<Original Papers>Mineralogical Study of the Manganese Silicate Ores in Northeastern Japan (XV) : Manganoan Phlogopite from Noda-Tamagawa Mine, Iwate Prefecture

Manganoan phlogopite occurs as banded or lenticular aggregate of small scaly crystals ; occassionally a single crystal of tabular of size about 3 mm in hausmannite essential mass at Tsudo-ko of Misago bedded manganese ore deposits of Noda-Tamagawa Mine, in the highly metamorphosed Jurassic quartzite by the intrusion of Tanohata granitic mass. On the basis of 24 (O, OH, F), the chemical analysis yields the formula (K_Ca_Ba_, Na_)_ (Mg_Mn_Al_Fe^_Ti_)_ (Si_Al_)_O_ (OH_F_)_, which corresponds closely to the general formula for the trioctahedral micas : X_2Y_Z_8O_(OH)_4. Structurally, the mineral is of 1M-polytype and monoclinic. The unit-cell parameters are α_0=5.35 ; b_0=9.29 ; c_0=10.29Å ; β=99°52\u27; and V=503.9Å^3. Megascopically, the color is yellowish-brown with strong pearly luster, and its specific gravity is 2.95. Optically it is negative, with α=1.578 ; β=1.606 ; γ=1.608 ; γ-α=0.030 ; and 2 V≒10°. It is weakly pleochroic with X=co1orless, Y and Z=very pale yellow, where X