A natural pearl necklace that once belonged to a maharajah sold at an auction at Christie's on Wednesday for nearly $7.1 million, more than double the world record price for any piece of natural pearl jewellery, the auctioneers said.

Christie's said the buyer of the Baroda Pearls, which once belonged to the Maharajah Khande Rao of Baroda, was an Asian private collector, who bid by phone.

Bidding for the piece, which featured pearls as big as gumballs, lasted about three minutes in a packed auction room.

The Baroda Pearls is a two-strand necklace of natural pearls that was strung with 68 of the finest and largest pearls from a seven-row necklace.

"The pearls sold at about what we estimated them to make and more than double the last world record price for a natural pearl necklace," Rahul Kadakia, head of jewellery for Christie's America, said after the auction.

The previous record was set by Christie's in Geneva in November 2004 at $3.1 million, for a two-strand natural pearl necklace, it said.

The necklace was auctioned as part of Christie's "Magnificent Jewels" sale. The sale totalled $39.1 million.

Also setting a world record was the 22 Kashmir sapphire sold on behalf of the Minnesota Historical Society which fetched $3.1 million, making it the most expensive sapphire in the world, according to Christie's.