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Hagidaira Mine

Konaka, Azuma village, Midori city, Gunma pref., Japan


Hornblende-hornfels facies bedded manganese deposit

Chert-hosted bedded manganese deposit in the Late Triassic (220 Ma) to Early Jurassic (175 Ma) chert block of the Late Jurassic (145 Ma) Kurohone-Kiryu Unit. The deposit has been subjected to Hornblende-hornfels facies contact metamorphism by the Sori granodiorite in the Late Cretaceous (90 Ma), and W, Te, Bi were supplied. Slate near this deposit was metamorphosed to Cordierite-bearing hornfels. The Kurohone-Kiryu Unit corresponds to the Kanayama Unit of the Tamba-Mino-Ashio accretionary complex. The Sori granodiorite is S-type (Ilmenite-series). Approximately 3 km apart from the Sori granodiorite, the heat source. Ages of sedimentary rocks were determined by radiolarians, and granodiorite by K-Ar or Ar-Ar radiometric dating of biotite.

Reported Minerals

Mineral Assemblages

  • Tephroite - Alleghanyite - Rhodochrosite - Manganosite - Alabandite
  • Rhodonite - Pyroxmangite - Spessartine - Quartz
  • Rhodonite - Spessartine - Pyrophanite - Hübnerite - Sphalerite


  • 1895: Mr. Sakamoto, a village person, discovered the deposit and mined manganese oxide ore.
  • 1951: Started to mine maganese ore.
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