Tone Mine
Kinkai-Tone village, Nagasaki city, Nagasaki pref., Japan
Occurrence
Greenschist facies bedded manganese deposit
Bedded manganese deposit in the Nishisonogi metamorphic rocks subjected to Greenschist facies metamorphism as a part of the high-P Nagasaki metamorphic rocks in the Late Cretaceous to Paleocene (90-60 Ma). The deposit is in piemontite schist associated with psammitic siliceous schist at the upper part of the Nishisonogi metamorphic rocks. The Nagasaki metamorphic rocks has been discussed on the relation to the Sambagawa Metamorphism and the Sangun Metamorphism. Metamorphic age was determined by K-Ar radiometric dating of muscovite.
Outcrop of a manganese deposit in Nishisonogi Metamorphic Rocks. The massive black part at the upper left is braunite. The red parts, for example at left end, are rich in piemontite. Braunite can co-exist with quartz, which is rare for high quality Mn-oxide minerals. That is clearly shown in this photograph: white quartz at the upper right contacts with massive black braunite at the left. The reference coin is on the coarse grained piemontite schist. Microscopic scale braunite is usually contained in piemontite schist even in Kanto and Shikoku area, Japan.
Reported Minerals
- Braunite
- Piemontite
- Mn-rich muscovite
- Hollandite
- Ardennite
- Mn bearing leuchtenbergite
Mineral Assemblages
- Braunite - Quartz
- Quartz - Piemontite - Ardennite
- Mn bearing leuchtenbergite - Braunite
Localities
- Tone Mine (Braunite, High-P)
- Oyahana Bridge (Piemontite, High-P)
- Tsukiyoshi (Piemontite, High-P)
Related Occurrences
- Bedded Mn (Diagenesis)
- Bedded Mn (Low-T zeolite facies)
- Bedded Mn (High-T zeolite facies)
- Bedded Mn (Prehnite-Pumpellyite facies)
- Bedded Mn (Pumpellyite-Actinolite facies)
- Bedded Mn (Greenschist facies)
- Bedded Mn (Epidote-Amphibolite facies)
- Bedded Mn (Amphibolite facies)
- Bedded Mn (Albite-Epidote-hornfels facies)
- Bedded Mn (Hornblende-hornfels facies)
- Bedded Mn (Pyroxene-hornfels facies)