The company says current weak prices for cobalt don't justify expanding daily throughput to 6,000 tonnes from 4,650 tonnes at its proposed Nico project.
Operations were suspended for security reasons in early August after an incident involving police left an artisanal miner dead and some equipment damaged.
In securities filings, Vale projected costs from halted operations related to its dam that burst to fall from $3-$4 per tonne of iron ore in the third quarter to $2.5-$3.5 per tonne in the fourth quarter.