Crystal structure determination of anandite-2M mica
-
Thomas J. Bujnowski
und
Toshio Kato
Abstract
Anandite, a trioctahedral mica, has an ideal chemical formula of Ba(FeMg)3(SiFe3+)O10(OH)S and a microprobe-derived formula of (Ba0.96K0.03Na0.01)Σ=1.00(Fe2+2.01Mg0.46Fe3+0.28Al0.10Mn3+0.04Mn2+0.04 Ti0.01)Σ=2.93(Si2.60Fe3+1.40)Σ=4.00O10[(OH)0.96S0.84Cl0.16F0.04]Σ=2.00, where S2- primarily substitutes for (OH)-. A single-crystal, X-ray structure determination of anandite-2M was refined to R1 = 0.0443 and wR2 = 0.1232 on F2 in space group Am. Cell parameters are: a = 5.4431(3), b = 9.4719(6), c = 20.042(1) Å, and β = 95.046(1)°. Layer stacking is analogous to a 1M stacking pattern (parallel unidirectional a/3 shifts within layers and octahedral set I only occupied), however cation order and (S,OH) positional disorder produce a two-layer repeat with β equaling ~95°. Subgroup symmetry of Am results from tetrahedral sheets within layers that are non-centrosymmetric with unequal compositions (Si0.61Fe3+0.39 vs. Si0.79Fe3+0.21) and thicknesses (difference of 0.209 Å), and there is positional and site-occupancy disorder (four sites with S of 0, 30, 52, and 58%) of (S,OH). Characteristics of anandite-2M, which are similar to those of anandite-2O, include (1) alternation of smaller tetrahedral rings containing four Si-rich tetrahedra (T1a: 1.643 Å, T2b: 1.657 Å) and two Fe3+-rich tetrahedra (T2a: 1.733 Å, T1b: 1.760 Å) and larger rings containing four Fe3+-rich tetrahedra and two Si-rich tetrahedra within each layer; (2) nearly in-phase wave forms of basal O atoms across the interlayer (Δz = -0.110 and 0.011 Å and across the interlayer Δz = -0.121 and 0.007 Å); and (3) attraction that results in Ba being shifted toward S (0.070 Å) and S being shifted toward Ba (0.117 Å average) along the c axis, relative to the ideal. Bond-valence calculations show that Ba is shifted toward the undersaturated, bridging-basal O atoms of the Fe3+-rich tetrahedra and toward S-rich sites to achieve charge balance. Comparison of anandite-2M and anandite-2O shows that they possess unit cells (2M setting) that have nearly equal a axes, unequal b and c axes, and β (anandite-2M is smaller by 0.0371 Å, larger by 0.08 Å, and smaller by 0.089°, respectively). Moreover, anandite-2O exhibits larger Fe3+-rich tetrahedral rings than anandite-2M, which allow for a greater shift in Ba (difference of 0.03 Å). The ordering and consequent absence of a twofold axis in anandite-2M allows the in-phase wave structure of basal O atoms, which was previously thought only possible in the orthorhombic P cell.
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
- Bonded interactions in silica polymorphs, silicates, and siloxane molecules
- Spatially heterogeneous burial and high-P/T metamorphism in the Crescent Formation, Olympic Peninsula, Washington
- Quantitative microstructural characterization of natrojarosite scale formed during high-pressure acid leaching of lateritic nickel ore
- Magnetic and microscopic characterization of magnetite nanoparticles adhered to clay surfaces
- Single crystal growth of wadsleyite
- Elastic behavior and phase stability of pollucite, a potential host for nuclear waste
- Crystal structure determination of anandite-2M mica
- Excess heat capacity and entropy of mixing in high structural state plagioclase
- Cannibalization of an amphibole-rich andesitic progenitor induced by caldera-collapse during the Matahina eruption: Evidence from amphibole compositions
- Experimental constraints on rutile saturation during partial melting of metabasalt at the amphibolite to eclogite transition, with applications to TTG genesis
- Mineralogical stability of phyllosilicates in hyperalkaline fluids: Influence of layer nature, octahedral occupation and presence of tetrahedral Al
- Plumbophyllite, a new species from the Blue Bell claims near Baker, San Bernardino County, California
- Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses
- Mineral chemistry and alteration of rare earth element (REE) carbonates from alkaline pegmatites of Mount Malosa, Malawi
- The carbonatation of gypsum: Pathways and pseudomorph formation
- Calcium L2,3-edge XANES of carbonates, carbonate apatite, and oldhamite (CaS)
- Thermochemistry of a synthetic Na-Mg-rich triple-chain silicate: Determination of thermodynamic variables
- Change in compressibility of δ-AlOOH and δ-AlOOD at high pressure: A study of isotope effect and hydrogen-bond symmetrization
- Crystal structure and iron topochemistry of erionite-K from Rome, Oregon, U.S.A.
- First-principles energetics and structural relaxation of antigorite
- Letter. Evidence in favor of small amounts of ephemeral and transient water during alteration at Meridiani Planum, Mars
- Letter. Native aluminum: Does it exist?
- Letter. Hydration state and activity of aqueous silica in H2O-CO2 fluids at high pressure and temperature
Artikel in diesem Heft
- Bonded interactions in silica polymorphs, silicates, and siloxane molecules
- Spatially heterogeneous burial and high-P/T metamorphism in the Crescent Formation, Olympic Peninsula, Washington
- Quantitative microstructural characterization of natrojarosite scale formed during high-pressure acid leaching of lateritic nickel ore
- Magnetic and microscopic characterization of magnetite nanoparticles adhered to clay surfaces
- Single crystal growth of wadsleyite
- Elastic behavior and phase stability of pollucite, a potential host for nuclear waste
- Crystal structure determination of anandite-2M mica
- Excess heat capacity and entropy of mixing in high structural state plagioclase
- Cannibalization of an amphibole-rich andesitic progenitor induced by caldera-collapse during the Matahina eruption: Evidence from amphibole compositions
- Experimental constraints on rutile saturation during partial melting of metabasalt at the amphibolite to eclogite transition, with applications to TTG genesis
- Mineralogical stability of phyllosilicates in hyperalkaline fluids: Influence of layer nature, octahedral occupation and presence of tetrahedral Al
- Plumbophyllite, a new species from the Blue Bell claims near Baker, San Bernardino County, California
- Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses
- Mineral chemistry and alteration of rare earth element (REE) carbonates from alkaline pegmatites of Mount Malosa, Malawi
- The carbonatation of gypsum: Pathways and pseudomorph formation
- Calcium L2,3-edge XANES of carbonates, carbonate apatite, and oldhamite (CaS)
- Thermochemistry of a synthetic Na-Mg-rich triple-chain silicate: Determination of thermodynamic variables
- Change in compressibility of δ-AlOOH and δ-AlOOD at high pressure: A study of isotope effect and hydrogen-bond symmetrization
- Crystal structure and iron topochemistry of erionite-K from Rome, Oregon, U.S.A.
- First-principles energetics and structural relaxation of antigorite
- Letter. Evidence in favor of small amounts of ephemeral and transient water during alteration at Meridiani Planum, Mars
- Letter. Native aluminum: Does it exist?
- Letter. Hydration state and activity of aqueous silica in H2O-CO2 fluids at high pressure and temperature
