Metasedimentary manganese ore; mine now closed.
References:
Fukushima, H., Minakawa, T. & Nishio, D. (2005): Ba-rich tweddillite from the Kamisugai mine in the Sambagawa metamorphic belt, Shikoku, Japan. Ganseki Kobutsu Kagaku 34, 69-76. (in Japanese)
Mineral List:7 entries listed. 7 valid minerals.
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