| 1. |
- Ghignone, Stefano, et al.
(författare)
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The Raman spectrum of florencite-(REE) [REEAl3(PO4)2(OH)6] : An integrated experimental and computational approach
- 2023
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555.
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Tidskriftsartikel (refereegranskat)abstract
- Florencite is a hydrous light rare-earth elements (LREE) aluminium phosphate [REEAl3(PO4)2(OH)6], that amongst the REE-rich minerals is quite common. The main end-members are Ce-, La- and Nd-rich terms that were found in several genetic environments. Despite the large occurrence worldwide, to the authors' knowledge, florencite has attracted very few studies, particularly concerning the characterization of its Raman spectrum. We present a detailed study of the Raman spectrum of florencite, combining experimental measurements and theoretical calculations. Experimental Raman spectra (in the 100–1300 cm−1 spectral range) are measured on four florencite samples characterized by different chemical composition, that is, different REE abundance. The results highlight a remarkable coincidence between different Raman spectra measured on each sample, despite the significantly different chemical compositions in terms of their REE content. The same similarities were also observed in the computed spectra at the ab initio level; moreover, the calculations allowed the attributions of the different Raman signals to specific vibrational modes.
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| 2. |
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| 3. |
- Bosi, Ferdinando, et al.
(författare)
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Experimental cation redistribution in the tourmaline lucchesiite, CaFe2+3Al6(Si6O18)(BO3)3(OH)3O
- 2018
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Ingår i: Physics and chemistry of minerals. - : Springer Science and Business Media LLC. - 0342-1791 .- 1432-2021. ; 45:7, s. 621-632
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Tidskriftsartikel (refereegranskat)abstract
- Natural Mg-rich lucchesiite was thermally treated in air and hydrogen atmosphere up to 800 °C to study potential changes in Fe-, Mg- and Al ordering over the octahedrally coordinated Y- and Z -sites, and to explore possible applications to intracrystalline geothermometry based on tourmaline. Overall, the experimental data (structural refinement, Mössbauer, infrared and optical absorption spectroscopy) show that thermal treatment of lucchesiite results in an increase of Fetot contents at Z balanced by an increase of Mg and Al at Y . This process is accompanied by a significant deprotonation of the O3 anion site. The Fe order–disorder reaction depends more on temperature, than on redox conditions. During heat treatment in H2 ,reduction of Fe3+ to Fe2+ was not observed despite strongly reducing conditions, indicating that the fO2 conditions do not exclusively control the Fe oxidation state at the present experimental conditions. On the basis of this and previous studies, the intersite order–disorder process induced by thermal treatment indicates that Fe redistribution is an important factor for Fe–Mg–Al-exchange and is significant at temperatures around 800 °C. As a result, Fe–Mg–Al intersite order–disorder is sensitive to temperature variations, whereas geothermometers based solely on Mg–Al order–disorder appear insensitive and involve large uncertainties. The presented findings are important for interpretation of the post-crystallization history of both tourmaline and tourmaline host rocks, and indicate that successful tourmaline geothermometers may be developed by thermal calibration of the Fe-Mg–Al order–disorder reaction.
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| 4. |
- Bosi, Ferdinando, et al.
(författare)
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Lowering R3m Symmetry in Mg-Fe-Tourmalines: The Crystal Structures of Triclinic Schorl and Oxy-Dravite, and the Mineral luinaite-(OH) Discredited
- 2022
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 12:4, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Discreditation of the monoclinic tourmaline mineral species luinaite-(OH), ideally (Na,▯)(Fe2+,Mg)3Al6(BO3)3Si6O18(OH)4 was approved by the IMA-CNMNC (proposal 21-L) and is described. We analyzed two luinaite-(OH) samples: one from the type locality Cleveland tin mine, Luina, Waratah, Tasmania, Australia, and the other from Blue Mountain Saddle (Bald Hornet Claim), North Bend, King County, Washington, DC, USA. Biaxial (−) crystals representative of the studied samples were spectroscopically (Mössbauer, polarized Fourier transform infrared, optical absorption spectroscopy), chemically (nuclear microprobe analysis and electron microprobe analysis), and structurally characterized (single-crystal X-ray diffraction). Results show the occurrence of a triclinic structure for the studied luinaite-(OH) samples, which differs only in terms of a slight structural distortion from typical trigonal tourmaline structure (the topology of the structure is retained). As a result, following the IMA-CNMNC and tourmaline nomenclature rules, the triclinic luinaite-(OH) from the type locality (Australia) can be considered as the triclinic dimorph of schorl, as its chemical composition corresponds to schorl, and thus it should be referred as schorl-1A. Similarly, the triclinic sample from the USA can be considered as the triclinic dimorph of oxy-dravite, as its chemical composition corresponds to oxy-dravite, and then is referred to as oxy-dravite-1A.
