Australia's richest woman Gina Rinehart has signalled her ambition to be a bigger player in the iron ore industry after lobbing a takeover bid for Atlas Iron that values the junior miner at $390 million.

The Rinehart offer, made through Hancock Prospecting subsidiary Redstone, is all cash and unconditional. It will be funded through Hancock Prospecting's $3 billion cash reserves and has sidelined fellow Perth-based rich listers Chris Ellison and Andrew Forrest in what had been a three-way battle over Atlas.