Trouble has spread to the eastern mining operations of Lonmin in South Africa, raising concerns of more unrest there.
The company says there have been incidents of intimidation towards workers in other mines other than the Marikana mine where 34 men were shot dead by police on 16 August.
Lonmin says only 13% of the miners reported for duty on Monday and says they have been threatened.
Last week 30% turned up for work and 57% at the weekend.
About 2000 men, some carrying sticks and whips, gathered on Monday near the scene of the shotings.
Five armoured police vehicles were parked nearby and a police helicopter had earlier hovered overhead.
Police insist they acted in self-defence on 16 August. Two police officers were among 10 other people killed at Marikana before the tragedy.
The dispute is complicated by a dispute between two unions, the National Union of Mineworkers and a breakaway orghanisation, the Association of Mineworkers and Construction Union.
Lonmin is the world's third largest producer of platinum, a white metal used in car catalytic converters and jewelry, and accounts for 12% of global output. It is losing about 2,500 ounces per day.