A strike for a R12 500 monthly wage by Rustenburg platinum mine workers spread to the chrome sector on Monday.
Workers at Samancor said they had been on strike since Friday.
"We demand R12 500 pay after deductions. This excludes bonuses," said Lawrance Kok, one of the workers' leaders.
He said they also demanded a R1500 sleep-out allowance and a R1500 underground allowance.
Comment from Samancor was not immediately available.
Last week, Anglo American Platinum (Amplats) and Aquarius Platinum, in Rustenburg, suspended operations for the safety of their workers.
However, groups of workers gathered at Amplats' Blesbok stadium said it was not a suspension but a strike.
On Friday, workers marched to Aquarius Platinum demanding that it shut down. They said they aimed to have all mines in the area closed this week.
On Monday, Aquarius Platinum said it had resumed operations and that none of the seven people arrested by police during an illegal gathering outside the mine on Friday were employees.
Workers at Lonmin's Marikana mine went on an unprotected strike five weeks ago. They were the first to demand an increase to R12 500.
Ten people, including two policemen and two security guards, died in the first week of the strike. On 16 August, police fired on a group of striking workers killing 34 of them.
On Tuesday, a union shop steward was found hacked to death near the mine.
Soldiers were deployed to the area around the mine at the weekend to help police restore order.
Soldiers could be seen in armoured vehicles at the entrance to Lonmin's Karee shaft.
At the smelter plant in Wonderkop, police maintained a high visibility.
Men carrying umbrellas stood along the road near the Amplats complex waiting to be told where a planned meeting would be held.
Expelled ANC Youth League leader Julius Malema was also expected to address workers.
Last week, while addressing striking workers at Gold Fields' KDC west mine, near Carletonville, Malema called for a national mining strike.
The Hawks said on Sunday that a charge of inciting violence was being investigated against Malema.
Meanwhile, talks under the auspices of the Commission for Conciliation, Mediation, and Arbitration were expected to continue on Monday in the hope of resolving the labour dispute at Lonmin.