The historic Farnese Blue diamond, which has been passed down through European royal families for the last three centuries, was put up for auction on Tuesday in Geneva and fetched $6.7m (£5m).
Auction house Sotheby's, who auctioned off the item at its Geneva branch, predicted that the diamond would go for between £2.7m and £3.9m as this was the first time the diamond had ever been put up for auction.
After four minutes of bidding at the Geneva auction, the gem went for more or less double the amount it was expected to fetch.
Philipp Herzog von Wurttemberg, chairman of Sotheby's Europe, said: “With its incredible pedigree, the Farnese Blue ranks among the most important historic diamonds in the world.”
“From the first minute I saw the stone, I could not resist its magic and as such, it is a huge privilege to have been entrusted with this sale,” he said.
The 6.16 carat diamond originates from the Golconda mines in India and was first given to Elisabeth Farnese when she married Spanish king Philip V in 1715.
In the last three centuries, the gem has passed through Spanish, Italian, French and Austrian royalty for more than seven generations.