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Sessho Creek

Hoshimata, Tsumagoi city, Agatsuma county, Gunma pref., Japan




Acidic metasomatic rocks of Minamiite-Alunite zone

Alunite deposit of alunitization alteration by volcanic gas in andesite of the early Pliocene Takai Volcanic Rocks.

Sessho creek

Outcrop of andesite subjected to alunitization alteration by volcanic gas. The gray host is andesite of Takai Volcanic Rocks. The andesite turns gray by alunitization. The white veins around the coin is alunite. Brown dirts on the outcrop is limonite crusts formed by oxidation of pyrite in altered andesite.

Reported Minerals

  • Minamiite
  • Huangite
  • Alunite
  • Natroalunite
  • Sulphur
  • Pyrite
  • Crandallite
  • Woodhouseite

Mineral Assemblages

  • Alunite - Natroalunite - Minamiite - Huangite - Sulphur - Pyrite
  • Andesite(Host) - Sulphur
  • Andesite(Host) - Pyrite


  • Sessho creek (Vein type)
  • Funabara mountain pass (Replaced type)
  • Ukusu Mine (Replaced type)

Related Occurrences

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