Historic gems to star at Geneva jewel auctions

Russian diamonds that reputedly helped broker peace between warring empires three centuries ago will go to the highest bidder at the Geneva jewel auctions this week.

The Swiss city's twice-annual sales of rare jewels are often dominated by stones the size of door-stoppers.

But this week, gems enriched by the weight of history will share centre-stage with those valued by their weight in carats.

Christie's begins the auction season on Tuesday at the luxury Four Seasons Hotel des Bergues on Lake Geneva, where a line of Bentleys or Porsches typically builds in the runup to the autumn sale.

Rival Sotheby's takes its turn on Wednesday across the road at the five-star Hotel Beau Rivage.

Among Sotheby's showcase offers is a parure featuring diamonds once owned by Russian empress Catherine I that were given to her by her husband, Czar Peter the Great, who led Russia until his death in 1725.

In 1711, Catherine was worried that a raging conflict with the Ottoman Empire posed an existential threat to Russia and ordered her husband -- in the middle of the night -- to draft a peace treaty, Sotheby's said, citing historical records.

Without telling Peter, Catherine sent the peace proposal and all the jewels she was travelling with to the Ottoman Sultan Ahmed III.

The Sultan "accepted these and was obviously delighted, and the truce was given and the (Russian) empire was saved", David Bennett, head of Sotheby's International Jewellery Division, told AFP.

The parure featuring Catherine's diamonds is expected to sell for between $3 million (2.8 million euros) and $5 million.

In an auction heavy on Russian imperial treasures, Sotheby's is also offering a diamond necklace with a detachable clasp owned by Empress Catherine II -- Catherine the Great, who ruled Russia from 1762 to 1796. It is similarly valued at up to $5 million.

- $30 million bling? -

Tuesday's top seller will almost certainly be a set of earings made of two flawless white diamonds weighing 52.55 carats and 50.47 carats, valued by Christie's at $20 million-$30 million for the pair.

Tobias Kormind, head of the 77 Diamonds firm that tracks the global diamond market, said elite collectors of rare gems are typically more attracted to loose stones and may shy away from the earings.

"These earrings are far more likely to be a gift for someone to wear for special occasions," he said, noting that the list of people interested in socialising with more than 100 carats worth of diamonds on their ears is limited.

"The buyer is highly likely to be a newly minted Russian or Chinese billionaire oligarch or business tycoon, who does not shy from flaunting their wealth," Kormind said.

While interest in the white diamond earnings may prove strong, they are unlikely to approach the eye-popping records set by coloured stones at recent sales.

Christie's set the current mark in May, selling the 14.62-carat "Oppenheimer Blue" for $57.54 million.

That beat a record set a year ago by Sotheby's, when Hong Kong billionaire Joseph Lau's bought the 12.03-carat "Blue Moon of Josephine" for $48.4 million.

Christie's is aiming to capitalise on the still-solid coloured stones market with a 9.14-carat Fancy Vivid Pink estimated at $16-$18 million.

The rare "Fancy Vivid" classification is awarded by the Gemological Institute of America to signify a stone's exceptional colour and clarity.

Sotheby's top coloured gem going under the hammer this week is the 8.01-carat "Sky Blue Diamond", with a pre-auction estimated price of $15-$25 million.

Sotheby's has estimated its 342-lot auction at a total of $100 million.

Christie's is offering 220 lots, with an estimated value of $80 million.