<報文>東北地方産ケイ酸マンガン鉱の鉱物学的研究(第29報) : 岩手県野田玉川鉱山産カリオピライト類似の鉱物

概要

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Caryopilite-like mineral occurs as lenticular aggregate of very fine crystals in rhodonite-tephroite ore-body at L13 of Misago bedded manganese ore deposits of the Noda-Tamagawa mine, in highly metamorphosed Jurassic quartzite by the intrusion of the granitic mass. It is black in color and colorless to very pale yellow-brown in thin section. Chemical analysis gives : SiO_2 34.65,TiO_2 0.00,Al_2O_3 0.00,Fe_2O_3 0.57,FeO 0.00,MnO 24.77,Mn_2O_3 0.99,MnO_2 10.79,MgO 11.77,CaO 0.57,Na_2O 0.12,K_2O 0.36,H_2O+ 9.68,H_2O- 5.49,total 99.76%. If it is postulated that all Mn^<3+> and Mn^<4+> were derived from Mn^<2+> by natural oxidation, the following empirical formula can be made by converting all Mn^<3+> and Mn^<4+> into Mn^<2+> : (Mn^<2+>_<3.56> Mg_<2.14> Ca_<0.08> K_<0.06> Na_<0.03> Fe^<3+>_<0.05>)_<5.92> Si_<4.22> O_<10.13> (OH)_<7.87>, which coresponds closely to the general formula for caryopilite : Mn_<6-x> Si_4 O_<10> (OH)_<8-2x>. The (0k0) and (00l) reflections of the mineral are 7.40 (001), 4.58 (020), 3.66 (002) and 1.531 (060) A. Thus the X-ray powder pattern of this type is closer to that of lizardite than to that of caryopilite. High temperature X-ray studies indicate that the mineral breaks down to a mixture of braunite + clinopyroxene (Mn, Mg)_2 Si_2 O_6 + Mg-pyroxmangite at about 950℃ and it changes to Mg-tephroite + Mg-rhodonite + Mg-pyroxmangite + braunite at about 1,150℃, in air.
東北大学の論文
1981-10-20