TrekGEO > Mineral Trail > Kanto region > Tochigi pref. > Pyrosmalite-(Mn)

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Kyurazawa Mine

Ashio village, Nikko city, Tochigi pref., Japan


Field of view: 30 mm. Pyrosmalite-(Mn) associated with rhodonite. The group of tabular pink crystals with a pearly luster are pyrosmalite-(Mn) exhibiting cleavage in a direction. The fine yellowish-brown parts at the bottom is rhodonite. The black crusts on the surface of the sample are manganese dioxide formed by weathering.

Recovered from a chert-hosted bedded manganese deposit subjected to Albite-Epidote-hornfels facies contact metamorphism. Formed in the early Paleocene (64 Ma).

This pyrosmalite-(Mn) can be interpreted as a reaction product of rhodonite with H2O or Cl fluid.

The first pyrosmalite-(Mn) from Japan was reported from this location in 1961.

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