The Cullinan Blue is expected to fetch more than $US45 million ($AU62.45 million) and is believed to be the largest and one of the only five blue diamonds in excess of 10 carats to be auctioned. Source: Sotheby's

Bruce Cleaver, De Beers Group

Discovered in April 2021 at the Cullinan Mines in South Africa by UK-based Petra Diamonds, the diamond was part of the special tender purchased by De Beers and diamond manufacturing firm Diacore for $US40.2 million ($AU55.79 million). Source: Sotheby's

The step-cut stone was taken from a 39.35-carat rough blue diamond sold by Petra to DeBeers and Diacore three months after it was unearthed, then cut and polished into the Cullinan Blue. Source: Sotheby's

The Zoe Diamond – Sold for US$32.6 million

The Blue Moon of Josephine – Sold for US$ 48.46 million

The Millennium Blue – Sold for US$31.83 million

The Sky Blue Diamond – Sold for US$17 million

The Blue Moon of Josephine – Sold for US$ 48.46 million

The Memory of Autumn Leaves – Sold for US$42 million

The Cullinan Blue was originally a 39.34-carat Type IIb rough recovered from the South African Cullinan diamond mine in April 2021 Source: Petra Diamonds