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- Cámara, Fernando, 1967-, et al.
(författare)
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Zinkgruvanite, Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, a new ericssonite-group mineral from the Zinkgruvan Zn-Pb-Ag-Cu deposit, Askersund, Örebro County, Sweden.
- 2021
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Ingår i: European journal of mineralogy. - : Nicolaus Copernicus University Press. - 0935-1221 .- 1617-4011. ; 33:6, s. 659-673
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Tidskriftsartikel (refereegranskat)abstract
- Zinkgruvanite, ideally Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, is a new member of the ericssonite group, found in Ba-rich drill core samples from a sphalerite+galena- and diopside-rich metatuffite succession from the Zinkgruvan mine, Örebro county, Sweden. Zinkgruvanite is associated with massive baryte, barytocalcite, diopside and minor witherite, cerchiaraite-(Al) and sulfide minerals. It occurs as subhedral to euhedral flattened and elongated crystals up to 4 mm. It is almost black, semi-opaque with a dark brown streak. The luster is vitreous to sub-adamantine on crystal faces, resinous on fractures. The mineral is brittle with an uneven fracture. VHN100 = 539 and HMohs ~4½. In thin fragments, it is reddish-black, translucent and optically biaxial (+), 2Vz > 70°. Pleochroism is strong, deep brown-red (E ⊥ {001} cleavage) to olive-pale brown. Chemical point analyses by WDS-EPMA together with iron valencies determined from Mössbauer spectroscopy, yielded the empirical formula (based on 26 O+OH+F+Cl anions): (Ba4.02Na0.03)Σ4.05(Mn1.79Fe2+1.56Fe3+0.42Mg0.14Ca0.10Ni0.01Zn0.01)Σ4.03 (Fe3+1.74Ti0.20Al0.06)Σ2.00Si4(S1.61Si0.32P0.07)Σ1.99O24(OH1.63Cl0.29F0.08)Σ2.00. The mineral is triclinic, space group P–1, with unit-cell parameters a = 5.3982(1) Å, b = 7.0237(1) Å, c = 14.8108(4) Å, α = 98.256(2)º, β = 93.379(2)º, γ = 89.985(2)º and V = 554.75(2) Å3 for Z = 1. The eight strongest X-ray powder diffraction lines are [d Å (I%; hkl)]: 3.508 (70; 103), 2.980(70; 11–4), 2.814 (68; 1–22), 2.777 (70; 121), 2.699 (714; 200), 2.680 (68; 20–1), 2.125 (100; 124, 204), 2.107 (96; –221). The crystal structure (R1 = 0.0379 for 3204 reflections) is an array of TS (titanium silicate) blocks alternating with intermediate blocks. The TS blocks consist of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the Mn2+-dominant MO(1,2,3) sites give ideally Mn2+4 pfu. In the H sheet, the Fe3+-dominant MH sites and AP(1) sites give ideally Fe3+2Ba2 pfu. In the intermediate block, SO4 oxyanions and eleven coordinated Ba atoms give ideally 2 × SO4Ba pfu. Zinkgruvanite is related to ericssonite and ferro-ericssonite in having the same topology and type of linkage of layers in the TS block. Zinkgruvanite is also closely compositionally related to yoshimuraite, Ba4Mn4Ti2(Si2O7)2(PO4)2O2(OH)2, via the coupled heterovalent substitution 2 Ti4+ + 2 (PO4)3- →2 Fe3+ + 2 (SO4)2-, but presents a different type of linkage. The new mineral probably formed during a late stage of regional metamorphism of a Ba-enriched, syngenetic protolith, involving locally generated oxidized fluids of high salinity.
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- Holtstam, Dan, 1963-, et al.
