Katayamalite, a new Ca-Li-Ti silicate mineral from Iwagi Islet, Southwest Japan.

Abstract

Katayamalite occurs as a fine-grained accessory mineral amounting to 0.3–0.5 percent by volume in the aegirine syenite from Iwagi Islet, Ehime Prefecture, Southwest Japan. It coexists usually with albite, aegirine and pectolite. To the naked eye, katayamalite is white in color and phosphorescent to the ultraviolet rays. Striation white, luster vitreous. Hardness (Mohs) 3.5–4.0. Specific gravity 2.899 (calc), 2.91 (meas.). (001) cleavage is perfect. In thin section it is colorless with strong absorption. α=1.670, β=1.671, γ=1.677, γ−α=0.007, 2V(+)=ca. 32°.Chemical analysis shows SiO2 52.31, TiO2 10.99, Fe2O3 0.29, MnO 0.22, Li2O 3.25, CaO 28.25, Na2O 0.22, K2O 2.89, H2O 1.21, F 0.34, –O=F2 0.14, total 99.83%, corresponding ideally to (K, Na)Li3Ca7(Ti, Fe+3, Mn)2[Si6O18]2(0H, F)2 with Z=4.Katayamalite is triclinic with a0=9.721, b0=16.923, c0=19.942A, α=91.43°, β=104.15°, γ=89.94°, Space group C1. The strongest lines in X-ray powder data are 3.23 (100) (006·0-44), 3.06 (30) (2-43), 2.943 (30) (-3-14·3-11·-153), 2.898 (30) (-2-44·2-42), 2.417 (30) (008), 1.933 (40) (00.10).Katayamalite resembles baratovite (Dusmatov et al., 1975) both structurally and also chemically, but it is distinguished from the latter by the difference in crystal system and unit cell parameters. Dominance of OH over F and lacking of Zr replacing Ti are another chemical features of katayamalite.The name katayamalite is given for the mineralogist, Emeritus Professor Nobuo Katayama.