Adranosite-(Fe), (NH₄)4NaFe₂(SO₄)₄Cl(OH)₂, a new ammonium sulfate chloride from La Fossa Crater, Vulcano, Aeolian Islands, Italy

Author(s)

Donatella Mitolo, Francesco Demartin, Anna Garavelli, Italo Campostrini, Daniela Pinto, Carlo Maria Gramaccioli, Pasquale Acquafredda, Uwe Kolitsch

Abstract

The new mineral adranosite-(Fe), ideally (NH4)4NaFe2(SO4)4Cl(OH)2, is the Fe3+-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 I41/acd (no. 142), with a = 18.261(2), c = 11.562(1) Å, V = 3855.5(7) Å3 (single-crystal data), and Z = 8. The six strongest reflections in the X-ray powder diffraction pattern are [dobs 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.%): Na2O 5.01, Fe2O3 15.77, Al2O3 5.11, K2O 0.82, (NH4)2O 15.76, SO3 50.96, Cl 3.71, H2O 2.75, -O=Cl-0.84, total 99.05; the corresponding empirical formula is: [(NH4)3.89K0.11]?4.00Na1.04[Fe1.27Al0.64]?1.91S4.10O16.40Cl0.67(OH)1.96. 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/cm3, and the calculated density is 2.195 g/cm3. Adranosite-(Fe) is uniaxial (-) with ?=1.58(1), ?=1.57(1) (? = 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(s(I)]. Adranosite-(Fe) is isostructural with its Al-analogue adranosite and contains NaO4Cl2 square tetragonal bipyramids, linked through their opposite Cl corners and helicoidal chains with composition [FeO4(OH)2SO4]n, 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 NH4+ ions are hosted.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Università degli Studi di Bari Aldo Moro, Università degli Studi di Milano-Bicocca

Journal

The Canadian Mineralogist

Volume

51

Pages

57-66

No. of pages

10

ISSN

0008-4476

Publication date

2013

Peer reviewed

Yes

Austrian Fields of Science 2012

105113 Crystallography, 104006 Solid state chemistry, 105116 Mineralogy

Portal url

https://ucrisportal.univie.ac.at/en/publications/20d28f7e-81d4-49ea-a72f-a4c31662344f