Rex in turn signed a note saying he had the stone set in the brooch and that he had passed it to his son John Hillary.
Veteran auctioneer Dunbar Sloane snr said yesterday he expected considerable interest from overseas, given the stone's rarity value and Sir Ed's fame as the first man with Sherpa Tenzing Norgay to conquer the world's highest peak.
Sir Ed gave five of the other stones to friends, family members and two members of his Everest expedition, its British leader John Hunt and fellow New Zealander George Lowe - to whom he uttered the phrase: "Well George, we knocked the bastard off."
John Hillary, a Papakura builder, told the Herald his late father gave him the stone "and told me to sell it - that it was worth a fortune".
Asked how realistic he considered the estimated price, he said: "I haven't got a clue - I have never been involved in anything like this before [but] you see some weird things being sold on Trade Me for ridiculous prices."
As far as he knew, his father was the only recipient of an Everest stone who made a special display of it.
Sir Ed's widow Lady June Hillary, who is Nepal's Honorary Consul-General to New Zealand, was surprised to hear of the auction.
Asked if she saw any cultural problems with it, she said although Everest was revered by the Sherpas, it was not considered too holy to allow people to climb.
But she did not believe the Nepalese Government would be keen on climbers removing stones from Everest now, given the numbers scaling it.
Sir Ed's son Peter Hillary said his father had given stones to people precious to him, and his cousin was entitled to do what he wished with his inheritance. He believed his father's legacy was reflected in the items given to museums by himself, his sister Sarah, and Lady June.
That legacy has stretched to London, where a ladder used by Sir Ed for his ascent of Everest was incorporated into the Queen's Diamond Jubilee State Coach, in which she travelled this month for the state opening of the British Parliament.
