ONE of the rarest precious stones in the world is being put on show to the public.
The fancy vivid blue diamond is expected to fetch between £4m and £6m at Sotheby’s Magnificent Jewels sale in Geneva, on May 12.
The gem, described as cushion-shaped and flawless, owes its distinctive colour to the presence of the chemi-cal element boron during the stone’s formation.
It was discovered last year in South Africa.




