More than 1.76-million people joined the ranks of the global super-rich last year as stock market gains and property prices swelled personal fortunes.
Neighbours of Glencore boss Ivan Glasenberg feel uneasy about the bounty they have received.
The companies were asked to attend the hearing to offer their views on how best to reform the role of the department.
Daniel Thakamakau, a South African miner who allegedly contracted TB after digging gold for Anglo American, has demanded compensation.
Anglo American SA could be facing legal action as workers say there are inadequate safety measures in place in their mining operations.