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qandilite

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Journal Article

QANDILITE FROM VESUVIUS SKARN EJECTA: CONDITIONS OF FORMATION AND MISCIBILITY GAP IN THE TERNARY SPINEL – QANDILITE – MAGNESIOFERRITE

Marie-Lola Pascal, Michel Fonteilles, Omar Boudouma, Claudia Principe
Published: 01 April 2011
The Canadian Mineralogist (2011) 49 (2): 459–485.
DOI: https://doi.org/10.3749/canmin.49.2.459
...Marie-Lola Pascal; Michel Fonteilles; Omar Boudouma; Claudia Principe Abstract Qandilite (Mg 2 TiO 4 ) and magnesioferrite occur in forsterite – spinel – calcite skarn ejecta from Mt. Vesuvius, Italy, with an exceptionally large compositional range that outlines the miscibility gap in the system...
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Crystal chemistry of the ulvöspinel-qandilite series

Ferdinando Bosi, Ulf Hålenius, Henrik Skogby
Published: 01 April 2014
American Mineralogist (2014) 99 (4): 847–851.
DOI: https://doi.org/10.2138/am.2014.4722
...Ferdinando Bosi; Ulf Hålenius; Henrik Skogby Abstract Five spinel single-crystal samples within the ulvöspinel-qandilite series [(Fe 2− x Mg x )TiO 4 , 0.15 < x < 0.94] were synthesized and structurally and chemically characterized by X-ray diffraction and electron microprobe techniques. Site...
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A computational model of cation ordering in the magnesioferrite-qandilite (MgFe 2 O 4 -Mg 2 TiO 4 ) solid solution and its potential application to titanomagnetite (Fe 3 O 4 -Fe 2 TiO 4 )

Richard J. Harrison, Erika J. Palin, Natasha Perks
Published: 01 April 2013
American Mineralogist (2013) 98 (4): 698–708.
DOI: https://doi.org/10.2138/am.2013.4318
...Richard J. Harrison; Erika J. Palin; Natasha Perks Abstract Cation ordering in the magnesioferrite-qandilite (MgFe 2 O 4 -Mg 2 TiO 4 ) solid solution has been investigated using an interatomic potential model combined with Monte Carlo simulations. The dominant chemical interaction controlling...
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A computational study of order-disorder phenomena in Mg 2 TiO 4 spinel (qandilite)

Erika J. Palin, Andrew M. Walker, Richard J. Harrison
Published: 01 August 2008
American Mineralogist (2008) 93 (8-9): 1363–1372.
DOI: https://doi.org/10.2138/am.2008.2896
...Erika J. Palin; Andrew M. Walker; Richard J. Harrison Abstract We have used a combination of classical and quantum-mechanical atomistic calculations, together with Monte Carlo simulations, to study order-disorder phenomena in the spinel mineral qandilite, Mg 2 TiO 4 . Using an interatomic potential...
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The free energy of formation of Mg 2 TiO 4 (synthetic qandilite), an inverse spinel with configurational entropy

Hugh St. C. O'NEILL, Dean R. SCOTT
Published: 01 March 2005
European Journal of Mineralogy (2005) 17 (2): 315–323.
DOI: https://doi.org/10.1127/0935-1221/2005/0017-0315
...Hugh St. C. O'NEILL; Dean R. SCOTT Abstract Synthetic qandilite (Mg 2 TiO 4 ) is an inverse spinel in which random mixing of Mg and Ti on the octahedral site should give rise to a configurational entropy of 11.5 J K -1 mol -1 . The free energy of formation of Mg 2 TiO 4 has been determined from...
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An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg 2 TiO 4 at high temperatures

Hugh ST. C. O’Neill, Simon A. T. Redfern, Sue Kesson, Simine Short
Published: 01 May 2003
American Mineralogist (2003) 88 (5-6): 860–865.
DOI: https://doi.org/10.2138/am-2003-5-615
... report the temperature dependence of the cation distribution in the 4–2 spinel synthetic qandilite (Mg 2 TiO 4 ) from in situ time-of-flight neutron powder diffraction experiments to 1416 °C. At room temperature, Mg 2 TiO 4 is confirmed to have completely inverse cation distribution, with Ti atoms...
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Calculated activity of SiO 2 (reference state is quartz) corresponding to ...

Calculated activity of SiO 2 (reference state is quartz) corresponding to ...

Published: 01 April 2011
to 0.045, indicates further desilication. The fields for Ti-minerals (italics) are labeled as white (perovskite), light gray (qandilite) and dark gray (geikielite). The qandilite field shown corresponds to the equilibrium conditions of qandilite solid-solutions with perovskite or geikielite, calculated
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Compositional profiles (EMPA) of spinel (A) and <span class="search-highlight">qandilite</span> (B) across the sk...

Compositional profiles (EMPA) of spinel (A) and qandilite (B) across the sk...

Published: 01 April 2011
F ig . 13. Compositional profiles (EMPA) of spinel (A) and qandilite (B) across the skarn nodule from sample AV2 (“Avellino” 3800 BP eruption of Vesuvius). The compositions of the spinel-group minerals are plotted versus the composition of associated calcite, instead of distance from
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Activity of SiO 2 (reference state is quartz) and fugacity of CO 2 profil...

