| 3. |
- Holtstam, Dan, 1963-, et al.
(författare)
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Arrheniusite-(Ce), CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11, a new member of the vicanite group, from the Östanmossa mine, Norberg, Sweden
- 2021
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Ingår i: Canadian Mineralogist. - : Geological and Mineralogical Association of Canada. - 0008-4476 .- 1499-1276. ; 59, s. 177-189
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Tidskriftsartikel (refereegranskat)abstract
- Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce) and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, up to 0.8 mm exceptionally. It is optically uniaxial (-), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85 for 2286 observed reflections [Fo > 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals, and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered as a Mg-As analog to hundholmenite-(Y). The three-fold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y), from the famous Ytterby pegmatite quarry.
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| 4. |
- Margheri, Simone, et al.
(författare)
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Structural and spectroscopic study of well-developed crystals of parahibbingite, β-Fe2(OH)3Cl, formed from terrestrial weathering of the Muonionalusta iron meteorite
- 2022
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Ingår i: Mineralogical magazine. - London : Mineralogical Society. - 0026-461X .- 1471-8022. ; 86:6, s. 891-896
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Tidskriftsartikel (refereegranskat)abstract
- Parahibbingite [β-Fe2(OH)3Cl], a new mineral recently described from ultramafic rocks in the Bushveld Complex (South Africa), has been found to form millimetric well-developed crystals as a terrestrial weathering product of the Muonionalusta iron meteorite. The mineral, initially identified by means of Raman spectroscopy, was found in a small cavity within a crust of rust on a granitic rock fragment that was in direct contact with the alteration crust of a meteorite specimen, collected in the Kitkiöjärvi area (Sweden). Its crystal structure [a = 6.9362(4), c = 14.673(1) Å, V = 611.35(7) Å3 for Z = 6] was refined from single-crystal X-ray diffraction data (R1 = 0.0331) in the space group R-3m, thus confirming the structural model of synthetic β-Fe2(OH)3Cl. It consists of a network of octahedrally coordinated Fe2+ atoms alternatively arranged in triangular and Kagomé layers, stacked along the c axis. The H position was determined, showing O-H···Cl bonds which provide a further link between layers. Parahibbingite is found to be not only an important constituent of the corrosion system of archaeological iron artefacts but can also play an important role as an alteration product of iron meteorites.
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