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 Wilancookite, (Ba,K,Na)8(Ba,Li,[])6Be24P24O96·32H2O, a new 2 beryllophosphate with a zeolite framework.(2017) Hatert, Frédéric; Philippo, Simon; Ottolini, Luisa; Bol, Fabrice Dal; Cipriano, Ricardo Augusto Scholz; Chaves, Mario Luiz de Sá Carneiro; Yang, Hexiong; Downs, Robert T.; Menezes Filho, Luiz Alberto DiasWilancookite, ideally (Ba,K,Na)8(Ba,Li,[])6Be24P24O96·32H2O, is a new mineral species from the Lavra Ponte do Piauí 19 complex granitic pegmatite, Minas Gerais, Brazil. It occurs as tiny dodecahedral {1 1 0} crystals, deposited on moraesite fibres. 20 Associated primary minerals are albite, montebrasite, Li-bearing micas, cassiterite, elbaite and quartz, while the secondary phosphate 21 association contains fluorapatite, childrenite, eosphorite, zanazziite, greifenstenite, guimarãesite, ushkovite, saléeite and moraesite. 22 The mineral is transparent and colourless, with a vitreous lustre; it is non-fluorescent, brittle, and its streak is white. The estimated 23 Mohs hardness is 4–5, and the calculated density is 3.05 g/cm3.Wilancookite is isotropic, colourless, non-pleochroic, with n = 1.560(2) 24 (measured under l = 590nm). Electron- and ion-microprobe analyses give (in wt%): P2O5 36.19, SiO2 0.04, Al2O3 0.41, BaO 25 34.65, Na2O 0.09, K2O 0.32, BeO 12.86, Li2O 0.50, and H2Ocalc 12.31, total 97.37wt%. The resulting empirical formula, calculated 26 on the basis of 96 anhydrous oxygen atoms, is (Ba7.54K0.32Na0.14)S8.00(Ba3.04Li1.57[]1.39)S6.00Be24.08(P23.88Al0.38Si0.03)S24.29 27 O96·32H2O. The single-crystal unit-cell parameters are a = 13.5398(2)A and V = 2482.21(7), space group I23. The eight strongest 28 lines in the powder X-ray diffraction pattern [d(in A )(I)(hkl)] are: 6.90(60)(2 0 0), 5.54(80)(2 1 1), 3.630(60)(3 2 1, 3 1 2), 3.212(70) 29 (3 3 0, 4 1 1), 3.043(100)(4 2 0, 4 0 2), 2.885(70)(3 3 2), 2.774(80)(4 2 2), and 2.398(60)(4 4 0). The crystal structure of wilancookite 30 has been refined, based on single-crystal X-ray diffraction data, to R1 = 4.58%; the beryllophosphate framework is similar to that 31 occurring in pahasapaite, and is based on zeolite-RHO cages. The mineral species and name were approved by the Commission on 32 New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2015-034).Item Magnesiovoltaite, K2Mg5Fe3+3Al(SO4)12·18H2O, a new mineral from the Alcaparrosa mine, Antofagasta region, Chile.(2016) Chukanov, Nikita V.; Aksenov, Sergey M.; Rastsvetaeva, Ramiza K.; Möhn, Gerhard; Rusako, Vyacheslav S.; Pekov, Igor V.; Cipriano, Ricardo Augusto Scholz; Eremina, Tatiana Alekseevna; Belakovskiy, Dmitriy I.; Lorenz, Joachim A.Magnesiovoltaite, a new voltaite-group mineral, was discovered in the Alcaparrosa mine, Cerro Alcaparrosa, El Loa province, Antofagasta region, Chile, in two associations, one of which includes coquimbite, tamarugite, alum-(Na), rhomboclase, yavapaiite, voltaite and opal, and the other one is botryogen, opal, tamarugite, alum-(K), pickeringite, magnesiocopiapite, and jarosite. Magnesiovoltaite forms yellow, brownish-yellow or pale yellowish-greenish isometric crystals up to 2 mm across. The main crystal forms are {111} and {100}; the subordinate forms are {110} and {211}. The new mineral is brittle, with subconchoidal fracture; cleavage is not observed. Mohs’ hardness is 2½. Dmeas = 2.51(2) g/cm3, Dcalc = 2.506 g/cm3. Magnesiovoltaite is optically anomalously anisotropic, uniaxial with ε = 1.584(2) and ω = 1.588(2), or biaxial (–) with α = 1.584(2), β = 1.587(2), and γ = 1.588 (2). Possible causes of the optical anomalies are discussed. The infrared spectrum is given. The chemical composition is (EDS-mode electron microprobe, all iron is considered as Fe3+ in accordance with Mössbauer data, H2O by gas chromatography of ignition products, wt. %): Na2O 0.13, K2O 4.64, MgO 9.13, MnO 1.73, ZnO 0.84, Al2O3 2.47, Fe2O3 13.36, SO3 50.83, H2O 17.6, total 100.73. The empirical formula based on 66 O atoms per formula unit (apfu) is (K1.85Na0.08)(Mg4.25Mn0.46Zn0.14)Fe3+ 3.14Al0.91(SO4) 11.91(H2O)18.325O0.035. The simplified formula is K2Mg5Fe3+ 3Al(SO4)12·18H2O. The crystal structure has been refined to R = 3.2% using 1147 unique reflections with I > 2σ(I). Magnesiovoltaite is cubic, Fd–3c, a = 27.161(1) Å, V = 20038(2) Å3, and Z = 16. Magnesiovoltaite is isostructural with other cubic voltaite-group minerals. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 9.56 (29) (022), 6.77 (37) (004), 5.53 (61) (224), 3.532 (68) (137), 3.392 (100) (008), 3.034 (45) (048), 2.845 (30) (139). The type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia.