TrekGEO > Mineral Trail > Kyushu region > Oita pref. > Stilpnomelane

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Obira Mine

Obira-Kozan, Ogata, Bungo-Ono city, Oita pref., Japan


Field of view: 50 mm. Stilpnomelane associated with grunerite. The radial groups of platy dark brown crystals are stilpnomelane. The surrounding massive pale brown parts are aggregate of fine grunerite crystals. The black parts with a resinous luster at the top are ilvaite.

Recovered from skarn formed by S-type (Ilmenite-series) granite of the caldera complex. Formed in the middle Miocene (14 Ma).

Stilpnomelane from this location was described in 1955.

Other localities

  • Obira Mine (Pneumatolytic Skarn, Radial)
  • Matsunaga Mine (High-P metamorphic, Radial)
  • Kami-Nagatoro (High-P metamorphic, Micaceous)
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