A colourless, pear-shaped diamond weighing 101.73 carats has sold for a record $23.8 million.

The diamond was bought by prestigious jeweller Harry Winston at a Christie's auction in Geneva.

"Twenty-three million (Swiss) francs! Your last chance! Twenty-three million, sold!" auctioneer Francois Curiel shouted clinching the deal before some 150 people gathered for the auction at a luxury Geneva hotel.

The auction house says the price, which does not include tax or commission, is the highest ever paid for a flawless colourless diamond.

Including tax and commission, the total ticked in at $27.04 million, though Christie's had hoped the gem would go for closer to $30 million.

As the first ever buyer of the new diamond, Mr Winston had the privilege of naming it and has decided to call it "Harry Legacy".

Christie's says the American Institute of Gemology classified the gemstone the top colourless grade "D" and the best clarity grade, "flawless", which is characterised by its "absolute symmetry".

In the rough, the diamond was 236 carats when it was extracted from the Jwaneng mine in Botswana, before it was meticulously sculpted for 21 months.

The previous auction-price record-holder in the category was the 84.37-carat Chloe round diamond, snapped up at a Sotheby's auction in Geneva in 2007 by Guess Jeans founder Georges Marciano for $16.2 million.

In the "colourless, flawless" category, the reigning world champion in terms of size is the Cullinan Diamond, a gem weighing 530.2 carats that is part of the British crown jewels.

AFP