Sonolite,a new manganese silicate mineral.

Sonolite, a new silicate mineral being the manganese analogue of clinohumite, occurs as fine-grained prismatic to anhedral crystals associat­ ed with rhodochrosite, galaxite, pyrochroite etc. from Sono, Hanawa, and Kusugi mines and other eight localities. Physical and optical properties of the mineral from Hanawa mine are: dull reddish orange in color; hardness, 5.5; specific gravity, 3.82 (meas.) and 3.97 (calc.); colorless in thin section; biaxial negative with a=l.763, {3=1.779, T=1.793, (-)2V=75.5"-82°, p > v, single or lamellae twinning on (001), (001)11X=9° -10°. Monoclinic with ao=l0.664A bo=4.882A, co=14.29gA, {3=100°34'. The chemical formula of sonolite from Hanawa mine is evaluated as (Mn7-8o Feo.1o Mg1.05 Cao.1B)9-l7 (Sis-45 Alo.o2 Tio.o1)4.os 016·91 [(OH)J.u5Fo.J4]2·09· Its ideal formula is MngSi4016 (OH, F)2 or 4Mn2Si04·Mn(OH, F)2. The mineral from Kusugi mine is also described. The mineral is named after Sono mine where the mineral was first found from. Relations of the mineral to alleghanyite and to humite group are discussed.