<報文>東北地方産ケイ酸マンガン鉱の鉱物学的研究(第27報) : 岩手県花輪鉱山産アレガニー石について

概要

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Alleghanyite occurs as aggregates of fine grained prismatic to anhedral crystals in the bedded manganese ore deposits of the Hanawa mine, in the highly metamorphosed Permian quatzite by the intrusion of the Miyako granitic mass. The mineral is associated closely with rhodochrosite. The mineral is brownish gray with vitreous luster. The specific gravity is 3.87 (measured); 3.91 (calculated). In thin section, it is colorless and biaxial negative with α=1.760,β=1.780,γ=1.790,2Vα=80°. Most of the crystals show lamellae twinning on (001) and the angle of extinction ((001) ΛX) is 24°. The mineral is monoclinic, space group P 2_1/b with a_0=4.86,b_0=10.75,c_0=8.27 A, α=108.73°and Z=2. Chemical analysis leads to an empirical formula (Mn_<4.64> Ca_<0.12> Mg_<0.11> Fe_<0.06> Al_<0.07>)_<5.00> Si_<1.99> O_<8.09> (OH)_<1.86> F_<0.05>, showing the mineral to be very close to theoretical Mn_5Si_2O_8 (OH, F)_2.
東北大学の論文
1980-09-30