Magnesiohögbomite-2N4S: A new polysome from the central Sør Rondane Mountains, East Antarctica
-
Toshiaki Shimura
,
Junji Akai
Abstract
Högbomite-group minerals are complex Fe-Mg-Zn-Al-Ti oxides related to the spinel group. Their polysomatic structure is composed of spinel (S) and nolanite (N) modules. The new polysome magnesiohögbomite-2N4S (IMA 2010-084) was found in the Sør Rondane Mountains, East Antarctica. It occurs in Mg-Al-rich, Si-poor skarns, characterized by a corundum-spinel-phlogopite-clinochlore assemblage. The new magnesiohögbomite polysome formed during the retrograde metamorphic stage.
Magnesiohögbomite-2N4S appears macroscopically orange red, the streak is light orange colored. Euhedral crystals are hexagonal plates or prisms with cleavage planes on {001}. The mineral is optically uniaxial (-) and pleochroic with O = reddish brown and E = pale brown. The mean refractive index calculated from reflectance data in air at 589 nm is 1.85(3). The calculated density is 3.702(2) g/cm3. The Mohs hardness is 6.5-7, and VHN300 = 1020-1051, mean 1032 kg/mm2.
The crystal structure of the new polysome magnesiohögbomite-2N4S has been solved and refined (R1 = 2.74%) from single-crystal XRD data. The crystal chemical formula is T10M24O46(OH)2 where T and M represent tetrahedral and octahedral sites. The mineral is hexagonal, space group P63mc (no. 186), a = 5.71050(10), c = 27.6760(4) Å, Z = 1, V = 781.60(2) Å3. The strongest lines in the powder XRD pattern [d (Å), I (%), hkl] are: 2.8561(4), 37, 110; 2.6120(3), 39, 109; 2.42818(16), 100, 116; 2.4160(4), 39, 1010; 2.01181(13), 50, 208; 1.54892(16), 35, 2110; 1.42785(6), 57, 220. Strongest peaks in Raman spectra are at 302, 419, 479, 498, 709, 780, and 872 cm-1, with a broad OH-characteristic absorption around 3400 cm-1. The mean chemical composition (wt%) is SiO2 0.05, TiO2 7.08, SnO2 0.15, Al2O3 66.03, Cr2O3 0.02, Fe2O3 0.50, FeO 4.87, MnO 0.06, MgO 18.71, CaO 0.01, ZnO 0.96, NiO 0.01, CoO 0.02, F 0.06, Cl 0.01, H2O 1.00, sum 99.51. The simplified formula is (Mg8.2Fe1.2Zn0.2)2+(Al22.7Fe0.1)3+ Ti4+1.6O46(OH)2 and ideal formula is Mg10Al22Ti2O46(OH)2. This mineral is a solid solution between the two ideal end-members, (Mg,Fe,Zn)102+(Al,Fe)223+Ti24+O46(OH)2 and (Mg,Fe,Zn)82+(Al,Fe)263+O46(OH)2.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Redetermination of the structure of 5C pyrrhotite at low temperature and at room temperature
- Thermal elastic behavior of CaSiO3-walstromite: A powder X-ray diffraction study up to 900 °C
- Magnesiohögbomite-2N4S: A new polysome from the central Sør Rondane Mountains, East Antarctica
- Hanjiangite, a new barium-vanadium phyllosilicate carbonate mineral from the Shiti barium deposit in the Dabashan region, China
- Combined neutron and X-ray diffraction determination of disorder in doped zirconolite-2M
- Focused ion beam preparation and characterization of single-crystal samples for high-pressure experiments in the diamond-anvil cell
- Phase stability and elastic properties of the NAL and CF phases in the NaMg2Al5SiO12 system from first principles
- Redistribution of REE, Y, Th, and U at high pressure: Allanite-forming reactions in impure meta-quartzites (Sesia Zone, Western Italian Alps)
- MAS NMR measurements and ab initio calculations of the 29Si chemical shifts in dumortierite and holtite
- Aluminum ordering and clustering in Al-rich synthetic phlogopite: {1H} → 29Si CPMAS HETCOR spectroscopy and atomistic calculations
- Cell assemblies for reproducible multi-anvil experiments (the COMPRES assemblies)
- Recrystallization rims in zircon (Valle d’Arbedo, Switzerland): An integrated cathodoluminescence, LA-ICP-MS, SHRIMP, and TEM study
- Temperature and humidity effects on ferric sulfate stability and phase transformation
- Unraveling complex <2 μm clay mineralogy from soils using X-ray diffraction profile modeling on particle-size sub-fractions: Implications for soil pedogenesis and reactivity
- Variations in elastic and anelastic properties of Co3O4 due to magnetic and spin-state transitions
- High-pressure behavior of space group P2/n omphacite
- Twinning in pyromorphite: The first documented occurrence of twinning by merohedry in the apatite supergroup
- Spectroscopic characterization of alkali-metal exchanged natrolites
- Coupled (Li+, Al3+) substitutions in hydrous forsterite
- Crystal chemistry of trioctahedral micas-2M1 from Bunyaruguru kamafugite (southwest Uganda)
- Menchettiite, AgPb2.40Mn1.60Sb3As2S12, a new sulfosalt belonging to the lillianite series from the Uchucchacua polymetallic deposit, Lima Department, Peru
- Adolfpateraite, K(UO2)(SO4)(OH)(H2O), a new uranyl sulphate mineral from Jáchymov, Czech Republic
- Amorphous materials: Properties, structure, and durability
- Amorphous materials: Properties, structure, and durability
- Letter. Determination of the oxidation state of Cu in substituted Cu-In-Fe-bearing sphalerite via μ-XANES spectroscopy
- Letter. Morphological quantification of hierarchical geomaterials by X-ray nano-CT bridges the gap from nano to micro length scales
