By Erika Winters
A rare 5.30-carat blue diamond ring will lead Bonhams Fine Jewelry sale on April 24, 2013. The fancy deep blue diamond is set in a Bulgari "Trombino" ring, made circa 1965. The ring is expected to fetch £1,000,000 to £1,500,000 ($1.6 to $2.4 million) at Bonhams' upcoming auction.
