About one-quarter of Lonmin's workers on the morning shift Monday complied with the company's ultimatum to return to the job, amid a wildcat strike that has left 44 people dead.
The world's third-largest platinum producer said 27 percent of workers reported for the morning shift, while unions said they were still in meetings to discuss the ultimatum.
The 11-day-old illegal strike by about 3,000 rock drill operators has shuttered production at the Marikana platinum mine, where 34 people were gunned down by police Thursday after 10 others were killed in clashes between rival unions.
While union leaders held meetings, about 1,000 workers gathered near the mine said they would not return to the job, with several accusing Lonmin of insensitivity by expecting them to go back to work while they are still in mourning.
Monday is the first day of a week of national mourning declared by President Jacob Zuma, with a memorial service planned for Thursday.
"They can fire us if they want, we are not going back to work. Zuma must shut down that mine," one worker said.
Lonmin has threatened to sack the workers who launched the strike on August 10, while urging 25,000 other employees and 10,000 contractors to return to the job, assuring them of their safety.
The upstart Association of Mineworkers and Construction Union (AMCU), which launched the strike calling for a tripling of the basic wage of 4,000 rand ($486, 400 euros) a month, said it expected to have a decision on the ultimatum later Monday.
"We are still engaged in a meeting discussing the issue," treasurer Jimmy Gama told AFP.
The powerful National Union of Mineworkers, whose membership has been eroded by the AMCU's emergence, said it was also in a meeting.
Lonmin management was reportedly in talks with a team of cabinet ministers tasked with organising funerals and aid for victims' families.
Workers meeting in the field near the mine were gathered without weapons, in a mood far calmer than that of similar gatherings over the last week.
Few police were seen on patrol, though a helicopter sometimes passed overhead.