The specimen was taken from the argillaceous altered zone (Tertiary rocks), which lies in the horizon corresponding to the foot-wall of the Daikokuzawa ore deposit of the Furutôbe mine. Two specimens, numbered F-11 and F-19, are studied in this paper. Their color is white but is slightly grayish. The specimens are composed almost entirely of dioctahedral chlorite, accompanied by small amounts of quartz, illite and pyrite. The chemical compositions of F-11-MR18-64, which is the sample purified from F-11, are as follows: SiO
2: 39.01%, TiO
2: 0.47%, Al
2O
3: 32.15%, Fe
2O
3: 0.90%, FeO: 0.10%, MgO: 10.14%, CaO: 0.54%, Na
20: 0.10%, K
2O: 1.52%, S: 0.42%, ignition loss at 1, 200°C: 14.15%, Total: 99.50%. The X-ray powder diffractions and thermal investigations reveal the net properties of the chlorite mineral. The 1.508Å spacing indicates dioctahedral type features of this mineral.
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