A type of epidote group mineral. It is also called sphalerite. Ca 2 Al 3 Si 3 O 12 (OH). Orthorhombic crystal system. Monoclinic epidote has a structure in which twin crystals are repeated on the scale of a unit cell. Columnar crystals elongated in the b-axis direction. Light gray to light green. It has low birefringence and can show anomalous blue interference colors under a polarized microscope. It often appears in impure calcareous regional metamorphic rocks, but can also rarely appear in amphibolites of basic igneous rock origin. It is rarer than the epidote group minerals. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
緑簾石 (りょくれんせき) 族鉱物の一種。黝簾石 (ゆうれんせき) ともいう。 Ca2Al3Si3O12(OH) 。斜方晶系。単斜晶系の緑簾石が単位胞のスケールで双晶を繰返した構造をしている。b軸方向に伸びた柱状結晶。淡灰ないし淡緑色。複屈折小さく,偏光顕微鏡下では青い異常干渉色を示すことがある。不純な石灰質広域変成岩中に出現することが多いが,まれには塩基性火成岩起源の角閃岩中に出ることもある。緑簾石族鉱物に比較して産出はまれである。
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