(IDEX Online) - Sotheby's Hong Kong is to auction one of the world's largest and most valuable blue diamonds, with an estimate of $26m to $37m.The Infinite Blue, an 11.28-carat radiant-cut fancy vivid blue stone, will be offered for sale in a single-lot live auction on 5 October.The Type IIb gem is set with a halo of pink and white trapezoid diamonds. Sotheby's said in an Instagram post that the auction "follows a series of record-breaking sales of rare blue diamonds at Sotheby's, including the 15.10-carat De Beers Blue in 2022 and the stunning 11.16-carat Bulgari Laguna Blu in 2023."The fancy-vivid-blue 15.10-carat De Beers Blue sold at Sotheby's Hong Kong in April 2022 for $57.5m, sharing a record with the 14.6-carat Oppenheimer Blue, which sold at Christie's Geneva in May 2016.The 11.16-carat pear-shaped Bulgari Laguna Blu - certified as the highest grade blue diamond ever by the GIA - was auctioned for just over $25m at Sotheby's Geneva in May.Pic courtesy Sotheby's.