gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1995.59.394.11 Mineralogy Morimotoite, Ca3TiFe2+Si3O12, a New Titanian Garnet from Fuka, Okayama Prefecture, Japan Henmi Chiyoko Department of Earth Sciences, Faculty of Science, Okayama University, Okayama 700, Japan Kusachi Isao Department of Earth Sciences, Faculty of Education, Okayama University, Okayama 700, Japan Henmi Kitinosuke 1-9-20, Ishima-Cho, Okayama 700, Japan 3 1995 59 394 115 120 3 12 1993 28 3 1994 Copyright © 1995, The Mineralogical Society 1995 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