(författare)
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Ferri-taramite, a new member of the amphibole supergroup, from the Jakobsberg Mn-Fe deposit, Varmland, Sweden
- 2022
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Ingår i: European Journal of Mineralogy. - : Copernicus GmbH. - 0935-1221 .- 1617-4011. ; 34:5, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- Ferri-taramite (IMA CNMNC 2021-046), ideally Na-A(B) (CaNa)(C) (Mg3Fe23+)(Si6Al2)O-22(W) (OH)(2), occurs in skarn from the Jakobsberg manganese mine, Varmland, Sweden. Associated minerals are celsian, phlogopite, aegirine-augite, andradite, hancockite, melanotekite, microcline (var. hyalophane), calcite, baryte, prehnite, macedonite and oxyplumboromeite. Conditions of formation, close to peak metamorphism (at circa 650 degrees C and 0.4 GPa), include silica undersaturation, a slightly peralkaline character and relatively high oxygen fugacities. Ferri-taramite forms poikiloblastic crystals up to 5 mm and is dark brownish black with a yellowish grey streak. The amphibole is brittle with an uneven to splintery fracture. Cleavage parallel to {110} is good. Hardness (Mohs) is similar to 6, and D-calc = 3.227(5) g cm(-3). Holotype ferri-taramite has the experimental unit formula (A)(Na0.79K0.16Pb0.01)(Sigma 0.96)(B) (Ca1.26Na0.72Mn0.022+)(Sigma 2)(C )(Mg2.66Mn0.582+ Fe0.162+Zn0.02Fe1.263+ Al0.26Ti0.06)(Sigma)(T)(5.00) (Al1.86Si6.14)Sigma 8O(22)(W) (OH)(2), based on chemical analyses (EDS, laser-ablation ICP-MS) and spectroscopic (Mossbauer, infrared) and single-crystal X-ray diffraction data. The mineral is optically biaxial (-), with alpha = 1.670(5), beta = 1.680(5) and gamma = 1.685(5) in white light and 2 V-meas = 70(10)degrees and 2 V-calc = 70.2 degrees. Ferri-taramite is distinctly pleochroic in transmitted light, with X pale yellow, Y dark brown, Z yellowish brown and absorption Y> Z> X. The eight strongest reflections in the X-ray powder pattern (d values (in angstrom), I-rel, hkl) are 8.44, 60, 110; 3.392, 25, 131; 3.281, 39, 240; 3.140, 100, 310; 2.816, 45, 330; 2.7104, 38, 151; 1.3654, 26, 461; and 1.4451, 33, (6) over bar 61. Refined unit-cell parameters from single-crystal diffraction data are a = 9.89596(13), b = 18.015(2), c = 5.32164(7) angstrom, beta = 105.003(13)degrees and V = 916.38(2) angstrom(3) for Z = 2. Refinement of the crystal structure yielded R = 2.26 % for 2722 reflections with I-0 >2 sigma (I). The Mn2+ and Fe2+ ions show preference for the M1 and M3 octahedrally coordinated sites, whereas Fe3+ is strongly ordered at M2. The A-group cations, K and Na, are split over two subsites, A (m) and A(2), respectively.
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- Holtstam, Dan, 1963-, et al.
(författare)
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Hjalmarite, a new Na-Mn member of the amphibole supergroup, from Mn skarn in the Långban deposit, Värmland, Sweden.
- 2019
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Ingår i: European journal of mineralogy. - : Schweizerbart. - 0935-1221 .- 1617-4011. ; 31, s. 565-574
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Tidskriftsartikel (refereegranskat)abstract
- Hjalmarite, ideally ANaB(NaMn)CMg5TSi8O22W(OH)2, is a new root-name member of the amphibole supergroup, discovered in skarn from the Långban Fe-Mn-(Ba-As-Pb-Sb-Be-B) deposit, Filipstad, Värmland, Sweden (IMA-CNMNC 2017-070). It occurs closely associated with mainly rhodonite and quartz. It is grayish white with vitreous luster and non-fluorescent. The crystals are up to 5 mm in length and display splintery fracture and perfect cleavage along {110}. Hjalmarite is colorless (non-pleochroic) in thin section and optically biaxial (-), with α = 1.620(5), β = 1.630(5), γ = 1.640(5). The calculated density is 3.12 Mg/m3. Average VHN100 is 782, corresponding to circa 5½ Mohs. An empirical formula, derived from EPMA analyses in combination with crystal structure refinements, is (Na0.84K0.16)Σ1(Na1.01Mn0.55Ca0.43Sr0.01) Σ2(Mg3.83Mn1.16Al0.01) Σ5(Si7.99Al0.01) Σ8O22(OH1.92F0.08)Σ2. An infra-red spectrum of hjalmarite shows distinct absorption bands at 3673 cm-1 and 3731 cm-1 polarized in the α direction. The eight strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 3.164, 100, (310); 2.837, 50, (330); 8.50, 44, (110); 3.302; 40, (240); 1.670, 34, (461); 1.448, 32, (-661); 2.727, 30, (151); 2.183, 18 (261).Single-crystal X-ray diffraction data were collected at 298 K and 180 K. The crystal structure was refined in space group C2/m to R1=2.6% [I>2(I)], with observed unit-cell parameters a = 9.9113(3), b = 18.1361(4), c = 5.2831(5) Å, β=103.658(5)° and V = 922.80(9) Å3 at ambient temperature. The A and M(4) sites split into A(m) (K+), A(2) (Na+), and M(4’) (Mn2+) subsites, respectively. Among the octahedrally coordinated C group cations, Mn2+ orders strongly at the M(2) site. No significant violation of C2/m symmetry or change in the structure topology is detected at low temperature (R1=2.1%). The hjalmarite-bearing skarn formed at peak regional metamorphism, T ≥ 600°C, at conditions of high SiO2 activity and relatively low oxygen fugacity. The mineral name honors the Swedish geologist and mineralogist S.A. Hjalmar Sjögren (1856–1922).
