Plunging commodity prices have knocked Clive Palmer off Australia's top 50 rich list.

Mr Palmer's estimated wealth has fallen below $US550 million - the cut off for the latest Forbes Australia list - as the value of his coal and iron ore assets fell.

Falls in commodity prices mean Clive Palmer missed the cut for Forbes' rich list for 2015. Credit:Alex Ellinghausen

He's not the only mining magnate whose fortune has been hit by tumbling commodity prices.

Gina Rinehart's wealth dropped by $US6 billion, but she remains the country's richest person with a net worth of $US11.7 billion.