A huge, internally flawless diamond from India's fabled Golconda mines was sold at auction in Geneva on Tuesday night (November 13) for a record 20.355 million Swiss francs ($21.48 million), Christie's said.

The rare, colourless stone weighing 76.02 carats, and roughly the size of a large strawberry, once belonged to Archduke Joseph August of Austria (1872-1962), a prince of the Hungarian line of the Habsburgs.

Its pre-sale estimate was 15-to-25 million Swiss francs and it fetched more than double the price paid for it at auction almost two decades ago.

"The Diamond was sold for 20 million Swiss Franc, 20,355.000 to be exact and about 23 million Dollars (Corrected $ 21,474.525). It's a world record price for a Golconda D colour flawless diamond and it's a world record price also per carat for a diamond of this importanceFrancois Curiel, director of the international jewellery department at Christie's, told reporters.

He added that the buyer wished to remain anonymous, but revealed that the underbidder was Fred Mouawad, an international dealer with offices in Dubai, the Middle East and Geneva.

The seller was American jeweller, Black, Starr & Frost.

"Listen, I've had the tremendous pleasure of being the steward of that stone for the last 13 years, and it's been an honor and I can only tell you I congratulate the buyer, because they've truly acquired something that is of tremendous history and one of the most beautiful, if not the most beautiful diamond in the world" said Black, Starr & Frost's chairman Alfredo Molina.

The diamond was the star lot at Christie's semi-annual jewellery sale in Geneva, which fetched 76.6 million francs, with 290 of 348 lots sold.

The bidding opened at 8 million Swiss francs but the price swiftly rose amid heated telephone bidding.

Historical diamonds originating in the Golconda mines, virtually exhausted by the 18th century, include the Koh-i-Noor, now in the British crown jewels, and the blue Hope Diamond, part of the Smithsonian Institute in Washington, D.C., Christie's said.

In 1933, records show the Archduke deposited the stone in the vault of the Hungarian General Credit Bank.

Decades later it surfaced at auction in 1961 and again at Christie's in November 1993, netting 9.7 million Swiss francs, equivalent to $6.5 million at the time, the auction house said.

The stone was subsequently "slightly recut".

Christie's is privately owned by French billionaire Francois Pinault.