Canadian Mineralogist
• Contributor：Donatella Mitolo ; Francesco Demartin ; Anna Garavelli ; Italo Campostrini ; Daniela Pinto ; Carlo Maria Gramaccioli ; Pasquale Acquafredda ; Uwe Kolitsch
• Publisher：Mineralogical Association of Canada
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.51.1.57
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：51
• issue：1
• firstpage：57
• section：Article

The new mineral adranosite-(Fe), ideally (NH<sub>4sub>)<sub>4sub>NaFe<sub>2sub>(SO<sub>4sub>)<sub>4sub>Cl(OH)<sub>2sub>, is the Fe<sup>3+sup>-analogue of adranosite. It was found on a pyroclastic breccia in two different fumaroles at “La Fossa” crater of Vulcano, Aeolian Islands, Italy, and corresponds to an anthropogenic product previously observed in a burning coal dump at the Anna mine, near Aachen, Germany. The mineral is tetragonal, space group I4<sub>1sub>/acd (no. 142), with a = 18.261(2), c = 11.562(1) Å, V = 3855.5(7) Å<sup>3sup> (single-crystal data), and Z = 8. The six strongest reflections in the X-ray powder diffraction pattern are [d<sub>obssub> in Å(I)(hkl)]: 9.134(100)(020), 4.569(83)(040), 3.047(79)(152), 6.462(36)(220), 3.232(29)(251), and 2.891(11)(004). The average chemical composition of the holotype is (wt.%): Na<sub>2sub>O 5.01, Fe<sub>2sub>O<sub>3sub> 15.77, Al<sub>2sub>O<sub>3sub> 5.11, K<sub>2sub>O 0.82, (NH<sub>4sub>)<sub>2sub>O 15.76, SO<sub>3sub> 50.96, Cl 3.71, H<sub>2sub>O 2.75, –O=Cl−0.84, total 99.05; the corresponding empirical formula is: [(NH<sub>4sub>)<sub>3.89sub>K<sub>0.11sub>]<sub>∑4.00sub>Na<sub>1.04sub>[Fe<sub>1.27sub>Al<sub>0.64sub>]<sub>∑1.91sub>S<sub>4.10sub>O<sub>16.40sub>C<sub>l0.67sub>(OH)<sub>1.96sub>. Adranosite-(Fe) forms aggregates of pale yellow acicular crystals up to 1 mm in length, the most common forms most probably being {100}, {110}, and {111}. The measured density is 2.18(1) g/cm<sup>3sup>, and the calculated density is 2.195 g/cm<sup>3sup>. Adranosite-(Fe) is uniaxial (−) with ω=1.58(1), ɛ=1.57(1) (λ = 589 nm). Using single-crystal X-ray diffraction data from the holotype, the structure was refined to a final R(F)= 0.0415 for 670 independent observed reflections [I > 2(σ(I)]. Adranosite-(Fe) is isostructural with its Al-analogue adranosite and contains NaO<sub>4sub>Cl<sub>2sub> square tetragonal bipyramids, linked through their opposite Cl corners and helicoidal chains with composition [FeO<sub>4sub>(OH)<sub>2sub>SO<sub>4sub>]<sub>nsub>, both extending along [001]. The framework resulting from the sharing of the sulfate ions between the different chains displays cages in which the nine-coordinated hydrogen-bonded NH<sub>4sub><sup>+sup> ions are hosted.