<報文>東北地方産ケイ酸マンガン鉱の鉱物学的研究(第20報) : 岩手県肘葛鉱山産バラ輝石について

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Four new chemical analyses of rhodonite and ferroan rhodonite are presented. The material occurs as main ore forming mineral at the high grade contact metamorphosed bedded manganese ore deposits of the Hijikuzu mine. Variation in optical properties, unit cell dimensions and density within rhodonite are presented graphically in variation diagrams. Fine and coarse grained rhodonite is fresh pink in color, and associated mainly with tephroite. Optical properties of fine and coarse grained specimens are α 1.724,1.728 ; β 1.728,1.732 ; γ 1.737,1.742 ; and 2Vγ 70°, 69°, respectively. Unit cell dimensions of these two are : a 7.639,7.617 ; b 11.838,11.835 ; c 6.709,6.701Å ; α 92°33', 92°54' ; β 94°10', 94°18' ; γ 105°39', 105°35' ; and V 581.37,573.69Å^3,respectively. On the basis of 15 oxygen, the following formulas were derived by the chemical analysis of these two specimens : (Mn^<2+>_<4.2>Ca_<0.5>Mg_<0.3>Fe^<2+>_<0.1>)_<5.1>(Si_<4.8>Al_<0.2>)_<5.0>O_<15.0> for the fine grained specimen and (Mn^<2+>_<4.26>Mg_<0.38>Ca_<0.29>Fe^<2+>_<0.07>)_<5.00>Si_<5.00>O_<15.00> for the coarse grained specimen. Ferroan rhodonite is brownish red to reddish brown in color, and associated minerals are pyroxmangite and ferroan bustamite. Optical properties of two varieties of this mineral of "brownish red" and "reddish brown" are : α 1.726,1.724 ; β 1.730,1.728 ; γ 1.739,1.736 ; and 2Vγ 70°, 72°, respectively. Unit cell dimensions of these two are : a 7.661,7.660 ; b 11.800,11.802 ; c 6.674,6.773Å ; α 92°28', 92°18' ; β 94°07', 94°03' : γ 105°26', 105°28'; and V 578.87,578.92Å^3,respectively. Chemical analysis of these two varieties lead to the formulas (Mn^<2+>_<3.32>Fe^<2+>_<1.01>Ca_<0.61>Mg_<0.18>)_<5.12>(Si_<4.83>Al_<0.09>Fe^<3+>_<0.06>)_<4.98>O_<15.00> for the "brownish red" variety and (Mn^<2+>_<3.05>Fe^<2+>_<0.88>Ca_<0.65>Mg_<0.24>Fe^<3+>_<0.10>Al_<0.09>Ti_<0.01>)_<5.02>(Si_<4.77>Al_<0.23>)_<5.00>O_<15.00> for the "reddish brown" variety. The differential thermal analysis was made up to 1,150℃ in air. Coarse grained pink rhodonite shows no thermal reaction in the temperature range studied. However, the thermal curves of both of the ferroan rhodonites show a broad exothermic peak at 860℃ followed by a sharp exothermic peak at 1,100℃ together with a distinct endothermic peak at 1,140℃. On the coarse grained pink rhodonite, an x-ray pattern taken after heating at 1,150℃ for 1 hour in air showed rhodonite (γ-MnSiO_3) and bustamite (β-MnSiO_3) lines, whereas on the brownish red ferroan rhodonite, it showed bustamite (β-MnSiO_3), jacobsite (MnFe_2O_4) and tridymite (SiO_2) lines.
東北大学の論文
1977-03-30

<報文>東北地方産ケイ酸マンガン鉱の鉱物学的研究(第20報) : 岩手県肘葛鉱山産バラ輝石について

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