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Mount Futago

Ogano city, Chichibu county, Saitama pref., Japan

Occurrence

Limestone

Calcite deposit in recrystallized limestone block of the Early Jurassic (180 Ma) Yusugawa unit or the Early Triassic (250 Ma) Sawadani unit, a member of the Northern Chichibu accretionary complex. The age of limestone is Carboniferous Late Pennsylvanian (300 Ma) to Permian Guadalupian (260 Ma). Ages of sedimentary rocks were determined by radiolarians, Limestone by Fusulina, a kind of Foraminifera.

Mount Futago

Old mine for limestone of the Yusugawa Unit or the Sawadani Unit. The walls at the both sides are composed of crystalline limestone. Recrystallized part of the limestone block was mined. The size of calcite crystals is up to a few cm. The distribution of the recrystallized calcite is restricted, and fresh fossils are in other parts of this limestone block.

Reported Minerals

Mineral Assemblages

  • Limestone(Host) - Calcite

History

  • 1910's: Toyama pharmacy at Asakusa-Kaminarion, Tokyo, mined calcite for medical use.
  • Tokijiro Mizuno made the first Japanese nicol prism using calcite specimens supplied by Toyama pharmacy.
  • After mined by a few people, the mine was closed.

Localities

  • Mount Futago (Limestone, Recrystalized)
  • Koma (Calcareous sandstone, Veins)

Related Occurrences

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