Metamorphosed sedimentary (bedded) manganese ore. Rhodonite was the main ore mineral, with lesser amounts of braunite and tephroite.
Ref.:
Matsubara, S., Miyawaki, R., Kato, A., Matsuyama, F., Mouri, T. and Suzuki, Y. (2001): Arseniopleite from the Gozaisho mine, Fukushima Prefecture, Japan. Bull. Natn. Sci. Mus., Tokyo, Ser. C, 27, 51-62.