LONDON.- One of the world’s rarest stones, a blue diamond, will be offered in the Fine Jewellery Sale at Bonhams, New Bond Street on September 21st and is estimated to sell for £600,000 – 800,000. The stunning diamond and blue diamond crossover ring made by Bulgari comes from a private European collector and has never been seen at auction before. The collector’s father commissioned the ring from the legendary Italian jewellery house as a gift for his wife in the mid 1960s, when Bulgari was at the height of fashion and innovation. It was a time where the world’s rich and famous sought Bulgari’s unique craftsmanship and high quality jewellery designs, including Elizabeth Taylor who bought much of her jewellery there. Typical of Bulgari’s elegant simplicity, the ring offered by Bonhams is set obliquely with a pear-shaped diamond, weighing 3.93 carats, D colour, VS2 clarity, and a pear-shaped fancy vivid,