TrekGEO > Mineral Trail > Kyushu region > Nagasaki pref. > Tone Mine

Japanese page

Tone Mine

Kinkai-Tone village, Nagasaki city, Nagasaki pref., Japan


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.

Tone Mine

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
Copyright (c) 2015 NariNari, All Rights Reserved.