The most-actively traded iron ore contract on the Dalian Commodity Exchange, for September delivery, fell as much as 1.3% to 887.5 yuan ($129.03) a tonne.
It's always going to be a fine balance between a company assessing how much of the value of the project it can afford to surrender to the host country.
The drop to 64.057 million tonnes came as several major operations remained fully or partially shut down in the second quarter following a deadly dam burst at the Corrego do Feijão mine.