Morimotoite, Ca3TiFe2+Si3O12, a New Titanian Garnet from Fuka, Okayama Prefecture, Japan

Chiyoko Henmi, Isao Kusachi and Kitinosuke Henmi
Department of Earth Sciences, Faculty of Science, Okayama University, Okayama 700, Japan
Department of Earth Sciences, Faculty of Education, Okayama University, Okayama 700, Japan
1-9-20, Ishima-Cho, Okayama 700, Japan

Abstract: Morimotoite, Ca3TiFe2+Si3O12, has been found in contaminated rocks which are considered to be a kind of endoskarn at Fuka, Bitchu-Cho, Okayama Prefecture, Japan. Morimotoite is derived from andradite, Ca3Fe23+Si3O12, by the substitution Ti + Fe2+ = 2Fe3+. It is associated with calcite, vesuvianite, grossular, wollastonite, hematite, prehnite, fluorapatite, perovskite, zircon, baddeleyite and calzirtite. It is cubic with space group Ia3d. The unit cell dimension a is 12.162(3) Å. Its refractive index n is 1.995(2) and the density 3.75(2) g cm−3 (meas.), 3.80 g cm−3 (calc.). The Mohs' hardness is 7.5. Calculation of the analytical data on the basis of twelve oxygen atoms and eight cations shows that this mineral has a simplified chemical formula Ca3(Ti,Fe2+Fe3+)2(Si,Fe3+)3O12 where Ti > Fe2+ > 0.5. Morimotoite was synthesized at low oxygen fugacities, 650 and 700°C and 1 kbar total pressure.

Keywords: morimotoite • titanium • garnet • skarn • Okayama Prefecture • Japan

Mineralogical Magazine; March 1995 v. 59; no. 394; p. 115-120; DOI: 10.1180/minmag.1995.59.394.11
© 1995, The Mineralogical Society
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