Uncertainty around the charter has deterred investment into a sector that accounts for 8 percent of gross domestic product in the world's top platinum producer.
Prices of steelmaking raw materials dropped to multi-week lows on Thursday as a festering trade row between China and the United States kept risk appetite low.
Eike Batista, who was once one of the richest men in the world, was found guilty of bribing former Rio de Janeiro governor Sergio Cabral in exchange for contracts.