(IDEX Online) - A 118.35-carat royal blue sapphire is to be sold later this by month by Phillips Hong Kong with a high estimate of $4.5m.It was set into a necklace by Bulgari in 2004 as party of its High Jewelry Collection and appears at auction for the first time.The Sri Lankan unheated, cushion-shaped sapphire scored what Phillips describes as an "impossible" 98 points in the Gubelin Gemstone Rating for quality, rarity, and salience.It is among the largest sapphires ever offered at international auctions in the past three decades.Larger gems include the 486.52-carat Giant of the Orient, the 422.99-carat Logan Blue Sapphire, which is on display at the Smithsonian Institution's Museum of Natural History, and the 392.52-carat Blue Belle of Asia.Pic courtesy Phillips