Tamaite, the Ca-analogue of ganophyllite, from the Shiromaru mine, Okutama, Tokyo, Japan

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Tamaite, (Ca, K, Ba, Na)3−4Mn24(Si, Al)40(O, OH)112·21H2O, the Ca-analogue of ganophyllite, is found from the Shiromaru mine, Okutama, Tokyo, Japan. It is monoclinic, P21/a, a=16.64(1), b=27.11(2), c=25.35(2)A, β=98.74(7)°, Z=4. The strongest lines in the X-ray powder diffraction pattern are 12.6 (vvs) (002), 3.46 (m) (027), 3.13 (s) (008), 2.84 (s) (38 -2), 2.69 (vs) (38 -4), 2.60 (s) (602), 2.46 (s) (60 -6), 2.38 (m) (604), 1.623 (m) (98 -2), 1.609 (m) (3 10 11). Electron microprobe and Karl-Fischer analyses gave SiO2 41.23, Al2O3 7.79, FeO 0.16, MnO 35.17, MgO 0.23, CaO 1.94, BaO 2.03, Na2O 0.34, K2O 0.82, H2O 11.07, total 100.78 wt%, and lead to the empirical formula, (Ca1.65K0.83Ba0.63Na0.53)Σ3.64(Mn23.71Mg0.27Fe0.11Al0.12)Σ24.21(Si32.81Al7.19)Σ40.00 O95.27(OH)16.73·21H2O on the basis of O=133. It is transparent and colorless to pale yellowish brown in color with vitreous to pearly luster. The streak is white and cleavage perfect on {001}. The Mohs hardness is about 4. The measured and calculated densities are 2.85(5) g/cm3 and 2.83 g/cm3, respectively. It is colorless in thin section and optically biaxial negative with β=1.612(2) and 2 V<15°. It occurs as veinlets up to 1.5 mm thick composed of micaceous platy crystals under 0.5 mm in diameter and as spotted crystals in celsian-barian orthoclase veinlets cutting host rocks of metamorphosed manganese ore deposit. The mineral is considered to be formed during later stage activity of low grade metamorphism.
日本鉱物科学会の論文

Tamaite, the Ca-analogue of ganophyllite, from the Shiromaru mine, Okutama, Tokyo, Japan

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