A 25.59-carat "pigeon blood" ruby sold for a world record $30.33 million at auction in Geneva on Tuesday, while a rare pink diamond believed to have once belonged to Napoleon's niece fetched $15.9 million, Sotheby's said.

After competitive bidding, the ruby went to an anonymous telephone bidder for 26.25 million Swiss francs ($28.27 million), with costs.

The "Sunrise Ruby" from Myanmar, part of a collection of Cartier jewels up for auction, had been expected to sell for between $12 million and $18 million. It set a record for a ruby and was also a record for a Cartier jewel at auction, Sotheby's said.

"The Sunrise Ruby sold for just over $30 million, $30.3 million, which is I think over three times the previous record, which was for the Graff Ruby," said David Bennett, head of Sotheby's international jewelry division, referring to a stone sold in November.

The large, pigeon-blood red ruby "is amongst the rarest of all gemstones".

"I mean, in 40 years I've ever only seen one this color, this size, so they are beyond rare," Bennett said.

Another "extremely rare" stone, a fancy vivid pink diamond weighing 8.72 carats, sold for 14.8 million Swiss francs at the spring Magnificent Jewels and Nobel Jewels auction.

The stone, known as "The Historic Pink" and mounted on a ring with a classic non-modified cushion cut, is believed to have been part of the collection of Princess Mathilde, niece of French Emperor Napoleon I, according to the Gemological Institute of America.

Another of its former owners was the reclusive US heiress and philanthropist Huguette Clark, who died in 2011.