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@article{1848604, author = {Tvrdý, Jaromír and Plášil, Jakub and Vrtiška, Luboš and Sejkora, Jiří and Škoda, Radek and Dolníček, Zdeněk and Petr, Martin and Veselovský, František}, article_number = {3}, doi = {http://dx.doi.org/10.1180/mgm.2022.15}, keywords = {ferroberaunite; new mineral; phosphate; crystal structure; Raman spectroscopy; XPS spectroscopy; Cornwall}, language = {eng}, issn = {0026-461X}, journal = {Mineralogical Magazine}, title = {Ferroberaunite, Fe2+Fe3+5(PO4)4(OH)5·6H2O, a mixed-valence iron member of the beraunite series, from the Gravel Hill mine, Perranzabuloe, Cornwall, UK}, url = {http://doi.org/10.1180/mgm.2022.15}, volume = {86}, year = {2022} }
TY - JOUR ID - 1848604 AU - Tvrdý, Jaromír - Plášil, Jakub - Vrtiška, Luboš - Sejkora, Jiří - Škoda, Radek - Dolníček, Zdeněk - Petr, Martin - Veselovský, František PY - 2022 TI - Ferroberaunite, Fe2+Fe3+5(PO4)4(OH)5·6H2O, a mixed-valence iron member of the beraunite series, from the Gravel Hill mine, Perranzabuloe, Cornwall, UK JF - Mineralogical Magazine VL - 86 IS - 3 SP - 363-372 EP - 363-372 PB - Cambridge University Press SN - 0026461X KW - ferroberaunite KW - new mineral KW - phosphate KW - crystal structure KW - Raman spectroscopy KW - XPS spectroscopy KW - Cornwall UR - http://doi.org/10.1180/mgm.2022.15 N2 - The new mineral ferroberaunite, Fe2+Fe3+5(PO4)4(OH)5·6H2O (IMA2021–36; symbol: Fbru), occurs in cavities of ‘limonite’ iron ore from the Gravel Hill mine, Perranzabuloe, Cornwall, England, United Kingdom. Its flattened prismatic crystals up to 400 μm long are dark green to olive green, transparent to translucent, with a vitreous lustre, pearly on cleavages. The Mohs hardness is ~3–4. The density measured by the flotation method is 2.94(2) g·cm–3, the calculated density is 2.907 g·cm–3. Ferroberaunite is biaxial (–), with α = 1.736(2), β = 1.765(3), γ = 1.786(5) at 589 nm, 2Vmeas. = 68(3)°, 2Vcalc. = 79°; dispersion of optical axes is strong, r > v; orientation is Y = b; X ≈ a, Z ≈ c. Pleochroism is strong: X = bluish-green >> Z = green > Y = yellow. Electron-microprobe analyses gave the empirical formula (Fe2+0.75Ca0.01Mn0.02Fe3+0.22)Σ1.00(Fe3+4.88Al0.04)Σ4.92(PO4)4O0.11(OH)4.76·6H2O. Ferroberaunite is monoclinic, C2/c, with a = 20.8708(3), b = 5.1590(8), c = 19.2263(3) Å, β = 93.3186(17)°, V = 2066.7(3) Å3 and Z = 4. The eight strongest lines in the powder X-ray diffraction pattern are [dmeas/Å (Irel. %) (hkl)]: 10.410 (100) (200), 9.606 (14) (002), 7.271 (11) (202 ̅), 5.203 (4) (400), 3.467 (12) (600), 3.325 (6) (602 ̅), 3.201 (6) (006), 2.600 (4) (800). The mineral is isostructural with beraunite, redefined recently as Fe3+6(PO4)4O(OH)4·6H2O. ER -
TVRDÝ, Jaromír, Jakub PLÁŠIL, Luboš VRTIŠKA, Jiří SEJKORA, Radek ŠKODA, Zdeněk DOLNÍČEK, Martin PETR a František VESELOVSKÝ. Ferroberaunite, Fe2+Fe3+5(PO4)4(OH)5·6H2O, a mixed-valence iron member of the beraunite series, from the Gravel Hill mine, Perranzabuloe, Cornwall, UK. \textit{Mineralogical Magazine}. Cambridge University Press, 2022, roč.~86, č.~3, s.~363-372. ISSN~0026-461X. Dostupné z: https://dx.doi.org/10.1180/mgm.2022.15.
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