Allanite (allanite)

Japanese: 褐レン石(褐簾石) - かつれんせき（英語表記）allanite

Its chemical composition is (Ca,R) ₂ (Al,Fe,Ti) _3Si3O12 (OH), where R = Ce,Mn, _La ,Y,Th. It is characterized by the presence _of rare earth elements and thorium (Th). It is a monoclinic rock-forming mineral belonging to the epidote group. It has black or blackish brown columnar or plate-like crystals elongated along the b axis. Its Mohs hardness is 5-6.5, its specific gravity is 3.4-4.2, and its cleavage is unclear. Allanite is widely found as an accessory mineral in granites, and is also found in gneisses and crystalline schists. It rarely occurs in large quantities in limestone skarns and pegmatites.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

化学組成は(Ca,R)₂(Al,Fe,Ti)₃Si₃O₁₂(OH)。ここでR＝Ce,Mn,La,Y,Th。希土類元素とトリウムThを含むのが特徴。単斜晶系で，緑レン石族に属する造岩鉱物の一つ。黒色ないし黒褐色のb軸方向に伸びた柱状または板状結晶。モース硬度5～6.5，比重3.4～4.2，へき開は不明確である。褐レン石は副成分鉱物として広く花コウ岩類に，また片麻岩や結晶片岩に含まれていることがある。まれに石灰岩スカルンやペグマタイト中に多量に産する。

出典　株式会社平凡社世界大百科事典第２版について　情報

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