Prince Philip has poked fun at Australia's richest person - mining entrepreneur Gina Rinehart - when the two met during a garden party in Perth.

The iron-ore queen was among 1800 guests, including some of Western Australia's most prominent business, sporting, legal, health and media identities, at the event in honour of the Queen at West Australian Government House yesterday.

Pointy hat ... Gina Rinehart, second left, meets the Queen. Credit:Getty Images

Ms Rinehart first chatted to Her Majesty, who was dressed in a Peter Enrione printed silk dress with a coat in sea green and a matching hat designed by Rachel Trevor-Morgan.

When the Duke met Ms Rinehart, who was wearing a white dress and wide-brimmed black hat, he made the entrepreneur laugh but the Australian refused to say what the royal had said.