Rare Kashmir sapphire glitters in Geneva auction

The largest Kashmir sapphire ever auctioned and a royal tiara which everyone can try on via Instagram are the stars of this year's May magnificent jewels sales in Geneva.

Gems worn by French emperor Napoleon Bonaparte's adopted daughter also dazzle among the historic treasures being sold by Sotheby's and Christie's auction houses on May 11 and 12.

The Kashmir sapphire, a 55.19 carat gem, was formerly in the collection of Maureen Constance Guinness, a marchioness of the aristocratic Anglo-Irish brewing family, who died in 1998.

Kashmir sapphires of over 30 carats are very rare. It is being sold alongside a cushion-shaped Kashmir sapphire weighing 25.97 carats and the pair are estimated to fetch $2-3 million.

Following their discovery in the early 1880s, the mining of Kashmir sapphires only lasted from 1882 and 1887, making such gems some of the most coveted on the market, according to Sotheby's.

They have a rich cornflower blue hue with a soft, velvety texture, and retain their lustre in any light.

"Kashmir sapphires are among the rarest coloured gemstones known to man," said Benoit Repellin, head of magnificent jewels sales at Sotheby's in Geneva.

"These gems have over the years acquired an almost legendary status."

- Instagram tiara -

Among the other historical pieces on sale is a tiara kept for more than 150 years in the Italian House of Savoy royal dynasty.

The diadem, containing 11 natural pearls and diamonds, dates from the second half of the 19th century and is estimated at $1-1.5 million.

The tiara is also a masterpiece of ingenuity as it can be separated into two parts, allowing it to be worn as a necklace, Repellin told AFP.

Sotheby's said it was witnessing unprecedented global demand for royal jewellery, particularly from younger clients in Asia.

Collectors from that continent have bought a third of the tiaras sold by the auction house in the past five years.

Keen to attract the interest of a new generation, Sotheby's created an Instagram filter that allows people to create a picture of themselves wearing the Savoy tiara in a sumptuous Italian palace.

In the big gems category, Christie's is offering a rectangular white 100.94-carat diamond called the Spectacle, valued at $12-18 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.

Other standout items include a pendant set with a 104.40 carat pear emerald, mounted by US jeweller Harry Winston, offered by Sotheby's for $1-1.5 million.

It is a "really exceptional weight for emeralds, which are more fragile stone", said Repellin.

- Napoleonic treasures -

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

The nine pieces, including a tiara valued at up to $275,000 and a necklace estimated at up to $350,000, "have remained in the same family since they were offered to Stephanie de Beauharnais, on the occasion of her wedding at the Tuileries Palace" in Paris, said Marie-Cecile Cisamolo, a jewellery specialist at Christie's.

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

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

Cisamolo also noted the growing Asian market for such gems.

"At the moment, we see a lot of Asians who like to wear these important jewels, for major events in their life," she said.

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

The crown, set with a Burmese sapphire in the centre, is estimated at $190,000-$385,000.