You won't be left feeling blue if you buy this $1.2m Bulgari diamond

One of the finest precious stones in the world, it should sell for a huge price

One of the rarest stones in the world, a blue diamond, will be offered in the Fine Jewellery Sale at Bonhams in New Bond Street, London, on September 21, and it is estimated to sell for £600,000 - 800,000 ($965,000-1,287,000).

The stunning diamond and blue diamond crossover ring, which was made by Bulgari, comes from a private European collector and has never been seen at auction before, making it even more attractive to prospective investors.

Bonhams' ring is similar to this one sold by Christie's for $15.7m in 2010

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 famous jewellery collection 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, natural blue diamond (the highest grading for a coloured diamond), weighing 3.72 and SI2 clarity.

Hollywood star Elizabeth Taylor famously bought lots of Bulgari jewellery

The term 'fancy' is used to describe a diamond of intense appearance, and the colour 'fancy vivid blue' is one of the rarest. Blue diamonds are structurally the purest of all diamonds, with barely any impurities within their crystal lattice. They account for less than a single % of all diamonds mined.

Jean Ghika, Bonhams' director of jewellery comments, 'Not only is this jewel an exquisite example of Bulgari's craftsmanship at this period, but the fancy vivid blue diamond is an incredibly rare gem in its own right.  Bonhams is honoured to have been chosen to handle the sale of this magnificent ring'.

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Image: Christie's