Workers at Wonderkop on Thursday carried symbolic knobkierries and umbrellas for shelter from the sun.
Mine security used water cannons on strikers at Anglo American Platinum's Khuseleka mine in Rustenburg, the Association of Mineworkers and Construction Union said on Friday.
It had remained adamant up until Thursday that the strike would be peaceful.​
"The situation is out of control, it is tense," said co-ordinator Evans Ramokga.
"Mine police [security] without any provocation sprayed workers with water. The workers had gathered to picket outside the mine's operation."
He said the workers retaliated by pelting the security staff with stones.
"If there was anything wrong, they should have informed marshals or contacted me."
Wage demand
Amcu members at Amplats, Impala Platinum and Lonmin went on strike on Thursday demanding entry-level monthly salaries of R12 500.
On Thursday, he said the union had roped in more marshals to ensure that the strike was peaceful.
North West police could not immediately confirm the incident.
Workers at Lonmin, Implats and Amplats downed tools on Thursday in a protected strike in the hopes of getting salary increases of up to R12 500.
Media warning
Amcu president Joseph Mathunjwa addressed about 1 500 workers at the Wonderkop Stadium at Marikana, warning them against talking to the media. He has accused the media of peddling lies about the prospects of the union's strike in the platinum sector.
They dispersed after Mathunjwa's address and promised to return to Wonderkop on Friday for a progress report on the wage negotiations.
Many of the striking workers were hopeful that the intervention of Deputy President Kgalema Motlanthe would advance their cause. Motlanthe vowed to intervene in the wage negotiations this week. – Sapa