A jewellery set worn by French emperor Napoleon Bonaparte's adopted daughter sold for $1.65 million in Geneva on Wednesday, soaring way above the pre-auction estimate.

Marking the 200th anniversary of Napoleon's death, Christie's auction house sold the nine imperial jewels adorned with sapphires and diamonds, which were from the collection of his adopted daughter Stephanie de Beauharnais.

Some 38 sapphires from Sri Lanka were used to create the set in the early 1800s.

Offered as separate lots, the jewels had remained in the same family ever since they were offered to Beauharnais on her wedding to Charles, the grand duke of Baden, at the Tuileries Palace in Paris in 1806.

Sapphire and diamond earrings c. 1800, made with pear and cushion-shaped sapphires and old-cut diamonds from the same set.

Besides their historical value, the jewels were also prized for their natural blue, as sapphires usually undergo heat treatment to accentuate the colour.

The nine pieces included a tiara, a necklace, a pair of earrings, two pendants, two brooches, a ring and a bracelet.

"There was a huge demand from collectors around the world, both in Asia and the Middle East, also Europe and the Americas," auctioneer Max Fawcett told reporters at the Magnificent Jewels sale.

It was thought that the collection might fetch $475,000 in total, but the tiara alone went for $462,000.

It contains octagonal step-cut and oval-shaped sapphires, rose and old-cut diamonds, and gold.

Portuguese crown, Russian diamond 

The sale also included a sapphire crown worn by Queen Mary II of Portugal, who was twice the country's reigning monarch before her death in 1853.

Set with a Burmese sapphire in the centre, the crown was estimated at $190,000-$385,000 but sold for far more, at $1.95 million.

From the same set - a sapphire and diamond brooch circa 1800, made with an oval-shaped sapphire and old-cut diamonds.

The priciest item in the sale was the last of the 146 lots – a rectangular white 100.94-carat diamond called the Spectacle, which sold for $14.1 million.

The internally flawless diamond is the largest stone ever to have been cut in Russia and was cut from a rough stone unearthed in the remote northeastern Yakutia region in 2016.

The preparation and cutting process took a year and eight months.