Llimestone mines across Japan, such as the Torigatayama Quarry...

Llimestone mines across Japan, such as the Torigatayama Quarry Complex in Kochi Prefecture, the largest mine in the country.
1 producing copper underground mine (Atacama Kozan : https://www.atacamakozan.cl/) in Chile.
Many exploration projects in Chile : https://www.mineranittetsu.cl/proyect-map/
Arqueros is the most advanced (construction will begin) : https://www.nittetsukou.co.jp/eng/ir/library/pdf/Commencement%20of%20the%20Construction%20Works%20of%20Arqueros%20Copper%20Mine%20in%20Chile.pdf
Exploration (Los Chapitos : copper) in Peru with Camino : https://caminocorp.com/news/camino-signs-contract-to-commence-copper-exploration-drilling-in-december-at-los-chapitos-peru/
Some less active exploration projects in Asia, Fiji and a small stake in a sleeping tin project in Morocco ( https://www.atlantictin.com.au/pdf/084db539-ed3b-4485-9ec5-00da20920e4c/Atlantic-Tin-Prepares-for-Achmmach-Development.pdf ).

If you have a look at history section? many projects in the past since 1899 : https://www.nittetsukou.co.jp/eng/company/history/
Coal at first. For now, they keep a machinery division with coal mines technologies. For example, Kaho Manufacturing produces monorail. Qaleh-Zari Copper Mine in Iran (sold in 1991)
El Roble Copper Mine in Columbia (sold in 1998)