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| 5. |
- Bosi, Ferdinando, et al.
(författare)
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Mn-bearing purplish-red tourmaline from the Anjanabonoina pegmatite, Madagascar
- 2021
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Ingår i: Mineralogical magazine. - : Mineralogical Society. - 0026-461X .- 1471-8022. ; 85:2, s. 242-253
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Tidskriftsartikel (refereegranskat)abstract
- A gem-quality purplish-red tourmaline sample of alleged liddicoatitic composition from the Anjanabonoina pegmatite, Madagascar, hasbeen fully characterised using a multi-analytical approach to define its crystal-chemical identity. Single-crystal X-ray diffraction, chem-ical and spectroscopic analysis resulted in the formula: X(Na0.41□0.35Ca0.24)Σ1.00Y(Al1.81Li1.00Fe3+0.04Mn3+0.02Mn2+0.12Ti0.004)Σ3.00ZAl6[T(Si5.60B0.40)Σ6.00O18](BO3)3(OH)3W[(OH)0.50F0.13O0.37]Σ1.00, which corresponds to the tourmaline species elbaite having the typical space group R3m and relatively small unit-cell dimensions, a= 15.7935(4) Å, c= 7.0860(2) Å and V= 7.0860(2) Å3.Optical absorption spectroscopy showed that the purplish-red colour is caused by minor amounts of Mn3+(Mn2O3= 0.20 wt.%).Thermal treatment in air up to 750°C strongly intensified the colour of the sample due to the oxidation of all Mn2+ to Mn3+ (Mn2O3 up to 1.21 wt.%). Based on infrared and Raman data, a crystal-chemical model regarding the electrostatic interaction betweenthe X cation and W anion, and involving the Y cations as well, is proposed to explain the absence or rarity of the mineral species ‘liddicoatite’.
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| 6. |
- Cámara, Fernando, et al.
(författare)
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As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy: IV. Lombardoite, Ba2Mn3+(AsO4)2(OH) and aldomarinoite, Sr2Mn3+(AsO4)2(OH), description and crystal structure
- 2022
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Ingår i: Mineralogical magazine. - : Mineralogical Society. - 0026-461X .- 1471-8022. ; 86:3, s. 447-458
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Tidskriftsartikel (refereegranskat)abstract
- Lombardoite, ideally Ba2Mn3+(AsO4)2(OH), and aldomarinoite, ideally Sr2Mn3+(AsO4)2(OH), are two new minerals of the arsenbrackebuschite group in the brackebuschite supergroup, discovered in Fe–Mn ore in metaquartzites of the abandoned mine of Valletta, Canosio, Val Maira, Cuneo Province, Piedmont, Italy. They occur as red–brown and orange brown, respectively, as subhedral crystals (< 0.5 mm) in thin masses, associated with quartz, aegirine, baryte, calcite, hematite, muscovite and Mn minerals such as cryptomelane, braunite and manganberzeliite. Both minerals are translucent, have yellow–orange streak and vitreous lustre. Both are brittle. Estimated Mohs hardness is 6–6½ for lombardoite (by analogy to canosioite), and 4½–5 for aldomarinoite (by analogy to tokyoite). Calculated densities are 5.124 g/cm3 for lombardoite and 4.679 g/cm3 for aldomarinoite. Both minerals are biaxial (+). Lombardoite shows 2Vz(meas.) = 78(4)° and is pleochroic with X = yellowish brown, Y = brown and Z = reddish brown (Z > Y > X). Aldomarinoite has 2Vz(meas.) = 67.1(1)°, and is pleochroic with X = brown, Y = brownish orange and Z = yellowish brown (Z > Y > X). Point analyses by electron microprobe using wavelength dispersive spectroscopy resulted in the empirical formula (based on 9 O anions): (Ba1.96Sr0.17Pb0.04Na0.02Ca0.02)Σ2.21(Mn3+0.62Fe3+0.13Al0.06Mg0.11)Σ0.92[(As0.87V0.12P0.01)Σ1.00O4]2(OH) for lombardoite, and (Sr1.93Ca0.21Ba0.04Pb0.01)Σ2.19(Mn3+0.48Al0.35Fe3+0.21Mg0.01)Σ1.05[(As0.92V0.03)Σ0.95O4]2(OH) for aldomarinoite. The absence of H2O was confirmed by Raman spectroscopy and infrared spectroscopy. Both minerals are monoclinic, P21/m, with unit-cell parameters a = 7.8636(1) Å, b = 6.13418(1) Å, c = 9.1197(1) Å, β = 112.660(2)° and V = 405.94(1) Å3, for lombardoite and a = 7.5577(4) Å, b = 5.9978(3) Å, c = 8.7387(4) Å, β = 111.938(6)° and V = 367.43(3) Å3, for aldomarinoite. The eight strongest powder X-ray diffraction lines are [d, Å (Irel) (hkl)]: 6.985 (39) (10$\bar{1}$), 3.727 (33) (111), 3.314 (100) (21$\bar{1}$), 3.073 (24) (020), 3.036 (33) (21$\bar{2}$, 10$\bar{3}$), 2.810 (87) (12$\bar{1}$, 112), 2.125 (20) (301, 11$\bar{4}$) and 1.748 (24) (321) for lombardoite and 3.191 (89) (21$\bar{1}$), 2.997 (45) (020), 2.914 (47) (21$\bar{2}$, 10$\bar{3}$), 2.715 (100) (112), 2.087 (39) (12$\bar{3}$, 1.833 (32) (31$\bar{4}$), 1.689 (36) (321), 1.664 (21) (132) for aldomarinoite. The minerals are isostructural with brackebuschite: infinite chains of edge sharing octahedra running parallel to the b axis and decorated with AsO4 groups are connected along the a and c axes through Ba and Sr atoms in lombardoite and aldomarinoite, respectively. The minerals are named after Bruno Lombardo (1944–2014), geologist and petrologist at C.N.R. (National Research Council of Italy), and Aldo Marino (b. 1942) the mineral collector and founding member of the AMI – Italian Micromineralogical Association.
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| 7. |
- Cámara, Fernando, et al.
(författare)
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Schorl-1A from Langesundsfjord (Norway)
- 2022
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Ingår i: Journal of Geosciences. - : Czech Geological Society. - 1802-6222 .- 1803-1943. ; 67:2, s. 129-139
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Roth, Phiippe, et al.
(författare)
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Rüdlingerite, Mn2+2V5+As5+O7·2H2O, a New Species Isostructural with Fianelite
- 2020
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 10:11, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The new mineral species rüdlingerite, ideally Mn2+2V5+As5+O7·2H2O, occurs in the Fianel mine, in Val Ferrera, Grisons, Switzerland, a small Alpine metamorphic Mn deposit. It is associated with ansermetite and Fe oxyhydroxide in thin fractures in Triassic dolomitic marbles. Rüdlingerite was also found in specimens recovered from the dump of the Valletta mine, Canosio, Cuneo, Piedmont, Italy, where it occurs together with massive braccoite and several other As- and V-rich phases in richly mineralized veins crossing the quartz-hematite ore. The new mineral displays at both localities yellow to orange, flattened elongated prismatic, euhedral crystals measuring up to 300 μm in length. Electron-microprobe analysis of rüdlingerite from Fianel gave (in wt%): MnO 36.84, FeO 0.06, As2O5, 25.32, V2O5 28.05, SiO2 0.13, H2Ocalc 9.51, total 99.91. On the basis of 9 O anions per formula unit, the chemical formula of rüdlingerite is Mn1.97(V5+1.17 As0.83Si0.01)Σ2.01O7·2H2O. The main diffraction lines are [dobs in Å (Iobs) hkl]: 3.048 (100) 022, 5.34 (80) 120, 2.730 (60) 231, 2.206 (60) 16-1, 7.28 (50) 020, 2.344 (50) 250, 6.88 (40) 110, and 2.452 (40) 320. Study of the crystal structure showcases a monoclinic unit cell, space group P21/n, with a = 7.8289(2) Å, b = 14.5673(4) Å, c = 6.7011(2) Å, β = 93.773(2)°, V = 762.58(4) Å3, Z = 4. The crystal structure has been solved and refined to R1 = 0.041 on the basis of 3784 reflections with Fo > 4σ(F). It shows Mn2+ hosted in chains of octahedra that are subparallel to [-101] and bound together by pairs of tetrahedra hosted by V5+ and As5+, building up a framework. Additional linkage is provided by hydrogen-bonding through H2O coordinating Mn2+ at the octahedra. One tetrahedrally coordinated site is dominated by V5+, T(1)(V0.88As0.12), corresponding to an observed site scattering of 24.20 electrons per site (eps), whereas the second site is strongly dominated by As5+, T(2)(As0.74V0.26), with, accordingly, a higher observed site scattering of 30.40 eps. The new mineral has been approved by the IMA-CNMNC and named for Gottfried Rüdlinger (born 1919), a pioneer in the 1960–1980s, in the search and study of the small minerals from the Alpine manganese mineral deposits of Grisons.
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