The new mineral adranosite-(Fe), ideally (NHub>4ub>)ub>4ub>NaFeub>2ub>(SOub>4ub>)ub>4ub>Cl(OH)ub>2ub>, is the Feup>3+up>-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 I4ub>1ub>/acd (no. 142), with a = 18.261(2), c = 11.562(1) Å, V = 3855.5(7) Åup>3up> (single-crystal data), and Z = 8. The six strongest reflections in the X-ray powder diffraction pattern are [dub>obsub> 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.%): Naub>2ub>O 5.01, Feub>2ub>Oub>3ub> 15.77, Alub>2ub>Oub>3ub> 5.11, Kub>2ub>O 0.82, (NHub>4ub>)ub>2ub>O 15.76, SOub>3ub> 50.96, Cl 3.71, Hub>2ub>O 2.75, –O=Cl−0.84, total 99.05; the corresponding empirical formula is: [(NHub>4ub>)ub>3.89ub>Kub>0.11ub>]ub>∑4.00ub>Naub>1.04ub>[Feub>1.27ub>Alub>0.64ub>]ub>∑1.91ub>Sub>4.10ub>Oub>16.40ub>Cub>l0.67ub>(OH)ub>1.96ub>. 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/cmup>3up>, and the calculated density is 2.195 g/cmup>3up>. 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 NaOub>4ub>Club>2ub> square tetragonal bipyramids, linked through their opposite Cl corners and helicoidal chains with composition [FeOub>4ub>(OH)ub>2ub>SOub>4ub>]ub>nub>, 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 NHub>4ub>up>+up> ions are hosted.
