The Tanzanian government submitted three bills to parliament on Thursday that would allow it to force mining and energy companies to renegotiate their contracts.
The company, which owns the Cullinan mine that has produced the two largest diamonds in the British Crown Jewels, said output and revenue will be lower than market expectations.
Ratings agency Moody's warned on Wednesday that new regulations seeking to accelerate black ownership in South Africa's mining industry would deter investment, raise costs and diminish cashflow generation.