Skip to main content Accessibility help

Experimental evidence for partial Fe2+ disorder at the Y and Z sites of tourmaline: a combined EMP, SREF, MS, IR and OAS study of schorl

  • Ferdinando Bosi (a1) (a2), Giovanni B. Andreozzi (a1), Ulf Hålenius (a2) and Henrik Skogby (a2)

An experimental study of an Al-rich schorl sample from Cruzeiro mine (Minas Gerais, Brazil) was carried out using electron microprobe analysis, structural refinement and Mössbauer, infrared and optical absorption spectroscopy in order to explore the disordering of Fe2+ over the Y and Z sites of the tourmaline structure.

A structural formula was obtained by merging chemical and structural data. The cation distribution at the two non-equivalent octahedrally coordinated sites (Y and Z) was obtained by two different optimization procedures which, minimizing the residuals between observed and calculated data, converged to the formula: X(Na0.650.32Ca0.02K0.01)Σ1.00 Y(Fe1.65 2+Al1.15Fe0.06 3+Mn0.05 2+Zn0.05Ti0.04 4+)Σ3.00 Z(Al5.52Fe0.30 2+Mg0.18)Σ6.00[T(Si5.87Al0.13)Σ6.00O18](BBO3)3 V(OH)3 W[(OH)0.34F0.28O0.38]Σ1.00.

This result shows a partial disordering of Fe2+ over the Y and Z sites which explains adequately the mean atomic number observed for the Z site (13.5±0.1). Such a disordering is also in line with the shoulder recorded in the Mössbauer spectrum (fitted by a doublet with isomer shift of 1.00 mm/s and quadrupole splitting of 1.38 mm/s) as well as with the asymmetric bands recorded in the optical absorption spectrum at ∼9000 and 14,500 cm–1 (modelled by four Gaussian bands, centred at 7677 and 9418 cm–1, and 13,154 and 14,994 cm–1, respectively).

The high degree of consistency in the results obtained using the different methods suggests that the controversy over Fe2+ order can be ascribed to the failure to detect small amounts of Fe2+ at Z (typically <<10% atoms/site) rather than a steric effect of Fe2+ on the tourmaline structure.

