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Clinotobermorite, Ca5Si6(O,OH)18·5H2O, a new mineral from Fuka, Okayama Prefecture, Japan

Published online by Cambridge University Press:  05 July 2018

C. Henmi
Affiliation:
Department of Earth Sciences, Faculty of Science, Okayama University, Okayama 700 Japan
I. Kusachi
Affiliation:
Department of Earth Sciences, Faculty of Education, Okayama University, Okayama 700 Japan

Abstract

Clinotobermorite, Ca5Si6(O,OH)18·5H2O, has been found as a vein-forming mineral in gehlenitespurrite skarns at Fuka, Okayama Prefecture. It is associated with tobermorite, plombierite, apophyllite, and calcite. The clinotobermorite is colourless or white and occurs as tabular or acicular crystals. It is monoclinic with the space group Cc or C2/c. The unit cell dimensions are a 11.331, b 7.353, c 22.67 Å, β 96.59°. Microtwinning and stacking disorder on (001) are observed. On heating the clinotobermorite at 300°C the 002 spacing is reduced from 11.3 to 9.3 Å. Its refractive indices are α 1.575, β 1.580, γ 1.585, and the density 2.58 g/cm3 (meas.), 2.69 g/cm3 (calc). The Moh's hardness is 4.5. Calculation of the analytical data on the basis of six tetrahedral cations shows that this mineral has a simplified chemical formula Ca5.3Si6(O,OH,F)18·5H2O. The chemical composition and the unit cell are closely related to those of tobermorite. It is most likely that clinotobermorite is a low-temperature polymorph of tobermorite.

Type
Mineralogy
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1992

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References

Gard, J.A. and Taylor, H.F.W. (1960) The crystal structure of foshagite. Acta Cryst., 13, 785–93.CrossRefGoogle Scholar
Hamid, S.A. (1981) The crystal structure of the 11 A natural tobermorite Ca2.25[Si3O7 5(OH)i 5]1H2O Zeit. Krist., 154, 189–98.Google Scholar
Heller, L. and Taylor, H.F.W. (1956) Crystallographic data for calcium silicates. H.M. Stationary Office, London.Google Scholar
Henmi, C. and Kusachi, I. (1989) Monoclinic tobermorite from Fuka, Bitchu-cho , Okayarna Prefecture, Japan. Journ. Min. Pet. Econ. Geol., 84, 374–9.(in Japanese).CrossRefGoogle Scholar
Ito, T. (1950) X-ray studies on polymorphism. Maruzen, Tokyo.Google Scholar
Jefferson, D.A. and Bown, M.G. (1973) Polytypism and stacking disorder in wollastonite. Nature, Physical Science, 245, 43–4.CrossRefGoogle Scholar
Kusaehi, I., Henmi, C., and Henmi, K. (1980) 10 A tobermorite from Fuka, the Town of Bitchu, Okayama Prefecture. Min. Journ., 14, 314–22.(in Japanese).Google Scholar
Kusaehi, I., Henmi, C., and Henmi, K. (1984) An oyelite-bearing vein at Fuka, the Town of Bitchu, Okayama Prefecture. Journ. Japan. Assoc. Min. Petr. Econ. Geol., 79, 267–75.CrossRefGoogle Scholar
Kusaehi, I., Henmi, C., and Henmi, K. (1989) Afwillite and jennite from Fuka, Okayama Prefecture, Japan. Min. Journ. 14, 279–92.CrossRefGoogle Scholar
McConnell, J.D.C. (1954) The hydrated calcium silicates riversideite, tobermorite and plombierite. Mineral. Mag., 30, 293305.Google Scholar
Megaw, H.D. and Kelsey, C.H. (1956) Crystal structure of tobermorite. Nature, 177, 390–1.CrossRefGoogle Scholar
Meyer, J.W. and Jaunarajs, K.L. (1961) Synthesis and crystal chemistry of gyrolite and reyerite. Amer. Min., 46, 913–33.Google Scholar
Mitsuda, T., Kusachi, I., and Henmi, K. (1972) Mixtures of 14 A and 11 A tobermorite from Fuka, Japan. Cement Assoc. Japan. Rev. 26th Gen. Meeting, 47-68.Google Scholar
Mitsuda, T., Kusachi, I., and Henmi, K. Taylor, H.F.W. (1978) Normal and anomalous tobermorites. Mineral. Mag., 42, 229–35.CrossRefGoogle Scholar
Morimoto, N. (1959) The structural relations among three polymorphs of MgSiO3—enstatite, proto-enstatite, and clinoenstatite. Carnegie Inst. Washington, Ann. Rept. Dir. Geophys. Lab. 1959, 197-8.Google Scholar
Taylor, H.E.W. (1977) The crystal structure of killalaite. Mineral Mag., 41, 363–9.CrossRefGoogle Scholar
Trojer, F.J. (1968) The crystal structure of parawollastonite. Zeit. Krist., 127, 291308.CrossRefGoogle Scholar