Crystal chemistry of the magnetite-ulvöspinel series
-
Ferdinando Bosi
,
Ulf Hålenius
Abstract
Spinel single crystals of 19 compositions along the magnetite-ulvöspinel join were synthesized by use of a flux-growth method. To obtain quantitative site populations, the crystals were analyzed by single-crystal X-ray diffraction, electron-microprobe techniques, and Mössbauer spectroscopy. All results were processed by using an optimization model. The unit-cell parameter, oxygen fractional coordinate, and tetrahedral bond length increase with increasing ulvöspinel component, whereas the octahedral bond length decreases marginally. These changes result in sigmoidal crystal-chemical relationships consistent with cation substitutions in fully occupied sites. As a first approximation, the Akimoto model T(Fe3+1-XFe2+x)M(Fe2+Fe3+1-XTiX)O4 describes the cation substitutions. Deviations from this model can be explained by an electron exchange reaction TFe2+ + MFe3+ = TFe3+ + MFe2+, which causes MFe2+ ≠ 1 and TFe2+/Ti ≠ 1. The resultant S-shaped trends may be related to a directional change in the electron exchange reaction at Ti ≈ 0.7 apfu. In general, variations in structural parameters over the whole compositional range can be split into two contributions: (1) a linear variation due to the TFe3+ + MFe3+ = TFe2+ + MTi4+ chemical substitution and (2) non-linear variations caused by the internal electron exchange reaction.
In accordance with bond-valence theory, strained bonds ascribable to steric effects characterize the structure of magnetite-ulvöspinel crystals. To relax the bonds and thereby minimize the internal strain under retained spinel space group symmetry, the electron exchange reaction occurs.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Amorphous materials: Properties, structure, and durability. The viscosity of hydrous NaAlSi3O8 and granitic melts: Configurational entropy models
- Alteration mineralogy and the effect of acid-leaching on the Pb-isotope systematics of ocean-island basalts
- Color origin and heat evidence of paleontological bones: Case study of blue and gray bones from San Josecito Cave, Mexico
- Coexistence of pyroxenes jadeite, omphacite, and diopside/hedenbergite in an albite-omphacite rock from a serpentinite mélange in the Kurosegawa Zone of Central Kyushu, Japan
- Amphibole equilibria in mantle rocks: Determining values of mantle aH2O and implications for mantle H2O contents
- Experimental fluoridation of nanocrystalline apatite
- Dehydration dynamics of barrerite: An in situ synchrotron XRPD study
- Structural features in Tutton’s salts K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn
- Incorporation of water in iron-free ringwoodite: A first-principles study
- Temperature dependence of reflectance spectra and color values of hematite by in situ, high-temperature visible micro-spectroscopy
- Lattice thermal expansion of zircon-type LuPO4 and LuVO4: A comparative study
- Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 °C and pressure from 50 to 500 MPa
- Multi-analytical approach to solve the puzzle of an allanite-subgroup mineral from Kesebol, Västra Götaland, Sweden
- Dislocation modeling in calcium silicate perovskite based on the Peierls-Nabarro model
- Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites
- Adding further complexity to the polybasite structure: The role of Ag in the B layer of the -M2a2b2c polytype
- Structural position of H2O molecules and hydrogen bonding in anomalous 11 Å tobermorite
- Electronic structures of siderite (FeCO3) and rhodochrosite (MnCO3): Oxygen K-edge spectroscopy and hybrid density functional theory
- Crystal growth and the fast reaction paradox: Mathematical resolution and implications for habit and compositional zoning
- The composition of KLB-1 peridotite
- Crystal chemistry of the magnetite-ulvöspinel series
- New insights into the crystal structure and crystal chemistry of the zeolite phillipsite
- Letter: Octahedral cation distribution in palygorskite
Articles in the same Issue
- Amorphous materials: Properties, structure, and durability. The viscosity of hydrous NaAlSi3O8 and granitic melts: Configurational entropy models
- Alteration mineralogy and the effect of acid-leaching on the Pb-isotope systematics of ocean-island basalts
- Color origin and heat evidence of paleontological bones: Case study of blue and gray bones from San Josecito Cave, Mexico
- Coexistence of pyroxenes jadeite, omphacite, and diopside/hedenbergite in an albite-omphacite rock from a serpentinite mélange in the Kurosegawa Zone of Central Kyushu, Japan
- Amphibole equilibria in mantle rocks: Determining values of mantle aH2O and implications for mantle H2O contents
- Experimental fluoridation of nanocrystalline apatite
- Dehydration dynamics of barrerite: An in situ synchrotron XRPD study
- Structural features in Tutton’s salts K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn
- Incorporation of water in iron-free ringwoodite: A first-principles study
- Temperature dependence of reflectance spectra and color values of hematite by in situ, high-temperature visible micro-spectroscopy
- Lattice thermal expansion of zircon-type LuPO4 and LuVO4: A comparative study
- Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 °C and pressure from 50 to 500 MPa
- Multi-analytical approach to solve the puzzle of an allanite-subgroup mineral from Kesebol, Västra Götaland, Sweden
- Dislocation modeling in calcium silicate perovskite based on the Peierls-Nabarro model
- Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites
- Adding further complexity to the polybasite structure: The role of Ag in the B layer of the -M2a2b2c polytype
- Structural position of H2O molecules and hydrogen bonding in anomalous 11 Å tobermorite
- Electronic structures of siderite (FeCO3) and rhodochrosite (MnCO3): Oxygen K-edge spectroscopy and hybrid density functional theory
- Crystal growth and the fast reaction paradox: Mathematical resolution and implications for habit and compositional zoning
- The composition of KLB-1 peridotite
- Crystal chemistry of the magnetite-ulvöspinel series
- New insights into the crystal structure and crystal chemistry of the zeolite phillipsite
- Letter: Octahedral cation distribution in palygorskite
