Rhodochrosite (rhodochrosite)

Japanese: リョウマンガン鉱(菱マンガン鉱) - りょうマンガンこう（英語表記）rhodochrosite

A type of manganese ore, its chemical composition is MnCO _3. It is rare to find it in pure form, and it usually contains Fe ²⁺ and Ca. It has a hexagonal or rhombohedral crystal system, but clear crystals are rare, and it often forms fine chunks. It can also be spherical or botryoidal. Its Mohs hardness is 3.5-4.5, its specific gravity is 3.70 for pure stones, usually 3.4-3.6, its cleavage is perfect {101}, and it is pink or rose, orange-red, yellow-brown, and translucent. The refractive index and birefringence increase as the amount of Fe contained increases.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

マンガン鉱石の一つで，化学成分はMnCO₃である鉱物。純粋なものは少なく，普通Fe^2＋とCaを含んでいる。六方晶系，菱面体であるが明瞭な結晶はまれで，細密な塊状をなすことが多い。また球状，ブドウ状を呈する。モース硬度3.5～4.5，比重は純粋なもので3.70，通常3.4～3.6，へき開は｛101｝に完全，ピンクないしばら色，橙赤色，黄褐色，半透明。屈折率および複屈折は，含まれるFeの量が増すにつれて増大する。

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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