TRUSCOTTITE FROM THE TOI MINE, SHIZUOKA PREFECTURE

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Abstract
Truscottite from the Toi mine was found in one of the auriferous quartz veins cutting Miocene pyroclastic rocks. The chemical composition is SiO2 63.56, TiO2 0.08, Al2O3 0.81, FeO 0.66, MgO 0.70, MnO 2.41, CaO 26.24, H2O(+) 4.31, H2O(-) 0.48, total 99.25%, which is recalculated as (Ca1.77Mn0.18Mg0.06Fe0.03)1.99(Si4.00Al0.06)4.06O9.18(OH)1.81 based on O=11, and the cell constants are a0=9.720Å and c0=18.84Å respectively calculated from the X-ray powder data. The mineral occurs as aggregates of small flakes in the quartz with small amounts of adularia and rhodochrosite. The temperature of formation of the ore deposits is estimated from the known results of the synthetic studies of this mineral carried out by previous investigators.