The rand, which tumbled to a four-year low against the dollar on Thursday on fears of a strike at Anglo American Platinum (Amplats), extended its slide on concerns about further disruptions to an already struggling economy.
The currency fell as low as 9.4334, its lowest since April 2009 when emerging markets were still reeling from the effects of the global financial crisis.
Joseph Mathunjwa, head of the Association of Mineworkers and Construction Union (AMCU), said Zuma's ruling African National Congress (ANC) was ignoring violence against its members in the platinum belt near the northwest city of Rustenburg.
"We are going to write another last letter to the office of the president that we need a meeting in order to talk about these issues at Rustenburg, of the killing of our members," he said on Johannesburg's Talk Radio 702.
"This is the show of AMCU's commitment to peace," he said. "We said we are going to bring the economy to a standstill."
AMCU's emergence since early 2012 as the most powerful platinum union has turned mining labor relations on their head and sparked fears of a wave of worker militancy stretching from the car plants of Durban to the vineyards around Cape Town.
The crumbling of the decades-long monopoly of the National Union of Mineworkers (NUM) has also opened the door to an array of worker committees and anti-capitalist activists opposed to the ANC and South Africa's post-apartheid economic status quo.
Faced with such a diverse and novel range of forces, the ANC is running blind even though the decline of NUM - its ally in the decades-long anti-apartheid struggle - is likely to hurt it in an election next year.
"It's very difficult to decipher properly what is going on," ANC deputy president and NUM founder Cyril Ramaphosa told the radio broadcaster.
"There's union rivalry, fighting for turf, and there are obviously other elements coming into the space. We keep hearing about the Socialist Workers Party or whatever and that seems also to be fanning the flames," he said.