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Refinement of the crystal structure of a synthetic non-stoichiometric Rb-feldspar

Published online by Cambridge University Press:  05 July 2018

A. Kyono  and
M. Kimata
A. Kyono*
Affiliation:
Institute of Geoscience, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8571, Japan
M. Kimata
Affiliation:
Institute of Geoscience, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8571, Japan
*
*E-mail: [email protected]
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Abstract

The crystal structure of hydrothermally synthesized Rb-feldspar (monoclinic, space group C2/m, a= 8.839(2)Å, b= 13.035(2)Å, c= 7.175(2)Å, β = 116.11(1)8, V= 742.3(3)Å3, Z= 4) has been refined to a final R of 0.0574 for 692 independent X-ray reflections. Microprobe analyses of the Rb-feldspar suggest deviation from stoichiometry, with excess Si and Al, resulting in a unit formula of Rb0.811□0.127Al1.059Si3.003O8. Infrared (IR) spectra indicate the structural occupancy of large H2O content, which implies that the □Si4O8 substitution favours the structural incorporation of the H2O molecule at the M-site. The mean T–O distances are 1.632 Å for T1 and 1.645 Å for T2, revealing highly disordered (Al,Si) distribution with Al/Si = 0.245/0.755 (T1 site) and 0.255/0.745 (T2 site).

There are two geochemical implications from this refinement: (1) identification of both rubicline triclinic with (Al,Si) ordered distribution and synthetic monoclinic RbAlSi3O8 with (Al,Si) disordered distribution implies that Rb cannot be one of factors disrupting the (Al,Si) ordered and disordered distributions in feldspars; and (2) natural and synthetic feldspars capable of accommodating the large cations tend to incorporate □Si4O8, excess Al and H2O components in their crystal structures.

Keywords

Rb-feldspar□Si4O8Al-excess substitutionH2O molecule
Type
Research Article
Information
Mineralogical Magazine , Volume 65 , Issue 4 , August 2001 , pp. 523 - 531
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

