Kyanite (English spelling)

Japanese: ラン晶石(藍晶石) - らんしょうせき（英語表記）kyanite

A mineral with the chemical composition Al ₂ SiO ₅ , it is polymorphous with andalusite and sillimanite. It belongs to the triclinic crystal system and often forms plate-like crystals elongated along the c- axis and parallel to (100). It has perfect cleavage along {100} and good cleavage along {010}. It has a vitreous luster, is transparent or translucent, and can be blue, white to gray, or greenish in color. Its cleavage planes have a pearlescent luster. Its specific gravity is 3.67, which is greater than that of both andalusite and sillimanite. Its Mohs hardness varies greatly depending on the crystal orientation, being 4-5 along the c -axis on the (100) plane and 6-7 along the b -axis, so it is also called disthene.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

化学成分Al₂SiO₅の鉱物で，紅柱石，ケイ線石とは多形の関係にある。三斜晶系に属し，c軸方向に伸び，(100)に平行な板状結晶をなすことが多い。｛100｝に完全，｛010｝に良好なへき開をもつ。ガラス光沢をもち，透明ないし半透明で，青色，白～灰色，帯緑色などを呈する。へき開面には真珠光沢がある。比重3.67で，紅柱石，ケイ線石のいずれよりも大きい。モース硬度は(100)面上のc軸方向で4～5,b軸方向では6～7と，結晶の方位によって大きく異なることから二硬石distheneとも称される。

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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