Abstract
The color and spectroscopic properties of ironbearing tourmalines (elbaite, dravite, uvite, schorl) do not vary smoothly with iron concentration. Such behavior has often been ascribed to intervalence charge transfer between Fe2+ and Fe3+ which produces a new, intense absorption band in the visible portion of the spectrum. In the case of tourmaline, an entirely different manifestation of the interaction between Fe2+ and Fe3+ occurs in which the Fe2+ bands are intensified without an intense, new absorption band. At low iron concentrations, the intensity of light absorption from Fe2+ is about the same for E∥c and E⊥c polarizations, but at high iron concentrations, the intensity of the E⊥c polarization increases more than ten times as much as E∥c. This difference is related to intensification of Fe2+ absorption by adjacent Fe3+. Extrapolations indicate that pairs of Fe2+-Fe3+ have Fe2+ absorption intensity ∼200 times as great as isolated Fe2+. Enhanced Fe2+ absorption bands are recognized in tourmaline by their intensity increase at 78 K of up to 50%. Enhancement of Fe2+ absorption intensity provides a severe limitration on the accuracy of determinations of Fe2+ concentration and site occupancy by optical spectroscopic methods. Details of the assignment of tourmaline spectra in the optical region are reconsidered.
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References
Amthauer G, Rossman GR (1984) Mixed valence of iron in minerals with cation clusters. Phys. Chem Minerals 11:37–51
Bence AE, Albee AL (1968) Empirical correction factors for electron microanalysis of silicates and oxides. J Geol 76:382–403
Buerger MJ, Burnham CW, Peacor DR (1962) Assessment of the several structures proposed for tourmaline. Acta Crystallogr 15:583–590
Burns RG (1970) Crystal field spectra and evidence of cation ordering in olivine minerals. Am Mineral 55:1608–1632
Burns RG (1972) Mixed valencies and site occupancies of iron in silicate minerals from Mössbauer spectroscopy. Can J Spectr 17:51–59
Donnay G, Barton R Jr (1972) Refinement of the crystal structure of elbaite and the mechanism of tourmaline solid solution. Tschermaks Mineral Petrogr Mitt 18:273–286
Faye GH (1972) Relationship between crystal-field splitting parameter, “Δvi”, and Mhost-O bond distance as an aid in the interpretation of absorption spectra of Fe2+-bearing materials. Can Mineral 11:473–487
Faye GH, Manning PG, Nickel EH (1968) The polarized optical absorption spectra of tourmaline, cordierite, chloritoid and vivianite: Ferrous-ferric electronic interaction as a source of pleochroism. Am Mineral 53:1174–1201
Faye GH, Manning PG, Gosselin JR, Tremblay RJ (1974) The optical absorption spectra of tourmaline: Importance of charge-transfer processes. Can Mineral 12:370–380
Fortier S, Donnay G (1975) Schorl refinement showing composition dependence of the tourmaline structure. Can Mineral 13:173–177
Goldman DG, Rossman GR (1979) Determination of quantitative cation distribution in orthopyroxenes from electronic absorption spectra. Phys Chem Minerals 4:43–53
Gorelikova NV, Perfil'yev YuD, Bubeshkin AM (1976) Mössbauer data on distribution of Fe ions in tourmaline. Zap Vses Mineral O-va 4:418–427 (transl. Int Geol Rev 20:982–990, 1978)
Hermon E, Simkin DJ, Donnay G, Muir WB (1973) The distribution of Fe2+ and Fe3+ in iron-bearing tourmalines: A Mössbauer study. Tschermaks Mineral Petrogr Mitt 19:124–132
Manning PG (1969a) Optical absorption spectra of chromium-bearing tourmaline, black tourmaline and buergerite. Can Mineral 10:57–70
Manning PG (1969b) An optical absorption study of the origin of colour and pleochroism in pink and brown tourmalines. Can Mineral 9:678–690
Manning PG (1973) Effect of second-nearest-neighbour interaction on Mn3+ absorption in pink and black tourmalines. Can Mineral 11:971–977
Mattson SM, Rossman GR (1984) Ferric iron in tourmaline. Phys Chem Minerals 11:225–234
Rossman GR (1975) Spectroscopic and magnetic studies of ferric iron hydroxy sulfates: intensification of color in ferric iron clusters bridged by a single hydroxide ion. Am Mineral 60:698–704
Saegusa N, Price DC, Smith G (1979) Mössbauer spectra of several iron-rich tourmalines (schorls). J Phys (Paris) 40:C2/456–C2/459
Simon HF (1973) Near-infrared and Mössbauer study of cation site occupancies in tourmalines. Unpublished MS Thesis MIT
Smith G (1978a) A reassessment of the role of iron in the 5,000-30,000 cm−1 region of the electronic absorption spectra of tourmaline. Phys Chem Minerals 3:343–373
Smith G (1978b) Evidence for absorption by exchange-coupled Fe2+-Fe3+ pairs in the near infra-red spectra of minerals. Phys Chem Minerals 3:375–383
Smith G (1980) Evidence for optical absorption by Fe2+-Fe3+ interactions in MgO:Fe. Phys Stat Sol A 61:K191-K195
Smith G, Strens RGJ (1976) Intervalence-transfer absorption in some silicate, oxide, and phosphate minerals. In: Strens RGJ (ed) The Physics and Chemistry of Minerals and Rocks, J Wiley and Sons, New York, pp 583–612
Townsend MG (1970) On the dichroism of tourmaline. J Phys Chem Solids 31:2481–2488
Wilkins RWT, Farrell EF, Naiman CS (1969) The crystal field spectra and dichroism of tourmaline. J Phys Chem Solids 30:43–56
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Mattson, S.M., Rossman, G.R. Fe2+-Fe3+ interactions in tourmaline. Phys Chem Minerals 14, 163–171 (1987). https://doi.org/10.1007/BF00308220
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DOI: https://doi.org/10.1007/BF00308220