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References

Afonina, G.G., Makagon, V.M., Shmakin, B.M., Glebov, M.P. and Makrygin, A.I. (1979) Effects of rubidium and cesium on the structural states of potash feldspars from rare-metal pegmatites. Int. Geol. Rev., 21, 597–604.CrossRefGoogle Scholar
Ballirano, P., Maras, A. and Buseck, P.R (1996) Crystal chemistry and IR spectroscopy of Cl- and SO4- bearing cancrinite-like minerals. Amer. Mineral., 81, 1003–12.CrossRefGoogle Scholar
Barrer, R.M. and McCallum, N. (1953) Hydrothermal chemistry of silicates. Part IV. rubidium and cesium aluminosilicate. J. Chem. Soc., 4029–35.CrossRefGoogle Scholar
Bell, D.R. and Rossman, G.R. (1992) Water in Earth's mantle: the role of nominally anhydrous minerals. Science, 255, 1391–6.CrossRefGoogle ScholarPubMed
Beran, A. (1986) A model of water allocation in alkali feldspar, derived from infrared-spectroscopic investigation. Phys. Chem. Miner., 13, 306–10.CrossRefGoogle Scholar
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters obtained from a systematic analysis of the inorganic crystal structure database. Acta Crystallogr., B41, 244–7.CrossRefGoogle Scholar
Bruno, E. and Pentinghaus, H. (1974) Substitutions of cations in natural and synthetic feldspars. Pp. 574–610 in: The Feldspars., (Mackenzie, W.S. and Zussmann, J., editors). Proceedings of NATO-ASI, Manchester, 1972. Manchester University Press, UK.Google Scholar
Enraf-Nonius, (1983) Structure determination package (SDP)., Enraf-Nonius, Delft, The Netherlands.Google Scholar
Gasperin, M. (1971) Structure cristalline de RbAlSi3O8 . Acta Crystallogr., B27, 854–5.CrossRefGoogle Scholar
Ghélis, M. and Gasperin, M. (1970) Evolution des paramétres dans le systéme KalSi3O8–RbAlSi3O8 . Compt. Rendu. Acad. Sci., 271, D1928–9.Google Scholar
Grove, T. and Ito, J. (1973) High temperature displacive transformations in synthetic feldspar. Trans. Amer. Geophys. Union., 54, 499.Google Scholar
Grundy, H.D. and Ito, J. (1974) The refinement of the crystal structure of a synthetic non-stoichiometric Sr feldspar. Amer. Mineral., 59, 1319–26.Google Scholar
Henderson, C.M.B. (1978) Thermal expansion of alkali feldspars. II. Rb-sanidine and maximum microcline. Progress Exp. Petrol. 4th Congr. Rep. Nat. Environ. Res. Council., , 51 4.Google Scholar
Hofmeister, A.M. and Rossman, G.R. (1985) A model for the irradiative coloration of smoky feldspar and the inhibiting influence of water. Phys. Chem. Miner., 12, 324–32.CrossRefGoogle Scholar
Kimata, M., Nishida, N., Shimizu, M., Saito, S., Matsui, T. and Arakawa, Y. (1995) Anorthite megacrysts from island arc basalts. Mineral. Mag., 59, 1–14.CrossRefGoogle Scholar
Kohn, S.C., Henderson, C.M.B. and Dupree, R. (1994) NMR studies of leucite analogues X2YSi5O12, where X = K, Rb, Cs; Y = Mg, Zn, Cd. Phys. Chem. Miner., 21, 176–90.CrossRefGoogle Scholar
Koval’skii, A.M., Kotel’nikov, A.R., Bychkov, A.M., Chichagov, A.V. and Samokhvalova, O.L. (2000) Synthesis and X-ray diffraction study of (K, Rb)- feldspar solid solution: preliminary data. Geochem. Int., 38, 220–4.Google Scholar
Kroll, H. and Ribbe, P.H. (1983) Lattice parameters, composition and Al,Si order in alkali feldspars. Pp. 57–99 in: Feldspar Mineralogy., 2nd ed. Reviews in Mineralogy., 2. Mineralogical Society of America, Washington D.C. CrossRefGoogle Scholar
McMillan, P.F., Brown, W.F. and Openshaw, R.E. (1980) The unit-cell parameters of an ordered K-Rb alkali feldspar series. Amer. Mineral., 65, 458–68.Google Scholar
Paulus, H. and Müller, G. (1988) The crystal structure of a hydrogen-feldspar. Neues Jahrb. Miner. Mh., 481–90.Google Scholar
Pentinghaus, H. and Bambauer, H. (1971) Substitution of Al(III), Ga(III), Fe(III), Si(IV) and Ge(IV) in synthetic alkali feldspars. Neues Jahrb. Mineral. Mh., 417–8.Google Scholar
Smith, J.V. (1983) Feldspar Minerals, 2. Chemical and Textural Properties., 2nd ed. Springer-Verlag, Berlin.Google Scholar
Smith, J.V. and Brown, W.L. (1988) Feldspar Minerals, 1. Crystal Structures, Physical, Chemical and Microtextural Properties., 2nd ed. Springer-Verlag, Berlin.Google Scholar
Teertstra, D.K., Černý, P. and Hawthorne, F.C. (1997) Rubidium-rich feldspars in a granitic pegmatite from the Kola peninsula, Russia. Canad. Mineral., 5, 1277–81.Google Scholar
Teertstra, D.K., Černý, P. and Hawthorne, F.C. (1998 a) Rubidium feldspars in granitic pegmatites. Canad. Mineral., 36, 483–96.Google Scholar
Teertstra, D.K., Černý, P. Hawthorne, F.C., Pier, J., Wang, L.M. and Ewing, R.C. (1998 b) Rubicline, a new feldspar from San Pietro in Campo, Elba, Italy. Amer. Mineral., 83, 1335–9.CrossRefGoogle Scholar
Teertstra, D.K., Hawthorne, F.C. and Černý, P. (1998 c), Identification of normal and anomalous compositions of minerals by electron-microprobe analysis: K-rich feldspar as a case study. Canad. Mineral., 36, 87–95.Google Scholar
Teertstra, D.K., Černý, P. and Hawthorne, F.C. (1999 a) Geochemistry and petrology of late K- and Rbfeldspars in Rubellite pegmatite, Lilypad lakes, NW Ontario. Mineral. Petrol., 65, 237–47.CrossRefGoogle Scholar
Teertstra, D.K., Černý, P. and Hawthorne, F.C. (1999 b) Subsolidus rubidium-dominant feldspar from the Morrua pegmatite, Mozambique: paragenesis and composition. Mineral. Mag., 63, 313–20.CrossRefGoogle Scholar
Voncken, J.H.L., Konings, R.J.M., Van der Eerden, A.M.J., Jansen, J.B.H., Schuiling, R.D and Woensdregt, C.F. (1993) Crystal morphology and X-ray powder diffraction of the Rb-analogue of high sanidine, RbAlSi3O8 . Neues Jahrb. Mineral. Mh., 10–16.Google Scholar
Wietze, R. and Wiswanathan, K. (1971) Rubidiumplagiokl as durch kationen austauch. Fortschr. Mineral., 9, 63.Google Scholar
Wilkinson, R.W.T. and Sabine, W. (1973) Water content of some nominally anhydrous silicates. Amer. Mineral., 58, 508–16.Google Scholar