South Africa's rand weakened on Friday, after nationwide electricity blackouts overnight by ailing state utility Eskom spooked investors and reignited worries about the economy.

At 1500 GMT the rand had slipped 0.46% to 14.8100 to the dollar, compared to a close of 14.7460 in the previous session.

Power firm Eskom implemented stage 2 power cuts, or loadshedding, shaving off 2,000 megawatts from the national grid starting at 2000 GMT on Thursday evening until 0300 GMT on Friday.

The firm said it had lost three generation units, pushing its emergency reserve capacity to "critical levels".

Eskom added the risk of power cuts on Friday was high as the system remained severely constrained, and that loadshedding on Friday could not be ruled out.

The rand had rallied on Thursday to its firmest since before a bleak Oct. 30 budget, mainly on the back of renewed hopes of a US-China trade deal that helped the currency shrug off a dip in business confidence and a contraction in manufacturing.

On the stock market, the benchmark JSE Top-40 Index fell 1.61% to 50,398.87 points while the broader All-Share Index closed down 1.54% at 56,600.46 points.

Gold mining companies fell to the bottom of the blue-chip index with Gold Fields down 6.31% and AngloGold Ashanti slipping 2.34% as a stronger dollar lead to weaker gold prices.