This was in a bid to end a strike that has hit half of global output of the precious metal.
Hopes for an immediate resolution to the strike, which began on Thursday, remained dim given AMCU's uncompromising approach to negotiations and with the two sides poles apart over wages.
The delegations for the talks at a Pretoria hotel were also low level, with no ministers or chief executives from Anglo American Platinum, Impala Platinum or Lonmin. AMCU president Joseph Mathunjwa was also absent.
South Africa's rand lost more than 1 per cent in early trade to hit new five-year lows against the dollar as the strikes coincided with an emerging-market selloff, dealing a double blow to investor confidence in Africa's biggest economy.
"It's a perfect storm. Aside from the offshore factors which are beyond our control, locally we have the strikes, a general election in a few months and a weak economy. So there is no good news for the rand at the moment," said Christie Viljoen of NKC Independent Economists.
Platinum's spot price climbed slightly to 1,425 US dollars an ounce, approaching 2-1/2-month highs, on concerns about the impact the stoppages will have on the metal used for emissions-capping catalytic converters in automobiles.
Under the populist battle cry of a "living wage", AMCU is demanding minimum entry-level pay of 12,500 rand a month from the three platinum producers - a more than doubling of current levels.
Companies say they can ill afford this as they grapple with soaring costs and depressed demand for platinum, especially in key markets such as Europe.