DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Item Eleonorite, Fe3+6 (PO4)4O(OH)4·6H2O : validation as a mineral species and new data.(2017) Chukanov, Nikita V.; Aksenov, Sergey M.; Rastsvetaeva, Ramiza K.; Schäfer, Christof; Pekov, Igor V.; Belakovskiy, Dmitriy I.; Cipriano, Ricardo Augusto Scholz; Oliveira, Luiz Carlos Alves de; Britvin, Sergey N.Eleonorite, ideally Fe3þ 6 (PO4)4O(OH)4·6H2O, the analogue of beraunite Fe2+Fe3þ 5 (PO4)4(OH)5·6H2O with Fe2+ completely substituted by Fe3+, has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification as a mineral species (IMA 2015-003). The mineral was first described on material from the Eleonore Iron mine, Dünsberg, near Giessen, Hesse, Germany, but during this study further samples were required and a neotype locality is the Rotläufchen mine, Waldgirmes, Wetzlar, Hesse, Germany, where eleonorite is associated with goethite, rockbridgeite, dufrénite, kidwellite, variscite, matulaite, planerite, cacoxenite, strengite and wavellite. Usually eleonorite occurs as red-brown prismatic crystals up to 0.2 mm × 0.5 mm × 3.5 mm in size and in random or radial aggregates up to 5 mm across encrusting cavities in massive ‘limonite’. The mineral is brittle. Its Mohs hardness is 3. Dmeas = 2.92(1), Dcalc = 2.931 g cm–3 . The IR spectrum is given. Eleonorite is optically biaxial (+), α = 1.765(4), β = 1.780(5), γ = 1.812(6), 2Vmeas = 75(10)°, 2Vcalc = 70°. The chemical composition (electron microprobe data, H2O analysed by chromatography of products of ignition at 1200°C, wt.%) is: Al2O3 1.03, Mn2O3 0.82, Fe2O3 51.34, P2O5 31.06, H2O 16.4, total 99.58. All iron was determined as being trivalent from a Mössbauer analysis. The empirical formula (based on 27 O apfu) is (Fe3þ 5:76Al0.18Mn3þ 0:09)Σ6.03(PO4)3.92O(OH)4.34·5.98H2O. The crystal structure (R = 0.0633) is similar to that of beraunite and is based on a heteropolyhedral framework formed by M(1–4)Ø6-octahedra (where M = Fe3+; Ø=O2– , OH– or H2O) and isolated PO4 tetrahedra, with a wide channel occupied by H2O molecules. Eleonorite is monoclinic, space group C2/c, a = 20.679(10), b = 5.148(2), c = 19.223(9) Å, β = 93.574(9)°, V = 2042.5(16) Å3 and Z = 4. The strongest reflections of the powder X-ray diffraction pattern [d,Å (I,%) (hkl)] are 10.41 (100) (200), 9.67 (38) (002), 7.30 (29) (202), 4.816 (31) (111, 004), 3.432 (18) (600, 114, 404, 313), 3.197 (18) (510, 511, 006, 314, 602), 3.071 (34) (314, 115).Item Ferrorhodonite, CaMn3Fe[Si5O15], a new mineral species from Broken Hill, New South Wales, Australia.(2016) Shchipalkina, Nadezhda V.; Chukanov, Nikita V.; Pekov, Igor V.; Aksenov, Sergey M.; McCammon, Catherine; Belakovskiy, Dmitriy I.; Britvin, Sergey N.; Koshlyakova, Natalya N.; Schäfer, Christof; Cipriano, Ricardo Augusto Scholz; Rastsvetaeva, Ramiza K.The new mineral ferrorhodonite, a Mn2+–Fe2+ ordered analogue of rhodonite with the idealized formula CaMn3Fe[Si5O15], was found in the manganese-rich metamorphic rocks of the Broken Hill Pb–Zn–Ag deposit, Yancowinna Co., New South Wales, Australia. Ferrorhodonite occurs as brownish red coarsely crystalline aggregates in association with galena, chalcopyrite, spessartine, and quartz. The mineral is brittle. Its Mohs hardness is 6. Cleavage is perfect on {201} and good on {021} and {210}. The measured and calculated values of density are 3.71 (2) and 3.701 g cm−3, respectively. Ferrorhodonite is optically biaxial positive, with α = 1.731 (4), β = 1.736 (4), γ = 1.745 (5) and 2 V (meas.) = 80 (10)°. The average chemical composition of ferrorhodonite is (electronmicroprobe data, wt%): CaO 7.09, MgO 0.24, MnO 32.32, FeO 14.46, ZnO 0.36, SiO2 46.48, and total 100.95. The empirical formula calculated on 15 O apfu (Z = 2) is Ca0 . 81Mn2.92Fe1.29Mg0.04Zn0.03Si4.96O15. The Mössbauer and IR spectra are reported. The strongest reflections in the powder X-ray diffraction pattern [(d, Å (I, %) (hkl)] are: 3.337 (32) (−1–13), 3.132 (54) (−210), 3.091 (41) (0–23), 2.968 (100) (−2–11), 2.770 (91) (022), 2.223 (34) (−204), 2.173 (30) (−310). Ferrorhodonite is isostructural with rhodonite. The crystal structure was solved based on single-crystal X-ray diffraction data and refined to R1 = 4.02% [for 3114 reflections with I > 2σ(I)]. The mineral is triclinic, space group P ¯ 1, a = 6.6766 (5), b = 7.6754 (6), c = 11.803 (1) Å, α = 105.501 (1)°, β = 92.275 (1)°, γ = 93.919 (1)°; V = 580.44 (1). The crystal-chemical formula of ferrorhodonite inferred to be: M5(Ca0.81Mn0.19) M1−3(Mn2.52Fe0.48) M4(Fe20.+81Mn0.12Mg0.04Zn0.03) [Si5O15]. .