التفاصيل البيبلوغرافية
| العنوان: |
Anortho-schorl from Langesundsfjord (Norway) |
| المؤلفون: |
CAMARA, FERNANDO, BOSI, FERDINANDO, SKOGBY, HENRIK, HÅLENIUS, ULF, CELATA, BEATRICE, CIRIOTTI, MARCO E. |
| المساهمون: |
Ferdinando Bosi, Federico Pezzotta, Giovanni Battista Andreozzi, Camara, Fernando, Bosi, Ferdinando, Skogby, Henrik, Hålenius, Ulf, Celata, Beatrice, Ciriotti, MARCO E. |
| سنة النشر: |
2021 |
| المجموعة: |
Sapienza Università di Roma: CINECA IRIS |
| الوصف: |
Some previous studies report of optically anomalous tourmaline with biaxial character, which is incompatible with its putative R3m symmetry. A crystal fragment of sample GEO-NRM19252409 (Swedish Museum of Natural History) coming from Langesundsfjord (Norway) showing zonation with biaxial optic behavior in the rims was studied by means of electron microprobe, singlecrystal X-ray diffraction, Mössbauer, infrared and optical absorption spectroscopy and optical measurements. The latter were performed with a spindle stage in a Leitz Dialux microscope equipped with a CCD camera using Excelibr spreadsheet (Steven & Gunter, 2018), using a 30 μm thin section of the crystal cut perpendicular to c axis. Conoscopic image showed a biaxial interference figure, with negative optic sign. Measure 2Vx was 15.6° (white light). The biaxial character of the sample is not due to internal stress since it cannot be removed by heating and cooling. Orientation of the optical indicatrix was obtained using the same crystal mounting at a Rigaku XtaLAB Synergy-S diffractometer (MoKα) and showed c^X = 2°, b^Z = 164.3° and a^Z = 75.8°. Complete data collection was obtained on a full sphere up to 0.50 Å. Diffraction data were refined with a standard R3m space group model [a 16.0013(2) Å, c 7.2263(1) Å] and with a nonconventional triclinic R1 space group model from Hughes et al. (2011), keeping the same hexagonal triple cell for comparison purposes but with unconstrained unit-cell parameters: a 16.0093(5) Å, b 16.0042(5) Å, c 7.2328(2) Å, α 90.008(3)°, β 89.856(3)°, γ 119.90(9)°. Trigonal Rint = 6.6%, Rall = 1.75% (3136 unique reflections) vs. triclinic Rint = 4.1%, Rall = 2.53% (17342 unique reflections). In both structure models, protons bonded to O3 sites were located and their coordinates refined. No proton was observed close to O1, in agreement with chemistry. Crystal- chemical analysis resulted in the chemical formula (Na0.98K0.010.01)Σ1.00 Y(Fe2+ 1.73Mg0.12Al0.90Ti0.21Mn0.02V0.0 1Zn0.01)Σ3.00 Z(Al4.88Fe3+ 0.30Fe2+ ... |
| نوع الوثيقة: |
conference object |
| اللغة: |
English |
| Relation: |
ispartofbook:Natura; TUR2021 3rd International Conference on Tourmaline; firstpage:13; lastpage:14; numberofpages:2; https://hdl.handle.net/11573/1670576 |
| الاتاحة: |
https://hdl.handle.net/11573/1670576 |
| رقم الانضمام: |
edsbas.61C0D34 |
| قاعدة البيانات: |
BASE |