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- Karlsson, Andreas, 1986-, et al.
(författare)
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Adding complexity to the garnet supergroup: monteneveite, Ca3Sb5+2(Fe3+2Fe2+)O12, a new mineral from the Monteneve mine, Bolzano Province, Italy
- 2020
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Ingår i: European Journal of Mineralogy. - : Copernicus GmbH. - 0935-1221 .- 1617-4011. ; 32:1, s. 77-87
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Tidskriftsartikel (refereegranskat)abstract
- Monteneveite, ideally Ca3Sb5+2(Fe3+2Fe2+)O12, is a new member of the garnet supergroup (IMA 2018-060). The mineral was discovered in a small specimen belonging to the Swedish Museum of Natural History coming from the now abandoned Monteneve Pb-Zn mine in Passiria Valley, Bolzano Province, Alto Adige (South Tyrol), Italy. The specimen consists of mainly magnetite, sphalerite, tetrahedrite-(Fe) and oxycalcioroméite. Monteneveite occurs as black, subhedral crystals with adamantine lustre. They are equidimensional and up to 400 μm in size, with a subconchoidal fracture. Monteneveite is opaque, grey in reflected light, and isotropic under crossed polars. Measured reflectance values (%) at the four COM wavelengths are 12.6 (470 nm), 12.0 (546 nm), 11.6 (589 nm) and 11.4 (650 nm). The Vickers hardness (VHN100/ is 1141 kgmm-2, corresponding to H D 6:5-7, and the calculated density is 4.72(1) g cm-3. A mean of 10 electron microprobe analyses gave (wt %) CaO 23.67, FeO 3.75, Fe2O3 29.54, Sb2O5 39.81, SnO2 2.22, ZnO 2.29, MgO 0.15, MnO 0.03 and CoO 0.03. The crystal chemical formula calculated on the basis of a total of eight cations and 12 anions, and taking into account the available structural and spectroscopic data, is (Ca2:97Mg0:03)6D3:00 (Sb5+1.73Sn4+0.10Fe3+0.17)6D2.00(Fe3+2.43Fe2+0.37Zn0:20)6D3:00O12. The most significant chemical variations encountered in the sample are related to a substitution of the type Y Sn4CCZFe3CY Sb5CCZFe2C. Mössbauer data obtained at RT and 77K indicate the presence of tetrahedrally coordinated Fe2C. Raman spectroscopy demonstrates that there is no measurable hydrogarnet component in monteneveite. The six strongest Bragg peaks in the powder X-ray diffraction pattern are [d (Å), I (%), (hkl)]: 4.45, 100, (220); 3.147, 60, (400); 2.814, 40, (420); 2.571, 80, (422); 1.993, 40, (620); 1.683, 60, (642). Monteneveite is cubic, space group Ia-3d, with a D 12:6093(2) Å, V D 2004:8(1)Å3, and Z D 8. The crystal structure was refined up to R1 D 0:0197 for 305 reflections with Fo 4.Fo/ and 19 parameters. Monteneveite is related to the other Ca-, Sb- and Fe-bearing, nominally Si-free members of the bitikleite group, but it differs in that it is the only known garnet species with mixed trivalent and divalent cations (2 V 1) at the tetrahedral Z site. Textural and mineralogical evidence suggests that monteneveite formed during peak metamorphism (at ca. 600 C) during partial breakdown of tetrahedrite-(Fe) by reactions with carbonate, under relatively oxidizing conditions. The mineral is named after the type locality, the Monteneve (Schneeberg) mine. © Author(s) 2020.
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