TrekGEO > Mineral Trail > Koshinetsu region > Nagano pref. > Ikenofukuro

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Sakai, Fujimi city, Suwa county, Nagano pref., Japan



Phenocryst of andesite of the Late Pleistocene (0.5 Ma) Ikenofukuro Lava (Shinano-sakai lava), a debris flow deposit of southern part of Mount Yatsugatake. The Ikenofukuro Lava is a part of Kiretto andesite. Volcanic rocks of southern Yatsugatake area were described only as Kiretto andesite. The Ikenofukuro Lava is probably a part of Okoyayama Lava erupted from Gongendake Volcano.


Outcrop of andesite of the Ikenofukuro Lava. The black crystals are hornblende phenocrysts. The fine white crystals are anorthite phenocrysts. Local people have called dispatched hornblende as "Roppo-ishi", hexagonal stone in Japanese, for more than 100 years.

Reported Minerals

Mineral Assemblages

  • Andesite (Host) - Hornblende


Related Occurrences

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