It's a good thing Anthony Pratt and Gina Rinehart are friends, because their respective empires are fighting to be Australia's largest private company by revenue.

Rinehart's Hancock Prospecting rode higher iron ore prices to $6.08 billion revenue in 2018-19, a 21.1 per cent increase on the previous year, to come a close second on the Top 500 Private Companies list, created by research house IBISWorld and published annually by The Australian Financial Review.