<報文>静岡県湯ケ島鉱山産ヨハンゼン輝石

概要

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The ore deposits of Yugashima mine are of four epithermal gold and silver bearing calcitequartz veins cutting Miocene volcanic rocks. Tne ore minerals are composed of native gold, argentite, pyrargyrite, pyrite, chalcopyrite, galena and sphalerite. Gangue minerals are quartz, calcite, manganoan calcite, rhodonite, inesite and adularia. Johannsenite occurs as radiative and spherulitic aggregates of prismatic crystals up to 2×0.4mm in size, in the small cavities in No.2 vein of N 1# of -170m level. The associate mineral is xonotlite. The color is pale green, and colorless in thin section. Calculated specific gravity is 3.54. The indices of refraction are α1.709,β1.719,γ1.737 and γ-α 0.028. Optical axial angle (2Vγ) is 70°and extinction angle (cΛZ) is 48°. Polysynthetic twinning lamellae are common. Chemical analysis gives the formula of (Ca_<0.93>Na_<0.02>K_<0.00>)_<0.95> (Mn_<0.93>Mg_<0.06>Fe^<2+>_<0.03>Fe^<3+>_<0.00>Al_<0.03>)_<1.05> (Al_<0.01>Si_<1.99>)_<2.00>O_<6.00>, which corresponds closely to the general formula for the pyroxene groups : W_<1-p>(X, Y)_<1+p>Si_2O_6. The mineral is monoclinic. The unit cell parameters are a_0 9.91,b_0 9.10,c_0 5.28A, β105.2°and V 459.7A^3.
東北大学の論文
1981-10-20