Activity of SiO 2 (reference state is quartz) and fugacity of CO 2 profil...

Published: 01 April 2011
for Ti-minerals (in italics), perovskite (white), qandilite (light gray) and geikielite (dark gray). The qandilite field is calculated for the composition of qandilite coexisting with geikielite. For details see text, section entitled Conditions of stability of qandilite .
Journal Article

Three novel isograds in metamorphosed siliceous dolomites from the Ballachulish aureole, Scotland

John M. Ferry
Published: 01 April 1996
American Mineralogist (1996) 81 (3-4): 485–494.
DOI: https://doi.org/10.2138/am-1996-3-422
...John M. Ferry Abstract Isograds were mapped in siliceous dolomites from the Ballachulish aureole on the basis of the formation of geikielite (MgTiO 3 ), baddeleyite (ZrO 2 ), and qandilite (Mg 2 TiO 4 ) by the following model reactions: rutile + dolomite = geikielite + calcite + CO 2 , zircon + 2...
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Unit-cell parameter against mole fraction Mg 2 TiO 4 in the ulvöspinel-qan...

Unit-cell parameter against mole fraction Mg 2 TiO 4 in the ulvöspinel-qan...

Published: 01 April 2014
Figure 1 Unit-cell parameter against mole fraction Mg 2 TiO 4 in the ulvöspinel-qandilite series. Symbol dimensions are proportional to 2σ. “USP” refers to the ulvöspinel end-member ( Bosi et al. 2009 ). “QAND” refers to average data for the qandilite end-member (see text).
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Compositions of spinel and <span class="search-highlight">qandilite</span> in the banded skarn sample Sez59–7 (16...

Compositions of spinel and qandilite in the banded skarn sample Sez59–7 (16...

Published: 01 April 2011
F ig . 4. Compositions of spinel and qandilite in the banded skarn sample Sez59–7 (1631 AD eruption of Vesuvius). A. Profile across the skarn. B. Projection according to Figure 1 ; equilibrium pairs are indicated by tie-lines.
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Solvus and tie-lines in the ternary system spinel – <span class="search-highlight">qandilite</span> – magnesiofer...

Solvus and tie-lines in the ternary system spinel – qandilite – magnesiofer...

Published: 01 April 2011
F ig . 16. Solvus and tie-lines in the ternary system spinel – qandilite – magnesioferrite calculated from Sack & Ghiorso (1991) , compared to analyzed spinel–qandilite and spinel–magnesioferrite pairs from Vesuvius skarns (this study, equilibrium pairs indicated by solid lines), and from
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MC simulation results for the enthalpy in <span class="search-highlight">qandilite</span> for three different sim...

MC simulation results for the enthalpy in qandilite for three different sim...

Published: 01 August 2008
F igure 6. MC simulation results for the enthalpy in qandilite for three different simulations performed with different J values. Enthalpies from the simulations are plotted relative to those of the ordered/lowest-energy structure (the system is poorly equilibrated at low temperature in b
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Thermodynamic integration results for entropy of <span class="search-highlight">qandilite</span>, compared with c...

Thermodynamic integration results for entropy of qandilite, compared with c...

Published: 01 August 2008
F igure 7. Thermodynamic integration results for entropy of qandilite, compared with configurational entropy. Horizontal dotted line at top of graph represents theoretical maximum entropy. Data for run 2 are smoothed below 600 K. Key to graph: “O and S 2005” = O’Neill and Scott (2005) ; “W
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Refined neutron diffraction pattern for synthetic <span class="search-highlight">qandilite</span> at 289 °C. Cros...

Refined neutron diffraction pattern for synthetic qandilite at 289 °C. Cros...

Published: 01 May 2003
F igure 1. Refined neutron diffraction pattern for synthetic qandilite at 289 °C. Crosses indicate data points (background subtracted), solid line indicates fit.
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Temperature dependence of the inversion parameter for synthetic <span class="search-highlight">qandilite</span>, ...

Temperature dependence of the inversion parameter for synthetic qandilite, ...

Published: 01 May 2003
F igure 2. Temperature dependence of the inversion parameter for synthetic qandilite, from neutron diffraction refinements. The solid line shows the fit to the data using our thermodynamic model for ordering. The uncertainties in the data are of the same order of magnitude for all three data
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Temperature dependence of the lattice parameter of synthetic <span class="search-highlight">qandilite</span>. The...

Temperature dependence of the lattice parameter of synthetic qandilite. The...

Published: 01 May 2003
F igure 3. Temperature dependence of the lattice parameter of synthetic qandilite. The uncertainties in the data are of the same order of magnitude for all three data sets and are smaller than the symbols.
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Temperature dependence of the T-O (tetrahedral, shown as squares) and M-O (...

Temperature dependence of the T-O (tetrahedral, shown as squares) and M-O (...

Published: 01 May 2003
F igure 5. Temperature dependence of the T-O (tetrahedral, shown as squares) and M-O (octahedral, shown as circles) bond lengths in qandilite.
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Comparison of experimental and simulated data for non-convergent ordering i...

Comparison of experimental and simulated data for non-convergent ordering i...

Published: 01 August 2008
F igure 4. Comparison of experimental and simulated data for non-convergent ordering in qandilite. Results from two different simulations, in which different J and μ parameters were used, are shown.