Christie's is to sell Leonore 'Lee' Annenberg's giant diamond ring as part of their New York October jewels auction, priced at $3-5m.
The Annenberg Diamond is currently touring Geneva, London, Hong Kong and Los Angeles to find a suitable buyer before next month's Christie's sale.
The diamond's most recent stop was London, before being secured shipped to Hong Kong in time for the popular September Hong Kong Jewelry and Gem Fair.
According to Forbes, the world tour is emblematic of why fine jewellery is withstanding the global economic downturn.
Buyers in the emerging markets in the Middle East and Asia are still happy to spend, Luca Solca, a luxury goods analyst at Sanford Bernstein in London, told Forbes.
Billionaire's stone is set to sparkle
The Annenberg Diamond is an emerald-cut square gem, top D-colour (or completely colourless) and weighs a vast 32.01 carats.
It was mined in South Africa and mounted as a ring designed by jeweller David Webb. The diamond is flanked by two pear-shaped diamonds of 1.50 and 1.61 carats.
Its closest competitor at the auction is a Tiffany and Co. diamond ring owned by the late New York socialite Lillian Booth: a G-color stone weighing a substantial 21.42 carats.
Christie's predict that the diamond's owner and her reputation will enhance what is already a flawless stone.
Lee Annenberg was listed at the world's 403rd richest person by Forbes, the day before her death in March of this year. She reportedly had a net worth of $1.7bn.
Forbes was formerly President Ronald Reagan's chief of protocol, the wife of publishing magnate Walter H. Anneberg and US Ambassador to London.
She was famed for her glamorous life, philanthropy - including setting up the Annenberg Foundation - and her fine taste in jewellery.