Abstract
The new mineral, nambulite, is a lithium- and sodium-bearing hydrous manganosilicate discovered at the Funakozawa manganese mine in the Kitakami mountains, northeastern Japan. Coarse prismatic crystals of the mineral occur in the veinlets in the braunite ore. It has vitreous reddish brown color with orange tint; and perfect (001), distinct (100) and (010) cleavages. Mohs' hardness is 6.5. Specific gravity is 3.51±0.01 (meas.) and 3.49 (calc.). Optically it is biaxial positive with refractive indices (Na-light) a=1.707, ,8=1.710, r=1.730 (all ±0.002); with 2V=300±2° and X'/\c=19°. Chemical analysis gives: SiOs 49.23, TiOs 0.01, AIsOs 0.37, FesOs 0.40, MnO 40.67, MgO 1.32, CaO 0.81, NasO 2.49, KsO 0.04, PS0 5 0.02, LisO 1.55, RsO+ 1.63, RsO- 0.26, COs 0.19, total 98.99%. The result yields the formula Li 1 . OO (NaO.9S K O •01) (Mns.95 Mgo.4o Lio.s7 CaO.1S Alo.o9 Feo~)SilO.OO OS7.79 (OR) s.S1> which may be written ideally as LiNaMnsSiloOss(OH)s'
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