The potential closures could cut a tenth of the state firm's 45,000 MW production capacity.

Implats will also delay closing Rustenburg's shaft 12 by one year and shaft 9 by about six months.

Indicated resources at the Ivorian greenfield project now total 1.2Moz.

Africa's No. 2 copper producer increased its sliding scale for royalties of 4 to 6% by 1.5 percentage points and introduced a new 10% tax when the price of copper exceeds $7,500 per tonne.

In April, the government's labour registrar said he intended to cancel registration of AMCU, one of the nation's largest and most militant unions.

The nickel mine, in Mpumalanga province, was hit by soaring costs and lower metals prices in the last few years.