Mount Nesugata
Shimoda city, Shizuoka pref., Japan
Synonym
Mount Manzo
Occurrence
Moderate-T hydrothermal deposit
Moderate temperature hydrothermal deposit in rhyolite of the middle Miocene (13 Ma) Yugashima Group. The ryolite was intruded in the middle Miocene (15 Ma) Shirahama Group. This ryolite contains 50-70% K-feldspar, and was mined as the K ore of 6-8% K2O. Ages were determined by microfossils.
Outcrop of rhyolite of the Yugashima Group associated with hydrothermal veins of manganese dioxide. The host is purple rhyolite. The rhyolite looks purple as it includes fine hematite crystals. The dark gray veins are mainly composed of ramsdellite. The thin black bed at the boundary between the host rhyolite and the ramsdelite vein is pyrolusite. It seems that ramsdellite filled the open spaces of rhyolite breccia.
Reported Minerals
- Ramsdellite
- Pyrolusite
- Quartz
Mineral Assemblages
- Ramsdellite - Pyrolusite
Localities
- Kisan-mori Mine (Cu-Pb-Zn)
- Mikawa Mine (Cu-Pb-Zn, Siderite)
- Takami Mine (Cu-Pb-Zn)
- Gunma Mine (Cu-Pb-Zn)
- Yunosawa Mine (Pb-Zn)
- Okuto Mine (Pb-Zn)
- Arakawa Mine (Cu-Zn)
- Osarizawa Mine (Cu-Zn)
- Sayama Mine (Cu-Zn)
- Washinosu Mine (Cu-Zn)
- Yashu Mine (Cu)
- Takaneyama Mine (Cu-Zn-Mn)
- Kawazu Mine (Zn-Au-Te-Mn)
- Manju Mine (Zn)
- Mount Nesugata (Mn oxide)
- Ryushima Mine (Mn carbonate)