Magnesium oxide (magnesium oxide) - Ryokudou

Japanese: リョウ苦土鉱(菱苦土鉱) - りょうくどこう

Magnesite is also known as magnesite. Its chemical composition is MgCO ₃ , with some of the Mg often replaced with Fe. It belongs to the hexagonal crystal system and is usually massive, granular, or dense and earthy. Crystals are rare, but it can sometimes be short columnar or rhombohedral. Its specific gravity is 3.0-3.1, its Mohs hardness is 3.5-4.5, it has perfect cleavage in {101}, and it is white to off-white, yellowish or brown in color, and transparent to opaque. The refractive index and birefringence increase with increasing Fe substitution.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

マグネサイトmagnesiteともいう。化学成分はMgCO₃の鉱物で，Mgの一部は，しばしばFeと置換されている。六方晶系に属し，通常は塊状，粒状ないし緻密で土状をなす。結晶はまれであるが，ときに短柱状，菱面体状などを示すことがある。比重3.0～3.1，モース硬度3.5～4.5，へき開は｛101｝に完全，白色ないし灰白色，帯黄色，褐色で，透明ないし不透明。Feの置換量の増加に伴い屈折率および複屈折が増大する。

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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