JOHANNESBURG, South Africa (AP) _ A strike by at least 35,000 miners shut down the world's second-largest platinum producer on Tuesday - the second major mine hit this week by worker disturbances.

Most of Impala Platinum Ltd.'s workers walked off the job Monday at the company's four mines to protest the dismissal of about 220 employees for taking part in a protest.

At the President Steyn Gold Mine south of Johannesburg, meanwhile, production was sharply curtailed following weekend clashes that killed at least 75 black miners, including six who died Tuesday from injuries.

The unrest reflects the growing importance of economic issues in black protests against the white-minority government.

The mines have been particularly hard hit by a combination of political violence and falling prices for many minerals. Workers' hostels at mines have been frequent flashpoints of black factional violence. The cramped, usually dilapidated single-sex dormitories bring blacks from different tribes and of different political persuasions into close contact.

The strike at Impala in the Bophuthatswana black homeland was called to protest the recent firing of employees who took part in a sit-in opposing worker violence, according to the National Union of Mineworkers.

Mine closures, wage disputes and strike-related violence since July have plagued the Impala mines, 150 miles west of Johannesburg, which produce about 40 percent of the world's platinum. At least 19 people have died in unrest since August, when clashes begun between workers supporting a strike and others opposing it.

The company said 35,000 of its 42,000 black workers were on strike, while the union put the number of strikers at 40,000.

The gold mine violence was also apparently started by disputes over whether to follow an anti-government strike. The African National Congress last week called the two-day strike to protest a new 10 percent food tax.

The fighting has left at 75 blacks dead and 177 injured at the mine, one of the world's largest.

On Monday, about 2,500 miners were sent home to ease tensions.

There were no reports of trouble Tuesday, according to the Anglo American Corp., the huge conglomerate that owns the mine 155 miles south of Johannesburg.

Officials of the National Union of Mineworkers described the atmosphere at the mine as extremely tense.

The ANC and its close ally, the Congress of South African Trade Unions, organized the nationwide general strike Nov. 4-5 that was supported by more than 3 million blacks, the majority of the country's work force.