島根県美都町北東部三郡変成岩中の淡紅色緑簾石

その他

Pink-colored epidote, from the Sangun metamorphic rocks in the northeastem part of Mito-cho, Shimane Prefecture, was described.
This mineraHorms thin layer, lens or veinlet in the pelitic schist. It occurs as euhedral to subhedral crystals up to about 0.8 mm long. lt is slightly reddish under the microscope and pleochroism is not distinct. It is optically biaxial negative, 2V(meas)=74～79°. It shows complex zonal stmcture, sector zoning and parallel intergrowth composed of relatively Fe-rich and Al-poor epidote and Fe-poor and Al-rich one. The pistacite component varies from 12.3 to 19.1 mol%. This mineral contains Mn as Mn_2O_3 up to 0.77 wt.%. According to the thermal analyses, it dehydrates at 932 and 973℃. Unit-cell parameters calculated from the X-ray powder diffraction patterns are : a=8.884(4), b-5.615(3), c=10.153(5)Å, β=115.41(2)°, V=457.4(4)Å^3.