<報文>東北地方産ケイ酸マンガン鉱の鉱物学的研究(第4報) : 岩手県野田玉川鉱山産含ホウ素含マノガンエッケルマン閃石について

概要

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Boron-manganiferous eckermannite occurs as prismatic crystals up to 1.5x 1.2x 1.0cm in size in manganiferous aegirine-rhodonite-alkali feldspar quartz bearing pegmatitic veinlets, cutting through the Misago bedded manganese silicate ore bodies of Noda-Tamagawa mine of older Cretaceous age. The color is brownish dark green in hand-specimen, the specific gravity is 3.03 and the hardness is 4(1/2). In a thin section the pleochroism weak : X=pale yellow, Y=Z=yellow. The indices of refraction are α=1.640 β=1.653 γ=1.658 γ-α=0.018,extinction angle is c∧Z=39° and optic axial angle is 2Vα=70°, X-ray powder data showed it to be isostructual with the alkali amphibole group, i.e., it is monoclinic with a_0=9.88,b_0=18.05,c_0=5.32Å, β=104.0° and Z=2. The chemical analysis gives the formula of (Na_<2.060>, K_<0.199>, Ca_<0.401>)_<2.660> (Mg_<2.167>, Mn_<1.506>, Fe^<+2>_<0.095>, Fe^<+3>_<0.706>, Al_<0.143>, Ti_<0.036>)_<5.153> (Si_<7.453>, B_<0.535>, Al_<0.012>)_<8.000> O_<21.894> (OH_<2.051>, F_<0.055>)_<2.106>, and the Si^<+4> atoms are replaced partly byB^<+3> atoms. The high-temperature X-ray diffraction and DTA indicate that the mineral breaks down to a mixture of clinopyroxene, jacobsite and glass when heated at about 1,100℃.
東北大学の論文
1969-01-30