Platinum Miners Tumble as Zim Turns up Heat_Shares in South Africa-listed platinum miners tumbled on Monday as Zimbabwe turned up the heat on foreign mining firms and gave them six months to sell majority stakes to local black investors.

While something along the lines of the ultimatum had long been expected, the sharp declines underscored how jittery investors are about the political risks of doing business in the region.

London- and Johannesburg-listed Aquarius Platinum, the world's fourth largest primary platinum producer, was down more than 7% to R38.05, its biggest single day fall since January.

Impala Platinum, the world's second-largest producer of the precious metal which has Zimbabwean operations, fell over 5% at one point to a 10-day low and was trading 3.55% lower at R190.56 in the afternoon.

The bourse's platinum mining index was down 3.43%.

Foreign mining firms in Zimbabwe must sell a majority stake to local black investors within six months, according to a release in the Government Gazette. It was released on Monday but dated from Friday.

It also said companies had 45 days in which to submit details of how they planned to transfer ownership.

Once it is published there it effectively becomes law.

The notice said that if a foreign - or "non-indigenous" mining company - showed "good cause", the deadline for the transfer of ownership could be extended for a "further period of not more than six months."

Investors are also concerned about regulatory uncertainty in South Africa, the world's largest platinum producer by far. The platinum price was about 0.8% lower on Monday.

"I think this is because of the Zimbabwean story," said Abri du Plessis, chief investment officer at Gryphon Asset Management, referring to the share price falls.

"That 51% that they want in local hands looks fairly fixed at this point in time so that's basically driving the platinum down."

Defiant Mugabe

Zimbabwean President Robert Mugabe on Sunday vowed his party would not back down from its drive to force foreign-owned companies to sell majorities to local blacks.

But Mugabe's ruling ZANU-PF party is in an uneasy unity government with the Movement for Democratic Change, which has called for more gradual policy changes on such fronts with the battered economy in the midst of a fragile recovery.

Zimbabwe's mining companies would be comfortable with selling stakes of 26% to local owners, the head of the country's mining chamber said earlier this month.

Aquarius Platinum said on Friday "its Zimbabwean operating subsidiary, Mimosa Mining Company (Pvt) Limited, is engaged in discussions with the relevant authorities in order to establish a position that will be compliant with the Act and beneficial to stakeholders".

Impala Platinum's Zimbabwe unit signalled in early March that it is committed to a $500m mine expansion, although the board will review progress in May amid the mine take-over talks.

Officials at Impala Platinum and Aquarius could not immediately be reached for comment.