A rare blue diamond that has spent the past 300 years in Europe's royal houses has been sold at auction in Geneva for $6.7m (£5m). The Farnese Blue was given as a wedding present to Elizabeth Farnese, daughter of the Duke of Parma, when she married Philip V of Spain in 1715. It then passed down through the generations, moving from Spain to France, Italy and Austria. The 6.1 carat diamond comes from the famous Golconda mine of India. It sold after just four minutes of bidding at Sotheby's, easily passing the auction house's estimate of $3.5m-$5m. "We were expecting a good result but we started from $3.5m and we ended ... (full story)