World’s ‘most beautiful’ diamond to be auctioned in Geneva with £23m guide price

The largest ever diamond of its kind to come to auction is being sold in Geneva with a guide price of £23m.

Described as "the most beautiful diamond in the world", the 163.41 carat flawless D-colour emerald-cut diamond will be auctioned off at Christie’s in the Swiss city on Tuesday evening.

Set in an emerald and diamond necklace, the massive gem has already been on tour to Hong Kong, London, Dubai and New York.

The stone was 404.20 carats when it was a rough diamond mined in eastern Angola on 4 February last year.

It is the largest diamond ever found in Angola and the 27th largest rough white diamond ever discovered.

The Gemological Institute of America (GIA) found the stone was a D-colour, Type IIA diamond – a variety highly valued for its transparency and colour.

A team of more than 10 specialists from the Julius Klein Group in New York transformed the rough diamond into the final cut and polished gem.

Diamond cleaver Ben Green analysed the gem for months and eventually started working on splitting the rough diamond in two in June last year.

It took the 80-year-old six months to polish the diamond down into an emerald-cut.

Geneva jewellers de Grisogono then took on the task of transforming the massive diamond into a piece of wearable jewellery.

Founder Fawaz Gruosi described the gem as "the most beautiful diamond in the world".

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However, he said it gave him "quite a big headache".

Mr Gruosi added: "I never thought I would work with a 163.41 carat diamond of this quality.

"I have never had a problem finding creative ideas, but this time there was the immense pressure of ‘dressing’ such an amazing diamond.

"I couldn’t do something very simple or that has already been seen. I needed a design that is outside the box."

Mr Gruosi and his team eventually came up with an asymmetric necklace featuring 18 emerald-cut diamonds on one side with the 163.41-carat diamond as the centrepiece.

The stone can be detached from the necklace and attached to other jewellery.

(c) Sky News 2017: World’s ‘most beautiful’ diamond to be auctioned in Geneva with £23m guide price