Several thousand workers affiliated to the NUM began striking in the coal sector on Sunday evening, the union said.
Talks over wage increases with employers collapsed this week and the Commission for Conciliation, Mediation and Arbitration issued a non-resolution certificate, the National Union of Mineworkers said in a statement.
The union wanted an increase of 14% for artisans, miners, and officials.
Their employers – Anglo Coal, Glencore, Exxaro, Kangra, Koornfontein, and Msobo – were offering increases of between 5% and 8.5%.
The union said 30 000 of its members would join the strike.
According to the Chamber of Mines the sector directly employed 90 000 people and coal accounted for 94% of South Africa’s energy production.