A model holds The Farnese Blue, an unknown historic blue diamond to be sold for first time in 300 years, during a preview of Sotheby's auction sale in Geneva, Switzerland, May 9, 2018. Expected to fetch between $3.7 and 5.3 million, the 6.1 carat, dark grey-blue stone from the Golconda diamond mines of India was first given to Elisabeth Farnese, daughter of the Duke of Parma, in 1715 when she married Philip V of Spain. (Photo/Agencies)
