LONDON, ENGLAND (REUTERS) - Two dazzling pink and blue pear-shaped diamonds are together expected to fetch close to US$70 million (S$89 million) when they go under the hammer next month.

Sotheby's said the Apollo and Artemis stones are "by far the most important pair of earrings ever offered at auction". They will be offered to buyers separately at the auction house's May 16 Magnificent Jewels and Noble Jewels sale in Geneva.

The 14.54 carat Apollo Blue is an "Internally Flawless Fancy Vivid Blue" stone with an estimated price tag of US$38 million-US$50 million while the Artemis Pink, a 16-carat "Fancy Intense Pink" stone, is seen at around US$12.5 million-$18 million.

"I am certain there hasn't been another pair of coloured diamonds of this size and importance ever put into auction - certainly the highest estimated pair of earrings ever to appear at auction," David Bennett, worldwide chairman of Sotheby's International Jewellery Division, told Reuters.

"We are selling them separately because there may well be somebody who wants them as a pair but it's also possible somebody might want just one or the other separately."

Last week, a 59.60-carat pink diamond sold for a record US$71.2 million in Hong Kong.