Corresponding author
Hide All
Andreozzi, G.B., Bosi, F. and Longo, M. (2008) Linking Mössbauer and structural parameters in elbaiteschorl-dravite tourmalines. American Mineralogist, 93, 658666.
Bosi, F. (2008) Disordering of Fe2+ over octahedrally coordinated sites of tourmaline. American Mineralogist, 93, 16471653.
Bosi, F. (2010) Octahedrally coordinated vacancies in tourmaline: a theoretical approach. Mineralogical Magazine, 74, 10371044.
Bosi, F. (2011) Stereochemical constraints in tourmaline: from a short-range to a long-range structure. The Canadian Mineralogist, 49, 1727.
Bosi, F. (2013) Bond-valence constraints around the O1 site of tourmaline. Mineralogical Magazine, 77, 343351.
Bosi, F. and Skogby, H. (2013) Oxy-dravite, Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup. American Mineralogist, 98, 14421448.
Bosi, F. and Lucchesi, S. (2004) Crystal chemistry of the schorl-dravite series. European Journal of Mineralogy, 16, 335344.
Bosi, F. and Lucchesi, S. (2007) Crystal chemical relationships in the tourmaline group: structural constraints on chemical variability. American Mineralogist, 92, 10541063.
Bosi, F. and Andreozzi, G.B. (2013) A critical comment on Ertl et al. (2012) “Limitations of Fe2+ and Mn2+ site occupancy in tourmaline: Evidence from Fe2+-and Mn2+-rich tourmaline”. American Mineralogist, 98, 21832192.
Bosi, F., Andreozzi, G.B., Federico, M., Graziani, G. and Lucchesi, S. (2005) Crystal chemistry of the elbaite-schorl series. American Mineralogist, 90, 17841792.
Bosi, F., Balić-Žunić, T. and Surour, A.A. (2010) Crystal structure analysis of four tourmalines from the Cleopatra’s Mines (Egypt) and Jabal Zalm (Saudi Arabia), and the role of Al in the tourmaline group. American Mineralogist, 95, 510518.
Bosi, F., Skogby, H., Agrosì, G. and Scandale, E. (2012) Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, a new mineral species of the tourmaline supergroup from Grotta d’Oggi, San Pietro in Campo, island of Elba, Italy. American Mineralogist, 97, 989994.
Bosi, F., Andreozzi, G.B., Agrosì, G. and Scandale, E. (2014) Fluor-tsilaisite, NaMn3Al6(Si6O18) (BO3)3(OH)3F, a new tourmaline from San Piero in Campo (Elba, Italy) and new data on tsilaisitic tourmaline from the holotype specimen locality. Mineralogical Magazine, 79, 89101.
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters obtained from a systematic analysis of the Inorganic Crystal Structure Database. Acta Crystallographica, B41, 244247.
Burns, R.G. (1972) Mixed valencies and site occupancies of iron in silicate minerals from Mössbauer spectroscopy. Canadian Journal of Spectroscopy, 17, 5159.
Dutrow, B.L. and Henry, D.J. (2011) Tourmaline: A geologic DVD. Elements, 7, 301306.
Dyar, M.D., Taylor, M.E., Lutz, T.M., Francis, C.A., Guidotti, C.V. and Wise, M. (1998) Inclusive chemical characterization of tourmaline: Mössbauer study of Fe valence and site occupancy. American Mineralogist, 83, 848864.
Ertl, A., Kolitsch, U., Dyar, M.D., Hughes, J.M., Rossman, G.R., Pieczka, A., Henry, D.J., Pezzotta, F., Prowatke, S., Lengauer, C.L., Körner, W., Brandstatter, F., Francis, C.A., Prem, M. and Tillmans, E. (2012) Limitations of Fe2+ and Mn2+ site occupancy in tourmaline: evidence from Fe2+-and Mn2+-rich tourmaline. American Mineralogist, 97, 14021416.
Federico, M., Andreozzi, G.B., Lucchesi, S., Graziani, G. and César-Mendes, J. (1998) Crystal chemistry of tourmalines. I. Chemistry, compositional variations and coupled substitutions in the pegmatite dikes of the Cruzeiro mine, Minas Gerais, Brazil. The Canadian Mineralogist, 36, 415431.
Filip, J., Bosi, F., Novák, M., Skogby, H., Tuček, J., Čuda, J. and Wildner, M. (2012) Redox processes of iron in the tourmaline structure: example of the hightemperature treatment of Fe3+-rich schorl. Geochimica et Cosmochimica Acta, 86, 239256.
Foit, F.F. Jr. (1989) Crystal chemistry of alkali-deficient schorl and tourmaline structural relationships. American Mineralogist, 74, 422431.
Fuchs, Y., Lagache, M. and Linares, J. (1998) Fetourmaline synthesis under different T and fO2 conditions. American Mineralogist, 83, 525534.
Gonzalez-Carren˜o, T., Fernandez, M. and Sanz, J. (1988) Infrared and electron micropobe analysis in tourmalines. Physics and Chemistry of Minerals, 15, 452460.
Grice, J.D. and Ercit, T.S. (1993) Ordering of Fe and Mg in the tourmaline crystal structure: the correct formula. Neues Jahrbuch für Mineralogie, Abhandlungen, 165, 245266.
Hawkins, K.D., MacKinnon, I. and Schneeberger, H. (1995) Influence of chemistry on the pyroelectric effect in tourmaline. American Mineralogist, 80, 491501.
Hawthorne, F.C. (1996) Structural mechanisms for lightelement variations in tourmaline. The Canadian Mineralogist, 34, 123132.
Hawthorne, F.C. (2002) Bond-valence constraints on the chemical composition of tourmaline. The Canadian Mineralogist, 40, 789797.
Henry, D.J. and Dutrow, B.L. (2011) The incorporation of fluorine in tourmaline: Internal crystallographic controls or external environmental influences? The Canadian Mineralogist, 49, 4156.
Henry, D.J., Novák, M., Hawthorne, F.C., Ertl, A., Dutrow, B., Uher, P. and Pezzotta, F. (2011) Nomenclature of the tourmaline supergroup minerals. American Mineralogist, 96, 895913.
Henry, D.J., Novák, M., Hawthorne, F.C., Ertl, A., Dutrow, B., Uher, P. and Pezzotta, F. (2013) Erratum. American Mineralogist, 98, 524. Lagarec, K. and Rancourt, D.G. (1998) RECOIL. Mössbauer spectral analysis software for Windows, version 1.0. Department of Physics, University of Ottawa, Canada. MacDonald, D.J. and Hawthorne, F.C. (1995) The crystal chemistry of Si = Al substitution in tourmaline. The Canadian Mineralogist, 33, 849858.
Mattson, S.M. and Rossman, G.R. (1984) Ferric iron in tourmaline. Physics and Chemistry of Minerals, 11, 225234.
Mattson, S.M. and Rossman, G.R. (1987) Fe2+-Fe3+ interactions in tourmaline. Physics and Chemistry of Minerals, 14, 163171.
Pieczka, A. and Kraczka, J. (2004) Oxidized tourmalines-a combined chemical, XRD and Mössbauer study. European Journal of Mineralogy, 16, 309321.
Pouchou, J.L. and Pichoir, F. (1991) Quantitative analysis of homogeneous or stratified microvolumes applying the model “PAP”. Pp. 3175. in: Electron Probe Quantitation (K.F.J. Heinrich and D.E. Newbury, editors). Plenum Press, New York.
Rozhdestvenskaya, I.V., Setkovab, T.V., Vereshchagina, O.S., Shtukenberga, A.G. and Shapovalovb, Yu.B. (2012) Refinement of the crystal structures of synthetic nickel-and cobalt-bearing tourmalines. Crystallography Reports, 57, 5763.
Shannon, R.D. (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chaleogenides. Acta Crystallographica, A32, 751767.
Sheldrick, G.M. (2013) SHELXL-2013. University of Göttingen, Germany.
Skogby, H., Bosi, F. and Lazor, P. (2012) Short-range order in tourmaline: a vibrational spectroscopic approach to elbaite. Physics and Chemistry of Minerals, 39, 811816.
Smith, G. (1978) A reassessment of the role of iron in the 5,000-30.000 cm-1 region of the electronic absorption spectra of tourmaline. Physics and Chemistry of Minerals, 3, 343373.
Taran, M.N., Lebedev, A.S. and Platonov, A.N. (1993) Optical absorption spectroscopy of synthetic tourmalines. Physics and Chemistry of Minerals, 20, 209220.
Vereshchagin, O.S., Rozhdestvenskaya, I.V., Frank-Kamenetskaya, O.V., Zolotarev, A.A. and Mashkovtsev, R.I. (2013) Crystal chemistry of Cubearing tourmalines. American Mineralogist, 98, 16101616.
Wright, S.E., Foley, J.A. and Hughes, J.M. (2000) Optimization of site occupancies in minerals using quadratic programming. American Mineralogist, 85, 524531.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Mineralogical Magazine
  • ISSN: 0026-461X
  • EISSN: 1471-8022
  • URL: /core/journals/mineralogical-magazine
Please enter your name
Please enter a valid email address
Who would you like to send this to? *


Type Description Title
Supplementary materials

Bosi et al. supplementary material

 Unknown (24 KB)
24 KB


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed