A rare and flawless cushion-shaped blue diamond is expected to sell for between $5.8 million and $8.5 million (£4.1m to £5.9m) when it goes up for auction at Sotheby's Magnificent Jewels auction in Geneva on May 12. The buyer will also choose a name..

De Beers, the world's leading diamond company, declared on Wednesday that it was selling its Cullinan Diamond Mine in South Africa, which is the producer of the largest diamond, The Cullinan, which weighed over 3000 carats, uncut. The grand mine will go..