* Unions say mining firm protected by powerful politicians
* Gold mines operated by Zuma, Mandela relatives
* Scandal exposes mess in South African mining sector
By Ed Cropley
JOHANNESBURG, Nov 15 (Reuters) - South African unions on Monday accused gold-mines run by a nephew of President Jacob Zuma of failing to pay thousands of workers, and the government of turning a blind eye due for political reasons.
The unions said they would sue the owners of Aurora Empowerment Systems, a black affirmative-action firm with limited mining experience, to recover 16 million rand ($2.3 million) in unpaid wages and pension claims.
The move is the latest twist to a saga that has laid bare the problems in South African mining 16 years after the end of apartheid.
"A slave is somebody who works for no payment, and that is what these workers have been reduced to," Gideon du Plessis, deputy secretary general of the white-collar Solidarity union, told a news conference.
Aurora, which also includes a grandson of former President Nelson Mandela as a director, has been running the once-mighty Orkney and Grootvlei mines on Johannesburg's East Rand on behalf of liquidators since October 2009.
At the time, they employed 5,000 miners but production has been mothballed since March, leaving a skeleton "care and maintenance" staff of just a few hundred, unions say.
Aurora commercial director Thulani Ngubane denied such large sums were outstanding and that Aurora was selling off the mines' assets, thereby jeopardising the chances of finding a new buyer by a Dec. 15 liquidation deadline.
"Those allegations are untrue. We've already paid (workers) up to 80 percent of what is owed to them," he told Reuters. "Labour are blowing things out of proportion because they are looking for more membership."
Mining Minister Susan Shabangu said on Monday she was powerless to respond to miners' demands that she step in because unpaid wages were an issue for the Labour Ministry.
The National Union of Mineworkers (NUM), a powerful black union, said the scandal smacked of corruption.
"How else can we explain it? They don't pay workers' salaries and there are no consequences," NUM general secretary Frans Baleni said. "The application of the law is selective depending on who you are and who you are associated with."
Although South Africa has slipped down the gold production rankings to number four, it sits on an estimated 90 percent of world platinum reserves. Citibank has estimated its untapped mineral assets at $2.5 trillion.
Despite this huge potential, its mining sector failed to grow in the 2001-08 global commodity boom due to investors' concerns about black-ownership targets, power shortages, byzantine regulation and labour activism.
The government has acknowledged the problem and embarked on a major clean-up three months ago in a bid to turn around a sector that employs nearly 500,000 people and accounts for nearly nine percent of output. (Editing by Jon Herskovitz and Jon Boyle)