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Kodo, Ueda city, Nagano pref., Japan


Water bottom deposits

Glendonite, mineral-like material, formed on the sea floor during mudstone deposition of the middle Miocene (13 Ma) Bessho Formation. The Bessho Formation is composed of abyssal sediments in a cool climate related to the cold current. The Bessho Formation conformably overlies the Uchimura Formation, and conformably underlies the Aoki Formation. The Uchimura Formation is composed of pyroclastic materials and sediments. Ages of sedimentary rocks were determined by microfossils, climate by fossil fish and plants.


Glendonite in mudstone of the Bessho Formation. A long bipyramidal grayish white glendonite is at the center of the photograph. The top of the glendonite is bulgy whereas the bottom is flatter with clear striations perpendicular to the photograph face. Bedding planes of the host mudstone is very clear and the glendonite is concordant to the bedding plane. The top side of the photograph is upper level.

Reported Minerals

Mineral Assemblages

  • Glendonite - Gypsum
  • Goethite


  • Tateya (Glendonite)
  • Kodo (Glendonite)
  • Iseyama (Glendonite)
  • Teradomari (Glendonite)
  • (Methane hydrate)

Related Occurrences

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