On Friday, Western Australia's Environmental Protection Agency opened a public consultation process on Hancock Prospecting's plan to develop several open pits and a processing facility about 210km south of Port Hedland.
The approvals are being sought for up to 20 million tonnes per annum over at least 30 years.
In 2013 Rinehart advanced the approval process for an initial 5Mtpa operation on the family cattle station, however the plan was paused in 2015 as iron ore prices fell.
The mine, which would be just 3.5km from the family homestead has been a long-held dream for Rinehart, whose first two developments, Roy Hill and Hope Downs, are joint ventures.
Other mines in the Hancock portfolio, which are 100%-owned, were either developed or planned by Atlas Iron, so Mulga Downs would realise a long-held family dream.
The tenements have been kept in good standing over the past few years, and the project is effectively shovel-ready.
Mugla Downs is close to Fortescue Metals Group's Cloudbreak mine, which also sits within the cattle station.
Mulga Downs ore is expected to be trucked to the existing rail line network for transport to the port.
If Hancock gets its approvals, and the market holds out, work on an initial 5Mtpa pit at Murray Hill, ramping up to 20Mtpa by the middle of the decade.
Hancock has been busy beefing up its iron ore portfolio in recent months.
Late last year it signed a deal with the Australian Premium Iron joint venture over the stalled Hardey iron ore deposit in the Pilbara. It also signed an agreement with Mineral Resources to jointly investigate the development of a new iron ore export facility at Port Hedland's Stanley Point Berth 3 at South West Creek.
Hancock booked a A$7.3 billion profit last financial year.
