Lucapa, the Australian diamond company which mined the stone, says that the diamond originally measured over seven centimetres in length, which makes it the largest diamond ever discovered in Angola.
Called The Art of Grisogono, the 163.41-carat diamond - attached to an emerald and diamond necklace - was sold to an unnamed telephone bidder at the Christie's autumn jewel auction in Geneva, Switzerland.
The necklace is made of 18 diamonds on one side and two rows of pear-shaped emeralds on the other.
It is the largest diamond ever found in Angola and the 27th largest rough white diamond ever discovered.More news: Toast overlay being used by malicious Android apps to install additional malware
The diamond itself was cut from a 404 carat rough rock which was found in February of 2016 in Angloa's Lulo mines.
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. He began splitting the rough diamond into two in June a year ago and eventually polished the diamond down to an emerald-cut.
The "Le Grand Mazarin", a 19.07-carat light pink diamond, was once set in the crown of Napolean.
Geneva jewellers de Grisogono then took on the task of transforming the massive diamond into a piece of wearable jewellery.More news: Incidence of non-communicable diseases in India rose by 25 % since 1990
Christie's described the stone as "a timeless symbol of beauty" and said it hoped to rake in $6.0-9.0 million (5.1-7.7 million euros) for the diamond.
However, he said it gave him "quite a big headache".
"I have never had a problem finding creative ideas, but this time there was the vast pressure of "dressing" such an awesome diamond".
He pointed out that when rival auction house Sotheby's sold an 118.28-carat flawless D diamond in 2013, it was sold for $30.6 million.More news: Roy Moore addresses church crowd in Alabama amidst sexual assault scandal
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